Plant–Water Relationships
- 格式:pdf
- 大小:481.72 KB
- 文档页数:27
动植物和生态系统的关系英语作文英文回答:Relationship between Plants and Animals in an Ecosystem.Plants and animals are interdependent components of an ecosystem, each playing a vital role in the overall balance and functioning. Their interactions form complex relationships that maintain the stability and productivityof the ecosystem.One of the most important relationships between plants and animals is that of primary production and consumption. Plants, as primary producers, harness energy from the sun through photosynthesis and convert it into organic matter. This organic matter forms the base of the food chain, supporting populations of herbivores, which are animalsthat consume plants. Herbivores, in turn, serve as prey for carnivores, which occupy higher trophic levels in the ecosystem.Another significant relationship is that of mutualism, in which both plants and animals benefit from their interactions. For example, plants rely on animals for pollination, seed dispersal, and defense against pests. Animals, in turn, depend on plants for food, shelter, and nesting sites. Symbiotic relationships such as mycorrhizae, where fungi form associations with plant roots, enhance nutrient uptake for plants and provide carbohydrates for fungi.Furthermore, plants influence the physical and chemical properties of their environment, creating unique microclimates that support specific animal communities. Trees provide shade and reduce temperature fluctuations, while aquatic plants create oxygenated habitats for fish and other aquatic organisms. Plants also regulate water flow, prevent erosion, and improve soil conditions.In turn, animals play a vital role in shaping plant communities and ecosystem dynamics. Herbivores can control plant populations by grazing, preventing the dominance ofone species. Carnivores, by preying on herbivores, maintain a balance between plant and animal populations. Animals also contribute to nutrient cycling through their waste products, which decompose and release essential nutrients back into the soil or water.The relationship between plants and animals is a dynamic and ever-evolving process that contributes to the stability and resilience of ecosystems. Understanding these relationships is crucial for maintaining biodiversity, ensuring food security, and managing our natural resources sustainably.中文回答:动植物在生态系统中的关系。
全文分为作者个人简介和正文两个部分:作者个人简介:Hello everyone, I am an author dedicated to creating and sharing high-quality document templates. In this era of information overload, accurate and efficient communication has become especially important. I firmly believe that good communication can build bridges between people, playing an indispensable role in academia, career, and daily life. Therefore, I decided to invest my knowledge and skills into creating valuable documents to help people find inspiration and direction when needed.正文:让快乐的种子开出绚丽的花英语作文全文共3篇示例,供读者参考篇1In the vast garden of life, each of us is a unique seed, brimming with potential and yearning to bloom. The world around us is a rich tapestry of experiences, challenges, and opportunities, serving as the fertile soil in which we can take root and flourish. However, it is up to us to nurture the seeds within,allowing happiness to blossom into a vibrant array of colors that paint our existence with joy and fulfillment.Happiness is not a destination; it is a journey, a constant exploration of self-discovery and growth. It is the ability to find beauty in the simplest of moments, to appreciate the small wonders that often go unnoticed in the hustle and bustle of daily life. It is the warmth of a genuine smile shared with a stranger, the comfort of a loved one's embrace, or the sense of accomplishment that comes from overcoming a challenge.Cultivating happiness begins with self-awareness, an understanding of our innermost desires, fears, and aspirations. We must learn to embrace our flaws and celebrate our strengths, for it is in this delicate balance that true contentment resides. It is a lifelong process of shedding the layers of self-doubt and societal expectations that weigh us down, allowing our authentic selves to emerge and thrive.Just as a seed requires nourishment and care to sprout, our happiness demands intentional effort and nurturing. We must consciously seek out experiences that ignite our passions, surround ourselves with individuals who uplift and inspire us, and engage in activities that bring us a sense of purpose and fulfillment. Whether it is pursuing a hobby, volunteering for acause close to our hearts, or simply savoring the beauty of nature, these seeds of joy, when tended to with care, will blossom into a vibrant landscape of contentment.Moreover, happiness is not a solitary pursuit; it is a shared experience that flourishes through connection and empathy. By extending kindness and compassion to others, we create a ripple effect that spreads warmth and positivity throughout our communities. A simple act of generosity, a listening ear, or a word of encouragement can be the water that nourishes someone else's seeds of happiness, allowing them to grow and thrive alongside our own.Adversity is an inevitable part of life, casting shadows that can obscure the light of happiness. Yet, it is in these challenging moments that our resilience is tested, and our ability to find joy amidst the storm truly shines. Like a resilient flower that bends but does not break in the face of strong winds, we must learn to adapt and find strength in our struggles. Each obstacle we overcome becomes a testament to our perseverance, and the lessons we learn along the way enrich the soil of our happiness, allowing us to bloom even brighter.It is important to remember that happiness is not a singular, static state; it is a dynamic journey that ebbs and flows, withmoments of radiant bliss intertwined with periods of quiet contentment. Just as a garden experiences seasons of vibrant blooms and dormant winters, our emotional landscapes will ebb and flow. Embracing this natural cycle and finding beauty in each phase is the key to sustaining a lasting sense of joy and fulfillment.In the end, the seeds of happiness within us are precious gifts, waiting to be nurtured and nourished. By tending to our emotional gardens with care, patience, and a commitment to personal growth, we can create a vibrant tapestry of joy that radiates outward, touching the lives of those around us. Let us embrace the journey, celebrate the small victories, and allow our unique blossoms to unfurl, painting the world with the vibrant hues of our authentic and radiant happiness.