Coordinate Responses of ABA Accumulation against Drought at Physiological, Ecological and Molecular Levels in Triticum aestivum

Much progress has been made toward understanding plant drought resistance. However, the coordinate responses of plant to drought on the basis of ABA level at physiological, ecological and molecular levels remains unclear. Here, the potted winter wheat (triticum aestivum) was cultivated under relative soil moisture (RSM ) respectively at 85% (well-watered), 65% (moderate stress), and 45% (severe stress), and a series of physiological and ecological parameters including ABA level, stomatal conductance, leaf temperature, leaf water potential, together with transcripts of ABA biosynthesis-metabolism key genes including 9-cis-epoxycarotenoid dioxygenase (TaNCED), ABA glucosyltransferase (TaGT), ABA 8'-hydroxylase (TaCYP707A), and β-glucosidase (TaBG) were carried out. We found that ABA contents responsive to soil water loss increased rapidly and showed a significantly-negative correlation with the stomatal conductance and the leaf water potential and a significantly-positive correlation with the leaf-air temperature difference, respectively. The continuous accumulation of ABA was resulted mainly from the increased transcripts of both TaNCEDs and TaBGs genes. The transcripts of TaCYP707A1 and TaGT declined sharply from 85% to 65% RSM and then increased slightly from 65% to 45% RSM, indicating that ABA metabolism not only accelerates the accumulation of ABA level but also contributes to maintain ABA homeostasis. In conclusion, the macroscopic-microscopic changes responsive to water deficient reflects the ABA-regulated, drought-resistance coordinate mechanisms at physiological, ecological and molecular levels in triticum aestivum.