铝胁迫下千年桐叶片角度及形态特征的变化

高等植物通过调整叶角大小,在弱光条件下提高光利用效率或者在光辐射强烈时有效避免强光的伤害,以此获得适度光照或者减弱叶片受到的光胁迫,促进植株生长。但胁迫条件会对叶片的适光行为产生不同程度的影响。为探究铝胁迫对红壤区常见生态树种千年桐叶片形态和行为调整的影响,以1年生千年桐苗木为试验材料,设置无铝0 mmol·L^(-1)(CK)、低铝0.555 mmol·L^(-1)(T1)、中铝0.746 mmol·L^(-1)(T2)、高铝1.111 mmol·L^(-1)(T3)4种不同浓度铝处理,比较不同浓度铝胁迫下,千年桐苗木的叶角度、叶片形态特征以及光合生理指标的差异,分析影响叶角变化的相关因子,从叶片形态可塑性和适光行为调整的角度揭示千年桐对铝胁迫的响应。结果表明,光照充足条件下,CK处理的千年桐叶片悬挂角在7:30时最小(106.00°),叶脉处于近水平位置,随着光照的增加叶悬挂角有所增大;不同铝浓度处理下叶悬挂角与叶方向角的日变幅按从小到大的排序均表现为T2<T3<CK<T1。在T1和T3处理时千年桐叶长、叶宽、叶柄长与叶面积下降明显,叶形指数在T3处理时达到最大值。千年桐叶片的净光合速率和蒸腾速率在T2处理时数值最小,与CK相比,其降幅分别为32.35%和46.22%;瞬时水分利用效率在T2处理下达到最大值。相关性分析显示,千年桐叶方向角与叶柄长度呈与叶形指数呈显著负相关;叶悬挂角与叶方向角呈显著负相关。由此可知,无铝胁迫时千年桐在强光条件下能通过减小叶方向角和增大叶悬挂角,降低叶面对光辐射的截获量以避免光损伤;在弱光条件下通过增大叶方向角和减小悬挂角使叶片两面能接受更多的光辐射。低铝浓度下,千年桐仍可进行积极的叶片适光调整。而中高铝浓度下,千年桐叶角变幅减小,但可通过光合生理指标的调整降低叶片失水量,实现叶柄对叶片角度的调节。

Application of landscape ecology to the research on wetlands

This review describes the characteristics and hot spots of wetland research, including biodiversity protection of wetland, management and restoration of wetland, function and process of wetland, and the theories, methods and scales of landscape ecology. Moreover, some deficits of landscape ecology theory and method were discussed, and the application of landscape ecology to research on wetlands was reviewed specially, involving in the application of landscape structure principle, landscape pattern, and scale and hierarchy theory. In conclusion, landscape ecology plays an enlightening and guiding function on the comprehensive research of wetlands at multi-scales.