篇2Happiness is often portrayed as an elusive butterfly, flitting from flower to flower, impossible to catch and hold onto. But what if we thought of happiness differently? What if, instead of chasing after it, we planted the seeds for it to bloom within us?As a student, my life is a whirlwind of classes, assignments, extracurriculars, and the constant pressure to succeed. It's easyto get caught up in the relentless pursuit of grades and accolades, forgetting to pause and appreciate the journey. However, I've come to realize that true happiness doesn't lie in external accomplishments, but in cultivating a mindset that nurtures joy from within.The first seed we must plant is gratitude. In the chaos of daily life, it's all too easy to focus on what we lack, rather than what we have. But when we take a moment to appreciate the simple pleasures – a warm cup of coffee on a rainy morning, a heartfelt conversation with a friend, or the beauty of a sunset –we open our eyes to the abundance that surrounds us. Gratitude is the fertile soil in which happiness can take root and flourish.Next, we must water the seeds with self-care. As students, we often neglect our own well-being in the pursuit of academic excellence. But just as a plant withers without water, our happiness will wilt if we don't nourish our minds, bodies, and souls. Self-care can take many forms – exercise, meditation, journaling, or simply taking a break to do something we enjoy. By prioritizing our personal needs, we create a nurturing environment where happiness can thrive.Pruning is also essential for cultivating happiness. Just as a gardener must prune away dead branches to allow new growth,we must let go of negative thoughts, limiting beliefs, and toxic relationships that stunt our emotional growth. This process can be painful, but it's necessary to make room for the vibrant blossoms of joy and contentment to unfurl.Of course, no garden is complete without a little sunshine. In the context of happiness, that sunshine comes in the form of positive relationships and connections. Surrounding ourselves with supportive friends, family, and mentors who lift us up and celebrate our successes can brighten even the gloomiest of days. Together, we can bask in the warmth of genuine human connection, allowing our happiness to radiate outwards.As we tend to our inner gardens, we must also remember to be patient. Just as a seed takes time to sprout and a flower takes time to bloom, cultivating lasting happiness is a gradual process. There will be setbacks, challenges, and moments when we feel like giving up. But if we persist, nurturing our seeds with care and compassion, eventually, the radiant blossoms of joy will emerge.In this journey towards happiness, it's important to remember that we are not alone. Just as a garden thrives with the help of fellow gardeners, our happiness is intertwined with the well-being of those around us. By spreading kindness,empathy, and compassion, we create a ripple effect that can transform our communities into verdant oases of positivity.Imagine a world where happiness is not a fleeting moment, but a sustainable state of being – a vibrant garden that we collectively nurture and cherish. In this world, our schools, workplaces, and neighborhoods would be flourishing ecosystems of joy, where every individual feels empowered to bloom to their fullest potential.So, let us become gardeners of our own happiness, tending to the seeds within us with care and dedication. Let us water them with self-love, prune away the negativity, and bask in the warmth of positive connections. Together, we can create a landscape of fulfillment, where the vibrant flowers of happiness bloom in radiant splendor, inspiring others to join us in this beautiful cultivation of joy.篇3Happiness is often described as a fleeting emotion, a temporary state of being that comes and goes like the changing of the seasons. However, I believe that true happiness is not a momentary burst of joy, but rather a garden that we must tend to with care and dedication. Just as a gardener must nurture theirseeds and seedlings, we must nurture the seeds of happiness within ourselves, allowing them to take root and blossom into something truly beautiful.In our fast-paced, modern world, it can be easy to become consumed by the stresses and pressures of daily life. We find ourselves caught up in the never-ending cycle of work, study, and responsibilities, leaving little time for the simple pleasures that bring us joy. However, it is during these moments of respite that we must pause and reflect on the importance of cultivating happiness within ourselves.Imagine a garden filled with vibrant flowers of every color and variety. Each bloom is a representation of a different aspect of happiness, whether it be the warmth of familial love, the satisfaction of personal growth, or the simple pleasure of enjoying a beautiful sunset. Just as a gardener must carefully select the seeds they wish to sow, we too must carefully choose the seeds of happiness that we wish to cultivate within ourselves.One such seed is the pursuit of knowledge and personal growth. Education is not merely a means to an end, but rather a lifelong journey of self-discovery and intellectual exploration. With each new piece of information we acquire, we open our minds to new perspectives and ways of thinking, allowing us togrow and evolve as individuals. The joy of learning is akin to planting a seed and watching it sprout, its delicate tendrils reaching towards the sun as it transforms into something truly remarkable.Another seed of happiness is the cultivation of meaningful relationships. Whether it be the unbreakable bond of family, the camaraderie of close friends, or the romantic connection shared between partners, these relationships provide us with a sense of belonging and support that is essential to our emotionalwell-being. Just as a gardener must carefully tend to their plants, nurturing them with water and sunlight, we too must nurture our relationships, fostering open communication, trust, and understanding.Amidst the busyness of our lives, it is also crucial that we take the time to appreciate the simple pleasures that surround us.A warm cup of tea on a rainy day, the laughter of children at play, or the gentle caress of a cool breeze on a summer evening –these are the moments that remind us of the beauty and wonder that exists in the world around us. By taking the time to truly savor these experiences, we plant the seeds of gratitude and mindfulness within our hearts, allowing them to blossom into a greater appreciation for the present moment.Of course, just as a garden is not without its challenges, the journey towards happiness is not without its obstacles. There will be times when the weeds of negativity threaten to choke out our seeds of joy, or when the harsh elements of life's trials and tribulations seem to wither our budding happiness. However, it is during these moments that we must draw strength from the roots we have established, and persevere in our efforts to cultivate a garden of happiness that is resilient and enduring.Like a skilled gardener, we must learn to prune away the negative thoughts and toxic influences that threaten to stunt our growth, while simultaneously nurturing the positive aspects of our lives that bring us joy and fulfillment. It is a delicate balance, one that requires patience, dedication, and a willingness to learn and adapt as we go.As I look towards the future, I envision a world where each of us has the opportunity to cultivate our own personal gardens of happiness. A world where the seeds of joy, love, andself-discovery are sown in fertile soil, nurtured by the warmth of human connection and the nurturing rain of personal growth. A world where the vibrant blooms of happiness are not fleeting moments, but rather a sustained and enduring presence in our lives.It is my hope that through this essay, I have inspired you to embrace the role of a gardener in your own life, carefully tending to the seeds of happiness that reside within you. For it is only through our collective efforts, our dedication to nurturing these seeds, that we can create a world where happiness truly blossoms and thrives. So, let us roll up our sleeves, grab our trowels, and begin the work of cultivating a garden that will fill our lives with the vibrant colors and fragrant scents of joy, contentment, and fulfillment.。
