GERMINATION AND INITIAL GROWTH OF COWPEA CULTIVARS UNDER OSMOTIC STRESS AND SALICYLIC ACID

ABSTRACT Cowpea is one of the major food crops in Northeast Brazil, where it is commonly cultivated in the semi-arid regions with limited water availability. It is important to study the elicitors associated with cowpea to mitigate any deleterious effects of abiotic stress on the initial establishment of this crop. In this study, we aimed to evaluate the morphophysiological changes in cowpea cultivars under osmotic stress with seeds soaked in salicylic acid. The germination test was conducted in B.O.D germination chambers. The seeds of three cowpea cultivars: BRS Tumucumaque, BRS Aracê, and BRS Guariba, were germinated at five osmotic potentials (0.0; -0.2; -0.4; -0.6, and -0.8 MPa) after three pre-treatments: pre-soaking in deionized water, pre-soaking in salicylic acid, and without pre-soaking. The following parameters were evaluated: germination, germination speed index, seedling height, total phytomass, contents of chlorophyll ‘a’ and ‘b’, carotenoid content, electrolyte leakage, water content, and proline content. Our results indicate that salicylic acid promotes reduction in the harmful effects of abiotic stress, which is reflected in the increase in germination percentage, seedling height, and chlorophyll and carotenoid content as well as in the adjustment of electrolyte leakage and increase in proline content under induced water stress conditions. The cultivar BRS Guariba proved to be more tolerant to water deficit during germination and initial growth stages, when the seeds were treated with salicylic acid (1 mM).

摘要 豇豆（Cowpea）是巴西东北部的主要粮食作物之一，该区域多为半干旱环境，水资源匮乏，常被种植于此。探究与豇豆相关的激发子（elicitors），以缓解非生物胁迫（abiotic stress）对该作物初始建植的不利影响，具有重要研究意义。本研究旨在评估经水杨酸（salicylic acid）浸种处理的豇豆品种在渗透胁迫（osmotic stress）下的形态生理变化。发芽试验在B.O.D发芽箱中开展。本试验选取3个豇豆品种：BRS Tumucumaque、BRS Aracê、BRS Guariba，分别经去离子水浸种预处理、水杨酸浸种预处理及不做预处理三种方式处理后，在5个渗透势梯度（0.0、-0.2、-0.4、-0.6及-0.8 MPa）下进行发芽试验。本试验测定的指标包括：发芽率、发芽速率指数、幼苗株高、总生物量、叶绿素a与叶绿素b含量、类胡萝卜素含量、电解质渗漏率、水分含量及脯氨酸含量。研究结果表明，水杨酸可减轻非生物胁迫的有害影响，具体表现为：在人工诱导水分胁迫条件下，发芽率、幼苗株高、叶绿素及类胡萝卜素含量均有所提升，同时电解质渗漏率得到调控，脯氨酸含量亦显著增加。经1 mM水杨酸处理的种子中，品种BRS Guariba在发芽及初期生长阶段对水分亏缺的耐受性更强。