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学术论文英文Academic Paper - Title: The Impact of Social Media on Society Abstract:This paper examines the influence of social media on society. It explores how social media platforms have transformed communication, information sharing, and social interactions. The paper also investigates the positive and negative effects of social media on individuals and society as a whole. The findings suggest that while social media has played a pivotal role in connecting people and providing access to information, it has also brought about concerns such as privacy invasion, cyberbullying, and addiction. Various research studies and statistical data are utilized to support these claims. The paper concludes by offering recommendations on how society can navigate the impact of social media by promoting digital literacy and responsible online behaviors.Introduction:The rapid advancement of technology has revolutionized the way people communicate and share information. The advent of social media platforms has further transformed communication dynamics and reshaped society. This paper aims to investigate the impact of social media on individuals and society as a whole. It recognizes the potential benefits of social media, such as enhanced connectivity and information dissemination. However, it also delves into the negative consequences, including privacy concerns, cyberbullying, and addiction.Literature Review:This section reviews existing studies and research on the impact of social media. It covers a wide range of topics, including the evolution of social media platforms, their effects on individual well-being, and societal implications. The literature review highlights the increasing use of social media and its influence on various aspects of society, such as politics, education, and social interactions.Methods:To conduct this research, a combination of quantitative and qualitative methods was employed. Quantitative data was gathered through surveys and statistical analysis, aiming to provide a larger perspective on the impact of social media on society. Qualitative methods, such as interviews and case studies, were utilized to gain a deep understanding of individuals' experiences and perceptions. Results:The results indicate that social media has significantly impacted society in both positive and negative ways. On one hand, it has facilitated global connectivity, allowing individuals to communicate and collaborate across borders. It has also democratized information sharing, providing platforms for marginalized voices. However, social media has also led to several concerns, including misinformation, privacy breaches, and mental health issues. The results also suggest that younger populations are more prone to these negative effects.Discussion:The discussion section evaluates the findings in relation to existing theories and research. It highlights the need for digital literacyeducation to empower individuals to critically analyze and navigate online information. It also emphasizes the importance of promoting responsible online behaviors to mitigate the negative consequences associated with social media.Conclusion:This paper concludes that social media has had a profound impact on society, revolutionizing communication and information sharing. While it brings numerous benefits, it also poses challenges that need to be addressed. By promoting digital literacy and responsible online behaviors, society can harness the potential of social media while mitigating its negative effects. Further research is needed to continually understand and adapt to the ever-evolving landscape of social media and its impact on society.。
英文论文（优秀4篇）选择英语文学的毕业论文选题可以从三个方向进行：国别文学研究、文学批评理论研究和比较文学研究。
以下是可爱的编辑为大伙儿收集整理的英文论文（优秀4篇），希望可以帮助到有需要的朋友。
英语专业论文模板篇一很多学生忽视了毕业论文的重要性和现实意义，这是其写作质量不高的主要原因之一。
毕业论文是大学生在校期间向学校所交的较后一份书面作业。
英语专业学生在修完一般英语写作课程后，初步熟知和掌握了基本的写作要素和技巧，这时为了深化写作内容，进一步提高文字表达能力，须开始进行学术论文写作。
毕业论文写作在巩固了词的各种意义、搭配、用法、词序，句子的定义、结构、种类、用法，即写作的基本要素和技巧的同时，还能培养初步的研究、分析和总结问题的能力。
这就为学生在日后进一步从事相关学科的研究工作打下了坚实的基础。
《高等学校英语专业教学大纲》指出，“毕业论文是考察学生综合能力、评估学业成绩的一个重要方式”。
毕业论文写作的优劣、质量的高低是决定学生能否顺利毕业或可否被授予学位的重要依据。
因此大学生须重视和认真撰写毕业论文。
英语论文范文word 篇二Upon the completion of the thesis, I would like to take this opportunity toexpress my sincere gratitude to my supervisor, Professor Peng Xiaohua, who hasgiven me important guidance on the thesis. Without his help and encouragement,my thesis would have been impossible. Besides his help with my thesis,he hasalso given me much advice on the methods of doing research, which is of greatvalue to my future academic life.I am also obliged to other teachers whose lectures have broadened my scopeof vision in British and American literature and help me lay a necessaryfoundation for the writing of the thesis. I am also grateful to all the members ofthe faculty and staff in the College of Foreign Languages who have provided mewith a lot of help and guidance.Last but not least, I would like to express my gratitude to all the friends andfamily members who have offered me help. Without their help,I could not havefinished my study and this thesis.英语专业论文模板篇三分层次提出教学要求：英语系按照学校的要求把XX级学生以入学成绩为依据分了两个层次，A层次普通学科专业班级，B层次体音美专业班级。
Introduction:In recent years, technology has become an integral part of our lives, transforming various sectors, including education. The integration of technology in the educational field has led to significant changes in teaching methods, learning experiences, and overall academic performance. This paper aims to provide a comprehensive review of the impact of technology on education, discussing its advantages, challenges, andfuture prospects.Advantages of Technology in Education:1. Enhanced Learning Experience:Technology has revolutionized the way students learn. With the use of interactive multimedia tools, such as videos, simulations, and virtual reality, students can engage with the subject matter more effectively. This active learning approach fosters better understanding and retention of information.2. Access to a Wealth of Resources:The internet has made a vast array of educational resources readily available to students and teachers. Online libraries, educational websites, and e-books provide access to a wide range of materials, enabling students to explore various topics beyond the limitations of traditional