Continual water loss through transpiration and evaporation as a result of drought leads to stomatal closure and subsequently the overproduction of reactive oxygen species (ROS) which causes oxidative stress in plants. A set of biochemical mechanisms are concurrently triggered to set in motion a defence line, which, among others, involves the synthesis of antioxidant and osmoprotectants compounds. These play a protective role to overcome stress. The objective of this study was to evaluate the effect of varying moisture regimes on the accumulation patterns and concentration of phenolic compounds, antioxidant activity and osmolyte proline in Moringa oleifera. The study was conducted in a greenhouse (25 ± 3°C) at ARC, Roodeplaat in Pretoria, South Africa. Moringa oleifera seeds were individually planted in pots using hygro-mix as the growth media. The experiment was laid out in a completely randomised design with four watering regimes of 100%, 75%, 50% and 35% field water capacity (FWC) each with 50 replicate plants. Proline content increased with the severity of moisture stress in all plant parts (root, stem and leaf), with the leaves under severe stress (35% FWC) recording the highest concentration. Folin C, aluminium chloride and butanol-HCL assays were used to determine total phenolic, flavonoid and condensed tannin concentrations, respectively, in the different plant parts at different growth stages and harvests. The concentrations of these secondary metabolites were consistently higher in leaves and increased with an increase in moisture stress. The highest concentrations were recorded in the second harvest under severe stress (35% FWC) for total phenolics and proanthocyanidins at 50% FWC for flavonoids . Leaves showed a better antioxidant ability and antioxidant activities increased with drought progression as determined by FRAP while DPPH radical scavenging and the β-carotene-linoleic acid model system did not show a distinct trend in antioxidant activities in relation to the different moisture levels. Based on the results of this study, antioxidant and osmoprotectant compounds as well as antioxidant activity appears to increase corresponding to severity of moisture stress in all plant parts at both harvests. This trend suggests that M. oleifera employs these mechanisms in adapting to moisture stress.

干旱导致的蒸腾作用和蒸发作用造成的持续水分流失导致气孔关闭，进而导致活性氧（ROS）过量产生，从而导致植物产生氧化胁迫。同时触发了一组生化机制以启动防御线，该防御线尤其涉及抗氧化剂和渗透保护剂化合物的合成。这些起到克服压力的保护作用。这项研究的目的是评估不同水分制度对辣木中酚类化合物的积累模式和浓度，抗氧化活性和渗透压脯氨酸的影响。这项研究是在南非比勒陀利亚Roodeplaat ARC的温室（25±3°C）中进行的。辣木将种子分别种植在使用潮气混合作为生长培养基的盆中。实验采用完全随机的设计进行，采用100个，75％，50％和35％的田间持水量（FWC）的四个浇水方案，每个浇水方案均带有50个重复植物。脯氨酸含量随所有植物部分（根，茎和叶）中水分胁迫的严重程度而增加，其中处于严重胁迫下（35％FWC）的叶片记录到最高浓度。使用Folin C，氯化铝和丁醇-HCL测定法分别确定了在不同生长阶段和收获期的不同植物部位中总酚，类黄酮和缩合单宁的浓度。这些次生代谢产物的浓度在叶片中始终较高，并随着水分胁迫的增加而增加。在第二次收割时，总酚和原花青素在重度胁迫下（35％FWC）记录了最高浓度，而黄酮类化合物在50％FWC下记录了最高浓度。FRAP测定表明，叶片表现出更好的抗氧化能力，并且抗氧化活性随着干旱的进行而增加，而DPPH自由基清除和β-胡萝卜素-亚油酸模型体系并未显示出与水分含量相关的明显趋势。根据这项研究的结果，在两个收获季节，抗氧化剂和渗透保护剂化合物以及抗氧化剂活性似乎都随着植物所有部位水分胁迫的严重性而增加。这种趋势表明 FRAP测定表明，叶片表现出更好的抗氧化能力，并且抗氧化活性随干旱的进行而增加，而DPPH自由基清除和β-胡萝卜素-亚油酸模型体系并未显示出与水分含量相关的明显趋势。根据这项研究的结果，在两个收获季节，抗氧化剂和渗透保护剂化合物以及抗氧化剂活性似乎都随着植物所有部位水分胁迫的严重性而增加。这种趋势表明 FRAP测定表明，叶片表现出更好的抗氧化能力，并且抗氧化活性随着干旱的进行而增加，而DPPH自由基清除和β-胡萝卜素-亚油酸模型体系并未显示出与水分含量相关的明显趋势。根据这项研究的结果，在两个收获季节，抗氧化剂和渗透保护剂化合物以及抗氧化剂活性似乎都随着植物所有部位水分胁迫的严重性而增加。这种趋势表明 在两个收获期，所有植物部分的抗氧化剂和渗透保护剂化合物以及抗氧化剂活性似乎都随着水分胁迫的严重性而增加。这种趋势表明 在两个收获期，所有植物部分的抗氧化剂和渗透保护剂化合物以及抗氧化剂活性似乎都随着水分胁迫的严重性而增加。这种趋势表明油松使用这些机制来适应水分胁迫。