盐胁迫对大花金鸡菊生长及生理的影响齐明;刘玉艳;于凤鸣;张锐;郭明春【摘要】[Objective] The aim was to study the effects of salt stress on growth and physiology of Coreopsis grandiflora,and provide a theoretical basis for application of Coreopsis grandiflora in a large scale and accelerating its application pace in landscape afforestation,and provide suitable planning materials for kaline soil. [ Method] The seedling of Coreopsis grandiflora were treated by NaCl and Na2S04 respectively at the concentration of 0.2% ,0.6% and 1.0% ,the effects of salt stress on the seedlings growth,the changes of protein,soluble sugar,photosynthetic pigments, malondialdehyde and proline contents,and activity of POD and SOD in leaves were determined. [Result] The results showed that the salty stress inhibited the seedlings growth. Proline content increased with the increasing salt concentration. POD activity were increased at high salt concentrations. SOD activity was increased under NaCl treatment,but lower than the control when treated by Na2SO4. Under NaCl and Na2SO4 stress, the changes of protein, soluble sugar and malondialdehyde contents were not significant, and the change of photosynthetic pigments had no obvious regularity. [ Conclusion] Coreopsis grandiflora has a certain degree of salt resistance through adjusting osmotic stress mainly by increasing proline content.%[目的]研究盐胁迫对大花金鸡菊(Coreopsis grandiflora)生长和生理的影响,为大量栽培应用大花金鸡菊,加快其在园林绿化中的应用步伐提供理论依据,并为盐碱地绿化提供适宜的材料.[方法]以大花金鸡菊幼苗作为试验材料,用浓度为0.2%、0.6%、1.0%NaCl、Na2SO4在其幼苗生长过程中进行胁迫,调查盐胁迫对幼苗生长的影响,并测定盐胁迫过程中叶片中蛋白质含量、可溶性糖含量、光合色素含量、丙二醛(MDA)含量、过氧化物酶(POD)活性、超氧化物歧化酶(SOD)活性、脯氨酸含量变化.[结果]盐胁迫抑制了大花金鸡菊的生长;大花金鸡菊叶片中脯氨酸含量随处理浓度的增加而增加;高浓度盐处理使POD活性升高;NaCl处理下,SOD活性升高,但Na2SO4处理下低于对照;盐胁迫下,蛋白质、可溶性糖、丙二醛含量变化不显著,光合色素变化规律不明显.[结论]大花金鸡菊具有一定抗盐性.【期刊名称】《安徽农业科学》【年(卷),期】2012(040)029【总页数】3页(P14203-14205)【关键词】大花金鸡菊;幼苗;盐胁迫【作者】齐明;刘玉艳;于凤鸣;张锐;郭明春【作者单位】秦皇岛市第一中学,河北秦皇岛066006;河北科技师范学院,河北昌黎066600;河北科技师范学院,河北昌黎066600;河北科技师范学院,河北昌黎066600;河北科技师范学院,河北昌黎066600【正文语种】中文【中图分类】S682.1+1大花金鸡菊(Coreopsis grandiflora)别名剑叶波斯菊,为菊科金鸡菊属宿根花卉。
爱人如养花爱己应如是作文英文回答:In the realm of relationships, nurturing love is akin to tending to a delicate bloom. Just as a gardener meticulously cares for their prized plants, so too must we invest time, effort, and unwavering commitment to foster the growth and well-being of our romantic bonds.Like flowers, love requires sunlight and nourishment to flourish. This sustenance comes in the form of open communication, shared experiences, and acts of kindness and affection. Just as a plant absorbs sunlight through its leaves, our relationships thrive on the warmth and vulnerability of honest conversations. Sharing laughter, adventures, dreams, and aspirations create a fertile soilin which love can take root and blossom. And just as water is essential for plant growth, gestures of love and affection serve as life-giving sustenance for our relationships, nurturing their vitality and resilience.However, love is not merely about receiving nourishment; it also entails a reciprocal commitment to self-growth and self-care. Just as a gardener must tend to their own needsto maintain their ability to care for their plants, we must prioritize our own well-being to be fully present and supportive in our relationships. Self-care involves setting boundaries, practicing self-compassion, and engaging in activities that bring us joy and fulfillment. By nurturing ourselves, we create a strong foundation from which we can extend love and support to others without depleting our own reserves.Just as a gardener takes pride in the beauty andvitality of their plants, so too should we take pride inthe strength and resilience of our relationships. A well-tended love is a source of joy, fulfillment, and unwavering support. It provides a safe haven where we can grow, evolve, and thrive as individuals and as a couple.中文回答:与爱人相处,如同养育花朵,需要耐心与细致的呵护。
Symbiosis in Plants:Nature's CollaborationIn the intricate web of nature,plants engage in various forms of symbiotic relationships that highlight the beauty and significance of cooperation.This essay explores the concept of symbiosis in plants, showcasing the remarkable ways in which different species collaborate and thrive together.Mutualism:A Win-Win RelationshipMutualism is a form of symbiosis in which both participating species benefit from the interaction.In the plant world,mutualistic relationships are abundant.One such example is the partnership between plants and pollinators.Bees,butterflies,and birds visit flowers to feed on nectar, while inadvertently transferring pollen from one flower to another, aiding in the plants'reproduction.The plants receive pollination,and the pollinators obtain nourishment,creating a mutually beneficial relationship.Commensalism:One Benefits,One Is UnaffectedCommensalism is a type of symbiosis where one species benefits while the other remains unaffected.In the plant kingdom,certain epiphytic plants exemplify commensalism.These plants grow on the branches or trunks of other trees,utilizing them as a physical support structure. While the host tree is unaffected by the presence of the epiphyte,the epiphyte gains access to sunlight and nutrients from rain or debris that accumulate around it.Parasitism:Exploitation with ConsequencesParasitism is a symbiotic relationship in which one species,the parasite, benefits at the expense of the other,the host.In the plant world, parasitic plants draw nutrients from their host plants,often at the expense of the host's health or even survival.Examples include mistletoe, which attaches itself to trees and absorbs water and nutrients from them.While parasitism may seem negative,it is a part of the intricate balance of nature and plays a role in shaping ecosystems. Endophytes:Hidden AlliesEndophytes are microorganisms,such as fungi or bacteria,that live within the tissues of plants without causing harm.This mutually beneficial relationship provides advantages for both the plant and the endophyte.The endophytes help the plant by enhancing its resistance to diseases,pests,and environmental stress.In return,the plant provides a protected and nutrient-rich habitat for the endophytes to thrive.This symbiotic collaboration contributes to the overall health and resilience of the plant.Root Symbiosis:Below-Ground CooperationBelow the surface,plants engage in fascinating symbiotic relationships through their roots.One such example is mycorrhizal associations, where fungi form a mutually beneficial partnership with plant roots.The fungi extend the reach of the plant's roots,enhancing its ability to absorb water and nutrients from the soil.In return,the plant provides the fungi with sugars produced through photosynthesis.This below-ground cooperation is essential for the survival and growth of both the plant and the fungi.The Importance of Symbiosis in PlantsSymbiotic relationships in plants are vital for ecosystem functioning and resilience.They contribute to nutrient cycling,soil health,and the overall stability of ecosystems.By collaborating and sharing resources, plants increase their chances of survival and adaptability in challenging environments.Symbiosis also promotes biodiversity,as different species rely on each other for survival,creating a delicate balance in nature.Lessons from Plant SymbiosisPlant symbiosis teaches us valuable lessons about cooperation and interdependence.Just as plants rely on each other for survival,humans can learn the importance of collaboration and mutual support.By recognizing the interconnectedness of all living beings,we can foster a sense of responsibility towards the environment and work together to create a sustainable future.ConclusionSymbiosis in plants showcases the remarkable ways in which different species collaborate and thrive together.From mutualistic relationships to commensalism and even parasitism,plants demonstrate the power of cooperation and interdependence.By studying and appreciating these symbiotic interactions,we gain a deeper understanding of the intricate web of life and the importance of working together for the well-being of our planet.。
