Salicylic acid improves physiological indicators of soursop irrigated with saline water

ABSTRACT Plants grown under salinity are subject to osmotic and ionic stresses that cause several physiological changes, so searching for strategies that minimize the deleterious effects is essential for the development of irrigated agriculture. In this context, the objective was to evaluate the effects of foliar applications of salicylic acid on the mitigation of the effects of salt stress on photosynthetic pigments and chlorophyll a fluorescence of soursop cv. Morada Nova. The study was conducted in a greenhouse, in a randomized block design and 5 × 4 factorial arrangement, with five values of electrical conductivity of irrigation water - ECw (0.8 - control, 1.6, 2.4, 3.2 and 4.0 dS m-1) and four concentrations of salicylic acid - SA (0, 1.2, 2.4 and 3.6 mM), with three replicates. Foliar application of salicylic acid at a concentration of 1.4 mM mitigated the effects of salt stress on chlorophyll a, chlorophyll b, chlorophyll total, and carotenoids of soursop when irrigated with water of up to 1.5 dS m-1. Salicylic acid at concentrations above 1.4 mM combined with irrigation with saline water intensified the deleterious effects on photosynthetic pigments. Chlorophyll a fluorescence was not influenced by salicylic acid sprays up to the concentration of 3.6 mM.摘要：盐胁迫下生长的植物会遭受渗透胁迫与离子胁迫，引发多种生理变化，因此探寻能够减轻其有害影响的策略，对灌溉农业的发展至关重要。在此背景下，本研究旨在评估叶面喷施水杨酸（salicylic acid, SA）对盐胁迫下‘莫拉达·诺瓦’（Morada Nova）品种刺果番荔枝光合色素及叶绿素a荧光的缓解效应。本研究于温室中开展，采用随机区组设计与5×4因子试验方案，设置5个灌溉水电导率（electrical conductivity of irrigation water, ECw）梯度：0.8 dS·m⁻¹（对照组）、1.6、2.4、3.2及4.0 dS·m⁻¹，以及4个水杨酸浓度梯度：0、1.2、2.4及3.6 mM，每组设置3次重复。当灌溉水的电导率不超过1.5 dS·m⁻¹时，喷施浓度为1.4 mM的水杨酸可减轻盐胁迫对刺果番荔枝叶绿素a、叶绿素b、总叶绿素及类胡萝卜素的不利影响。当水杨酸浓度高于1.4 mM且配合咸水灌溉时，会加剧对光合色素的有害影响。当水杨酸喷施浓度不超过3.6 mM时，叶绿素a荧光未受其显著影响。