Munné-Bosch Sergi, Alegre Leonor
Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal 645, E-08028 Barcelona, Spain. Corresponding author; email:
Departament de Biologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Avinguda Diagonal 645, E-08028 Barcelona, Spain.
Funct Plant Biol. 2004 May;31(3):203-216. doi: 10.1071/FP03236.
Leaf senescence is a highly regulated physiological process that leads to leaf death and is, as such, the last developmental stage of the leaf. Plant aging and environmental stresses may induce the process of senescence. Here we will focus on the role of leaf senescence in field-grown plants as a response to adverse climatic conditions and, more specifically, on how it contributes to plant survival under drought stress. Drought induces several responses in plants including leaf senescence, which plays a major role in the survival of several species. Drought-induced leaf senescence contributes to nutrient remobilisation during stress, thus allowing the rest of the plant (i.e. the youngest leaves, fruits or flowers) to benefit from the nutrients accumulated during the life span of the leaf. In addition, drought-induced leaf senescence, especially when accompanied by leaf abscission, avoids large losses through transpiration, thus contributing to the maintenance of a favourable water balance of the whole plant. Drought-induced leaf senescence occurs gradually and is characterised by specific macroscopic, cellular, biochemical and molecular changes. Leaf yellowing (i.e. chlorophyll degradation) and specific changes in cell ultrastructure (e.g. chromatin condensation, thylakoid swelling, plastoglobuli accumulation), metabolism (e.g.protein degradation, lipid peroxidation) and gene expression occur during leaf senescence in drought-stressed plants. Cytokinins and ABA have been shown to be involved in the regulation of drought-induced leaf senescence, although the possible role of other plant hormones should not be excluded. Reactive oxygen species, whose concentrations increase during drought-induced leaf senescence, are also known to be regulators of this process. The complex mechanisms of regulation of leaf senescence in drought-stressed plants are discussed, and attention is drawn to those aspects that still require investigation.
叶片衰老 是一个受到高度调控的生理过程，它会导致叶片死亡，因此是叶片发育的最后阶段。植物衰老和环境胁迫可能会诱导衰老过程。在这里，我们将重点关注田间生长的植物中叶片衰老作为对不利气候条件的响应所起的作用，更具体地说，关注它如何有助于植物在干旱胁迫下存活。干旱会在植物中引发多种反应，包括叶片衰老，这在多个物种的存活中起着重要作用。干旱诱导的叶片衰老有助于在胁迫期间进行养分再分配，从而使植物的其余部分（即最幼嫩的叶片、果实或花朵）能够从叶片生命周期中积累的养分中受益。此外，干旱诱导的叶片衰老，尤其是伴有叶片脱落时，可避免因蒸腾作用造成大量水分损失，从而有助于维持整个植物良好的水分平衡。干旱诱导的叶片衰老逐渐发生，其特征是特定的宏观、细胞、生化和分子变化。在干旱胁迫植物的叶片衰老过程中会发生叶片变黄（即叶绿素降解）以及细胞超微结构（如染色质浓缩、类囊体肿胀、质体小球积累）、代谢（如蛋白质降解、脂质过氧化）和基因表达的特定变化。细胞分裂素和脱落酸已被证明参与干旱诱导的叶片衰老的调控，不过其他植物激素的可能作用也不应被排除。活性氧在干旱诱导的叶片衰老过程中浓度会增加，它们也是这一过程的调节因子。本文讨论了干旱胁迫植物中叶片衰老的复杂调控机制，并提请注意那些仍需研究的方面。