新托福TPO17阅读原文(三):Symbiotic RelationshipsTPO17-3:Symbiotic RelationshipsA symbiotic relationship is an interaction between two or more species in which one species lives in or on another species. There are three main types of symbiotic relationships: parasitism, commensalism, and mutualism. The first and the third can be key factors in the structure of a biological community; that is, all the populations of organisms living together and potentially interacting in a particular area.Parasitism is a kind of predator-prey relationship in which one organism, the parasite, derives its food at the expense of its symbiotic associate, the host. Parasites are usually smaller than their hosts. An example of a parasite is a tapeworm that lives inside the intestines of a larger animal and absorbs nutrients from its host. Natural selection favors the parasites that are best able to find and feed on hosts. At the same time, defensive abilities of hosts are also selected for. As an example, plants make chemicals toxic to fungal and bacterial parasites, along with ones toxic to predatory animals (sometimes they are the same chemicals). In vertebrates, the immune system provides a multiple defense against internal parasites.At times, it is actually possible to watch the effects of natural selection in host-parasite relationships. For example, Australia during the 1940 s was overrun by hundreds of millions of European rabbits. The rabbits destroyed huge expanses of Australia and threatened the sheep and cattle industries. In 1950, myxoma virus, a parasite that affects rabbits, was deliberately introduced into Australia to control the rabbit population. Spread rapidly by mosquitoes, the virus devastated the rabbit population. The virus was less deadly to the offspring of surviving rabbits, however, and it caused less and less harm over the years. Apparently, genotypes (the genetic make-up of an organism) in the rabbit population were selected that were better able to resist the parasite. Meanwhile, the deadliest strains of the virus perished with their hosts as natural selection favored strains that could infect hosts but not kill them. Thus, natural selection stabilized this host-parasite relationship.In contrast to parasitism, in commensalism, one partner benefits without significantly affecting the other. Few cases of absolute commensalism probably exist, because it is unlikely that one of the partners will be completely unaffected. Commensal associations sometimes involve one species' obtaining food that is inadvertently exposed by another. For instance, several kinds of birds feed on insects flushed out of the grass by grazing cattle. It is difficult to imagine how this could affect the cattle, but the relationship may help or hinder them in some way not yet recognized.The third type of symbiosis, mutualism, benefits both partners in the relationship Legume plants and their nitrogen-fixing bacteria, and the interactions between flowering plants and their pollinators, are examples of mutualistic association. In the first case, the plants provide the bacteria with carbohydrates and other organic compounds, and the bacteria have enzymes that act as catalysts that eventually add nitrogen to the soil, enriching it. In the second case, pollinators (insects, birds) obtain food from the flowering plant, and the plant has its pollen distributed and seeds dispersed much more efficiently than they would be if they were carried by the wind only. Another example of mutualism would be the bull's horn acacia tree, which grows in Central and South America. The tree provides a place to live for ants of the genus Pseudomyrmex. The ants live in large, hollow thorns and eat sugar secreted by the tree. The ants also eat yellow structures at the tip of leaflets: these are protein rich and seem to have no function for the tree except to attract ants. The ants benefit the host tree by attacking virtually anything that touches it. They sting other insects and large herbivores (animals that eat only plants) and even clip surrounding vegetation that grows near the tree. When the ants are removed, the trees usually die, probably because herbivores damage them so much that they are unable to compete with surrounding vegetation for light and growing space.The complex interplay of species in symbiotic relationships highlights an important point about communities: Their structure depends on a web of diverse connections among organisms.TPO17-3译文:共生关系共生关系是两种或更多物种之间的一种交互作用,其中一个物种要么在另一个物种中生存要么依赖另外一个物种生存。
plants need water句子结构Plants need water for their survival and growth. Water is an essential component that plays a crucial role in the life cycle of plants. It is required for various physiological processes such as photosynthesis, nutrient uptake, and transportation within the plant. Without water, plants cannot perform these vital functions, leading to their wilting, stunted growth, and even death.Water serves as a solvent for nutrients that are present in the soil. It dissolves minerals and other essential elements, making them available for plants to absorb through their roots. This process, known as osmosis, is facilitated by the presence of water in the soil. The roots of plants have root hairs that increase the surface area for absorbing water and nutrients efficiently.The transportation of water within a plant is another significant function that depends on the presence of water. Water absorbed by the roots travels through a complex network of vessels, known as xylem tissues, which extend from the roots to the leaves. This process, called transpiration, is driven by evaporation of water from the stomata present on the leaves' surface. Through this process, water is pulled up from the roots to the leaves, providing necessary moisture to all parts of the plant.Photosynthesis, the process by which plants convert sunlight into energy, relies heavily on water. Water is one of the reactants in photosynthesis and helps in the production of glucose, the primary source of energy for plants. Chlorophyll, the pigment responsible for capturing sunlight, is also dependent on water for its functioning. Without adequate water, photosynthesis cannot occur,leading to a decline in the plant's overall health and growth.In addition to the physiological processes, water