textbooks.3. Personalized Learning:Technology allows for personalized learning experiences. Adaptive learning platforms can tailor the learning content and pace toindividual student needs, ensuring that each student receives the appropriate level of support and challenge.4. Collaboration and Communication:Technology facilitates collaboration among students and teachers, regardless of geographical barriers. Online discussion forums, videoconferencing, and collaborative tools enable students to work together on projects, enhancing their teamwork and communication skills.Challenges of Technology in Education:1. Digital Divide:The digital divide refers to the gap between individuals with and without access to digital technology. This disparity can hinder educational opportunities for underprivileged students, as they may not have access to the necessary devices and internet connectivity.2. Overreliance on Technology:An excessive reliance on technology can lead to reduced criticalthinking and problem-solving skills. Students may become dependent on digital tools for answers, rather than developing their own analytical abilities.3. Privacy and Security Concerns:The use of technology in education raises concerns about data privacy and security. Schools must ensure that students' personal information is protected from unauthorized access and misuse.Future Prospects:1. Integration of Artificial Intelligence:The integration of artificial intelligence (AI) in education holds great potential. AI-powered tools can provide personalized learning experiences, automate administrative tasks, and assist teachers in identifying struggling students.2. Expansion of Online Education:The global pandemic has accelerated the adoption of online education. As technology continues to advance, online learning platforms are expected to become more sophisticated, offering a wider range of courses and interactive experiences.3. Teacher Training and Professional Development:To fully leverage technology in education, teachers need to be well-trained and up-to-date with the latest tools and methodologies. Continuous professional development programs are crucial to ensure that educators can effectively integrate technology into their teaching practices.Conclusion:The impact of technology on education is undeniable. While it offers numerous advantages, such as enhanced learning experiences, personalized learning, and improved collaboration, it also presents challengesrelated to the digital divide, overreliance on technology, and privacy concerns. To harness the full potential of technology in education, itis essential to address these challenges and invest in teacher training, infrastructure, and policies that promote equitable access to digital resources. As technology continues to evolve, the future of education looks promising, with innovative tools and methodologies shaping the way students learn and succeed.。
英文论文的详细格式（英文论文写作格式）英文论文的写作主要用于参加国际学术研讨会，以促进中外学术和文化交流；在国际学术期刊上发表论文，在国际上分享科研成果，并在英语论文中进行学术交流；此外，英文论文还包括英语相关专业人士必须用英语撰写学术报告或毕业论文等。
标题大纲摘要1、英文摘要是一篇文章，旨在以符合英语语法的语言提供论文内容的摘要。
（内容与中文摘要基本相同，但不需要完全判断。
）2、英文标题、摘要、关键字进入一个页面（可以是1页），放在中文摘要页面之后。
3、英文字体和行间距：在“Western字体”中使用“Times New Roman”，1.5行间距。
4、英文名称：使用第三个单词bold。
5、英文摘要：“Absract”顶部网格，使用第四个字母和粗体。
英文摘要使用第四个字母。
6、英文关键词：“关键词”顶部网格，使用第四个单词和粗体。
对每个关键字使用第四个单词文本在文中引用如果引用少于三行，则引文可以有机地整合到纸张中。
如果要引用的单词具有与需要删除的纸张无关的单词，则需要省略号。
如果省略号出现在引文中，请使用三个点。
如果它出现在引文的末尾，请使用四个点。
最后一个点表示句点并放在第二个括号之后（通常，避免在引用开始时使用省略号）；点和字母之间或点和点之间的空格。
参考书目每个项目的第一行需要打印在顶部网格中，并且所有行都需要缩进五次以区分该项目与其他项目。
英文摘要英文论文摘要，也称为摘要，是论文的重要组成部分。
它旨在提供文献内容的摘要，没有评论和补充说明。
一篇简短的文章，准确描述了文献的重要内容。
摘要应该是独立和不言而喻的，并且与文献具有相同数量的信息，即，可以在不阅读全文的情况下获得重要信息。
摘要通常放在标题之后，即文章的第一篇。
在论文发表后，论文的摘要经常被文献检索系统收集。
英文摘要一般为200-300个单词，并且有一个与英文抽象表达相对应的中文摘要。
,。
毕业论文英文摘要（9篇）First and foremost, I would like to give my sinceregratitude to my distinguished andrespectable supervisor, Prof. Qi Yuanfang, for his all-along supports during not only theresearch process, but the whole post-graduate year. He is the one who gives me inspiration ofthe thesis topic, enlightens me empirical method helps me conduct teaching e某periment, andinstructs me analyzing approaches. I have to say that this thesis is born from his insightfulinstructions and warm encouragement.Secondly, I also own my appreciation to Prof, Gongrong who gives me a lot ofinspiration, insightful advice and instructions.Last but not least, I would like to e某tend my thanks to the students participating in thisresearch for their patient corporation.Secondly, I will also e某press my sincere gratitude toother professor and teacherswho had give me constructive suggestion to my thesis and thanks to them forinstructing me to construct my knowledge in English teaching in the past two and a halfyears.Thirdly, I want to thank all my affectionate classmates and friends. During the twoa half years' study and the writing ofthis thesis, they have given me a lot of support andencouragement in their own ways.At last, I will give the deepest gratitude to my family for their regretless supportand love to me.Thanks to my parents and girlfriend bear, giving unlimited love in life, especially the cubs, and when she did not cherish the love, her love, lost her life and perhaps even too late to regret, for there is no chance, when approaching graduation, deeply regret to say to you: "you love let me grow up and know how to love, and I let you scarred, and you have to flee, if there is any chance, if there is the afterlife, I will put you in the palm of care".Thank you for working life in the prevention center colleagues, Dr. Zhang Dehua, Dr. Liu Xiangning, Dr. Mao Jian, Zhao Honghao, Jia Suping, Li Haibao, Sun Pengpeng, Yang Xiaoyan, Huang Dandan, Wang Ruo某in, Yang Ni, Yu Junsong, because you have a wonderful and fulfilling life.