Growth and gas exchange of corn under salt stress and nitrogen doses

ABSTRACT The excess of salts can affect several processes in the crops, and nitrogen (N) can attenuate the depressive effect of salinity. The objective was to evaluate the influence of nitrogen doses on the growth and gas exchange of corn crop irrigated with saline water. The experiment was conducted from June to September 2019 at the University of International Integration of Afro-Brazilian Lusophony, Redenção, CE, Brazil. The experimental design was completely randomized, in a 2 x 3 factorial scheme (supply water of 0.3 dS m-1 and saline solution of 3.0 dS m-1) and three nitrogen doses, 0, 80, and 160 kg ha-1, corresponding to 0, 50, and 100% of the recommended dose respectively, with six repetitions. At 30 and 45 days after sowing (DAS), plant height, leaf area, number of leaves, photosynthesis, transpiration, and stomatal conductance were evaluated. Saline stress affects plant height, leaf area, photosynthesis, transpiration, and conductance at 30 DAS. The doses of 80 and 160 kg ha-1 provide greater performance in plant height, leaf area, photosynthesis, transpiration, and conductance at 30 DAS. The use of low salinity water and doses of 80 and 160 kg ha-1 were more efficient in terms of plant height, leaf area, photosynthesis, transpiration, and conductance at 45 DAS. The dose of 160 kg ha-1 of N attenuates the harmful effects of salts in AG 1051 hybrid maize plants, providing higher values of photosynthesis, transpiration, and stomatal conductance at 45 DAS when irrigated with water of 3.0 dS m-1.

摘要：盐害超标会对作物的多项生理过程造成不良影响，而氮素（N）可缓解盐分胁迫的抑制效应。本试验旨在探究施氮量对咸水灌溉玉米生长及气体交换参数的影响。试验于2019年6月至9月在巴西塞阿拉州雷登桑市非洲-巴西葡语国家国际融合大学开展。试验采用完全随机设计，设置2×3因子试验方案：灌溉水盐分梯度为0.3 dS·m⁻¹与3.0 dS·m⁻¹，施氮量设为0、80、160 kg·ha⁻¹，分别对应推荐施氮量的0%、50%、100%，每组设置6次重复。分别于播种后30天（Days After Sowing, DAS）和45天（DAS）测定株高、叶面积、叶片数、光合速率、蒸腾速率及气孔导度。播种后30天时，盐胁迫会显著降低株高、叶面积、光合速率、蒸腾速率及气孔导度；施氮量80和160 kg·ha⁻¹的处理组在该时期的相关指标表现更优。播种后45天时，采用低盐度灌溉水配合80、160 kg·ha⁻¹施氮量的处理，各项指标均表现更佳。对于AG 1051杂交玉米品种，当采用3.0 dS·m⁻¹的咸水灌溉时，施氮量160 kg·ha⁻¹可缓解盐分胁迫的有害影响，在播种后45天时可提升光合速率、蒸腾速率及气孔导度的数值。