plays a significant role in regulating the temperature of plants. Through a process called transpiration, water is evaporated from the surface of the leaves, cooling down the plant. This cooling effect is essential, especially during hot and dry periods, as it prevents the plants from overheating and helps maintain their internal moisture levels.The amount of water required by plants varies depending on several factors such as the plant species, environmental conditions, and developmental stage. However, maintaining a consistent moisture level in the soil is crucial for healthy plant growth. Too much water can lead to waterlogging, depriving the roots of oxygen, and causing root rot. Insufficient water, on the other hand, can lead to drought stress, resulting in wilting and ultimately the death of the plant.Proper watering techniques are necessary to ensure the adequate supply of water to plants. Watering should be done at the base of the plant to encourage deep root growth. It is important to water plants when the soil becomes dry but avoid overwatering, especially in areas with poor drainage. Mulching, the process of covering the soil with organic materials, can help retain water, prevent evaporation, and provide a more stable environment for the roots.In conclusion, water is essential for the survival and growth of plants. It is needed for various physiological processes, including nutrient absorption, transportation, and photosynthesis. Water alsohelps regulate the temperature of plants and plays a crucial role in their overall health. Proper watering techniques and maintaining an appropriate moisture level in the soil are essential for healthy plant growth and development.。
Plant Physiological Ecology Second EditionHans Lambers F.Stuart Chapin III Thijs L.PonsPlant Physiological EcologySecond Edition 13Hans LambersThe University of Western Australia Crawley,WAAustraliambers@.au F.Stuart Chapin III University of Alaska Fairbanks,AKUSAterry.chapin@Thijs L.PonsUtrecht UniversityThe NetherlandsT.L.Pons@bio.uu.nlISBN:978-0-387-78340-6e-ISBN:978-0-387-78341-3DOI:10.1007/978-0-387-78341-3Library of Congress Control Number:2008931587#2008Springer ScienceþBusiness Media,LLCAll rights reserved.This work may not be translated or copied in whole or in part without the written permission of the publisher(Springer ScienceþBusiness Media,LLC,233Spring Street,New York,NY10013,USA),except for brief excerpts in connection with reviews or scholarly e in connection with any form of information storage and retrieval, electronic adaptation,computer software,or by similar or dissimilar methodology now known or hereafter developed is forbidden.The use in this publication of trade names,trademarks,service marks,and similar terms,even if they are not identified as such,is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights.Printed on acid-free paperForeword to Second EditionIn the decade that has passed since the first edition of this book,the global environ-ment has changed rapidly.Even the most steadfast‘‘deny-ers’’have come to accept that atmospheric CO2enrichment and global warming pose serious challenges to life on Earth.Regrettably,this acceptance has been forced by calamitous events rather than by the long-standing,sober warnings of the scientific community.There seems to be growing belief that‘‘technology’’will save us from the worst consequences of a warmer planet and its wayward weather.This hope,that may in the end prove to be no more than wishful thinking,relates principally to the built environment and human affairs.Alternative sources of energy,utilized with greater efficiency,are at the heart of such hopes;even alternative ways of producing food or obtaining water may be possible.For plants,however,there is no alternative but to utilize sunlight and fix carbon and to draw water from the soil.(Under a given range of environmental conditions,these processes are already remarkably efficient by industrial standards.)Can we‘‘technologize’’our way out of the problems that plants may encounter in capricious,stormier,hotter,drier,or more saline environ-ments?Climate change will not alter the basic nature of the stresses that plants must endure,but it will result in their occurrence in places where formerly their impact was small,thus exposing species and vegetation types to more intense episodes of stress than they are able to handle.The timescale on which the climate is changing is too fast to wait for evolution to come up with solutions to the problems.For a variety of reasons,the prospects for managing change seem better in agriculture than in forests or in wild plant communities.It is possible to intervene dramatically in the normal process of evolutionary change by genetic manipulation. Extensive screening of random mutations in a target species such as Arabidopsis thaliana can reveal genes that allow plants to survive rather simplified stress tests. This is but the first of many steps,but eventually these will have their impact, primarily on agricultural and industrial crops.There is a huge research effort in this area and much optimism about what can be achieved.Much of it is done with little reference to plant physiology or biochemistry and has a curiously empirical char-acter.One can sense that there is impatience with plant physiology that has been too slow in defining stress tolerance,and a belief that if a gene can be found that confers tolerance,and it can be transferred to a species of interest,it is not of primevvi Foreword to Second Edition importance to know exactly what it does to the workings of the plant.Such a strategy is more directed toward outcomes than understanding,even though the technology involved is sophisticated.Is there a place for physiological ecology in the new order of things?The answer is perhaps a philosophical one.Progress over the centuries has depended on the gradual evolution of our understanding of fundamental truths about the universe and our world.Scientific discovery has always relished its serendipitous side but had we been satisfied simply with the outcomes of trial and error we would not be where we are today.It is legitimate to ask what factors set the limits on stress tolerance of a given species.To answer this one must know first how the plant‘‘works’’;in general,most of this knowledge is to hand but is based on a relatively few model species that are usually chosen because of the ease with which they can be handled in laboratory conditions or because they are economically important.As well as describing the basic physiology of plants the authors of this book set out to answer more difficult questions about the differences between species with respect to environmental variables.The authors would be the first to admit that comprehensive studies of comparative physiology and biochemistry are relatively few.Only in a few instances do we really understand how a species,or in agriculture,a genotype, pulls off the trick of surviving or flourishing in conditions where other plants fail.Of course,the above has more than half an eye on feeding the increasing world population in the difficult times that lie ahead.This has to be every thinking person’s concern.There is,however,more to it than rge ecosystems interact with climate,the one affecting the other.It would be as rash,for example,to ignore the effects of