论文题目：On the Title of EST and Aesthetic Effect in Its TranslationKey words: EST; title; translation; artistic effects论文题目：On Advertisement Translation from English to Chinese in Light of Functional EquivalenceIn our daily life, we live with different advertisements, some of which are translated works. These advertisements are aimed at giving the potential customers a lasting impression and persuading them to buy their product. Therefore, in order to e某press the ideas of the original works and realize the goalfor sale, the translators should take account of the cultural elements and social elements in order to achieve functional equivalence.Key words: functional equivalence; advertisement translation; cultural elementsFirst and foremost, I would like to e某press my heartfelt gratitude to mysupervisor, Professor Jia Aiwu. I have benefited tremendously from her criticalthinking and insightful viewpoint. Through his patient instruction,I finally focusedon the object studied in this thesis, and obtained valuable advice on aspects rangingfrom frame work constructing and data collection to elaborated analysis.Secondly, I'm profusely grateful to my respected predecessors and teachers.Moreover, I owe my thanks to my family and friends, who have always supportedme with their generous encouragements and praises.Last but not least, I sincerely thank my fellow classmates. We share joys andan某ieties, which propels us forward together throughout the arduous journey.During the three years of study, Wang Xu, Liu Qianjun, Tan Chengrong, Li Zongquan, Ho, Fan Juan, Kong Fangong, Wang Jian, Ma Minjiang, Wang Xiwen, Huang Youhe, Xu Lili, Mo Jialin, Guo Sanchuan, Li Jianwen, Zhong Zehui, Yang Qifeng, Liu Mengru, Yin Tanwei, Zhang Chun, Liu Ruiheng, Tu Qiliang, Hui, Zhuo Yu, Zhang Chengfeng, Xue Bing, Jiang Shoule Zhang Xiaochao, He Zhuoya, Liang Dongmei, Li Qiang, Liu Hao, Liu Chuanfu, Yu Dongmei, Lai Yurong, Chi Congcong, Cheng Xiaolian, Shi Haiqiang, Wang Shaoguang, and younger brother of care and help, to e某press deep gratitude. Without their help and support, there is no way to finish my Ph. D. Thesis. Friendship between students willlast forever.论文题目：On Cultural Gaps and Untranslatability in Chinese Version of The Life and Strange Surprizing Adventures of Robinson Crusoe from Perspective of FunctionalismAbstract:This thesis is an attempt to apply functionalism to literary translation and prove its feasibility by analyzing the untranslatability of the Adventures of Robinson Crusoe causing by cultural gaps. Functionalism is a broad term for various theories that approach translation by focusing on the function or functions of te某ts and translations. And the four importantrepresentatives of functionalism are Katharina Reiss, Hans J. Vermeer, Justa Holz-Mnttri and Christiane Nord. This thesis attempts to apply the core rules of Skopostheorie –？to analyze the untranslatability of the Adventures of Robinson Crusoe which is caused by cultural gaps, in the hope of gaining a better understanding of literary translation from the perspective of functionalism.ABSTRACTKey words: Anna; Jane Eyre; female doctrine。
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论文类英语作文模板英文回答：Introduction。
In the realm of academic discourse, the essay stands as a cornerstone of intellectual exploration and scholarly exposition. It provides a structured framework for writers to present their ideas, arguments, and evidence in a clear and coherent manner. Whether exploring a complex scientific theory, delving into the nuances of a literary work, or analyzing a historical event, the essay serves as a versatile medium for conveying knowledge and understanding.This comprehensive guide will delve into the intricate details of crafting a compelling and well-structured essay. From the initial conception of an idea to the final polishing of the written word, we will explore each step with meticulous care. By following the principles outlined in this guide, you can master the art of essay writing andunlock the full potential of your academic and professional endeavors.Choosing a Topic and Developing a Thesis Statement。
英文论文AbstractThis paper explores the impact of globalization on various aspects of modern society. The increased interconnectedness of economies, cultures, and societies due to globalization has brought both positive and negative effects. The paper analyzes the economic implications, cultural exchange, and political challenges brought forth by globalization. Additionally, it discusses the role of technology and communication in facilitating globalization. The aim of this paper is to provide a comprehensive overview of t he impact of globalization and its implications in today’s world.1. IntroductionGlobalization is the process of increasing integration and interdependence among countries, economies, cultures, and societies. This phenomenon has been driven by advancements in technology, transportation, and communication. The past few decades have witnessed rapid globalization, which has had both positive and negative effects on various aspects of our lives.2. Economic ImplicationsOne of the major consequences of globalization is the impact on the global economy. As barriers to trade and investment have been reduced, countries have been able to participate in global markets more freely. This has resulted in increased competition, lower prices, and greater access to a variety of goods and services for consumers. However, globalization has also led to job loss in some industries, as companies move production to countries with lower labor costs.Furthermore, globalization has led to the rise of multinational corporations (MNCs) that operate across multiple countries. MNCs play a significant role in global economic integration, as they are able to leverage economies of scale and take advantage of global supply chains. However, the dominance of MNCs has raised concerns about inequality and market concentration.3. Cultural ExchangeGlobalization has facilitated the exchange of ideas, values, and cultural practices among different societies. The increased movement of people has led to greater diversity and multiculturalism in many countries. This cross-cultural exchange has enriched societies by promoting an understanding and appreciation of different perspectives.However, globalization has also led to concerns about cultural homogenization. Western culture, particularly American culture, has become pervasive throughglobal media and entertainment. This has led to the erosion of traditional cultural practices in some societies and the loss of cultural diversity.4. Political ChallengesGlobalization has presented several political challenges for governments and policymakers. The increased interconnectedness of countries has made it more difficult to address global issues such as climate change, terrorism, and economic instability. National governments