In cultivating guar [Cyamopsis tetragonoloba (L.) Taub], a drought-tolerant legume, producers anticipate soil N credits through biological N fixation (BNF), but it has been speculated that root nodulation is poor under dry conditions and little is known about how nodules recover from drought stress. To provide better insight, two greenhouse studies were conducted to investigate static (25%, 50%, 75% and 100% ET replacement in two soils) and dynamic (50%, 75% and 100%, plus 50% and 75% relieved to 100% at 20 and 30 days after planting) water regimes on guar over 50 days. Water stress generally had the greatest negative impact on nodule weight, followed by aboveground biomass, reproductive nodes, height and then nodule number. Parameter responses were either linear or quadratic with ET replacement and response slopes differed between soils for nodule weight and biomass. The relatively minor effect on nodule number indicated the basic machinery for BNF (nodules) remained largely intact until water stress was extreme. This was likely a key factor that enabled strong and rapid recovery of nodule growth following relief of water stress. Biomass recovery was likewise robust, with production equal to the stress-free control, regardless of the intensity and duration of the stress. These results show that nodule growth in guar is highly sensitive to water stress, but the plant is resilient in maintaining nodules under water stress and recovering nodule growth upon moisture restoration.

中文翻译：

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瓜尔豆 [Cyamopsis tetragonoloba (L.) Taub.] 的耐旱性是否在地下延伸到根瘤？

在栽培瓜尔豆 [ Cyamopsis tetragonoloba(L.) Taub] 是一种耐旱豆科植物，生产者预计通过生物固氮 (BNF) 获得土壤 N 积分，但据推测，在干燥条件下根结瘤较差，并且对于根瘤如何从干旱胁迫中恢复知之甚少. 为了提供更好的见解，进行了两项温室研究以调查静态（两种土壤中 25%、50%、75% 和 100% 的 ET 置换）和动态（50%、75% 和 100%，加上 50% 和 75% 的释放量）在种植后 20 天和 30 天达到 100%）瓜尔胶水状态超过 50 天。水分胁迫通常对结核重量的负面影响最大，其次是地上生物量、生殖节点、高度，然后是结核数量。参数响应是线性或二次与 ET 置换和响应斜率不同土壤之间的结核重量和生物量。对结节数量的影响相对较小，这表明 BNF（结节）的基本机制在水分胁迫极端之前基本保持完好。这可能是在缓解水分胁迫后使结核生长强劲和快速恢复的一个关键因素。生物质回收同样强劲，无论压力的强度和持续时间如何，产量都等于无压力控制。这些结果表明，瓜尔胶的根瘤生长对水分胁迫高度敏感，但植物在水分胁迫下维持根瘤并在水分恢复后恢复根瘤生长方面具有弹性。这可能是在缓解水分胁迫后使结核生长强劲和快速恢复的一个关键因素。生物质回收同样强劲，无论压力的强度和持续时间如何，产量都等于无压力控制。这些结果表明，瓜尔胶的根瘤生长对水分胁迫高度敏感，但植物在水分胁迫下维持根瘤并在水分恢复后恢复根瘤生长方面具有弹性。这可能是在缓解水分胁迫后使结核生长强劲和快速恢复的一个关键因素。生物质回收同样强劲，无论压力的强度和持续时间如何，产量都等于无压力控制。这些结果表明，瓜尔胶的根瘤生长对水分胁迫高度敏感，但植物在水分胁迫下维持根瘤并在水分恢复后恢复根瘤生长方面具有弹性。