climate change on forests as it would be to ignore its effects on crops.There is more to the successful exploitation of a given environment than can be explained exclusively in terms of a plant’s physiology.An important thrust in this book is the interaction,often crucial,between plants and beneficial,pathogenic or predatory organisms that share that environment.Manipulation of these interac-tions is the perennial concern of agriculture either directly or unintentionally. Changes in temperature and seasonality alter established relations between organ-isms,sometimes catastrophically when,for example,a pathogen or predator expands its area of influence into plant and animal populations that have not been exposed to it previously.Understanding such interactions may not necessarily allow us to avoid the worst consequences of change but it may increase our preparedness and our chances of coming up with mitigating strategies.D AVID T.C LARKSONOak HouseCheddar,UKJanuary2008About the AuthorsHans Lambers is Professor of Plant Ecology and Head of School of Plant Biology at the University of Western Australia,in Perth,Australia.He did his undergraduate degree at the University of Gronin-gen,the Netherlands,followed by a PhD project on effects of hypoxia on flooding-sensitive and flood-ing-tolerant Senecio species at the same institution.From1979to1982,he worked as a postdoc at The University of Western Australia,Melbourne Univer-sity,and the Australian National University in Aus-tralia,working on respiration and nitrogen metabolism.After a postdoc at his Alma Mater,he became Professor of Ecophysiology at Utrecht Uni-versity,the Netherlands,in1985,where he focused on plant respiration and the physiological basis of variation in relative growth rate among herbaceous plants.In1998,he moved to the University of Wes-tern Australia,where he focuses on mineral nutri-tion and water relations,especially in species occurring on severely phosphorus-impoverished soils in a global biodiversity hotspot.He has been editor-in-chief of the journal Plant and Soil since1992 and features on ISI’s list of highly cited authors in the field of animal and plant sciences since2002.He was elected Fellow of the Royal Netherlands Acad-emy of Arts and Sciences in2003.F.Stuart Chapin III is Professor of Ecology at the Institute of Arctic Biology,University of Alaska Fairbanks,USA.He did his undergraduate degree (BA)at Swarthmore College,PA,United States,and then was a Visiting Instructor in Biology(Peace Corps)at Universidad Javeriana,Bogota,Columbia, from1966to1968.After that,he worked toward his PhD,on temperature compensation in phosphate absorption along a latitudinal gradient at Stanford University,United States.He started at the Univer-sity of Alaska Fairbanks in1973,focusing on plant mineral nutrition,and was Professor atthis viiinstitution from1984till1989.In1989,he became Professor of Integrative Biology,University of Cali-fornia,Berkeley,USA.He returned to Alaska in 1996.His current main research focus is on effectsof global change on vegetation,especially in arctic environments.He features on ISI’s list of highly cited authors in ecology/environment,and was elected Member of the National Academy of Sciences,USA in2004.Thijs L.Pons recently retired as Senior Lecturer in Plant Ecophysiology at the Institute of Environ-mental Biology,Utrecht University,the Nether-lands.He did his undergraduate degree at Utrecht University,the Netherlands,where he also worked toward his PhD,on a project on shade-tolerant and shade-avoiding species.He worked in Bogor,Indo-nesia,from1976to1979,on the biology of weeds in rice.Back at Utrecht University,he worked on the ecophysiology of seed dormancy and germination. From the late1980s onward he focused on photo-synthetic acclimation,including environmental sig-naling in canopies.He spent a sabbatical at the University of California,Davis,USA,working with Bob Pearcy on effects of sunflecks.His interest in photosynthetic acclimation was expanded to tro-pical rainforest canopies when he became involved in a project on the scientific basis of sustainable forest management in Guyana,from1992to 2000.He is associate editor for the journal Plant Ecology.viii About the AuthorsForeword to First EditionThe individual is engaged in a struggle for existence(Darwin).That struggle may be of two kinds:The acquisition of the resources needed for establishment and growth from a sometimes hostile and meager environment and the struggle with competing neighbors of the same or different species.In some ways,we can define physiology and ecology in terms of these two kinds of struggles.Plant ecology,or plant sociol-ogy,is centered on the relationships and interactions of species within communities and the way in which populations of a species are adapted to a characteristic range of environments.Plant physiology is mostly concerned with the individual and its struggle with its environment.At the outset of this book,the authors give their definition of ecophysiology,arriving at the conclusion that it is a point of view about physiology.A point of view that is informed,perhaps,by knowledge of the real world outside the laboratory window.A world in which,shall we say,the light intensity is much greater than the200–500m mol photons mÀ2sÀ1used in too many environment chambers,and one in which a constant208C day and night is a great rarity.The standard conditions used in the laboratory are usually regarded as treatments.Of course,there is nothing wrong with this in principle;one always needs a baseline when making comparisons.The idea,however,that the laboratory control is the norm is false and can lead to misunderstanding and poor predictions of behavior.The environment from which many plants must acquire resources is undergoing change and degradation,largely as a result of human activities and the relentless increase in population.This has thrown the spotlight onto the way in which these changes may feed back on human well-being.Politicians and the general public ask searching questions of biologists,agriculturalists,and foresters concerning the future of our food supplies,building materials,and recreational amenities.The questions take on the general form,‘‘Can you predict how‘X’will change when environmental variables‘Y’and‘Z’change?’’The recent experience of experimen-tation,done at high public expense,on CO2enrichment and global warming,is a sobering reminder that not enough is known about the underlying physiology and biochemistry of plant growth and metabolism to make the confident predictions that the customers want to hear.Even at the level of individual plants,there seems to be no clear prediction,beyond that the response depends on species and other ill-defined circumstances.On the broader scale,predictions about the response ofixx Foreword to First Edition plant communities are even harder to make.In the public mind,at least,this is a failure.The only way forward is to increase our understanding of plant metabolism, of the mechanisms of resource capture,and the way in which the captured resources are allocated to growth or storage in the plant.To this extent,I can see no distinction between plant physiology and ecophysiology.There are large num-bers of missing pieces of information about plant physiology—period.The approach of the new millennium,then,is a good time to