Effects of Developmental Changes on the Physiological Processes that Regulate Photosynthetic Responses to Climate Change

大气中二氧化碳浓度的增加以及其他大气和气候变化可能会大大改变植物的生长。植物物种内部和物种之间的生长响应差异可能通过改变群落组成和改变碳、营养物质和水在生态系统中的运动，对生物多样性、碳固存和其他生态系统功能产生重大影响。然而，尽管在过去的几十年里进行了广泛的研究，预测气候变化对植物的影响仍然存在根本性的问题。例如，植物的二氧化碳吸收量（衡量气候变化对碳固存潜力影响的标准指标）已被发现与植物的碳积累有很大差异。为了解释这种可变性，经常调用源-汇反馈机制，将碳吸收（光合作用）的变化与影响碳积累的发育变化联系起来。这一机制是由源活动（碳吸收）和汇能力（碳积累）之间平衡的变化驱动的。然而，很少有研究真正操纵植物发育来分析正常发育变化对调节光合作用对气候变化响应的生理过程的影响。因此，人们对植物发育在调节光合作用对气候变化的反应中的作用知之甚少。拟议研究的总体目标是发展对植物发育变化的机制理解，因为植物年龄对调节光合作用对气候变化的生理过程的影响。为了确定调节光合作用的关键发育和生理过程，两个关键的发育过程，植物个体发育（发育事件的时间和持续时间）和植物年龄的形态变化，将被独立操纵。在不同的日期种植植株，并诱导所有植株同时开花，将独立地控制个体发育和植株大小。为了避免在二氧化碳浓度升高的环境中生长所引起的加速个体发育的混淆效应，我们将使用一种发育决定的短日照物种（苍耳菌）。此外，由于温度是气候变化的关键组成部分，氮供应是调节发育和生理过程之间相互作用的关键因素，因此这些因素将被操纵以研究它们如何介导发育变化对光合作用的影响。本研究结果将增加我们对植物个体发育和形态变化对光合作用对气候变化响应的认识。更广泛地说，这项研究将增加我们对碳吸收与植物对环境变化的生长反应之间联系的理解。

Increasing atmospheric carbon dioxide concentrations and other atmospheric and climate changes may substantially alter plant growth. Differences in growth responses within and between plant species may have substantial impacts on biodiversity, carbon sequestration and other ecosystem functions by altering community composition and changing the movement of carbon, nutrients and water through ecosystems. However, despite extensive research over the last several decades, fundamental problems remain with predicting effects of climate change on plants. For example, carbon dioxide uptake by plants, a standard measure of climate change effects on carbon sequestration potential, has been found to vary substantially from carbon accumulation in plants. To account for this variability, a source-sink feedback mechanism is frequently invoked that links changes in carbon uptake (photosynthesis) with developmental changes that affect carbon accumulation. This mechanism is driven by changes in the balance between source activity (carbon uptake) and sink capacity (carbon accumulation). However, few studies have actually manipulated plant development to analyze the effects of normal developmental changes on physiological processes that regulate photosynthetic responses to climate change. As a result, the role of plant development in regulating photosynthetic responses to climate change is poorly understood. The overall goal of the proposed research is to develop a mechanistic understanding of the effects of developmental changes as plants age on the physiological processes that regulate photosynthetic responses to climate change. To identify key developmental and physiological processes that regulate photosynthesis, two key developmental processes, plant ontogeny (the timing and duration of developmental events) and morphological changes as plants age, will be independently manipulated. Planting cohorts of plants on different dates and inducing all cohorts to flower simultaneously will independently manipulate ontogeny and plant size. To avoid the confounding effect of accelerated ontogeny induced by growth in elevated carbon dioxide concentrations, a developmentally determinate, short-day species (Xanthium strumarium L.) will be used. In addition, because temperature is a key component of climate change and nitrogen supply is a critical factor regulating interactions between developmental and physiological processes, these factors will be manipulated to examine how they mediate the effects of developmental changes on photosynthesis. The results of this study will increase our understanding of the effects of changes in plant ontogeny and morphology on photosynthetic responses to climate change. More broadly, this study will increase our understanding of the links between carbon uptake and growth responses of plants to environmental change.