Ufa Research Centre, Russian Academy of Sciences, Ufa, Russia.
Planta. 2011 Jan;233(1):87-94. doi: 10.1007/s00425-010-1286-7. Epub 2010 Oct 6.
We studied the possible involvement of ABA in the control of water relations under conditions of increased evaporative demand. Warming the air by 3°C increased stomatal conductance and raised transpiration rates of hydroponically grown Triticum durum plants while bringing about a temporary loss of relative water content (RWC) and immediate cessation of leaf extension. However, both RWC and extension growth recovered within 30 min although transpiration remained high. The restoration of leaf hydration and growth were enabled by increased root hydraulic conductivity after increasing the air temperature. The use of mercuric chloride (an inhibitor of water channels) to interfere with the rise on root hydraulic conductivity hindered the restoration of extension growth. Air warming increased ABA content in roots and decreased it in shoots. We propose this redistribution of ABA in favour of the roots which increased the root hydraulic conductivity sufficiently to permit rapid recovery of shoot hydration and leaf elongation rates without the involvement of stomatal closure. This proposal is based on known ability of ABA to increase hydraulic conductivity confirmed in these experiments by measuring the effect of exogenous ABA on osmotically driven flow of xylem sap from the roots. Accumulation of root ABA was mainly the outcome of increased export from the shoots. When phloem transport in air-warmed plants was inhibited by cooling the shoot base this prevented ABA enrichment of the roots and favoured an accumulation of ABA in the shoot. As a consequence, stomata closed.
我们研究了在增加蒸发需求的条件下 ABA（脱落酸）在控制水分关系中的可能作用。将空气升温 3°C 会增加水培生长的硬质小麦植株的气孔导度和蒸腾速率，导致相对水分含量（RWC）暂时丧失和叶片伸长立即停止。然而，尽管蒸腾作用仍然很高，RWC 和延伸生长在 30 分钟内都恢复了。通过增加空气温度来提高根液压导率，从而使叶片重新水化和生长得以恢复。汞氯化物（水通道抑制剂）的使用干扰了根液压导率的上升，阻碍了延伸生长的恢复。空气升温增加了根系中的 ABA 含量，减少了地上部分的含量。我们提出这种 ABA 在根中的重新分配有利于根，根液压导率的增加足以使地上部分的水合作用和叶片伸长率迅速恢复，而不需要关闭气孔。这一建议基于 ABA 增加液压导率的已知能力，在这些实验中通过测量外源 ABA 对木质部汁液渗透驱动流的影响得到了证实。根 ABA 的积累主要是由于从地上部分输出增加的结果。当空气升温植物中的韧皮部运输被冷却茎基部抑制时，这阻止了 ABA 在根部的富集，并有利于 ABA 在地上部分的积累。因此，气孔关闭。