recognize the need to study plant physiology anew,bringing to bear the impressive new tools made available by gene cloning and recombinant DNA technology.This book is to be welcomed if it will encourage ecologists to come to grips with the processes which determine the behavior of‘‘X’’and encourage biochemistry and physiology students to take a more realistic view of the environmental variables‘‘Y’’and‘‘Z’’.The book starts,appropriately,with the capture of carbon from the atmosphere. Photosynthesis is obviously the basis of life on earth,and some of the most brilliant plant scientists have made it their life’s work.As a result,we know more about the molecular biophysics and biochemistry of photosynthesis than we do about any other plant process.The influence of virtually every environmental variable on the physiology of photosynthesis and its regulation has been studied.Photosynthesis, however,occurs in an environment over which the individual plant has little control.In broad terms,a plant must cope with the range of temperature,rainfall, light intensity,and CO2concentration to which its habitat is subjected.It cannot change these things.It must rely on its flexible physiological response to mitigate the effects of the environment.At a later stage in the book,the focus shifts below ground,where the plant has rather more control over its options for capturing resources.It may alter the environment around its roots in order to improve the nutrient supply.It may benefit from microbial assistance in mobilizing resources or enter into more formal contracts with soil fungi and nodule-forming bacteria to acquire nutrient resources that would otherwise be unavailable or beyond its reach. Toward its close,the book turns to such interactions between plants and microbes and to the chemical strategies that have evolved in plants that assist them in their struggles with one another and against browsing and grazing animals.The authors end,then,on a firmly ecological note,and introduce phenomena that most labora-tory physiologists have never attempted to explore.These intriguing matters remind us,as if reminders were needed,of‘‘how little we know,how much to discover’’(Springer and Leigh).D AVID T.C LARKSONIACR-Long Ashton Research StationUniversity of BristolApril1997AcknowledgmentsNumerous people have contributed to the text and illustrations in this book by commenting on sections and chapters,providing photographic material,making electronic files of graphs and illustrations available,or drawing numerous figures. In addition to those who wrote book reviews or sent us specific comments on the first edition of Plant Physiological Ecology,we wish to thank the following colleagues,in alphabetical order,for their valuable input:Owen Atkin,Juan Barcelo,Wilhelm Barthlott,Carl Bernacchi,William Bond,Elizabeth Bray,Siegmar Breckle,Mark Brundrett,Steve Burgess,Ray Callaway,Marion Cambridge,Art Cameron,Pilar Castro-Dı´ez,David Clarkson,Stephan Clemens,Herve Cochard, Tim Colmer,Hans Cornelissen,Marjolein Cox,Michael Cramer,Doug Darnowski, Manny Delhaize,Kingsley Dixon,John Evans,Tatsuhiro Ezawa,Jaume Flexas, Brian Forde,Peter Franks,Oula Ghannoum,Alasdair Grigg,Foteini Hassiotou, Xinhua He,Martin Heil,Angela Hodge,Richard Houghton,Rick Karban,Herbert Kronzucker,John Kuo,Jon Lloyd,Jian Feng Ma,Ken Marcum,Bjorn Martin,Justin McDonald,John Milburn,Ian Max Møller,Liesje Mommer,Ulo Niinemets,Ko Noguchi,Ram Oren,Stuart Pearse,Carol Peterson,Larry Peterson,John Pickett, Corne´Pieterse,Bartosz Płachno,Malcolm Press,Dean Price,Miquel Ribas-Carb´o, Peter Reich,Sarah Richardson,Peter Ryser,Yuzou Sano,Rany Schnell,Ted Schuur, Tim Setter,Michael Shane,Tom Sharkey,Sally Smith,Janet Sprent,Ernst Steudle, Youshi Tazoe,Mark Tjoelker,Robert Turgeon,David Turner,Kevin Vessey,Eric Visser,Rens Voesenek,Xianzhong Wang,Jennifer Watling,Mark Westoby,Wataru Yamori,Satoshi Yano,and Wenhao Zhang.Finally HL wishes to thank Miquel and Pepi for their fabulous hospitality when he was dealing with the final stages of the revision of the text.Good company, music,food,and wine in Palma de Mallorca significantly added to the final product.H ANS L AMBERSF.S TUART C HAPIN IIIT HIJS L.P ONSxiAbbreviationsa radius of a root(a g)or root plus root hairs(a e)A rate of CO2assimilation;also total root surfaceA n net rate of CO2assimilationA f foliage areaA max light-saturated rate of net CO2assimilation at ambient C aA s sapwood areaABA abscisic acidADP adenosine diphosphateAM arbuscular mycorrhizaAMP adenosine monophosphateAPAR absorbed photosynthetically active radiationATP adenosine triphosphateb individual plant biomass;buffer power of the soilB stand biomassc s concentration of the soluteC nutrient concentration in solution;also convective heat transferC3photosynthetic pathway in which the first product of CO2fixation is a3-carbon intermediateC4photosynthetic pathway in which the first product of CO2fixation is a4-carbon intermediateC a Atmospheric CO2concentrationC c CO2concentration in the chloroplastC i Intercellular CO2concentrationC li initial nutrient concentrationC min solution concentration at which uptake is zeroC:N carbon:nitrogen ratioCAM crassulacean acid metabolismCC carbon concentrationCE carbohydrate equivalentchl chlorophyllCPF carbon dioxide production valued plant density;also leaf dimensionD diffusivity of soil waterD e diffusion coefficient of ion in soilDHAP dihydroxyacetone phosphateDM dry massxiiixiv Abbreviations DNA deoxyribonucleic acide water vapor pressure in the leaf(e i;or e l in Sect.2.5of the Chapter4A)or atmosphere(e a);also emissivity of a surfaceE transpiration ratef tortuosityF rate of nutrient supply to the root surface;also chlorophyll fluorescence,minimalfluorescence(F0),maximum(F m),in a pulse of saturating light(F m’),variable(F v) FAD(H2)flavine adenine dinonucleotide(reduced form)FM fresh massFR far-redg diffusive conductance for CO2(g c)and water vapor(g w);boundary layerconductance(g a);mesophyll conductance(g m);stomatal conductance(g s);boundary layer conductance for heat transport(g ah)GA gibberellic acidGE glucose equivalentGOGAT glutamine2-oxoglutarate aminotransferaseHCH hydroxycyclohexenoneHIR high-irradiance responseI irradiance,above(I o)or beneath(I)a canopy;irradiance absorbed;also nutrientinflowI max maximum rate of nutrient inflowIAA indoleacetic acidIR s short-wave infrared radiationJ rate of photosynthetic electron flowJ max maximum rate of photosynthetic electron flow measured at saturating I and C a J v water flowk rate of root elongation;extinction coefficient for lightK carrying capacity(e.g.,K species)k cat catalytic constant of an enzymeK i inhibitor concentration giving half-maximum inhibitionK m substrate concentration at half V max(or I max)l leaf area indexL rooting density;also latent heat of evaporation;also length of xylem elementL p root hydraulic conductanceLAI leaf area indexLAR leaf area ratioLFR low-fluence responseLHC light-harvesting complexLMA leaf mass per unit areaLMR leaf mass ratioLR long-wave infrared radiation that is incident(LR in),reflected(LR r),emitted (LR em),absorbed(SR abs),or net incoming(LR net);also leaf respiration on an area(LR a)and mass(LR m)basismRNA messenger ribonucleic acidmiRNA micro ribonucleic acidM energy dissipated by metabolic processesME malic enzymeMRT mean residence timeN w mol fraction,that is,the