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.

中文翻译：

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遮荫预处理增强大豆抗旱性

摘要 遮荫和干旱被认为是限制作物正常生长的最剧烈的非生物胁迫因素，特别是对于干旱和半干旱地区的高密度间作作物。然而，这两种胁迫因素对作物的交互作用的关系和机制尚不清楚。在这里，我们报告了我们对遮荫和干旱之间关系的鉴定及其对大豆植物的交互影响。我们的定量实时 PCR (q-PCR) 结果显示，树荫显着上调脱落酸 (ABA) 生物合成（NCED3 和 AAO3）和信号（ABI4 和 ABI5）基因。此外，阴影极大地提高了 ABA 含量。基于这些结果，我们对大豆幼苗进行了遮荫 (Pre-SH) 和正常光照 (Pre-NL) 的预处理，然后是聚乙二醇 6000 诱导的干旱胁迫。干旱导致两种光照条件下的相对含水量、形态生理和生化参数降低。然而，与 Pre-NL 植物相比，在 Pre-SH 处理下生长的植物通过增强其防御系统清除更多的活性氧 (ROS)，从而保护其细胞免受干旱的破坏性影响。因此，我们的研究结果表明，在 Pre-NL 条件下生长的植物比在 Pre-SH 条件下生长的植物更容易受到干旱胁迫的影响，这表明遮荫预处理可以增强大豆幼苗的抗旱性。与 Pre-NL 植物相比，在 Pre-SH 处理下生长的植物通过增强其防御系统清除更多活性氧 (ROS)，从而保护其细胞免受干旱的破坏性影响。因此，我们的研究结果表明，在 Pre-NL 条件下生长的植物比在 Pre-SH 条件下生长的植物更受干旱胁迫的影响，这表明遮荫预处理可以增强大豆幼苗的抗旱性。与 Pre-NL 植物相比，在 Pre-SH 处理下生长的植物通过增强其防御系统清除更多活性氧 (ROS)，从而保护其细胞免受干旱的破坏性影响。因此，我们的研究结果表明，在 Pre-NL 条件下生长的植物比在 Pre-SH 条件下生长的植物更容易受到干旱胁迫的影响，这表明遮荫预处理可以增强大豆幼苗的抗旱性。