Involvement of root ABA and hydraulic conductivity in the control of water relations in wheat plants exposed to increased evaporative demand |
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Authors: | Guzel Kudoyarova Svetlana Veselova Wolfram Hartung Rashit Farhutdinov Dmitry Veselov Guzyal Sharipova |
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Institution: | 1.Ufa Research Centre,Russian Academy of Sciences,Ufa,Russia;2.Julius von Sachs Institut für Biowissenschaften der Universit?t,Lehrstuhl Botanik I,Würzburg,Germany |
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Abstract: | 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. |
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