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植物生长与发育的调控Title: Regulation of Plant Growth and DevelopmentIntroduction:Plants are living organisms that exhibit remarkable diversity in their growth and development. Through a complex interplay of intrinsic genetic factors and extrinsic environmental cues, plants navigate their way from seed germination to maturity, adapting to various challenges along the way. This article explores the intricate mechanisms involved in regulating plant growth and development, emphasizing the key processes and factors that govern these essential biological phenomena.1. Germination and Seedling Growth:1.1 Seed Germination:Seed germination marks the beginning of a plant's life cycle. It is triggered by a series of environmental stimuli, including temperature, light, humidity, and availability of water and nutrients. These factors activate specific signaling pathways, leading to the degradation of inhibitory compounds and initiation of cell division in the embryo.1.2 Early Seedling Growth:Upon germination, the embryo develops into a seedling, which requires favorable conditions to establish itself. During this stage, the plant undergoes cotyledon expansion, establishment of the root system, and development of true leaves. Phytohormones, such as auxins and cytokinins,play vital roles in coordinating cell elongation, tissue differentiation, and overall seedling growth.2. Vegetative Growth:2.1 Shoot Development:During vegetative growth, the plant focuses on the development of shoots, which are responsible for photosynthesis and resource acquisition. Shoot apical meristems, composed of specialized undifferentiated cells, continuously divide and produce new tissues. The balance between cell proliferation and differentiation is regulated by phytohormones, particularly auxins and gibberellins.2.2 Root Development:Roots, in parallel with shoots, perform essential functions, including water and nutrient uptake, anchorage, and symbiotic interactions. Root development is influenced by various internal and external cues, mediated by phytohormones such as auxins and ethylene. These phytohormones regulate root growth, lateral root formation, and root hair development.3. Reproductive Growth:3.1 Flowering Induction:Flowering, a crucial reproductive process in plants, is influenced by photoperiod, temperature, and hormonal signals. Photoperiodic flowering responses are regulated by the interaction between light receptors (phytochromes) and the florigen genes. Environmental cues, such as day length, enable the transition from vegetative to reproductive growth.3.2 Pollination and Fertilization:Successful reproduction in plants relies on pollination, which involves the transfer of pollen grains from the male reproductive organs (anthers) to the female ones (stigma). Pollen tubes grow down the stigma to deliver sperm cells to the ovules, leading to fertilization. Mutualistic relationships with pollinators and specific floral characteristics ensure efficient reproduction.4. Ripening and Senescence:4.1 Fruit Development:After successful fertilization, ovaries develop into fruits, responsible for protecting and dispersing seeds. Hormones, especially auxins, gibberellins, and ethylene, regulate fruit growth, color, texture, and ripening. Fruit development involves cell expansion, complex metabolic changes, and the deposition of various compounds.4.2 Leaf Senescence and Abscission:Senescence is a programmed process in plants that optimizes resource allocation by triggering the breakdown of chlorophyll, proteins, and other cellular components. Ethylene and abscisic acid are major regulators of leaf senescence and the subsequent shedding of leaves, allowing plants to conserve resources during unfavorable conditions.Conclusion:The regulation of plant growth and development is a multifaceted process governed by an intricate network of genetic and environmentalfactors. From seed germination to reproductive success and senescence, plants adeptly respond to stimuli, ensuring their survival in diverse ecological niches. Understanding these regulatory mechanisms opens avenues for improving crop yield, enhancing plant adaptability, and safeguarding global food security.。
四年级英语植物生长作文Plants are fascinating and essential components of our natural world. As living organisms, they possess the remarkable ability to grow and thrive, transforming their environments and providing vital resources for countless other species. In this essay, we will explore the intriguing process of plant growth, delving into the key stages and factors that contribute to their development.At the heart of plant growth lies the remarkable process of photosynthesis. This is the fundamental process by which plants convert light energy from the sun, along with carbon dioxide and water, into glucose – the primary fuel that sustains their growth and survival. Through the intricate interplay of chlorophyll, enzymes, and specialized organelles within plant cells, photosynthesis allows plants to harness the sun's energy and transform it into the chemical energy they need to grow and flourish.The journey of plant growth begins with the seed. Contained within the seed is the embryo, a tiny structure that holds the potential for an entire new plant. When the seed is exposed to the rightenvironmental conditions – adequate moisture, warmth, and soil nutrients – the embryo is triggered to germinate and begin its remarkable transformation. The seed coat softens, and the embryo's radicle, or root, emerges first, anchoring the plant in the soil and drawing in water and essential minerals. Shortly after, the stem and leaves push upward, breaking through the soil and reaching towards the sun.As the plant continues to grow, it undergoes a series of distinct developmental stages. The first of these is the seedling stage, where the young plant develops its initial set of leaves and begins to establish its root system. During this phase, the plant is particularly vulnerable and requires careful tending to ensure its survival. With the proper care and favorable conditions, the seedling will gradually transition into the vegetative stage, where it focuses on increasing its size and developing a sturdy stem, branches, and foliage.Once the plant has reached a certain level of maturity, it will enter the reproductive stage. This is the phase where the plant shifts its energy towards the production of flowers, fruits, and seeds – the means by which it ensures the continuation of its species. The development of these reproductive structures is often triggered by environmental cues, such as changes in day length or temperature. The flowers, in particular, play a crucial role in the plant's life cycle, as they facilitate the process of pollination, which is essential for theformation of fruits and seeds.Throughout the plant's life cycle, various factors can influence its growth and development. Chief among these are the availability of essential nutrients, such as nitrogen, phosphorus, and potassium, which are crucial for healthy plant growth. The plant's access to water is also a critical factor, as it is necessary for the transport of nutrients, the maintenance of structural integrity, and the process of photosynthesis. Additionally, environmental conditions like temperature, light, and soil pH can have a significant impact on a plant's ability to thrive.One fascinating aspect of plant growth is the way in which plants respond to their environment and adapt to changing conditions. For example, some plants have evolved specialized mechanisms to conserve water in arid environments, such as the development of waxy coatings on their leaves or the ability to store water in their stems or roots. Other plants have adapted to thrive in shaded areas by developing larger, more efficient leaves that can capture even the smallest amounts of available light.The study of plant growth and development is an ongoing and ever-evolving field of scientific inquiry. Researchers continue to uncover new insights into the complex processes that govern the life cycles of plants, from the molecular mechanisms underlying photosynthesis tothe intricate signaling pathways that coordinate growth and development. As we deepen our understanding of these remarkable organisms, we gain valuable knowledge that can be applied to various fields, from agriculture and horticulture to environmental conservation and sustainable urban planning.In conclusion, the process of plant growth is a captivating and multifaceted phenomenon that showcases the incredible adaptability and resilience of living organisms. From the humble seed to the towering tree, plants demonstrate a remarkable ability to transform their environments and sustain life on our planet. By exploring the intricacies of plant growth, we not only satisfy our innate curiosity about the natural world but also gain valuable insights that can help us address the pressing challenges of our time, such as food security, climate change, and environmental preservation.。
