Gas exchanges and growth of passion fruit seedlings under salt stress and hydrogen peroxide1

ABSTRACT The semi-arid region of the Brazilian Northeast has adequate edaphoclimatic conditions for the passion fruit production, but the water used for irrigation commonly has high concentrations of salts that are harmful to the plant growth and development. A previous supply of hydrogen peroxide induces the acclimation of plants under saline stress conditions, reducing deleterious effects on their growth and physiology. This study aimed to evaluate the gas exchanges and growth of passion fruit as a function of irrigation with saline water and exogenous application of hydrogen peroxide. The experiment was carried out under greenhouse conditions, using a randomized block design, in a 4 x 4 factorial arrangement, being four levels of irrigation water electrical conductivity (0.7 dS m-1, 1.4 dS m-1, 2.1 dS m-1 and 2.8 dS m-1) and four hydrogen peroxide concentrations (0 µM, 25 µM, 50 µM and 75 µM), with four replicates and two plants per plot. The hydrogen peroxide application attenuated the deleterious effects of the irrigation water salinity on transpiration, CO2 assimilation rate, internal carbon concentration, plant height and leaf area of yellow passion fruit, at 60 days after sowing, with the concentration of 25 µM being the most efficient. Irrigation using water with electrical conductivity above 0.7 dS m-1 negatively affects the gas exchanges and growth of passion fruit, being the stomatal conductance and leaf area the most sensitive variables to the salt stress.

摘要：巴西东北部半干旱地区具备西番莲（passion fruit）种植所需的适宜土壤气候条件，但灌溉用水通常含盐量较高，会对植株生长发育造成危害。预先施用过氧化氢（hydrogen peroxide）可诱导植物在盐胁迫条件下产生驯化效应，减轻其生长与生理过程受到的有害影响。本研究旨在评估不同盐度灌溉水与外源施加过氧化氢对西番莲气体交换特性及生长状况的影响。本试验于温室条件下开展，采用随机区组设计，设置4×4因子试验方案，包含4个灌溉水电导率（electrical conductivity）梯度（0.7 dS m⁻¹、1.4 dS m⁻¹、2.1 dS m⁻¹及2.8 dS m⁻¹）与4个过氧化氢浓度梯度（0 µM、25 µM、50 µM及75 µM），每个处理设置4次重复，每小区种植2株植株。播种后60天的测定结果显示，施加过氧化氢可缓解灌溉水盐分对西番莲蒸腾速率、CO₂同化速率、胞间二氧化碳浓度、株高及叶面积产生的不利影响，其中25 µM浓度的处理效果最优。当灌溉水电导率高于0.7 dS m⁻¹时，会对西番莲的气体交换特性与生长产生负面影响，其中气孔导度与叶面积对盐胁迫最为敏感。