Gas exchange and growth of zucchini crop subjected to salt and water stress

ABSTRACT Semi-arid regions present the inherent problem of accumulation of salts in the soil due to the use of brackish water for irrigation, and water deficit compromises the growth and physiological indices of crops. This study evaluated the effect of salt and water stress on growth and gas exchange in the zucchini cv. Caserta crop. The study was conducted at the University of International Integration of Afro-Brazilian Lusophony, Redenção, Ceará State, Brazil. The experimental design was completely randomized, in a 5 × 2 factorial scheme with five levels of electrical conductivity of the irrigation water - ECw (0.5, 1.0, 1.5, 2.0, and 2.5 dS m-1) and two water regimes (50 and 100% of the potential crop evapotranspiration - ETc), with five replicates. At 36 days after sowing, the following traits were evaluated: CO2 assimilation rate, transpiration, stomatal conductance, internal carbon concentration, leaf temperature, relative chlorophyll index, and water use efficiency. At 45 days after sowing, the plant height, stem diameter, number of leaves, and leaf area were also evaluated. The use of brackish water (1 to 2.5 dS m-1) reduced the growth parameters of zucchini cv. Caserta. The increase in ECw caused a decline in the physiological traits. Under 100% ETc, higher values of CO2 assimilation rate, transpiration, and instantaneous water use efficiency were recorded, and there was 50% ETc for internal carbon concentration, even with the increase in ECw.

摘要：半干旱地区因使用咸水灌溉，存在土壤盐分累积的固有问题，而水分亏缺会损害作物生长与生理指标。本研究以‘Caserta’品种西葫芦为试材，评估盐分与水分胁迫对其生长及气体交换参数的影响。试验于巴西塞阿拉州雷登松市的巴非葡语国家国际融合大学（University of International Integration of Afro-Brazilian Lusophony）开展，采用完全随机设计，设置5×2因子试验方案：灌溉水电导率（electrical conductivity of the irrigation water, ECw）设5个水平（0.5、1.0、1.5、2.0、2.5 dS·m⁻¹），供水制度设2个水平（分别为作物潜在蒸散量（crop potential evapotranspiration, ETc）的50%和100%），每个处理重复5次。播种后36天，测定以下指标：二氧化碳同化速率、蒸腾速率、气孔导度、胞间二氧化碳浓度、叶温、相对叶绿素指数及水分利用效率。播种后45天，额外测定株高、茎粗、叶片数及叶面积。研究结果表明，使用电导率1~2.5 dS·m⁻¹的咸水灌溉会降低‘Caserta’品种西葫芦的生长参数；灌溉水电导率升高会导致生理指标下降。在100%ETc供水条件下，二氧化碳同化速率、蒸腾速率及瞬时水分利用效率均呈现更高值；而即便灌溉水电导率升高，50%ETc供水条件下的胞间二氧化碳浓度仍维持相对稳定。