Wingler Astrid, Purdy Sarah, MacLean Jamie A, Pourtau Nathalie
Department of Biology, University College London, Gower Street, London WC1E 6BT, UK.
J Exp Bot. 2006;57(2):391-9. doi: 10.1093/jxb/eri279. Epub 2005 Sep 12.
Although leaf senescence results in a loss of photosynthetic carbon fixation, the senescence-dependent release of nutrients, especially of nitrogen, is important for the growth of young leaves and for reproduction. Environmental regulation of senescence is therefore a vital factor in the carbon and nitrogen economy of plants. Leaf senescence is a highly plastic trait that is affected by a range of different environmental factors including light, nutrient supply, CO2 concentration, and abiotic and biotic stress. In this review, the focus is on the impact of environmental conditions on sugar accumulation and sugar signalling during senescence. By signalling a high availability of carbon relative to nitrogen in the old leaves, sugar accumulation can trigger leaf senescence. Sugar-induced senescence is therefore particularly important under low nitrogen availability and may also play a role in light signalling. Whether or not sugars are involved in regulating the senescence response of plants to elevated CO2 remains unresolved. Senescence can be delayed or accelerated in elevated CO2 and no clear relationship between sugar accumulation and senescence has been found. Plasticity in the response to environmental factors, such as daylength and sugar accumulation, varies between different Arabidopsis accessions. This natural variation can be exploited to analyse the genetic basis of the regulation of senescence and the consequences for growth and fecundity. Different evolutionary strategies, i.e. early senescence combined with a high reproductive effort or late senescence combined with a low reproductive effort, may be an important adaptation of Arabidopsis accessions to their natural habitat.
尽管叶片衰老会导致光合碳固定能力丧失，但衰老依赖的养分释放，尤其是氮的释放，对幼叶生长和繁殖很重要。因此，衰老的环境调控是植物碳氮经济中的一个关键因素。叶片衰老是一个高度可塑性的性状，受一系列不同环境因素影响，包括光照、养分供应、二氧化碳浓度以及非生物和生物胁迫。在本综述中，重点是环境条件对衰老过程中糖积累和糖信号传导的影响。通过表明老叶中碳相对于氮的高可用性，糖积累可以触发叶片衰老。因此，在低氮供应情况下，糖诱导的衰老尤为重要，并且可能在光信号传导中也发挥作用。糖是否参与调节植物对二氧化碳浓度升高的衰老反应仍未明确。在二氧化碳浓度升高时，衰老可能会延迟或加速，并且尚未发现糖积累与衰老之间存在明确关系。对环境因素（如日照长度和糖积累）的反应可塑性在不同的拟南芥生态型之间存在差异。这种自然变异可用于分析衰老调控的遗传基础以及对生长和繁殖力的影响。不同的进化策略，即早期衰老与高繁殖力相结合或晚期衰老与低繁殖力相结合，可能是拟南芥生态型对其自然栖息地的重要适应方式。
