Gas exchange, growth and quality of guava seedlings under salt stress and salicylic acid

Abstract

Guava is a popular Brazilian fruit that is widely produced in Northeastern Brazil, a region with water sources that commonly have high concentrations of salts. Thus, searching for techniques that allow the management of these waters is extremely important for the expansion of irrigated agriculture. In this context, salicylic acid is a phytohormone that can contribute to reducing the effects of salt stress on plants. Given the above, this study evaluated the effect of foliar application of salicylic acid at different concentrations in the mitigation of salt stress on gas exchange, growth, and quality of 'Paluma' guava seedlings. The experiment was conducted in a greenhouse, in Campina Grande - PB, Brazil, using a randomized block design in a 5 × 5 factorial arrangement, corresponding to five levels of electrical conductivity of water (0.6, 1.5, 2.4, 3.3, and 4.2 dS m-1) and five concentrations of salicylic acid (0 - Control; 0.8, 1.6, 2.4, and 3.2 mM), with four replicates and two plants per plot. Foliar application of salicylic acid at a concentration of up to 1.4 mM reduced the deleterious effects of salt stress on the instantaneous water use efficiency of 'Paluma' guava seedlings at 180 days after sowing. The concentrations of salicylic acid applied via foliar did not mitigate the harmful effects of irrigation water salinity on the growth and quality of 'Paluma' guava seedlings.
 Keywords: Abiotic stress, Psidium guajava L., water scarcity.

Production of guava seedlings with increasing water salinity and nitrogenpotassium fertilizations

“…There was a significant effect (p<0.01) of irrigation water salinity on the RGR LA from 85 to 125 DAS, with a quadratic response according to the regression equation (Figure 4C), whose highest (0.018 cm 2 cm -2 per day) and lowest (0.012 cm 2 cm -2 per day) values were obtained, respectively, with the ECw levels of 1.1 and 3.5 dS m -1 . The inhibition in the relative growth rate of leaf area in guava seedlings could be associated with the decrease in the number of leaves and leaf area (Figures 2A and 3A), as the reduction of the transpiration surface is a plant adaptation mechanism to reduce transpiration rates and mitigate the stress caused by excess salts (XAVIER et al, 2022). Abrantes et al (2017) observed a decreasing linear effect on the RGR LA with the increase in ECw from 50 to 100 days after emergence, causing a 6.85% decrease per unit increase in ECw.…”

“…Seedlings irrigated with 3.5 dS m -1 showed a 29.44% reduction in DMS compared to those irrigated with the lowest salinity level. The high NaCl concentrations in the root zone possibly increased the uptake of these salts in the mesophyll, decreasing the uptake of other ions, causing toxicity by specific ions, leading to the appearance of physiological and nutritional damage in the crops (XAVIER et al, 2022), and, consequently, affecting biomass production. For the same cultivar, Silva et al (2015) Figure 5B shows that the DMS was lower in plants fertilized with the C4 combination, whereas the C1 combination resulted in a higher DMS increase.…”

Formation of guava seedlings under irrigation with water of different cationic natures and salicylic acid

“…Lima et al (2019), when evaluating gas exchange in castor bean plants as a function of the cationic nature of irrigation water (S1-Control; S2 -Na + ; S3 -Ca 2+ ; S4 -Na + + Ca 2+ ; S5 -K + , and S6 -Na + + Ca 2+ + Mg 2+ ), also observed that, except for waters containing potassium and salinity of 4.5 dS m -1 , caused a decrease in stomatal conductance, regardless of the cationic nature of the water. In another study, Xavier et al (2022) evaluated the gas exchange of 'Paluma' guava seedlings as a function of irrigation with saline waters (ECw: 0.6 to 4.2 dS m -1 ) prepared with Na + +Ca 2+ +Mg 2+ in the equivalent proportion of 7:2:1 and found that stomatal conductance reduced quadratically with the increase in water salinity levels, at 180 days after sowing.…”

“…The quantitative and qualitative reduction of water sources has led to the search for strategies aimed at more efficient use of water, as well as rational use of waters considered of inferior quality since using saline water in agriculture is a necessity in semi-arid regions. In this context, several authors have studied the effect of irrigation with water of different salinity levels on the cultivation of guava (SOUZA et al, 2016;BEZERRA et al, 2018;XAVIER et al, 2022;LACERDA et al, 2022a); however, these studies are restricted to the use of waters with different levels of electrical conductivity, making it imperative to conduct new studies, particularly to assess the use of waters with different cationic natures on the guava crop in the seedling formation phase.…”

“…Among the strategies that allow mitigating the effects of salt stress on plants, a prominent one is the use of elicitor substances, such as salicylic acid, an important signaling molecule that mitigates the adverse effects of salt stress on plants through the improvement in physiological and metabolic processes, resulting in their acclimatization to abiotic stresses, including salt stress (SILVA et al, 2020;LACERDA et al, 2022b;XAVIER et al, 2022).…”