photosynthesise翻译photosynthesise是一个动词，表示进行光合作用。
光合作用是植物和某些微生物中的一种重要生理过程，它利用光能将二氧化碳和水转化为有机物质，并释放出氧气。
下面是一些关于photosynthesise的用法和中英文对照例句：1. Plants photosynthesise to produce energy in the form of glucose.植物通过光合作用产生葡萄糖形式的能量。
2. Algae and some bacteria can also photosynthesise.藻类和一些细菌也能进行光合作用。
3. Chlorophyll is the pigment that enables plants to photosynthesise.叶绿素是使植物能够进行光合作用的色素。
4. During photosynthesis, plants convert sunlight into chemical energy.在光合作用过程中，植物将阳光转化为化学能。
5. The rate at which plants photosynthesise can be affected by factors such as light intensity and temperature.植物的光合作用速率可以受到光照强度和温度等因素的影响。
6. Scientists are studying ways to enhance the efficiency with which plants photosynthesise.科学家们正在研究提高植物光合作用效率的方法。
7. Understanding how plants photosynthesise is crucial for agricultural and environmental research.理解植物的光合作用对农业和环境研究至关重要。
植物的认识英语作文英文回答：Plants: A Vital Part of the Earth's Ecosystem.Plants are essential organisms that play a crucial role in the functioning of the Earth's ecosystem. They are responsible for producing oxygen, which is vital for the survival of all aerobic organisms, and they serve as the primary source of food for a vast majority of animals. Additionally, plants provide us with numerous essential resources, including food, clothing, shelter, and medicine.The study of plants, known as botany, has been practiced for centuries. Early botanists sought to understand the diversity and classification of plant species, and they developed methods for identifying and describing plants. In the 19th century, scientists began to investigate the physiology and biochemistry of plants, and they made important discoveries about photosynthesis, plantgrowth, and development.Modern botany continues to be a vibrant and growing field. Botanists use a variety of approaches to study plants, including field research, laboratory experiments, and computer modeling. Their research has led to a greater understanding of plant evolution, ecology, and genetics.Importance of Plants.Plants are essential for life on Earth. They provide us with the following:Oxygen: Plants produce oxygen through the process of photosynthesis. Oxygen is essential for the survival of all aerobic organisms, including humans, animals, and plants themselves.Food: Plants are the primary source of food for a vast majority of animals, including humans. Plants provide us with carbohydrates, proteins, vitamins, and minerals.Shelter: Plants provide shelter for animals and humans. Trees and other large plants can provide shade andprotection from the elements.Medicine: Plants have been used for medicinal purposes for centuries. Many modern medicines are derived from plants, including aspirin, penicillin, and morphine.Plant Structure and Function.Plants have a variety of structures that enable them to carry out their essential functions. These structures include:Roots: Roots anchor plants in the ground and absorb water and nutrients from the soil.Stems: Stems support the leaves and flowers and transport water and nutrients throughout the plant.Leaves: Leaves are the site of photosynthesis. They contain chlorophyll, a green pigment that absorbs sunlightand converts it into energy.Flowers: Flowers are the reproductive organs of plants. They contain pollen and ovules, which are necessary for fertilization and seed production.Plant Growth and Development.Plants grow and develop through a series of stages. These stages include:Seed germination: A seed germinates when it absorbs water and begins to grow.Seedling growth: The seedling grows into a small plant with roots, stems, and leaves.Vegetative growth: The plant continues to grow and develop its vegetative structures, such as leaves, stems, and roots.Reproductive growth: The plant produces flowers andseeds.Plant Diversity.There is a tremendous amount of diversity among plant species. Plants can be classified into two main groups:Vascular plants: Vascular plants have specialized tissues that transport water and nutrients throughout the plant. Vascular plants include ferns, gymnosperms, and angiosperms.Non-vascular plants: Non-vascular plants do not have specialized tissues that transport water and nutrients. Non-vascular plants include mosses and liverworts.Plant Ecology.Plants interact with each other and with their environment in complex ways. Plant ecology is the study of these interactions. Plant ecologists study how plants adapt to different environmental conditions, how they competewith each other for resources, and how they form communities.Conclusion.Plants are essential organisms that play a vital rolein the Earth's ecosystem. They provide us with oxygen, food, shelter, and medicine. Botanists continue to study plantsto learn more about their diversity, evolution, and ecology.中文回答：植物，地球生态系统中的重要组成部分。
种子开花过程的作文英文回答：The process of seed germination and flowering is a fascinating natural phenomenon. It involves a series of complex biochemical and physiological changes that transform a tiny seed into a mature plant. Here is a detailed explanation of the seed germination and flowering process:1. Imbibition: The first step in seed germination is imbibition, where the seed absorbs water and swells. This process activates the metabolic processes within the seed and initiates the production of enzymes.2. Germination: Germination occurs when the seed embryo resumes growth. The radicle, or primary root, emerges from the seed coat, followed by the hypocotyl, which is the stem that connects the root to the cotyledons. The cotyledons are the first leaves of the plant.3. Photosynthesis: Once the seedling has emerged from the soil, it begins to photosynthesize. This process converts sunlight, carbon dioxide, and water into glucose, which provides energy for the plant.4. Vegetative Growth: During the vegetative growth stage, the plant develops roots, stems, and leaves. Theroots anchor the plant in the soil and absorb water and nutrients. The stems transport water and nutrients from the roots to the leaves, while the leaves conduct photosynthesis.5. Reproductive Growth: When the plant reaches maturity, it enters the reproductive growth stage. This stage is characterized by the formation of flowers, which are the reproductive organs of plants.6. Flowering: Flowering involves the development of various floral structures, including sepals, petals, stamens, and pistils. The sepals and petals form the outer protective layers of the flower, while the stamens andpistils are involved in reproduction.7. Pollination: Pollination is the process by which pollen grains are transferred from the male stamens to the female pistils. This transfer can occur through various mechanisms, including wind, insects, or birds.8. Fertilization: Fertilization occurs when a pollen grain lands on the stigma of the pistil and germinates. The pollen tube grows down the style into the ovary, where it fuses with the egg cell.9. Seed Development: After fertilization, the ovules in the ovary develop into seeds. The seeds contain the embryo, which has the potential to grow into a new plant.中文回答：种子发芽过程：1. 吸水，种子吸收水分后膨胀，启动种子内部的代谢过程，并产生酶。