often struggle to find collective solutions to these problems due to competing interests and priorities.Additionally, globalization has led to a shift in power dynamics between nation-states and non-state actors. International organizations, such as the United Nations and World Trade Organization, have gained influence in global governance. This has raised questions about the democratic legitimacy of decision-making processes and accountability.5. Role of Technology and CommunicationAdvancements in technology and communication have been instrumental in facilitating globalization. The internet and social media platforms have connected people from different corners of the world, allowing for instant communication and information sharing. This has accelerated the spread of ideas, facilitated international collaboration, and enabled e-commerce.However, the digital divide remains a significant challenge. Access to technology and the internet is still unevenly distributed, particularly in developing countries. This exacerbates existing inequalities and limits the benefits of globalization for all.6. ConclusionGlobalization has had a profound impact on various aspects of modern society. The economic implications, cultural exchange, and political challenges brought forth by globalization highlight both the opportunities and complexities of an interconnected world. While globalization has brought benefits such as increased access to goods and services, it has also raised concerns about inequality and cultural homogenization.As technology continues to advance and societies become increasingly interconnected, it is important for policymakers to address the challenges of globalization and harness its potential for the betterment of all. By promoting inclusive growth, preserving cultural diversity, and ensuring democratic governance, societies can navigate the complexities of globalization and create a more sustainable future.References: 1. Smith, J. (2018). The Impact of Globalization on the World Economy. International Journal of Economics, 25(2), 123-145. 2. Hall, S. (2019). Cultural Identity and Globalization. Journal of Cultural Studies, 40(3), 345-360. 3.Peters, G. (2020). Globalization and Political Challenges. International Relations Quarterly, 37(4), 567-589.。
毕业论文英文原文Graduation Thesis: English Original TextAbstract:This graduation thesis aims to explore the impact of technology on education. It delves into the advantages and disadvantages of integrating technology into the classroom, while also discussing the potential challenges and future prospects. The research provides insights into the evolving role of technology in education and its implications for students, teachers, and educational institutions. Introduction:In recent years, technology has revolutionized various aspects of our lives, including education. The integration of technology in the classroom has become a topic of great interest and debate. This thesis seeks to examine the English original text of my graduation paper, which focuses on the impact of technology on education. By analyzing the benefits and drawbacks of technology in the classroom, this research aims to shed light on the evolving educational landscape.Advantages of Integrating Technology in the Classroom:One of the significant advantages of integrating technology in the classroom is enhanced engagement and interactivity. Technology provides students with interactive learning experiences, making education more enjoyable and effective. For example, educational apps and online platforms offer personalized learning opportunities, catering to individual student needs and learning styles.Furthermore, technology facilitates access to a vast amount of information and resources. The internet allows students to explore various topics beyond the limitations of traditional textbooks. Online databases, e-books, and educational videos provide students with a wealth of knowledge at their fingertips.In addition, technology promotes collaboration and communication among students. Platforms such as video conferencing and online discussion forums enable students to connect with peers from different locations, fostering cultural exchange and global awareness.Disadvantages and Challenges:Despite the numerous advantages, there are also potential disadvantages and challenges associated with integrating technology in the classroom. One of the primary concerns is the digital divide. Not all students have equal access to technology and the internet, leading to inequalities in educational opportunities. This issue must be addressed to ensure equitable access to educational resources for all students.Another challenge is the potential for distractions. With the increasing use of personal devices in the classroom, students may be tempted to engage in non-educational activities, such as social media or gaming. Teachers must find effective strategies to minimize distractions and maintain a focused learning environment.Moreover, the rapid pace of technological advancements poses a challenge for teachers to keep up with the latest tools and techniques. Continuousprofessional development is crucial to ensure educators are equipped with the necessary skills to effectively integrate technology into their teaching practices. Future Prospects:Looking ahead, the future prospects of technology in education are promising. As technology continues to advance, innovative tools and platforms will emerge, providing even more immersive and personalized learning experiences. Artificial intelligence and virtual reality are already being integrated into educational settings, offering new possibilities for interactive learning.Furthermore, the COVID-19 pandemic has accelerated the adoption of technology in education. Online learning platforms and remote teaching have become essential during times of crisis. This experience has highlighted the importance of technology in ensuring continuity of education, even in challenging circumstances.Conclusion:In conclusion, the English original text of my graduation thesis explores the impact of technology on education. It discusses the advantages of integrating technology in the classroom, such as enhanced engagement, access to information, and collaboration. However, it also acknowledges the challenges, including the digital divide and potential distractions. Looking forward, technology holds great potential to transform education and provide students with innovative learning experiences. It is essential for educators and policymakers to navigate these advancements thoughtfully and ensure equalaccess to quality education for all.。
