Saradadevi Renu, Bramley Helen, Palta Jairo A, Edwards Everard, Siddique Kadambot H M
School of Plant Biology, The University of Western Australia, Perth, WA 6009, Australia.
The UWA Institute of Agriculture, The University of Western Australia, Perth, WA 6009, Australia.
Funct Plant Biol. 2015 Feb;43(1):62-74. doi: 10.1071/FP15216.
Terminal drought is a common abiotic stress affecting wheat yield in Mediterranean-type environments. As terminal drought develops, top layers of the soil profile dry, exposing the upper part of the root system to soil water deficit while deeper roots can still access soil water. Since open stomata rapidly exhausts available soil water, reducing stomatal conductance to prolong availability of soil water during grain filling may improve wheat yields in water-limited environments. It was hypothesised that genotypes with more root biomass in the drying upper layer of the soil profile accumulate more abscisic acid in the leaf and initiate stomatal closure to regulate water use under terminal drought. The wheat cultivar Drysdale and the breeding line IGW-3262 were grown in pots horizontally split into two segments by a wax-coated layer that hydraulically isolated the top and bottom segments, but allowed roots to grow into the bottom segment. Terminal drought was induced from anthesis by withholding water from (i) the top segment only (DW) and (ii) the top and bottom segments (DD) while both segments in well-watered pots (WW) were maintained at 90% pot soil water capacity. Drysdale, initiated stomatal closure earlier than IGW-3262, possibly due to higher signal strength generated in its relatively larger proportion of roots in the drying top segment. The relationship between leaf ABA and stomatal conductance was strong in Drysdale but weak in IGW-3262. Analysis of ABA metabolites suggests possible differences in ABA metabolism between these two genotypes. A higher capability of deeper roots to extract available water is also important in reducing the gap between actual and potential yield.
终末期干旱是影响地中海型环境中小麦产量的常见非生物胁迫。随着终末期干旱的发展，土壤剖面表层变干，使根系上部暴露于土壤水分亏缺中，而深层根系仍可获取土壤水分。由于开放的气孔会迅速耗尽可用土壤水分，在灌浆期降低气孔导度以延长土壤水分的可用性，可能会提高水分受限环境下的小麦产量。据推测，在土壤剖面干燥上层具有更多根生物量的基因型，在叶片中积累更多脱落酸，并在终末期干旱条件下启动气孔关闭以调节水分利用。小麦品种Drysdale和育种系IGW - 3262种植在花盆中，花盆通过一层蜡涂层水平分成两段，该蜡涂层在水力上隔离了上部和下部，但允许根系生长到下部。从开花期开始通过对以下情况停水来诱导终末期干旱：(i)仅上部段（DW）和(ii)上部和下部段（DD），而充分浇水花盆（WW）中的两段均保持在花盆土壤持水量的90%。Drysdale比IGW - 3262更早启动气孔关闭，这可能是由于其在干燥上部段中相对较大比例的根系产生了更高的信号强度。在Drysdale中，叶片脱落酸与气孔导度之间的关系很强，但在IGW - 3262中较弱。对脱落酸代谢物的分析表明这两个基因型之间在脱落酸代谢方面可能存在差异。深层根系提取可用水分的更高能力对于缩小实际产量和潜在产量之间的差距也很重要。