植物的生长过程作文豌豆英文回答：Stages of Plant GrowthA Study of the Pisum Sativum.Seed Germination.The first stage of plant growth is seed germination. In peas, this process begins when the seed absorbs water and swells. The seed coat breaks, and the radicle, or primary root, emerges. The hypocotyl, or stem, follows, arching upward towards the light.Seedling Growth.The next stage of plant growth is seedling growth. During this stage, the plant develops its first leaves, called cotyledons. These leaves are simple and often heart-shaped. The plant also begins to develop its true leaves, which are more complex and have a greater surface area forphotosynthesis.Vegetative Growth.Vegetative growth is the period of growth during which the plant increases in size and produces new leaves and stems. In peas, vegetative growth occurs rapidly, and the plant can reach a height of several feet within a few weeks.Flowering.Flowering is the next stage of plant growth. In peas, flowering occurs when the plant has reached sexual maturity. The flowers are small and white, and they grow in clustersat the ends of the stems.Fruit Development.After flowering, the plant begins to produce fruit. In peas, the fruit is a pod, which contains several seeds. The pods are green when they are young, but they turn brown and dry as they ripen.Seed Maturation.The final stage of plant growth is seed maturation. During this stage, the seeds inside the pods mature and ripen. The seeds are hard and brown, and they contain the embryo of the new plant.中文回答：豌豆生长过程。
花的生长过程英语作文英文回答：The growth of a flower is a fascinating process that involves multiple stages. Let's explore the different phases in more detail:1. Germination:The journey begins with a seed, which contains an embryo and a food supply. When placed in favorable conditions such as moisture, warmth, and oxygen, the seed absorbs water and swells. The embryo then emerges as a tiny root, breaking through the seed coat. This initial stage is crucial for the plant's survival.2. Seedling Stage:As the root develops, it anchors the seedling into the soil, absorbing water and nutrients. Simultaneously, theother part of the embryo grows upward, forming the stem and leaves. The leaves are responsible for photosynthesis, converting sunlight into energy for growth.3. Vegetative Growth:This stage is characterized by the rapid growth of the plant above and below ground. The stem elongates, new leaves emerge, and the root system expands. During this period, the plant focuses on establishing a strong foundation for future growth and reproduction.4. Flowering Stage:As the plant matures, it enters the flowering stage. Specialized structures called buds develop at the tips of stems or branches. These buds contain the developing flowers. When conditions are right, such as appropriate day length and temperature, the buds open, revealing the beautiful and delicate blooms.5. Pollination:Pollination is essential for sexual reproduction in flowering plants. Pollen grains, produced by the male anthers, must be transferred to the female stigma. This can occur through wind, insects, birds, or even humans. Once pollination occurs, the pollen germinates and grows a pollen tube, delivering the sperm cells to the ovules.6. Fertilization and Seed Development:When a sperm cell fuses with an egg cell, fertilization occurs. The fertilized egg then develops into an embryo, and the surrounding tissue forms the seed. The seed stores a food supply and an embryo, ready to start the growth process anew.7. Fruit Development (Optional):In some flowering plants, the ovary, which contains the seeds, develops into a fleshy or dry structure called a fruit. Fruits serve as a protective casing for the seeds and aid in their dispersal through animals or other means.中文回答：花朵的生长过程是一个迷人的过程，涉及多个阶段。
四下沪教版牛津英语作文植物生长过程全文共3篇示例，供读者参考篇1Plant Growth ProcessPlants are living organisms that go through a fascinating process of growth and development. From seed germination to mature plant, the life cycle of a plant involves several stages that are crucial for its survival and reproduction. In this essay, we will explore the different stages of plant growth process.Germination is the first stage in the plant growth process. It is the process where a seed sprouts and begins to grow into a seedling. When a seed is placed in soil with the right conditions of moisture, warmth, and oxygen, it absorbs water and swells. This triggers the embryo inside the seed to start growing and a root emerges from the seed, followed by a shoot.The next stage is seedling development, where the young plant continues to grow and develop leaves and stems. The plant relies on photosynthesis to produce energy and nutrients from sunlight, water, and carbon dioxide. As the plant grows, itdevelops a strong root system to absorb water and nutrients from the soil.As the plant matures, it enters the flowering stage where it produces flowers. Flowers are essential for plant reproduction as they contain the reproductive organs needed for pollination and seed production. Pollination occurs when pollen grains are transferred from the male reproductive organs to the female reproductive organs of a flower. This can happen through wind, insects, or other animals.After pollination, the plant produces fruits that contain seeds. The seeds are dispersed through various means such as wind, water, animals, or humans. When the seeds find a suitable environment, they germinate, and the life cycle of the plant continues.In conclusion, the plant growth process is a complex and beautiful journey that starts from a tiny seed and ends with a mature plant capable of producing seeds for the next generation. Understanding the stages of plant growth is essential for gardeners, farmers, and anyone interested in the beauty and importance of plants in our ecosystem. Let's appreciate the miracle of plant growth and the role they play in sustaining life on Earth.篇2The Growth Process of PlantsPlants play a crucial role in our ecosystem by providing oxygen, food, and shelter for various organisms. Understanding the growth process of plants is essential for farmers, gardeners, and botanists alike. In this article, we will explore the stages of plant growth, from seed germination to maturity.Seed GerminationThe first stage of a plant's life cycle is seed germination. When a seed is planted in the soil, it absorbs water and swells up. This triggers the seed to break open and allows the embryo to grow roots downwards into the soil and shoots upwards towards the sun. The seedling emerges from the soil, usually with two cotyledons, or seed leaves, which provide nutrients until the plant can photosynthesize on its own.Vegetative GrowthDuring the vegetative growth stage, the plant focuses on developing a strong root system and producing leaves. The roots absorb water and nutrients from the soil, while the leaves use sunlight, carbon dioxide, and water to generate energy through photosynthesis. As the plant grows larger, it produces moreleaves and branches, increasing its ability to capture sunlight and produce energy.FloweringOnce the plant has grown enough and received adequate sunlight and water, it will enter the flowering stage. The plant will produce flowers, which contain the reproductive organs necessary for pollination and seed production. Pollination can occur through wind, insects, or other animals transferring pollen from one flower to another. Once pollinated, the flower will begin to develop seeds within the ovary.Fruit FormationAfter successful pollination, the ovary of the flower will develop into a fruit. The fruit protects the seeds and aids in their dispersal. As the fruit grows, it may change color and flavor to attract animals that will eat the fruit and spread the seeds through their droppings. The seeds within the fruit are mature and ready to grow into new plants.Seed DispersalOnce the seeds are fully developed, they need to be dispersed to new locations to ensure the survival of the species. This can happen through various methods, including winddispersal, animal dispersal, and water dispersal. Some plants have evolved specialized structures, such as wings or hooks, to assist in seed dispersal.MaturityAfter the seeds have been dispersed, they will germinate and begin the life cycle anew. The plant will continue to grow and reproduce, ensuring the survival of the species. Some plants may live for only a season, while others may live for years or even centuries.In conclusion, the growth process of plants is a complex and fascinating journey that is essential for the survival of all living organisms. By understanding the stages of plant growth, we can better appreciate the beauty and importance of these vital organisms in our world.