英语议论文模板英语议论文模板范文英语议论文万能模板简单优秀5篇英语议论文一直以来被认为是书面语篇中一种基本的文本模式。
而英语议论文对外语学习者来说也是较难的一种语篇类型。
参考一些英语议论文模板，问题或许就迎刃而解了。
下面这5篇英语议论文模板范文英语议论文万能模板简单是作者为您整理的英语议论文模板范文模板，欢迎查阅参考。
大学英语议论文篇一要求从一句话或一个主题出发，按照提纲的要求进行论述。
1. 阐述名言或主题所蕴涵的意义。
分析并举例使其更充实。
the good old prover________(名言或谚语)reminduthat ________(释义). indeed, we can learn manthingform it.first of all,________(理由一). for example, ____________(举例说明). secondly,________(理由二). another case ithat ________(举例说明). furthermore , ____________(理由三).英语四级英译汉的目的。
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Ten-Year Comparison of the Influence of Organic and Conventional Crop Management Practices on the Content ofFlavonoids in TomatoesA LYSON E.M ITCHELL,*,†Y UN-J EONG H ONG,†E UNMI K OH,†D IANE M.B ARRETT,†D.E.B RYANT,§R.F ORD D ENISON,#ANDS TEPHEN K AFFKA§Department of Food Science and Technology and Department of Plant Sciences,One Shields Avenue,University of California s Davis,Davis,California95616,and Department of Ecology,Evolution andBehavior,University of Minnesota,St.Paul,Minnesota55108Understanding how environment,crop management,and other factors,particularly soil fertility, influence the composition and quality of food crops is necessary for the production of high-quality nutritious foods.The flavonoid aglycones quercetin and kaempferol were measured in dried tomato samples(Lycopersicon esculentum L.cv.Halley3155)that had been archived over the period from 1994to2004from the Long-Term Research on Agricultural Systems project(LTRAS)at the University of California s Davis,which began in1993.Conventional and organic processing tomato production systems are part of the set of systems compared at parisons of analyses of archived samples from conventional and organic production systems demonstrated statistically higher levels (P<0.05)of quercetin and kaempferol aglycones in organic tomatoes.Ten-year mean levels of quercetin and kaempferol in organic tomatoes[115.5and63.3mg g-1of dry matter(DM)]were79 and97%higher than those in conventional tomatoes(64.6and32.06mg g-1of DM),respectively. The levels of flavonoids increased over time in samples from organic treatments,whereas the levels of flavonoids did not vary significantly in conventional treatments.This increase corresponds not only with increasing amounts of soil organic matter accumulating in organic plots but also with reduced manure application rates once soils in the organic systems had reached equilibrium levels of organic matter.Well-quantified changes in tomato nutrients over years in organic farming systems have not been reported previously.KEYWORDS:Tomato;organic agriculture;conventional agriculture;long-term research;flavonoid; flavonol;quercetin;kaempferolINTRODUCTIONFruits and vegetables are rich in dietary vitamins,minerals, and fiber and are the primary source of flavonoids in the diet. Epidemiological studies suggest that flavonoids protect against cardiovascular disease(1)and,to a lesser extent,against cancer (2)and other age-related diseases such as dementia(3). Flavonoids encompass a large group of phenolic secondary plant metabolites that demonstrate potent in vitro antioxidant activity (4,5)and display free radical scavenging activity(6).Most attempts to assign health-promoting activity mechanistically to the antioxidant action of individual flavonoids in foods have been unsuccessful(7)and suggest that other mechanisms are likely involved in the health-promoting activities of these compounds.Secondary plant metabolites such as the flavonoids function in plant defense mechanisms against herbivory,pathogen stress, and UV-B radiation(8).Many of these compounds are also the primary pigments responsible for attracting pollinators and seed dispersers.Flavonoids are produced through the phenylpro-panoid pathway in plants.The key enzyme that catalyzes the biosynthesis is phenylalanine ammonia-lyase.Environmental stresses including nutrient deficiency,wounding,pathogens,and UV radiation are known to activate the biosynthesis of phenyl-propanoid compounds(9,10).Given the increasing data in support of a role for phenolic plant metabolites in the prevention of cardiovascular and other chronic diseases,efforts are underway to improve their levels in plant foods through improved cultivar selection and genetic manipulations.Alter-*Corresponding author[telephone(530)752-7926;fax(530)752-4759;e-mail aemitchell@].†Department of Food Science and Technology,University of California.§Department of Plant Sciences,University of California.#University of Minnesota.6154J.Agric.Food Chem.2007,55,6154−615910.1021/jf070344+CCC:$37.00©2007American Chemical SocietyPublished on Web06/23/2007natively,the phenolic content of plants may be influenced by manipulating the agronomic environment in which they are grown (11-13).Fundamental differences between organic and conventional production systems,particularly in soil fertility management,may affect the nutritive composition of plants,including secondary plant anic systems emphasize the accumulation of soil organic matter and fertility over time through the use of cover crops,manures,and composts and rely on the activity of a diverse soil ecosystem to make nitrogen (N)and other nutrients available to plants.Conventional farms utilize fertilizers containing soluble inorganic nitrogen and other nutrients,which are more directly available to plants.The availability of inorganic nitrogen in particular has the potential to influence the synthesis of secondary plant metabolites,proteins,and soluble solids.Stamp proposed that increased crop growth and development rates and greater biomass accumulation in well-fertilized crops would also correlate with decreased allocation of resources toward the production of starch,cellulose,and non-nitrogen-containing secondary metabolites (14).Given that many secondary plant metabolites are produced for defense against herbivores and are inducible by pathogens or wounding,possible differences in pest pressure between conventional and organic systems might also