Influence of Salicylic Acid Concentrations and Spraying Times on Growth and Physiology of Eggplant
Pages 1-17
https://doi.org/10.66224/gppj.3.2.1
Seyed Mohammad Javad Arvin, Ehsan Salari, Hamid Reza Soufi
Abstract Salicylic acid (SA) is a key signaling molecule that regulates plant growth, flowering, and responses to abiotic and biotic stresses. This study evaluated the effects of different SA concentrations (0, 0.5, and 1.0 mM) and application frequencies (once and twice) on the growth, pigment composition, and yield of eggplant (Solanum melongena L.) under field conditions during the 2023–2024 growing season. Eggplant seeds were sown in a cocopeat and perlite growing medium at a ratio of 3:1 and the seedlings were watered daily in greenhouse. Foliar spraying was done in two stages before transplanting (four-leaf stage) in greenhouse and before flowering in farm. After the first foliar spray, the eggplant seeds were transferred to the field and the plants were irrigated every three days throughout the growth period. A factorial experiment arranged in a completely randomized design revealed significant SA effects on most measured traits, with 0.5 mM producing the most favorable outcomes. Compared with the control, this treatment increased relative water content by 11%, reduced electrolyte leakage by 30–35%, and enhanced SPAD values, total chlorophyll, and carotenoid contents by up to 120%. Plant height, fruit number, and total yield rose by 38.1%, 85.7%, and 88.6%, respectively. Two applications further improved growth and yield compared to a single spray, indicating that repeated applications amplify the physiological benefits of SA. In contrast, 1.0 mM SA provided no additional improvement, suggesting a threshold beyond which inhibitory effects are not observed. The observed enhancements were associated with improved water balance, enhanced photosynthetic efficiency, and increased membrane integrity. Overall, applying 0.5 mM SA twice during both the vegetative and reproductive stages proved to be an optimal, low-cost, and environmentally safe strategy for enhancing eggplant growth and productivity. Future studies should elucidate SA’s molecular mechanisms and interactions with other biostimulants and stresses to optimize its use across crops and production systems.


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