篇3The Growth Process of PlantsPlants are an essential part of our ecosystem, providing oxygen, food, and beauty to the world around us. Understanding the life cycle of plants can help us appreciate their importance and learn how to better care for them. In this essay, we will explore the growth process of plants, from seed to maturity.First of all, the growth process of a plant begins with a seed. Seeds contain all the genetic material needed for a plant to grow and develop. When a seed is planted in soil, it absorbs water and nutrients from the soil, which triggers germination. During germination, the seed begins to sprout and grow roots that anchor the plant in the soil and absorb water and nutrients.As the plant continues to grow, it develops leaves that are crucial for photosynthesis. Photosynthesis is the process by which plants convert sunlight into energy, which is used to fuel their growth and development. Leaves contain chlorophyll, a pigment that captures sunlight and converts it into energy. This energy is used to produce glucose, a type of sugar that serves as the plant's primary food source.As the plant grows, it will eventually produce flowers. Flowers are the reproductive organs of plants, containing both male and female reproductive cells. Pollination occurs when pollen from the male reproductive cells is transferred to the female reproductive cells, either by wind, insects, or other animals. This fertilization process results in the production of seeds, which can then be dispersed to grow new plants.After fertilization, the plant will continue to grow and mature, producing fruit that contains seeds. The fruit serves as aprotective covering for the seeds and helps to disperse them to new locations. Some fruits are eaten by animals, which then scatter the seeds through their droppings. Other fruits, such as coconuts, are designed to float on water and disperse their seeds to new locations.Once the seeds are dispersed, the cycle begins again as the seeds germinate and grow into new plants. This growth process is essential for the survival of plants and ensures that they can reproduce and continue to thrive in their environment.In conclusion, the growth process of plants is a fascinating journey that begins with a seed and ends with the production of new seeds. Understanding this process can help us appreciate the importance of plants in our ecosystem and learn how to care for them properly. By nurturing and protecting plants, we can ensure a healthy and vibrant environment for future generations.。
橘子生长过程英语作文Title: The Growth Process of Oranges。
Oranges, the vibrant and nutritious citrus fruits, undergo a fascinating growth process from seed to fruit-bearing tree. Let's delve into the stages of their development in detail.1. Germination:The journey of an orange begins with the germination of its seed. Once planted in fertile soil, the seed absorbs moisture and nutrients, triggering the emergence of a tiny root, followed by a shoot. This marks the inception of a new orange tree.2. Seedling Stage:During this phase, the young orange plant focuses on establishing a robust root system and developing its above-ground structure. Adequate sunlight, water, and nutrients are crucial for healthy growth. The seedling undergoes photosynthesis, converting light energy into chemical energy to fuel its growth.3. Vegetative Growth:As the orange tree matures, it enters a period of vigorous vegetative growth. Branches elongate, leaves proliferate, and the tree's overall size increases. This stage requires optimal conditions, including sufficient sunlight, water, and nutrients, to support the tree's burgeoning biomass.4. Flowering:The most visually stunning stage in the orange tree's growth cycle is flowering. Typically occurring in spring, the tree adorns itself with clusters of delicate white flowers. These flowers contain reproductive organs essential for fruit formation. Pollination, facilitated by insects or wind, is crucial for fertilization to occur.5. Fruit Set:Following successful pollination, the fertilized flowers transform into young fruit, known as fruit set. Initially, these fruits are tiny and green, resembling miniature versions of the mature oranges they will become. The tree allocates resources to nurture these nascent fruits, ensuring their development.6. Fruit Development:As the weeks progress, the green fruit undergoes a remarkable transformation. It swells in size, gradually acquiring its characteristic orange hue. Throughout this phase, the fruit accumulates sugars, organic acids, and essential nutrients, enhancing its flavor and nutritional profile.7. Maturation:The final stage in the orange's growth process ismaturation. This is when the fruit reaches its optimal ripeness for harvesting. Factors such as color, firmness, and sugar content are indicators of maturity. Once ripe, the oranges are ready to be picked and enjoyed, whether fresh or processed into various products.8. Harvesting:Harvesting oranges requires careful timing to ensure peak flavor and quality. Depending on the variety and geographical location, harvesting may occur from late autumn to early spring. Commercial orchards employ specialized equipment and techniques to efficiently harvest large quantities of fruit.9. Post-Harvest Handling:After harvesting, oranges undergo post-harvest handling to preserve their freshness and extend their shelf life. This may involve cleaning, sorting, grading, and packaging. Proper storage conditions, including temperature and humidity control, are essential to maintain fruit qualityduring transportation and distribution.10. Consumption:The culmination of the orange's growth journey is its consumption by humans. Whether enjoyed as a refreshing snack, juiced for a revitalizing beverage, or incorporated into culinary delights, oranges are cherished for their delightful flavor and myriad health benefits.In conclusion, the growth process of oranges is a remarkable testament to nature's ingenuity. From humble seeds to bountiful fruits, each stage in the orange tree's development is a testament to the intricate interplay of biological processes and environmental factors. As consumers, we appreciate the efforts of growers in nurturing these citrus treasures and bringing them to our tables.。