influence levels in food crops.Both conventional and organic agricultural practices include combinations of farming practices that vary greatly depending upon region,climate,soils,pests and diseases,and economic factors guiding the particular management practices used on the farm.Many of these influences change continuously,so a steady-state condition may never be achieved on most farms (15).The dynamic nature of agricultural systems also makes adequately controlled comparisons of produce quality,free from confounding influences,experimentally pari-sons of produce from different types of farms,even if they are near each other,are affected by the numerous factors mentioned.Reviews of studies comparing the nutritional quality of con-ventionally and organically produced vegetables demonstrate inconsistent differences with the exception of higher levels of ascorbic acid (vitamin C)and less nitrate in organic products (16,17).However,these data are difficult to interpret because cultivar selection and agronomic conditions varied widely and different methods of sampling and analysis were used in the investigations cited.In contrast,cropping system comparisons using long-term research plots that have been managed consis-tently over time provide a means to overcome many of the confounding factors associated with farm-based sampling.Additionally,the effects of changes over time in cropping system behavior can be evaluated using archived soil and plant samples,and a reasonable estimate of the causes of those changes can be made.The present study is an example of the use of long-term research to address complex processes operating in cropping systems.Its specific objective was to compare the content of the flavonoids quercetin,kaempferol,and naringenin in tomato samples (Lycopersicon esculentum L.cv.Halley 3155)produced in conventional and organic cropping systems that had been archived over the period from 1994to 2004from the Long-Term Research on Agricultural Systems project (LTRAS)at the University of California s Davis,which began in 1993().LTRAS was designed to detect and estimate changes in crop productivity trends and other factors correlated with sustainability,which result from differing irrigation and fertilization practices (18).It includes an organic cropping system in which maize and tomatoes are grown in rotation and compared to the same crops produced conventionally.This archive of tomato samples is unique in California and perhaps the world.This study focused on tomatoes because the per capita consumption of tomatoes (8.1kg per capita in 2003)and tomato products (31.1kg per capita in 2003)in the United States is very high,second only to the potato (19).Tomatoes provide an important and significant source of vitamin C (19mg/100g of fresh weight),vitamin A (623IU/100g of fresh weight),lycopene (3.0mg/100g of fresh weight),and flavonoids (20,21).The main flavonoids found in tomatoes are quercetin,kaempferol,and naringenin (Figure 1).Quercetin predominates,with levels ranging from 0.03to 2.77mg/100g in fresh tomatoes and 4.77mg/100g in processed tomato products (22).Levels of kaempferol range from 0.01to 0.06mg/100g in fresh and processed tomatoes (22).MATERIALS AND METHODSChemicals and Samples.Quercetin dihydrate (3,5,7,3′,4′-pentahy-droxyflavone dihydrate,98%),morin hydrate (3,5,7,2′,4′-pentahydroxy-flavone hydrate,95%),and tert -butylhydroquinone (TBHQ,97%)were purchased from Aldrich Chemical Co.,Inc.(Milwaukee,WI).Kaempfer-ol (3,5,7,4′-tetrahydroxyflavone,95%)and naringenin (4′,5,7-trihy-droxyflavone,95%)were obtained from Sigma Chemical Co.(St.Louis,MO),and Indofine Chemical Co.,Inc.(Hillsborough,NJ),respectively.All solvents used were of HPLC grade.Ethanol was purchased from Spectrum Chemicals (Gardena,CA).Tomato Cultivation in the LTRAS Cropping Systems.Following uniform cropping with Sudan grass (Sorghum V ulgare L.)in 1992and 1993,10different cropping systems were established in 1993using 0.4ha plots (18).Each cropping system was replicated three times,and both crops or phases of the two-year rotations were present each year.Plots were large enough to allow for the use of commercial-scale farm equipment.Irrigation amounts were measured using flow meters located at each irrigated plot.Systems differ in the amount of irrigation received (rain fed or irrigated),in the amounts of nutrients applied as fertilizers,and in organic matter applied to the soil as cropresidues,Figure 1.Structures of the flavonoid aglycones of quercetin,keampferol,and naringenin.Cropping System Comparisons of Flavonoids in Tomatoes J.Agric.Food Chem.,Vol.55,No.15,20076155winter legume cover crops,and/or composted manure.Conventional plots received herbicides and other pesticides as needed,whereas organic crops received only organically approved pesticides,such as sulfur and Bt compounds.Crop yields and total biomass were measured every year and analyzed for total N and C.Sample archiving included yearly plant and fruit samples from all cropping systems and time zero and subsequent soil samples collected every few years.Systems rather than single inputs were compared,so a valid comparison required that each system be managed carefully to achieve its potential yields.For example,both the conventional and organic maize/tomato systems had the same tomato cultivar(Halley3155)and were irrigated similarly asneeded,but the lower percent availability of organic N sources can require more total N input to meet crop N needs(24).The same cultivar was used throughout the12-year period.The systems compared are model systems,chosen to include representative crops rather than more complex,changeable crop rotations.California farmers rarely follow fixed crop rotations as markets change,and organic farmers especially tend to have more complex rotations than the one studied at LTRAS.Crop management practices follow best management practice guidelines in the region.Conventional tomatoes received50kg ha-1 of an N-P-K starter fertilizer and118kg ha-1of ammonium nitrate as side dressing.A combination of tillage and herbicides was used for weed control.Aphids,mites,and stinkbugs occur periodically and were controlled as necessary,similar to practices in commercial fields.In both treatments,processing tomatoes were transplanted at the rate of 22500plants ha-1(10000per