Department of Horticultural Sciences and Engineering, Faculty of Agricultural Sciences and Engineering, Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran.
Department of Horticultural Sciecne, Faculty of Agriculture, University of Maragheh, Maragheh, Iran.
Sci Rep. 2024 Jul 10;14(1):15883. doi: 10.1038/s41598-024-66677-8.
Salinity stress poses a significant treat to crop yields and product quality worldwide. Application of a humic acid bio stimulant and grafting onto tolerant rootstocks can both be considered sustainable agronomic practices that can effectively ameliorate the negative effects of salinity stress. This study aimed to assess the above mentioned ameliorative effects of both practices on cucumber plants subjected to saline environments. To attain this goal a factorial experiment was carried out in the form of a completely randomized design with three replications. The three factors considered were (a) three different salinity levels (0, 5, and 10 dS m of NaCl), (b) foliar application of humic acid at three levels (0, 100, and 200 mg L), and (c) both grafted and ungrafted plants. Vegetative traits including plant height, fresh and dry weight and number of leaf exhibited a significant decrease under increasing salinity stress. However, the application of humic acid at both levels mitigated these effects compared to control plants. The reduction in relative water content (RWC) of the leaf caused by salinity, was compensated by the application of humic acid and grafting. Thus, the highest RWC (86.65%) was observed in grafting plants with 0 dS m of NaCl and 20 mg L of humic acid. Electrolyte leakage (EL) increased under salinity stress, but the application of humic acid and grafting improved this trait and the lowest amount of EL (26.95%) was in grafting plants with 0 dS m of NaCl and 20 mg L of humic acid. The highest amount of catalase (0.53 mmol HO g fw min) and peroxidase (12.290 mmol HO g fw min) enzymes were observed in the treatment of 10 dS m of NaCl and 200 mg L humic acid. The highest amount of total phenol (1.99 mg g FW), total flavonoid (0.486 mg g FW), total soluble carbohydrate (30.80 mg g FW), soluble protein (34.56 mg g FW), proline (3.86 µg g FW) was in grafting plants with 0 dS m of NaCl and 200 mg L of humic acid. Phenolic acids and phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) enzymes increased with increasing salinity and humic acid levels. Contrary to humic acid, salt stress increased the sodium (Na) and chlorine (Cl) and decreased the amount of potassium (K) and calcium (Ca) in the root and leaf of ungrafted cucumber. However, the application 200 mg L humic acid appeared to mitigate these effects, thereby suggesting a potential role in moderating physiological processes and improving growth of cucumber plants subjected to salinity stress. According to the obtained results, spraying of humic acid (200 mg L) and the use of salt resistant rootstocks are recommended to increase tolerance to salt stress in cucumber. These results, for the first time, clearly demonstrated that fig leaf gourd a new highly salt-tolerant rootstock, enhances salt tolerance and improves yield and quality of grafted cucumber plants by reducing sodium transport to the shoot and increasing the amount of compatible osmolytes.
盐胁迫对全球作物产量和产品质量构成重大威胁。施用腐植酸生物刺激素和嫁接耐盐砧木均可被视为可持续的农业实践，可以有效改善盐胁迫的负面影响。本研究旨在评估这两种方法对黄瓜植株在盐环境下的上述改良效果。为了达到这个目的，采用完全随机设计的三因子析因试验，设三个重复。三个考虑的因素是：(a) 三种不同的盐度水平（0、5 和 10 dS m 的 NaCl）；(b) 叶面喷施腐植酸的三个水平（0、100 和 200 mg L）；(c) 嫁接和未嫁接的植株。在盐胁迫下，植物的生长特性包括株高、鲜重和干重以及叶片数量均显著下降。然而，与对照植株相比，腐植酸在两个水平上的应用减轻了这些影响。盐胁迫导致叶片相对水含量（RWC）下降，但腐植酸和嫁接的应用补偿了这种下降。因此，在 0 dS m NaCl 和 20 mg L 腐植酸处理下，嫁接植株的 RWC 最高（86.65%）。电解质渗漏（EL）在盐胁迫下增加，但腐植酸和嫁接的应用改善了这一特性，在 0 dS m NaCl 和 20 mg L 腐植酸处理下，嫁接植株的 EL 最低（26.95%）。过氧化氢酶（0.53 mmol HO g fw min）和过氧化物酶（12.290 mmol HO g fw min）的最高酶活出现在 10 dS m NaCl 和 200 mg L 腐植酸处理中。总酚（1.99 mg g FW）、总类黄酮（0.486 mg g FW）、总可溶性碳水化合物（30.80 mg g FW）、可溶性蛋白（34.56 mg g FW）、脯氨酸（3.86 μg g FW）的最高含量出现在 0 dS m NaCl 和 200 mg L 腐植酸处理下的嫁接植株中。酚酸和苯丙氨酸解氨酶（PAL）和多酚氧化酶（PPO）酶随着盐度和腐植酸水平的增加而增加。与腐植酸相反，盐胁迫增加了未嫁接黄瓜根和叶中的钠（Na）和氯（Cl）含量，而降低了钾（K）和钙（Ca）的含量。然而，施用 200 mg L 腐植酸似乎减轻了这些影响，因此在调节生理过程和提高耐盐性黄瓜植株的生长方面可能具有潜在作用。根据获得的结果，建议喷洒腐植酸（200 mg L）和使用耐盐砧木来提高黄瓜对盐胁迫的耐受性。这些结果首次清楚地表明，印度榕叶葫芦是一种新的高度耐盐砧木，通过减少向地上部运输钠和增加相容性渗透物的量，增强了盐胁迫耐受性，并提高了嫁接黄瓜植株的产量和品质。