树的生长过程英语作文英文回答：The growth process of a tree is a fascinating and intricate phenomenon that involves several stages and adaptations.Germination and Seedling Stage.The journey of a tree begins with germination, a process triggered by favorable conditions such as moisture and warmth. Within the seed, the embryo swells and absorbs water, leading to the emergence of a radicle, the primary root of the future plant. The radicle penetrates the soil, anchoring the seedling and providing access to nutrients. As the seedling grows, the hypocotyl, the stem beneath the cotyledons (seed leaves), elongates, pushing the cotyledons above the soil surface. The cotyledons expand and begin photosynthesis, providing nourishment to the developing plant.Vegetative Growth.During the vegetative growth stage, the tree undergoes rapid growth in height and width. Meristematic tissues in the shoot and root tips produce new cells, contributing to the elongation of the stem and the formation of new leaves and branches. Auxin, a plant hormone, plays a crucial role in regulating apical dominance, ensuring the primary stem remains dominant and suppresses the growth of lateral branches. The tree's root system also expands, forming a network that anchors the tree and absorbs water and nutrients from the soil.Reproductive Growth.As the tree matures, it enters the reproductive growth stage. Flowers develop on specialized branches, and pollination occurs through the transfer of pollen from male to female reproductive structures. Fertilization results in the formation of seeds, which contain the embryo and the nutrients necessary for germination.Environmental Adaptations.Throughout its life, a tree displays remarkable adaptations that enable it to thrive in various environments.Phototropism: Trees respond to light by orientingtheir leaves and stems towards the sun, maximizing light absorption for photosynthesis.Geotropism: The tree's root system responds to gravity by growing downwards, ensuring stable anchorage andefficient nutrient and water uptake.Dormancy: Deciduous trees adapt to seasonal changes by entering dormancy during winter, shedding their leaves to conserve energy and protect themselves from harsh conditions.Cambium: The cambium, a layer of meristematic tissue beneath the bark, allows for secondary growth, contributingto the tree's increase in girth and wood production.Ecological Significance.Trees play a pivotal role in ecosystems, providing numerous ecological benefits:Carbon sequestration: Trees absorb carbon dioxide from the atmosphere through photosynthesis, contributing to climate regulation.Water cycle: Trees regulate the water cycle by intercepting rainwater, releasing it through transpiration, and replenishing groundwater reserves.Habitat: Trees provide shelter and nesting sites for diverse wildlife, supporting biodiversity and ecological balance.Soil conservation: The extensive root system of trees stabilizes soil, preventing erosion and maintaining soil fertility.Conclusion.The growth process of a tree is a complex and dynamic journey that encompasses germination, vegetative growth, reproductive growth, and environmental adaptations. Throughout its life, a tree displays remarkable resilience and contributes significantly to the health and stability of ecosystems. Understanding the growth process of trees is essential for appreciating their ecological value and implementing conservation strategies that ensure their longevity and the well-being of the environment.中文回答：树的生长过程。
PHOTOSYNTHETICA 45 (3): 455-461, 2007455Vegetative growth and photosynthesis in coffee plants under different watering and fertilization managements in Yunnan, SW ChinaC.-T. CAI *, Z.-Q. CAI, T.-Q. YAO, and X. QIXishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, 666303, ChinaAbstractIn a field experiment Coffea arabica L. was subjected to various moisture and fertilizer regimes in Simao, Yunan, SW China. The experimental treatments consisted of eight factorial combinations of two fertilization levels (high and low) and four watering treatments applied in the dry season: application of dry rice straw mulch, drip irrigation, mulching plus drip irrigation on the soil surface, and control (no mulching or irrigation). The growth of the coffee plants was monitored throughout the course of a full year. Two clear growth peaks were detected (one at the beginning and one in the middle of the wet season) in plants subjected to all treatments, and the growth rhythm of coffee plants was not regulated by extrinsic abiotic factors. High fertilization resulted in a significantly higher relative growth rates for both height and length of the branches during the growth peaks than the low fertilization treatment. In the dry season, increasing the soil moisture contents by irrigation and/or mulching enhanced the plants’ gas exchange, but the soil water status had no significant effects on the internal fluorescence parameters of photosystem 2. More fertilized plants had a greater ability to acclimate to high-irradiance environments than the lightly fertilized plants, showing significant lower diurnal photoinhibition, associated with higher energy utilization through photochemistry and energy dissipation through the xanthophyll cycle. Hence the wet season is the optimum period for photosynthetic carbon fixation and vegetative growth of coffee plants. Higher than routinely applied levels of fertilization are required to optimize the coffee plants’ photosynthetic acclimation and growth in the studied environment. Both soil moisture conserving practices tested, mulching and drip irrigation, had significant effects on the growth and photosynthesis of the coffee plants, but the former was more practical than the latter.Additional key words : chlorophyll fluorescence kinetics; Coffea arabica ; drip irrigation; gas exchange parameters; mulching; photochemical efficiency; relative growth rate; stomatal conductance; transpiration rate; water use efficiency.IntroductionCoffee was introduced to China more than 100 years ago. Coffea arabica L. was the dominant planted coffee species and was widely cultivated in the tropical and subtropical regions in southwest China (Long and Wang 1997). Coffee was originally classified as obligatory shade species. Strong irradiation at midday usually induces severe photoinhibition and photo-oxidative damage of photosynthetic apparatus of coffee leaves (Nunes et al. 1993, Da Matta and Maestri 1997). A number of environmental stresses, including drought and malnutrition, may increase coffee plants’ sensitivity to photoinhibition and photodamage, induce cellular damage, and thus decrease their productivity (Nunes et al. 1993, Da Matta et al . 1997, 2002, Da Matta 2004,Cai et al. 2005).Coffee plants require high levels of nutrients and are sensitive to drought (Barros et al. 1995, Da Matta et al . 2003, Cai et al . 2004). The growth and yield of coffee are confined to both dry and nutrient-poor soils because most lands for coffee plantation are located in mountainous areas in China. Soil water deficit in the dry season is amongst the main environmental factors that largely limit the productivity of coffee (Long and Wang 1997), although the ability of different coffee plant lines to sur-vive water stress and maintain satisfactory levels of productivity in areas subjected to water deficit varies. Resistant lines display a suit of morphological and physiological adaptations, including leaf area reductions,———Received 5 September 2005, accepted 19 June 2006.*Corresponding author; phone-fax: +86 (0) 691 8715070, e-mail: caict@Acknowledgements : We are grateful to two field assistants for their support in the field work and suggestions. The research was financially supported by the Chinese National Science Foundation (30500065) and the Chinese Academy of Sciences (YK99005).C.-T. CAI et al.456adjustment to their stomatal closure response, osmotic status, and non-radiative energy dissipation mechanisms (Da Matta et al. 2002, 2003, Cai et al. 2005). In addition, agricultural practices can help reduce potential water deficits and, thus, boost crop productivity. Supplementary drip irrigation and rice straw mulching on the soil surface have been employed in many parts of China for centuries to increase soil moisture in the field (Sun et al. 2001). Mulching is one of the simplest and most beneficial crop cultivation practices, which, in addition to improving the water status of many soils, help control weed growth (Erenstien 2002), retain soil moisture (Enrique et al. 1999, Rahmana et al. 2005), and reduce losses of nutrients applied in fertilizers (Bhagat and Verma 1991). The agronomic traits of coffee plants are well charac-terized (Barros et al . 