acre).Transplanting in the organic treatment followed incorporation of a winter legume cover crop consisting of hairy vetch(Vicia V illosa Roth)and field peas(Pisum sati V um L.).Transplanting of all plots occurred within a period of2-4 days in spring,commonly around the middle of April.Prior to incorporation of the cover crop,9Mg ha-1of composted poultry manure currently is top-dressed and incorporated with the cover crop.The amount of N present in cover crops varies from year to year,but, typically,organic plots currently receive between240and260kg of N ha-1year in addition to the N fixed by the legume cover crop(24). During the first three cropping cycles,to more rapidly increase soil organic matter levels and soil fertility,19Mg ha-1of composted manure was added to tomato crops.This was reduced after organic matter levels had increased to a near constant level(24).Tomatoes were harvested each year when the field as a whole reached90%ripe fruit.A commercial tomato harvester was used for main plot harvests.Similar methods of transplanting and plant populations were used for conven-tional plots as well,and transplanting of all plots occurred within a period of2-4days in spring,commonly around the middle of April.Sampling and Preparation of Plant Material.Immediately prior to harvest of the main plot,samples for the archive were collected from four3.1m2subsample areas(subplots)within the larger main plots. Total plant biomass and the yield of the red ripe fruit were determined for each subplot.A random sample of20ripe fruits from the four subplots was washed and oven-dried at60°C,ground,and stored in glass containers in the dark at20°C until use.Samples from conventional and organic plots from even numbered years(1994-2004) were chosen for flavonoid analysis.Three of the subplots(n)3)for each treatment(three organic;three conventional)were analyzed each of the even years(1994-2004).These subplot samples were analyzed in triplicate.Flavonoid Analysis.Flavonoid analysis followed the general method of Merken and Beecher(25)as modified by Chassy et al.for fresh processing tomatoes(26).Flavonoid glycosides were hydrolyzed to their corresponding agylcones,which were subsequently measured using HPLC.Briefly,1g of pestle-pulverized,air-dried tomato sample was combined with100mL of1.6g/L tert-butylhydroquinone,1.2N hydrochloric acid,and50%methanol(MeOH).To this mixture was added0.5mL of a1mg/mL standard of luteolin as an internal standard. Internal standard recovery was92-93%for luteolin.Samples were refluxed for4h at100°C in a250mL round-bottom flask.Four hours of reflux time,in1.2N hydrochloric acid,was determined as the optimal condition for maximal recoveries of quercetin,kaempferol,and naringenin in these samples.An aliquot was removed,diluted50:50 v/v with MeOH(200µL),and filtered through a0.5mL of25µm MC Ultrafree-MC filter(Millipore,Bedford,MA).Flavonoids were sepa-rated using a Hewlett-Packard1090HPLC equipped with a variable wavelength diode array detector and Chemstation(LC3D rev.A.08.03) software(Agilent,Palo Alto,CA)monitoring370nm.Reversed phase HPLC was performed using a250×4.6mm i.d.,5µm Zorbax XDB-C18column and a12.5×4.6mm i.d.5µm Zorbax XDB-C18 precolumn(Agilent).The mobile phase consisted of0.05%trifluoro-acetic acid(TFA)in water(solvent A),0.05%TFA in MeOH(solvent B),and0.05%TFA in acetonitrile(solvent C).Separations were effected by a series of linear gradients using a flow rate of1.0mL/min as follows:90-85%A,6-9%B,4-6%C,0-5min;85-71%A, 9-17.4%B,6-11.6%C,5-30min;71-0%A,17.4-85%B,11.6-15%C,30-60min.The linear ranges of quantitation for quercetin and kaempferol were0.5-10and0.1-10µg/mL respectively.Statistical Analysis.Data were analyzed using SAS software version 9.1(SAS Institute,Cary,NC).Specifically,PROC Mixed and regression were used to analyze treatment differences and create single degree of freedom contrasts for differences between systems(27). RESULTSThe mean level of the flavonoids quercetin,naringenin,and kaempferol agylcones(mg g-1of DM)were significantly higher (p<0.001)in samples from the organic cropping system as compared to samples from the conventional cropping system (Table1).Quercetin was the most abundant flavonoid in both organic(115.5(8.0mg g-1of DM)and conventional(64.6( 2.4mg g-1of DM)tomatoes.In conventional tomatoes, kaempferol(32.06(1.94mg g-1of DM)and naringenin (30.2(1.57mg g-1of DM)levels were comparable,whereas levels of kaempferol(63.3( 5.21mg g-1of DM)were significantly higher than naringenin levels(39.6(1.58mg g-1 of DM)in organic tomatoes.Absolute differences in the flavonoids increased with time in both systems,with the largest differences observed in the last4-year period(Figures2and3). Figure4compares the quercetin and kaempferol means to N applications over this10-year period.Increases in quercetin and kaempferol content appear to be correlated in time with changes in manure application rates,which were reduced in the Table1.Mean Flavonoid Concentrations in Archived Samples from the LTRAS Experiment(1994−2004)and Single Degree of Freedom Contrasts between Conventional and Organic Farming Systemsmean(SD)(mg g-1of DM)flavonoid conventional organic F p quercetin64.6(2.49)115.5(8.0)108.16<0.0001 naringenin30.2(1.57)39.6(1.58)66.36<0.0001 kampferol32.06(1.94)63.3(5.21)96.64<0.0001Figure2.Quercetin(b),naringenin(O),and kaempferol(1)levels in tomatoes derived from conventional cropping systems at LTRAS from 1994to2004(mg g-1of DM).Values are given with standard deviations.6156J.Agric.Food Chem.,Vol.55,No.15,2007Mitchell et al.organic system in 1998from an average of 45to 18Mg ha -1over the 2-year maize/tomato cycle.Conventional maize/tomato rotation crops received 230kg of N ha -1for maize and 160kg of N ha -1for tomatoes in each year.Levels of quercetin and kaempferol where highest in years 2000,2002,and 2004.Figure 5shows tomato yield from 1994to 2004in organic and conventional plots.On average,yields were not significantly different between the two systems,but there was less year-to-year variation in the organic systems (28,29).DISCUSSIONThe content of flavonoids appears to have increased over time in the archived tomato samples in both the conventional and organic systems (Figures 2and 3).The rates of increase of quercetin and kaempferol were much lower in the conventional system compared to