The objective of this study is to investigate whether pre-treatment (priming) of chlorophyll precursor 5-aminolevulinic acid (ALA) assumes a huge part in moderating harms caused by UV-B exposure on two varieties of Cajanus cajan L. seedlings namely BAHAR and KB-17. Healthy seeds were primed with two doses of ALA (lower dose: ALA₁; 25µM and higher dose: ALA₂; 100 µM) for 24 h at 25±2 °C and thereafter 17-day old seedlings were exposed to an enhanced dose of UV-B radiation i.e. 2.2 kJ m⁻²d⁻¹. Results showed that UV-B exposure significantly declined growth attributes, photosynthetic pigments (chlorophyll a, b and carotenoids contents), photosynthetic gas exchange characteristics (A, Ci, Gs, E, and WUE). This decrease was also accompanied by the accumulation of reactive oxygen species: superoxide radical (SOR; O₂˙ˉ), hydrogen peroxide (H₂O₂), and lipid peroxidation (MDA contents). The antioxidative enzyme activities: catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST), and peroxidase (POD) and non-enzymatic antioxidants: total phenolics content (TPC) and total flavonoids content (TFC) were increased. On contrary to this, damaging effects of UV-B radiations were markedly alleviated with the exogenous application (priming) of ALA by enhancing plant growth and growth-regulating parameters. Furthermore, ALA application decreased the UV-B induced oxidative stress in Cajanus cajan L. seedlings by further improving the activity of enzymatic and the contents of non-enzymatic antioxidants of test plant defense system. Furthermore, priming with ALA decreased the germination time and increased the germination index which additionally served as a significant purpose behind the improvement in the harvest quality and amount. The BAHAR variety of Cajanus cajan was discovered to be more tolerant against UV-B stress due to its more efficient defense system with a higher rate of antioxidant enzyme activities. On the other hand, KB-17 variety of Cajanus cajan was discovered to be sensitive against UV-B stress due to its feeble defense system with higher accumulation of reactive oxygen species. Thus, these findings suggest that priming of seeds with ALA act as a sustainable remedial strategy in reducing the hazardous effects of UV-B induced stress on crop productivity of Cajanus cajan seedlings by triggering the up-regulation of photosynthesis and antioxidant system to counterbalance the ROS-mediated damage to macromolecules.

这项研究的目的是调查叶绿素前体5-氨基乙酰丙酸（ALA）的预处理（启动）是否在减轻由UV-B暴露对两种Cajanus cajan L.幼苗BAHAR和幼苗造成的伤害中起很大作用。KB-17。在25±2°C下，用两剂ALA（低剂量：ALA ₁； 25µM；高剂量：ALA ₂； 100 µM）对健康种子进行整整24小时，然后将17天大的幼苗暴露于高剂量的ALA中。 UV-B辐射，即2.2 kJ m ^-2 d ^-1。结果表明，UV-B暴露显着降低了生长特性，即光合色素（叶绿素a，b和类胡萝卜素含量），光合气体交换特性（A，Ci，Gs，E和WUE）。这种减少还伴随着活性氧的积累：超氧自由基（SOR；O ₂），过氧化氢（H ₂ O ₂）和脂质过氧化（MDA含量）。抗氧化酶活性：过氧化氢酶（CAT），超氧化物歧化酶（SOD），谷胱甘肽-S-转移酶（GST），过氧化物酶（POD）和非酶抗氧化剂：总酚含量（TPC）和总黄酮含量（TFC）增加。与此相反，通过增强植物生长和生长调节参数，通过外源施用（引发）ALA可明显减轻UV-B辐射的破坏作用。此外，ALA的施用通过进一步提高试验植物防御系统的酶活性和非酶抗氧化剂的含量，降低了UV-B诱导的Cajanus cajan L.幼苗的氧化胁迫。此外，用ALA引发减少了发芽时间并增加了发芽指数，这在改善收割质量和收成量之后还具有重要作用。BAHAR的各种由于其更有效的防御系统和更高的抗氧化酶活性，Cajanus cajan被发现对UV-B胁迫更具耐受性。另一方面，由于其防御系统薄弱，活性氧种类较高，KB-17 Cajanus cajan变种被发现对UV-B胁迫敏感。因此，这些发现表明，通过触发光合作用和抗氧化剂系统的上调来平衡ROS ，用ALA引发种子可以作为可持续的补救策略，减少UV-B诱导的胁迫对Cajanus cajan幼苗的生产力的危害。介导的大分子损伤。