1995, Da Matta 2004) and the inter-active effects of nutrition and water availability on their growth and leaf photosynthesis have been well docu-mented (e.g . Da Matta et al. 2002). However, physiologi-cal and biochemical characteristics of coffee plants under water- and nutrient-limited conditions have been less thoroughly studied, and information relating to mulch management and fertilization requirements in field-grown coffee plants is scarce. The objectives of this study were: (1) to study the vegetative growth and photosynthesis of coffee plants in the field under both optimal water and nutrient conditions and suboptimal conditions, i.e . under water and/or nutrient stress, and (2) to compare the effects of various water managements on the growth and photosynthesis of coffee plants.Materials and methodsSoil and climate : The experiment was conducted during two consecutive years of 2002–2003 in the field in the Coffee Plant Centre in Simao (22°67’N, 100°88’E, 1 050 m a.s.l.), Yunnan, China, where 4 500 coffee plants per ha were cultivated. The soil (0–20 cm) at this site is characterized as an acidic lateritic red soil with pH 5.4 and 2.0 g kg −1 exchangeable calcium. Organic matter and total N and P contents of the soil were 2.870, 0.169, and 0.116 g kg −1, respectively, while the available N and P contents were 145.1 and 10.1 mg kg −1, respectively. The texture of the soil surface layer was loam, but there was a thin sub-surface layer of sand that enhanced percolation and drainage of the soil. Monthly rainfall and average air temperature in 2002, recorded at the meteorological station nearby, are presented in Fig. 1. There was a clear alternation of dry (November to April) and wet (May to October) seasons in the local area. The monthly rainfall at the research field ranged from less than 65 mm in February in the dry season to over 350 mm in July and August during the wet season. The mean air temperature is 19.8 °C, and the lowest temperature (13.6 °C) occurs in December.Fig. 1. Average monthly air temperatures (T air ) and rainfall in 2002 at the studied site.Experimental design and treatments : Five-year-old coffee plants were separated to eight sub-groups that were each subjected to one of eight factorial combi-nations of four watering treatments and two fertilizer levels. The four watering treatments were application of: 3.0 Mg ha −1 sun-dried rice straw mulch; drip irrigation; mulch plus drip irrigation on the soil surface; and control (no irrigation or mulching). In the drip irrigation treatments, which were applied from December 2001 to April 2002 in the dry season, the soil was irrigated every week from 08:00 to 10:00 in the morning using plastic tubes with three dripping pores per meter at the rate of 3 800 cm 3 pore −1 h −1. Two levels of fertilizations were: normal fertilization that is actually used in the field by the local farmers (300 g oilseed rape, 60 g urea, 100 g compound fertilizer, and 1 000 g manure for one plant per year); high fertilization (another 60 g compound fertilizer with N:P:K ratio at 1:1:1 was added per plant besides the normal fertilization). Twelve to fifteen coffee individuals were selected for each treatment. The fertilization treat-ments were started in December 2001 and plants were fertilized once every three months.Soil water status and leaf N content : Samples from the upper 20 cm soil layer representing each treatment were collected during the wet and dry seasons to determine soil moisture content gravimetrically. The soil water holding capacity (23.1 %) was determined following Piper (1944) and the relative soil water content (RSWC %) was calcu-lated. Total N content of leaves in the wet season was measured by the semi-micro-Kjeldahl digestion method.Growth : In January 2002, eight coffee plants per treatment were labelled for the growth measurement and four primary plagiotropic branches per plant were tagged in the upper third of the canopy for periodical length measurements. The height of the plants and the length of branch were determined every month from February 2002 to January 2003. The numbers of branch pairs of coffee and new sprouting branches were also counted. The relative growth rate (RGR) was calculated as: RGR = (H t+1 – H t ) t −1, where t is the time in months.VEGETATIVE GROWTH AND PHOTOSYNTHESIS IN COFFEE PLANTS 457Photosynthesis and leaf reflectance measurements : Gas exchange was determined in the morning between 10:00 and 11:00 h, which was presumed to be the diurnal period when photosynthetic rates would be maximal. Gas exchange parameters (net photosynthetic rate, P N ; stoma-tal conductance, g s ; transpiration rate, E ; and water use efficiency, WUE) were measured using a portable infra-red gas analyzer in open system mode (LI-6400, Li-Cor ) under ambient CO 2 concentration and saturating irradiance (1 100 µmol m −2 s −1, provided by a built-in red LED radiation source). Chlorophyll a fluorescence was measured using a portable pulse-modulated fluorescence system (FMS2.02, Hansatech , UK). Leaves, dark-adapted for 30 min, were irradiated with a weak modulated measuring beam to obtain the initial fluorescence (F 0). A saturating “white light” pulse of 6 000 μmol m –2 s –1 was applied for 0.7 s to obtain the maximum fluorescence emission (F m ). F s was determined when the fluorescence became stable and F m ’ was obtained by applying a strong pulse. The initial and actual photochemical efficiencies of PS2 were then calculated as F v /F m = (F m – F 0)/F m and ΔF v ’/F m ’ = (F m ’ – F s )/F m ’. ΔF v ’/F m ’ was determined between 10:00 and 11:00 h in the morning. F v /F m was measured at predawn (06:30) and midday (13:00). The diurnal change was estimated as: % diurnal photoinhi-bition = 100 – [(F v /F m13:00)/(F v /F m06:30)]×100.A UniSpec Spectral Analysis System (PP Systems, Haverhill, MA, USA) was used to measure spectral reflectance at wavelengths from 306 to 1 138 nm. A spec-tral reflectance standard was regularly referenced and scans were corrected for the instrument’s dark current.Each scan represented the mean of four passes and the instrument’s integration time was set at 125 ms. The photochemical reflectance index, which was calculated as PRI = (R 531 – R 570)/(R 531＋R 570) (Gamon and Surgus 1999), was correlated with the epoxidation state of xanthophyll cycle pigments and photosynthetic radiation-use efficiency (net photosynthesis/incident PAR) (Gamon et al . 1992). The method used to estimate xanthophyll pigment activity was to sample PRI under both predawn and midday irradiances on the same leaf to derive a ΔPRI (expressed as the predawn PRI minus the midday PRI values), and thus the resulting values provided indications of the conversion of xanthophyll cycle pigments used in photo-protection under ambient irradiance (Gamon and Surgus 1999). All measurements were made on fully expanded and healthy upper canopy leaves from plagio-tropic branches in March (dry season) and June (wet season) in 2002. The number of plants per light treatment for physiological measurements ranged from four to six; one leaf per plant was measured.Statistical analyses : The statistical differences of between-treatment and between-season differences in the measured growth and photosynthetic parameters were analyzed using Student’s t -test with SPSS 11.0 (Chicago, IL, USA). Main and interactive effects of watering and fertilization treatments on physiological traits in the dry season were tested by two-way ANOVA. Differences were considered significant at a probability level of p <0.05.ResultsSoil moisture and leaf N content : The relative water content (RSWC) of the surface layer (0–20 cm) of the soil in the wet season was over 95 % of the field water-holding capacity and was similar among different treatments. Soil moisture was not affected by fertilization, but RSWC clearly increased following applications of rice straw mulch, drip irrigation, and mulch plus drip irrigation in the dry season (p <0.05). The leaf N contents of the coffee plants ranged from 2.34 to 3.12 % (Table 1). Compared to the low fertilization treatment, high ferti-lization significantly increased leaf N contents of the coffee plants in the wet season, but watering treatments applied in the dry season did not affect leaf N content.Vegetative growth : The