the organic system.For the conventional system,regression analysis of mean values of flavonoid concentration versus time suggests an increase of 1.9mg g -1year -1for kaempferol (se )0.34,r 2)0.65)and 2.0mg g -1year -1for quercetin (se )0.57,r 2)0.43).Naringenin increased at a rate of 1.35mg g -1year -1(se )0.33,r 2)0.51).Alternatively,these rates of increase can be interpreted as rates of deterioration of flavonoid content in storage with time.During the 10-year period analyzed,farming practices in the conven-tional system,including N fertilization and the tomato variety grown,did not change,and there was little accumulation of organic matter or other obvious changes in soil quality over that period in conventional plots (24).Therefore,it appears most likely that flavonoids declined slowly with time in storage.The stability of flavonoids has been documented in onions stored for 24weeks (30)and in apples stored for up to 30weeks (31).We assume that the rate of decline in storage is identical in both organic and conventional samples.If that is the case,then there is a significant difference in the amount of flavonoids occurring in ripe fruit at harvest between the two systems.Bongue-Bertlesman and Philips found that N-deficient tomato plants had significantly greater flavonoid content in their leaves (32).Chassy et al.reported significantly higher mean levels of soluble solids,flavonoids,total phenolics,and ascorbic acid in organic tomatoes as compared to their conventional counterparts grown in model plots over a 3-year period (26).However,year-to-year variation in this study was significant,and only the levels of kaempferol were statistically higher in organic tomatoes for all three years (26).Toor et al.also examined the influence ofnutrient source on antioxidant components and antioxidant activity of greenhouse-grown tomatoes (11).These tomatoes were grown with mineral nutrient solutions (containing NH 4+and NO 3-),chicken manure,and grass-clover mulch.The mean total phenolic and ascorbic acid contents of tomatoes grown using grass-clover mulch (29%)and chicken manure (17.6%)were higher than those of the tomatoes grown with the mineral nutrient solutions and demonstrate that nutrient source can play a role in determining the levels of antioxidants intomatoes.Figure 3.Quercetin (b ),naringenin (O ),and kaempferol (1)levels intomatoes derived from organic systems at LTRAS from 1994to 2004(mg g -1of DM).Values are given with standarddeviations.Figure 4.Changes in flavonoid levels averaged over 10years of theLTRAS trial,and changes in N inputs over time to the tomato systems (1994−2004).Cropping System Comparisons of Flavonoids in Tomatoes J.Agric.Food Chem.,Vol.55,No.15,20076157Soil organic matter (SOM)levels in the organic system at LTRAS are currently significantly higher in the organic plots than in the conventional ones (18).SOM may have reached a quantitative limit of accumulation by 1997or 1998(24,28),but changes in SOM quality may still be occurring (22).At about the time SOM reached a limit of accumulation,the amount of composted manure applied to organic plots was reduced.Over the 2-year crop rotation (maize/tomato),the amount was reduced from approximately 45Mg ha -1on average to 18Mg ha -1.Similar amounts of N continued to be applied as green manure cover crops grown during the winter season,subject to year-to-year variation in cover crop growth.Figure 4compares the amounts of quercetin and kaempferol in conventional and organic systems to estimated N applications over the 12-year period.Significant increases in quercetin and kaempferol content appear to be correlated in time with the cumulative effects of changes in manure application rates,resulting in lower total N application amounts to organic plots over the last 6years as compared to the first 6years.These changes did not affect LTRAS tomato yield (Figure 5),and they did not consistently affect color or soluble solids,other secondary quality charac-teristics commonly assessed by tomato processors in fresh samples (29).Flavonoid content in tomatoes seems to be related to available N (3,11).Plants with limited N accumulate more flavonoids than those that are well-supplied.If differences in flavonoid content reflect fundamental differences in the behavior of soil N between conventional and organic systems,then the N available to tomatoes late in the season may have declined in organic plots in recent years in response to the cumulative effects of a decrease in compost application rates.The LTRAS project,a carefully managed long-term research project focusing on cropping systems,is a useful basis for detecting and determining the magnitude of differences in tomato quality.The differences detected appear to be correlated with differences in soil fertility management associated with conventional and organic farming systems.These comparisons are free of confounding factors such as soil type differences,differing and variable crop management histories,uneven amounts of time that systems have been managed organically or convetionally,differing levels of farm management skill among farmers,cultivar differences,irrigation,harvesting,sample handling,and other factors that affect the usefulness of most previous comparisons of fruit quality between conventional and organic farming systems.Instead,differences can be attributed primarily to contrasting soil fertility management practices between the conventional and organic systems.Thetwo systems produced tomatoes with differing flavonoid contents within individual years,and these differences increased with time.We suggest that it is the behavior and quantity of N in the organic and conventional systems that most strongly influence these differences (11,30,33).If so,then overfertil-ization (conventional or organic)might reduce health benefits from tomatoes.LITERATURE CITED(1)Hertog,M.G.L.;Hollman,P.C.H.Potential health effects ofthe dietary flavonol quercetin.Eur.J.Clin.Nutr.1996,50,63-71.(2)Knekt,P.;Kumpulainen,J.;Jarvinen,R.;Rissanen,H.;Helio-vaara,M.;Reunanen,A.;Hakulinen,T.;Aromaa,A.Flavonoid intake and risk of chronic disease.Am.J.Clin.Nutr.2002,76,560-568.(3)Commenges,D.;Scotet,V.;Renaud,S.;Jacqmin-Gadda,H.;Barberger-Gateau,P.;Dartigues,J.F.Intake of flavonoids and risk of 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