Gas exchange, photosynthetic pigments, and photochemical efficiency of sesame under salt stress and phosphate fertilization

Abstract

Salt stress is a threat to irrigated agriculture, especially in semi-arid regions, as it can cause irreversible damage to the photosynthetic apparatus at any stage of plant development, reducing chlorophyll biosynthesis, which compromises the photochemical efficiency and the photosynthetic process of plants. In this respect, phosphorus fertilization stands out as an alternative to mitigate the effects of salt stress on plants. Therefore, the present study investigated the growth, gas exchange, photosynthetic pigments, and photochemical efficiency of sesame cv. BRS Seda irrigated with saline water and fertilized with phosphorus. The experiment was carried out in pots adapted as lysimeters in a greenhouse in Pombal - PB, Brazil. Treatments were distributed in randomized blocks and analyzed in a 5 × 4 factorial arrangement with five levels of electrical conductivity of water (ECw: 0.3, 1.1, 1.9, 2.7, and 3.5 dS m-1) and four phosphorus rates (40, 70, 100, and 130% of the recommended dose for pot trials), in three replicates. The 100% recommendation consisted of applying 300 mg P2O5 kg-1 of soil. Sesame growth, chloroplast pigments, and gas exchange decreased with water salinity above 0.3 dS m-1. The application of 100 and 130% of the recommended phosphorus rate minimized the effects of salt stress on CO2 assimilation rate and photosynthetic pigment synthesis. The increase from 40 to 130% of the recommended phosphorus rate did not change the photochemical efficiency of sesame cv. BRS Seda at 60 days after sowing.

Biomass, Gas Exchange and Production of Cherry Tomato Cultivated Under Saline Water and Nitrogen Fertilization

“…Plants subjected to irrigation with ECw of 4.3 dS m -1 reduced their E by 25.68% compared to those that received the lowest salinity level (Figure 3A). Due to the stomatal closure, there was lower transpiration of the plants, which may have resulted in lower absorption of water and nutrients, because transpiration generates a negative water pressure in the aerial part that can only be balanced through greater water absorption by the roots (FERNANDES et al, 2021;DIAS et al, 2022). Tatagiba et al (2014), evaluating the effect of different salt concentrations in the nutrient solution on tomato cultivation, also correlated the decrease in E of plants under the effect of higher salinity (150 mmol L -1 of NaCl) to stomatal closure.…”