height and lateral branch length growth rates of all the monitored coffee plants showed two clear peaks during the course of the study year under all of the watering and fertilization treatments (Fig. 2). The first highest growth peak appeared in May and the second one in August and September. At two growth peaks, the high fertilization group had significantly higher relative growth rate (RGR) of height and length of lateral branch than those of the low fertilization groupTable 1. Effect of watering and fertilization treatments on relative soil water content (20 cm depth) and leaf nitrogen content of Coffea arabica (means±SD, n = 5). The data in parentheses are the percentages accounted for field water-holding capacity. HF: high fertilization, LF: low fertilization, M: rice straw mulch, I: drip irrigation, MI: mulch plus drip irrigation, CK: control (bare soil). *Measured in May 2002. The different letters represent statistical significance between means for each parameter within each treatment (p <0.05).Treatment RWC [%] Leaf N Dry season Wet season [%] M16.2±0.5 (70.0) b22.1±0.3 (96.7) a 3.11±0.23 a I 18.8±0.6 (72.7) b 22.7±1.4 (98.3) a 3.15±0.09 a MI 22.7±1.1 (98.2) a 23.8±0.4 (103.0) a 3.17±0.16 a HF CK 13.3±0.7 (57.5) c 22.9±1.1 (99.1) a 3.14±0.21a LF M 14.5±0.9 (63.0)bc 22.3±0.7 (96.5) a 2.48±0.24 b I 16.8±0.2 (72.7) b 22.5±2.1 (97.4) a 2.50±0.21 b MI 22.1±1.5 (95.7) a 22.4±0.3 (97.0) a 2.54±0.17 bCK13.6±0.6 (58.8) c21.9±1.0 (95.0) a2.34±0.31 b(p <0.01), while no difference was found in the RGR of shoot numbers (i.e . the sprouting of new shoots) betweenC.-T. CAI et al.458the two fertilization groups. Watering treatments slightly increased the height and branch length RGR of coffee plants in both the low and high fertilization groups, with mulching plus drip irrigation having the strongest effect, and mulching or drip irrigation having similar effects.Photosynthesis : P N in leaves of the coffee plants in the dry season was significantly lower than that in the wet season for all treatments (p <0.01). In the dry season, P N values of the high-fertilization group were somewhathigher than those of the low-fertilization group, but no significant differences were found. Within fertilization groups, the watering treatments mulching, drip irrigation, and mulching plus drip irrigation increased P N by 24.1–56.0 %, g s by 7.1–28.6 %, E by 5.0–36.8 %, and water use efficiency (WUE) by 13.3–30.8 % (P N /E ). However, the effects of various watering treatments on the gas exchange parameters in the dry season did not continue throughout the wet season. High fertilization increased P N (p <0.01) in the wet season, but had no effects on g s , E , orTable 2. Effect of watering and fertilization treatments on the gas exchange parameters in leaves of C. arabica. HF: high fertilization, LF: low fertilization; M: rice straw mulch; DS: dry season, WS: wet season; P N : net photosynthetic rate, g s : stomatal conductance, E : rate of transpiration, WUE: water use efficiency. The abbreviations for the watering treatments are as defined in Table 1.Treatment P N [μmol m −2 s −1] g s [mmol m −2 s −1] E [mmol m −2 s −1] WUE [mmol mol −1] DS WS DS WS DS WS DS WS M3.6 b 5.7 a 0.091 b 0.118 a 2.1 b 2.6 a 1.7 ab 2.2 a I 3.8 ab 5.8 a 0.097 b 0.114 a 2.2 b 2.8 a 1.9 a 2.1 a MI4.5 a 6.1 a 0.119 a 0.121 a 2.4 a 2.9 a 1.9 a 2.1 a HF CK 2.9 bc5.5 ab 0.085 c 0.116 a 2.0 c 2.7 a 1.5 bc 2.0 a LF M 3.3 b 5.0 b 0.088 b 0.117 a 2.2 b 2.7 a 1.5 bc 1.8 b I 3.6 b 5.3 b 0.092 b 0.113 a 2.3 b 2.9 a 1.6 b 1.8 b MI 3.9 ab 5.4 ab 0.114 a 0.119 a 2.6 a 2.8 a 1.7 ab 1.9 abCK2.5 c4.8 b0.078 c0.112 b1.9 c2.8 a1.3 c1.7 bTable 3. Effect of watering and fertilization treatments on the potential and actual photochemical efficiency, diurnal photoinhibition, and thermal dissipation efficiency as estimated from leaf reflectance indices in leaves of C. arabica . The abbreviations for the watering treatments are as defined in Table 1.Treatment Predawn F v /F m Dayphotoinhib. [%] ΔF v ’/F m ’ ΔPRI×100 DS WS DS WS DS WS DS WS M0.825 a 0.826 a 19.1 b 18.9 b 0.51 a 0.52 a 3.1 a 3.4 a I 0.823 a 0.831 a 18.9 b 18.1 b 0.52 a 0.55 a 3.5 a 3.6 a MI 0.832 a 0.843 a 18.5 b 17.8 b 0.53 a 0.57 a 3.5 a 3.7 a HF CK 0.829 a 0.828 a 21.4 ab 20.5 ab 0.48 ab 0.52 a 3.4 a 3.3 a LF M 0.827 a 0.831 a 23.1 a 22.7 a 0.46 b 0.47 b 2.7 b 2.8 b I 0.831 a 0.833 a 22.6 a 22.5 a 0.45 b 0.48 b 2.4 b 2.7 b MI 0.829 a 0.838 a 23.4 a 21.8 ab 0.48 ab 0.49 ab 2.8 ab 2.9 bCK0.819 b0.828 a24.2 a23.5 a0.45 b0.46 b2.3 b2.6 bTable 4. Results of two-way ANOVA for some physiologicalparameters of C. arabica in the dry season. ns: no significant difference (p >0.05), *p <0.05, **p <0.01.Source of variation Water Fertilization W×F Net photosynthetic rate (P N ) ** **Stomatal conductance (g s ) **ns nsTranspiration rate (E ) *ns ns Water use efficiency (WUE) ** ** % diurnal photoinhibition ns * ns ΔF v ’/F m ’ ns * ns ΔPRI ns * nsWUE (all comparisons, p >0.05) (Table 2). The predawn values of the initial photochemical efficiency (F v /F m ) in leaves of the coffee plants ranged from 0.82 to 0.85 andthere were no significant differences in this parameteramong treatments. The actual photochemical efficiency (ΔF v ’/F m ’) and thermal energy dissipation efficiencyestimated from the photochemical reflectance index (ΔPRI) were significantly higher in the wet season than the corresponding efficiencies in the dry season (twot -tests, each p <0.05). Watering treatments had no effects on the photochemical parameters, while high fertilization significantly reduced diurnal photoinhibition and increased both ΔF v ’/F m ’ and ΔPRI (Table 3).VEGETATIVE GROWTH AND PHOTOSYNTHESIS IN COFFEE PLANTS 459The two-way ANOVA for the photosynthetic para-meters in the dry season showed that the watering treatments had significant effects on the gas exchange parameters, while the photochemical parameters wereonly affected by fertilization (Table 4). The interaction effects on P N and WUE of the fertilization and watering treatments in the dry season were significant.DiscussionThe lowest N content in leaves of our studied coffee plants was 2.34 %, higher than the nutrient deficit thresh-olds reported by various authors (Barros et al . 1995, Müller 1996), indicating that both fertilization levels provided well-balanced nutrition for the coffee plants in our study. In the dry season, the lowest soil water content of bare soil in coffee plantation was around 57 % of the field water-holding capacity (Table 1), which is regarded as a moderate drought level for coffee plants (Da Matta et al . 1997, 2002, 2003, Cai et al . 2005).In most coffee plantations worldwide, vegetative growth of coffee trees shows active and quiescent growth phases modulated by the local duration of conductive growing conditions (Da Matta et al . 1999). During the growth period in the monitored year, the coffee plants showed two growth peaks in the wet season (Fig. 2). The fertilization and watering treatments did not change this basic growth rhythm of coffee, implying that it is con-trolled by intrinsic rather than extrinsic abiotic factors, at least within the tested range of environmental conditions. Crops are often subjected to periods of water shortage, which ultimately lead to reduced growth and produc-tivity. Biochemical constraints may limit photosynthetic CO 2 fixation directly when plants are subject to severe drought, while photosynthesis reductions are mainly due to stomatal limitations in moderate water deficit condi-tions (Lawlor and Cornic 2002). The reductions in g s observed in coffee plants grown under the control conditions, compared to those grown under the mulched or irrigated conditions (Table 2), appear to reflect avoidance mechanisms that minimize water loss. Such responses have previously been observed in coffee seedlings (Da Matta et al . 1997, Cai et al . 2005).The pre-dawn F v /F m ratios (0.82–0.85) in leaves of all coffee plants approached values (0.83) reported for healthy, unstressed C 3 plants (Demmig-Adams and Adams 1992), indicating that no photo-damage to PS2 reaction centres or slowly relaxing excitation energy quenching mechanisms had been induced by environ -mental stress (Foyer et al . 