Influence of Plant Bio-regulators on Physiological Traits, Gas Exchange and Yield of Clusterbean (Cyamopsis tetragonoloba L. Taub) under Water Stress

Abstract

Clusterbean (Cyamopsis tetragonoloba L.Taub) is the most important summer
legume crop grown in hot arid regions. However, little is known of its morphological,
physio-biochemical responses, and yield traits to drought and sulphydryl compounds
(-SH compounds) application. Drought had significant negative effects on growth and
metabolism, as revealed by reduced leaf area, net assimilation rate, leaf relative water
content photosynthetic rate, photosynthetic pigments and weakened yield traits. A field
experiment was conducted for two consecutive years to investigate the effect of foliar
application of two plant bio-regulators (PBR’s) applied at different concentrations namely,
thioglycollic (TGA) acid at 200 mg L-1, 300 mg L-1 and 400 mg L-1; thiourea at 500 mg
L-1, 750 mg L-1 and 1000 mg L-1 on morpho-physiological traits and yield parameters.
Foliar application of PBRs at different concentrations increased 16-35%, 11-20%, 9-30%,
8-39% and 14-21% higher growth attributes, water relations, photosynthetic pigments,
gas exchange parameters, and seed yield, respectively. Although eliciting behavior
of bio-regulators improved morpho-physiological attributes against drought stress
condition, the application of TGA 400 mg L-1 and TU 1000 mg L-1 recorded maximum
net assimilation rate, leaf area, RWC, total chlorophyll, carotenoid content, pods, 100
seed weight and seed yield over control.