Zait Yotam, Shapira Or, Schwartz Amnon
The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, 76100, Israel.
Plant Cell Environ. 2017 Jul;40(7):1143-1152. doi: 10.1111/pce.12907. Epub 2017 Mar 30.
Stomatal oscillations are cyclic opening and closing of stomata, presumed to initiate from hydraulic mismatch between leaf water supply and transpiration rate. To test this assumption, mismatches between water supply and transpiration were induced using manipulations of vapour pressure deficit (VPD) and light spectrum in banana (Musa acuminata). Simultaneous measurements of gas exchange with changes in leaf turgor pressure were used to describe the hydraulic mismatches. An increase of VPD above a certain threshold caused stomatal oscillations with variable amplitudes. Oscillations in leaf turgor pressure were synchronized with stomatal oscillations and balanced only when transpiration equaled water supply. Surprisingly, changing the light spectrum from red and blue to red alone at constant VPD also induced stomatal oscillations - while the addition of blue (10%) to red light only ended oscillations. Blue light is known to induce stomatal opening and thus should increase the hydraulic mismatch, reduce the VPD threshold for oscillations and increase the oscillation amplitude. Unexpectedly, blue light reduced oscillation amplitude, increased VPD threshold and reduced turgor pressure loss. These results suggest that additionally, to the known effect of blue light on the hydroactive opening response of stomata, it can also effect stomatal movement by increased xylem-epidermis water supply.
气孔振荡是气孔的周期性开闭，推测是由叶片水分供应与蒸腾速率之间的水力不匹配引发的。为了验证这一假设，在香蕉（Musa acuminata）中通过操纵蒸汽压亏缺（VPD）和光谱来诱导水分供应与蒸腾之间的不匹配。利用气体交换与叶片膨压变化的同步测量来描述水力不匹配。当VPD增加到一定阈值以上时，会导致气孔以不同幅度振荡。叶片膨压的振荡与气孔振荡同步，且仅在蒸腾等于水分供应时达到平衡。令人惊讶的是，在恒定VPD条件下，将光谱从红蓝光改为仅红光也会诱导气孔振荡——而在红光中添加10%的蓝光只会终止振荡。已知蓝光会诱导气孔开放，因此应该会增加水力不匹配，降低振荡的VPD阈值并增加振荡幅度。出乎意料的是，蓝光降低了振荡幅度，提高了VPD阈值并减少了膨压损失。这些结果表明，除了蓝光对气孔水分活性开放反应的已知影响外，它还可以通过增加木质部-表皮水分供应来影响气孔运动。
