Genotypes in crop species have been identified that initiate partial stomata closure at elevated atmospheric vapor pressure deficit (VPD), which results in conserved soil water for crop use during subsequent water-deficit episodes and thereby allowing for possible yield increase. In sweet corn (Zea mays L), 17 genotypes have been previously identified with the VPD-responsive trait, although the VPD value at the initiation of stomata closure varied among genotypes. A hypothesis to explain variation in transpiration response to VPD is that water flow capacity in the leaves differs among genotypes. To gauge water flow capacity in leaves, the rate of stomata opening was observed visually after stomata closure was induced by 3 kPa VPD. The stomata opening time was rapid and varied among genotypes from 90 to 179 s. However, there was no correlation between opening time and the VPD at which partial stomata closure was initiated in intact plants. An additional set of experiments was done to examine whether genotypic differences in a subpopulation of silver-inhibited aquaporins might contribute to differences in leaf water flow. There was a correlation among genotypes between slow opening time of the stomata and greater inhibition of transpiration rate following feeding leaves with silver ion. However, the response to the silver treatment did not correlate with the VPD at which transpiration decrease of intact plants was initiated. These results indicate that the differences observed in the water flow capacity in sweet corn leaves were not major factors accounting for the genotypic differences in whole-plant transpiration response to elevated VPD.

中文翻译：

---

甜玉米基因型叶片水分流动能力比较作为植物蒸腾速率对蒸汽压亏缺敏感性的基础

已确定作物物种的基因型在大气蒸汽压亏缺 (VPD) 升高时启动部分气孔关闭，这导致在随后的缺水事件期间保留土壤水供作物使用，从而可能增加产量。在甜玉米（玉米L), 17 种基因型先前已被鉴定为具有 VPD 反应性状，尽管气孔关闭开始时的 VPD 值因基因型而异。解释对 VPD 的蒸腾反应变化的一个假设是叶片中的水流量能力因基因型而异。为了测量叶片的水流能力，在 3 kPa VPD 诱导气孔关闭后，肉眼观察气孔打开的速率。气孔开放时间迅速，基因型之间从 90 到 179 秒不等。然而，开放时间与在完整植物中开始部分气孔关闭的 VPD 之间没有相关性。进行了一组额外的实验来检查银抑制水通道蛋白亚群的基因型差异是否可能导致叶片水流的差异。气孔开放时间缓慢与用银离子喂食叶片后对蒸腾速率的更大抑制之间的基因型之间存在相关性。然而，对银处理的反应与启动完整植物蒸腾减少的 VPD 无关。这些结果表明，在甜玉米叶片中观察到的水流量差异并不是导致全植物蒸腾响应升高的 VPD 的基因型差异的主要因素。