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烟如何帮助植物在火灾后恢复

一项研究说,烟的一种成分可能通过诱发种子感光从而促进植物生长。Steven Smith及其同事分析了karrikins对经常被研究的植物的作用,karrikins是一种存在于野火的烟中的化合物,已知能够刺激种子发芽。野火能减少植被林冠和地面覆盖,并改变到达地面的阳光的光谱和强度。许多植物通过烟或热激发的种子发芽从而在火后环境的资源竞争减少中获益。这组科学家报告说,karrikins影响了植物种子发芽和成苗的光依赖过程。这组作者说,而且与没有接触karrikins的植物相比,karrikins促进了低光照度下的种子发芽,而且增强了新出现的幼苗茎的光感受,或许引发了接触到烟的植株感受到土壤表面火灾引发的阳光的变化。这组科学家还发现,这种化合物影响了莴苣和芜青的光调控生长,这是另外两种已知对光高度敏感的植物。这组作者说,这项研究增加了当前对植物的karrikin信号传导机制的理解,而且可能有助于科学家发现这种化合物对于植物发芽的影响。

参考文献:Published online before print March 29, 2010, doi: 10.1073/pnas.0911635107

Karrikins enhance light responses during germination and seedling development in Arabidopsis thaliana

David C. Nelsona, Gavin R. Flemattib, Julie-Anne Riseborougha,c, Emilio L. Ghisalbertib, Kingsley W. Dixonc,d, and Steven M. Smitha,b,1

Abstract
Karrikins are a class of seed germination stimulants identified in smoke from wildfires. Microarray analysis of imbibed Arabidopsis thaliana seeds was performed to identify transcriptional responses to KAR1 before germination. A small set of genes that are regulated by KAR1, even when germination is prevented by the absence of gibberellin biosynthesis or light, were identified. Light-induced genes, putative HY5-binding targets, and ABRE-like promoter motifs were overrepresented among KAR1-up-regulated genes. KAR1 transiently induced the light signal transduction transcription factor genes HY5 and HYH. Germination of afterripened Arabidopsis seed was triggered at lower fluences of red light when treated with KAR1. Light-dependent cotyledon expansion and inhibition of hypocotyl elongation were enhanced in the presence of germination-active karrikins. HY5 is important for the Arabidopsis hypocotyl elongation, but not seed germination, response to karrikins. These results reveal a role for karrikins in priming light responses in the emerging seedling, and suggest that the influence of karrikins on postfire ecology may not be limited to germination recruitment.

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