在经过长时间的缺水处理后对植物进行复水，结果表明，在叶片明显达到其最终大小时，叶表皮细胞仍保留其扩张能力。
Rewatering plants after a long water-deficit treatment reveals that leaf epidermal cells retain their ability to expand after the leaf has apparently reached its final size.
作者信息
Lechner Leandra, Pereyra-Irujo Gustavo A, Granier Christine, Aguirrezábal Luis A N
机构信息
Unidad Integrada Balcarce, Facultad de Ciencias Agrarias, Universidad Nacional de Mar del Plata, Instituto Nacional de Tecnología Agropecuaria, CC 276, 7620 Balcarce, Argentina.
出版信息
Ann Bot. 2008 May;101(7):1007-15. doi: 10.1093/aob/mcn029. Epub 2008 Mar 13.
BACKGROUND AND AIMS
Leaves expand during a given period of time until they reach their final size and form, which is called determinate growth. Duration of leaf expansion is stable when expressed in thermal-time and in the absence of stress, and consequently it is often proposed that it is controlled by a robust programme at the plant scale. The usual hypothesis is that growth cessation occurs when cell expansion becomes limited by an irreversible tightening of cell wall, and that leaf size is fixed once cell expansion ceases. The objective of this paper was to test whether leaf expansion could be restored by rewatering plants after a long soil water-deficit period.
METHODS
Four experiments were performed on two different species (Arabidopsis thaliana and Helianthus annuus) in which the area of leaves that had apparently reached their final size was measured upon reversal of water stresses of different intensities and durations.
KEY RESULTS
Re-growth of leaves that had apparently reached their final size occurred in both species, and its magnitude depended only on the time elapsed from growth cessation to rewatering. Leaf area increased up to 186% in A. thaliana and up to 88% in H. annuus after rewatering, with respect to the leaves of plants that remained under water deficit. Re-growth was accounted for by cell expansion. Increase in leaf area represented actual growth and not only a reversible change due to increased turgor.
CONCLUSIONS
After the leaf has ceased to grow, leaf cells retain their ability to expand for several days before leaf size becomes fixed. A response window was identified in both species, during which the extent of leaf area recovery decreased with time after the 'initial' leaf growth cessation. These results suggest that re-growth after rewatering of leaves having apparently attained their final size could be a generalized phenomenon, at least in dicotyledonous plants.
背景与目的
叶片在特定时期内扩展，直至达到其最终大小和形态，这被称为有限生长。在以热时间表示且无胁迫的情况下，叶片扩展的持续时间是稳定的，因此人们常认为它在植物尺度上受一个稳健的程序控制。通常的假设是，当细胞扩展因细胞壁不可逆收紧而受到限制时，生长停止，并且一旦细胞扩展停止，叶片大小就固定了。本文的目的是测试在长期土壤水分亏缺后给植物重新浇水，叶片扩展是否能够恢复。
方法
对两种不同的物种（拟南芥和向日葵）进行了四项实验，在不同强度和持续时间的水分胁迫解除后，测量那些显然已达到最终大小的叶片的面积。
主要结果
在这两个物种中，那些显然已达到最终大小的叶片都出现了重新生长，其程度仅取决于从生长停止到重新浇水所经过的时间。重新浇水后，拟南芥的叶片面积增加了高达186%，向日葵的叶片面积增加了高达88%，相对于仍处于水分亏缺状态的植物的叶片。重新生长是由细胞扩展引起的。叶片面积的增加代表实际生长，而不仅仅是由于膨压增加导致的可逆变化。
结论
叶片停止生长后，叶片细胞在叶片大小固定之前的几天内仍保留扩展能力。在这两个物种中都确定了一个响应窗口，在此期间，在“初始”叶片生长停止后的一段时间内，叶片面积恢复的程度随时间下降。这些结果表明，对于那些显然已达到最终大小的叶片，重新浇水后的重新生长可能是一种普遍现象，至少在双子叶植物中是如此。
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