1994). The lower P N values observed in the control coffee plants than in the watered plants might have been due to a mechanism dependent on stomatal closure, rather than damage to PS2. Therefore, in our study, it is unlikely that PS2 photochemistry appreciably affected carbon gain, and diurnal photo -inhibition may reflect down-regulation of photosynthesis (Demmig-Adams and Adams 1992) related to the main -tenance of zeaxanthin contents or seasonal acclimation processes involving thylakoid lipids (Müller et al . 2001).Fig. 2. Effects of watering and fertilization treatments on the relative growth rate (RGR) of the height, branch length, and shoot numbers of coffee plants. HF, high fertilization; LF, low fertilization. The abbreviations for the watering treatments are as defined in Table 1.Photo-protection of PS2 was not achieved by an increase in non-radiative energy dissipation during drought con-ditions, because ΔPRI values did not differ significantly among the watering treatments in the dry season. Watering treatments, such as mulching and/or drip irriga-tion, had no significant effects on actual photochemical efficiency (ΔF v ’/F m ’), diurnal thermal energy dissipation (ΔPRI), or diurnal photoinhibition of the coffee plants (Table 3), indicating that seasonal drought did not affect the ‘internal’ fluorescence characteristics of the plants. High nutrient availability may either increase or decrease the g s of plants (Lima et al. 1999, Livingston et al . 1999). In our study, high fertilization had a slight influence on g s and E in the wet season (Table 2); the increase in P N may be attributed to the improvement of the action of photosynthetic enzymes in coffee plants influenced by high fertilization. There were significant interaction effects of water and fertilization on the P N andC.-T. CAI et al.460WUE of the coffee plants, as previously found in controlled experiments in the laboratory and/or with pot-plants (Da Matta et al . 2002, Rahmana et al . 2005). High fertilization increased ΔF v ’/F m ’ values and decreased the diurnal photoinhibition of the plants (Table 3), suggesting that high levels of nutrients increased the photochemical efficiency of coffee and alleviated diurnal photoinhi-bition, in accordance with the results of other studies (Da Matta et al . 2002, Dugald et al . 2003). Under restricted nutrient conditions, increases in the thermal energy dissipation of spinach (Spinacia oleracea ) (Verhoeven et al . 1997), maize (Khamis et al . 1990), and eucalypt (Eucalyptus nitens ) (Dugald et al . 2003) have been observed, but nutrient levels reportedly have no influence on the thermal energy dissipation of Clematis vitalba , at least within the ranges investigated by Bungard et al . (1997). In present study, the high ΔPRI values in the high fertilized coffee plants showed high nutritionwould contribute to promoting of thermal energy dissi-pation capability and benefit coffee plants for adaptation under high-irradiance.In conclusion, enhancement of the soil water content significantly promoted gas exchanges in leaves of coffee plants in the dry season, but had no influence on the inter-nal fluorescence features of PS2. High-fertilized coffee plants have evolved the mechanism to acclimate to the high irradiance. The wet season is the optimal period for the photosynthetic carbon fixation and vegetative growth of coffee plants. Mulching and drip irrigation applied in the dry season have similar effects on vegetative growth and photosynthesis, but the former is more economical than the latter. Therefore, we recommend application of high levels of fertilization, together with straw mulching, in coffee plantations in Yunnan.ReferencesBarros, R.S., Maestri, M., Rena, A.B.: Coffee crop ecology. – Trop. Ecol. 36: 1-19, 1995.Bhagat, R.M., Verma, T.S.: Impact of rice straw management on soil physical properties wheat yield. – Soil Sci. 152: 108-115, 1991.Bungard, R.A., McNeil, D., Morton, J.D.: Effects of nitrogen on the photosynthetic apparatus of Clematis vitalba grown at several irradiances. – Aust. J. Plant Physiol. 24: 205-214, 1997.Cai, Z.Q., Cai, C.T., Qi, X., Yao, T.Q.: Effects of fertilization on the growth, photosynthetic characteristics and yield of Coffea arabica . – Chin. J. appl. Ecol. 15: 1561-1564, 2004. Cai, Z.-Q., Chen, Y.-J., Guo, Y.-H., Cao, K.-F.: Responses of two field-grown coffee species to drought and re-hydration. – Photosynthetica 43: 187-193, 2005.Da Matta, F.M.: Ecophysiological constraints on the production of shaded and unshaded coffee: a review. – Field Crops Res. 86: 99-114, 2004.Da Matta, F.M., Amaral, J.A.T., Rena, A.B.: Growth periodicity in trees of Coffea arabica L. in relationship to nitrogen supply and nitrate reductase activity. – Field Crops Res. 60: 223-229, 1999.Da Matta, F.M., Chaves, A.R.M., Pinheiro, H.A., Ducatti, C., Loureiro, M.E.: Drought tolerance of two field-grown clones of Coffea canephora . – Plant Sci. 164: 111-117, 2003.Da Matta, F.M., Loos, R.A., Silva, E.A., Loureiro, M.E., Ducatti, C.: Effects of soil water deficit and nitrogen nutrition on water relations and photosynthesis of pot-grown Coffea canephora Pierre. – Trees 16: 555-558, 2002.Da Matta, F.M., Maestri, M.: Photoinhibition and recovery of photosynthesis in Coffea arabica and C. canephora . – Photosynthetica 34: 439-446, 1997.Da Matta, F.M., Maestri, M., Barros, R.S.: Photosynthetic performance of two coffee species under drought. – Photo-synthetica 34: 257-264, 1997.Demmig-Adams, B., Adams, W.W., III: Photoprotection and other responses of plants to high light stress. – Annu. Rev. Plant Physiol. Plant mol. Biol. 43: 599-626, 1992.Dugald, C.C., Beadle, C.L., Hovenden, M.J.: Interactive effects of nitrogen and irradiance on sustained xanthophyll cycle engagement in Eucalyptus nitens leaves during winter. –Oecologia 134: 32-36, 2003.Enrique, G.S., Braud, I., Louis, T.J., Michel, V., Pierre, B., Christophe, C.J.: Modeling heat and water exchange of fallow land coverage with plant residue mulch. – Agr. Forest Meteorol. 97: 151-169, 1999.Erenstien, O.: Crop residue mulching in tropical and semi-tropical countries: An evaluation of residue availability and other technological implications. – Soil Tillage Res. 67: 115-133, 2002.Foyer, C.H., Lelandais, M., Kunert, K.J.: Photooxidative stress in plant. – Physiol. Plant. 92: 696 -717, 1994.Gamon, J.A., Penuelas, J., Field, C.B.: A narrow-waveband spectral index that tracks diurnal changes in photosynthetic efficiency. – Remote Sensing Environ. 41: 35-44, 1992.Gamon, J.A., Surgus, J.S.: Assessing leaf pigment content and activity with a reflectometer. – New Phytol. 143: 105-117, 1999.Khamis, S., Lamaze, T., Lemoine, Y., Foyer, C.: Adaptation of the photosynthetic apparatus in maize leaves as a result of nitrogen limitation. Relationships between electron transport and carbon metabolism. – Plant Physiol. 94: 1436-1443, 1990. Lawlor, D.W., Cornic, G.: Photosynthetic carbon assimilation and associated metabolism in relation to water deficits in higher plants. – Plant Cell Environ. 25: 275-294, 2002.Lima, J.D, Mosquim, P.R., Da Matta, F.M.: Leaf gas exchange and chlorophyll fluorescence parameters in Phaseolus vulgaris as affected by nitrogen and phosphorus deficiency. – Photosynthetica 37: 113-121, 1999.Livingston, N.J., Guy, D., Sun, Z.J., Ethier, G.J. : The effects of nitrogen stress on the stable carbon isotope composition, pro-ductivity and water use efficiency of white spruce (Picea glauca (Moench) Voss) seedlings. – Plant Cell Environ. 22: 281-289, 1999.Long, Y.M., Wang, J.W.: Yunnan Coffea arabica L. – Yunnan Science Press, Kunming 1997.Müller, L.E.: Coffee nutrition. – In: Childers, N.F. (ed.): Nutrition of Fruit Crops. Pp. 685-776. Somerset Press, New Jersey 1996.Müller, P., Li, X.P., Niyogi, K.K.: Non-photochemical quen-ching. A response to excess light energy. – Plant Physiol. 125: 1558-1566, 2001.。
