LAUSR

Abstract Shade and drought are considered the most drastic abiotic stress factors which restrict normal crop growth especially for those high-density and intercropped crops in arid and semi-arid areas. However, relationship and mechanisms of the interactive effects of these two stress factors on crops are elusive. Here, we report our identification of relationship between shade and drought and their interactive effects on soybean plants. Our quantitative-real time PCR (q-PCR) results showed that shade significantly up-regulated Abscisic Acid (ABA) biosynthesis (NCED3 and AAO3) and signaling (ABI4 and ABI5) genes. Moreover, shade massively enhanced the ABA contents. Based on these results, we subjected soybean seedlings to pretreatment of shade (Pre-SH) and normal light (Pre-NL) followed by polyethylene glycol 6000 induced drought stress. Drought resulted in the reduction of relative water content, morphophysiological and biochemical parameters under both light regimes. However, plants grown under Pre-SH treatment protected their cells from damaging effects of drought by scavenging more reactive oxygen species (ROS) through enhancement of its defense system as compared to Pre-NL plants. Hence, our findings demonstrated that plants grown under Pre-NL conditions were more affected with drought stress than those of Pre-SH ones which suggested that pretreatment of shade can enhance the drought resistance of soybean seedlings.