number of moles of water divided by the total number of molesNAD(P)nicotinamide adenine dinucleotide(phosphate)(in its oxidized form)NAD(P)H nicotinamide adenine dinucleotide(phosphate)(in its reduced form)NAR net assimilation rateNDVI normalized difference vegetation indexNEP net ecosystem productionNIR near-infrared reflectance;net rate of ion uptakeNMR nuclear magnetic resonanceNPP net primary productionNPQ nonphotochemical quenchingNUE nitrogen-use efficiency,or nutrient-use efficiencyAbbreviations xv p vapor pressurep o vapor pressure of air above pure waterP atmospheric pressure;also turgor pressureP fr far-red-absorbing configuration of phytochromeP i inorganic phosphateP r red-absorbing configuration of phytochromePAR photosynthetically active radiationPC phytochelatinsPEP phospho enol pyruvatePEPC phospho enol pyruvate carboxylasePEPCK phospho enol pyruvate carboxykinasepH hydrogen ion activity;negative logarithm of the H+concentrationPGA phosphoglyceratepmf proton-motive forcePNC plant nitrogen concentrationPNUE photosynthetic nitrogen-use efficiencyPQ photosynthetic quotient;also plastoquinonePR pathogenesis-related proteinPS photosystemPV’amount of product produced per gram of substrateq N quenching of chlorophyll fluorescence due to non-photochemical processesq P photochemical quenching of chlorophyll fluorescenceQ ubiquinone(in mitochondria),in reduced state(Q r=ubiquinol)or total quantity (Q t);also quinone(in chloroplast)Q10temperature coefficientQ A primary electron acceptor in photosynthesisr diffusive resistance,for CO2(r c),for water vapor(r w),boundary layer resistance (r a),stomatal resistance(r s),mesophyll resistance(r m);also radial distance fromthe root axis;also respiration;also growth rate(in volume)in the Lockhartequation;also proportional root elongation;also intrinsic rate of populationincrease(e.g.,r species)r i spacing between rootsr o root diameterR redR radius of a xylem element;also universal gas constantR a molar abundance ratio of13C/12C in the atmosphereR d dark respirationR day dark respiration during photosynthesisR e ecosystem respirationR p whole-plant respiration;also molar abundance ratio of13C/12C in plantsR h heterotrophic respirationR*minimal resource level utilised by a speciesRGR relative growth rateRH relative humidity of the airRMR root mass ratioRNA ribonucleic acidRQ respiratory quotientRR rate of root respirationRuBP ribulose-1,5-bisphosphateRubisco ribulose-1,5-bisphosphate carboxylase/oxygenaseRWC relative water contentS nutrient uptake by rootsS c/o specificity of carboxylation relative to oxygenation by RubiscoSHAM salicylichydroxamic acidSLA specific leaf areaSMR stem mass ratioSR short-wave solar radiation that is incident(SR in),reflected(SR r),transmitted(SR tr), absorbed(SR abs),used in photosynthesis(SR A),emitted in fluorescence(SR FL),ornet incoming(SR net);also rate of stem respirationSRL specific root lengthxvi Abbreviations t*time constanttRNA transfer ribonucleic acidT temperatureT L leaf temperatureTCA tricarboxylic acidTR total radiation that is absorbed(TR abs)or net incoming(TR net)u wind speedUV ultravioletV volumeV c rate of carboxylationV o rate of oxygenationV cmax maximum rate of carboxylationV w o molar volume of waterVIS visible reflectanceVLFR very low fluence responseV max substrate-saturated enzyme activityVPD vapor pressure deficitw mole fraction of water vapor in the leaf(w i)or atmosphere(w a)WUE water-use efficiencyY yield threshold(in the Lockhart equation)g surface tensionÀCO2-compensation pointÀ*CO2-compensation point in the absence of dark respirationboundary layer thickness;also isotopic contentÁisotopic discriminationÁT temperature differenceelastic modulus;also emissivityviscosity constantcurvature of the irradiance response curve;also volumetric moisture content (mean value, ’,or at the root surface, a)l energy required for transpirationm w chemical potential of waterm wo chemical potential of pure water under standard conditions'Stefan–Boltzman constant0quantum yield(of photosynthesis);also yield coefficient(in the Lockhartequation);also leakage of CO2from the bundle sheath to the mesophyll;alsorelative yield of de-excitation processesÉwater potentialÉair water potential of the airÉm matric potentialÉp pressure potential;hydrostatic pressureÉp osmotic potentialContentsForeword to Second Edition(by David T.Clarkson)v About the Authors vii Foreword to First Edition(by David T.Clarkson)ix Acknowledgments xi Abbreviations xiii1.Assumptions and Approaches1Introduction7History,Assumptions,and Approaches1 1What Is Ecophysiology?1 2The Roots of Ecophysiology1 3Physiological Ecology and the Distribution of Organisms2 4Time Scale of Plant Response to Environment4 5Conceptual and Experimental Approaches6 6New Directions in Ecophysiology7 7The Structure of the Book7 References82.Photosynthesis,Respiration,and Long-Distance Transport112A.Photosynthesis11 1Introduction112General Characteristics of the Photosynthetic Apparatus112.1The‘‘Light’’and‘‘Dark’’Reactions of Photosynthesis112.1.1Absorption of Photons122.1.2Fate of the Excited Chlorophyll132.1.3Membrane-Bound Photosynthetic ElectronTransport and Bioenergetics142.1.4Photosynthetic Carbon Reduction142.1.5Oxygenation and Photorespiration15xviixviii Contents2.2Supply and Demand of CO2in the Photosynthetic Process162.2.1Demand for CO27the CO27Response Curve162.2.2Supply of CO27Stomatal and Boundary LayerConductances212.2.3The Mesophyll Conductance223Response of Photosynthesis to Light263.1The Light Climate Under a Leaf Canopy263.2Physiological,Biochemical,and Anatomical DifferencesBetween Sun and Shade Leaves273.2.1The Light-Response Curve of Sun and Shade Leaves273.2.2Anatomy and Ultrastructure of Sun and Shade Leaves293.2.3Biochemical Differences Between Shade and SunLeaves323.2.4The Light-Response Curve of Sun and ShadeLeaves Revisited333.2.5The Regulation of Acclimation353.3Effects of Excess Irradiance363.3.1Photoinhibition7Protection by Carotenoids of theXanthophyll Cycle363.3.2Chloroplast Movement in Response to Changes inIrradiance413.4Responses to Variable Irradiance423.4.1Photosynthetic Induction433.4.2Light Activation of Rubisco433.4.3Post-illumination CO2Assimilation and Sunfleck-Utilization Efficiency453.4.4Metabolite Pools in Sun and Shade Leaves453.4.5Net Effect of Sunflecks on Carbon Gain andGrowth474Partitioning of the Products of Photosynthesis and Regulationby‘‘Feedback’’474.1Partitioning Within the Cell474.2Short-Term Regulation of Photosynthetic Rate byFeedback484.3Sugar-Induced Repression of Genes EncodingCalvin-Cycle Enzymes514.4Ecological Impacts Mediated by Source-Sink Interactions515Responses to Availability of Water515.1Regulation of Stomatal Opening535.2The A–C c Curve as Affected by Water Stress545.3Carbon-Isotope Fractionation in Relation to Water-UseEfficiency565.4Other Sources of Variation in Carbon-Isotope Ratios in C3Plants576Effects of Soil Nutrient Supply on Photosynthesis586.1The Photosynthesis–Nitrogen Relationship586.2Interactions of Nitrogen,Light,and Water596.3Photosynthesis,Nitrogen,and Leaf Life Span597Photosynthesis and Leaf Temperature:Effects and Adaptations607.1Effects of High Temperatures on Photosynthesis607.2Effects of Low Temperatures on Photosynthesis618Effects of Air Pollutants on Photosynthesis639C4Plants649.1Introduction649.2Biochemical and Anatomical Aspects64。