Gas Exchange and Hydroponic Production of Zucchini Under Salt Stress and H2o2 Application

Abstract

Knowledge about the effect of chemical conditioners on the reduction of the deleterious effects caused by salinity on crops is of great importance for the expansion of the cultivation of vegetable crops such as zucchini in the semi-arid region of the Northeast. In this context, the objective of the present study was to evaluate the effect of the foliar application of hydrogen peroxide as a mitigator of salt stress on the gas exchange, production, and postharvest fruit quality of zucchini cultivated in a hydroponic system. The study was conducted in NFT-type (Nutrient Film Technique) hydroponic system in a greenhouse, in Pombal — PB, Brazil. The experimental design was completely randomized, in a 4 × 4 factorial scheme, corresponding to four levels of electrical conductivity of the nutrient solution - ECns (2.1 (control); 3.6; 5.1 and 6.6 dS m−1), and four concentrations of hydrogen peroxide - H2O2 (0; 20; 40 and 60 μM), with three replicates. Nutrient solution with electrical conductivity above 2.1 dS m−1 caused a reduction in gas exchange and the total number of fruits of zucchini. An increase in nutrient solution salinity levels increased the total soluble solids content of the fruits and the initial fluorescence of zucchini. Under conditions of nutrient solution salinity above 2.1 dS m−1, hydrogen peroxide could not mitigate the effects of salt stress. Application of 20 μM of H2O2 when the plants were grown in a nutrient solution of 2.1 dS m−1 promoted higher total fruit weight and basal diameter of the fruits.

Peróxido de hidrogênio na mitigação do estresse salino em pimentão

“…The reduction in E is directly related to partial stomatal closure, since less opening of the stomata will cause transpiration to decrease, restricting the loss of water from the Chl t iCE Ramos et al (2022) worked with the passion fruit crop (Passiflora edulis Sims) under ECw ranging from 0.6 to 3.0 dS m -1 and foliar application of H 2 O 2 and also found beneficial effects on growth and photosynthetic pigments when the plants received the H 2 O 2 concentration of 15 µM. Dantas et al (2022) studied Italian zucchini (Cucurbita pepo L.) under ECw ranging from 2.1 to 6.6 and exogenous application of H 2 O 2 at 20 µM and described similar findings for growth rates and gas exchange. These authors attributed these results to the action of hydrogen peroxide as a signaling molecule that regulates several metabolic pathways, including responses to salt stress.…”

“…The H 2 O 2 concentrations used in this study were adapted from the work carried out with Italian zucchini cv. Caserta (Dantas et al, 2022).…”

“…Research has been done to determine the effects of foliar application of H 2 O 2 on the acclimatization of crops to salt stress in various crops, e.g. passion fruit (Andrade et al, 2022), tomato (Nazir et al, 2021), and in Italian zucchini (Dantas et al, 2022). These studies found that the H 2 O 2 concentrations of 20, 0.1, and 20 µM, respectively, alleviated the deleterious effects of salt stress on photochemical and photosynthetic efficiency, in addition to altering the chloroplast ultrastructure and the stomatal behavior of the plants.…”

“…photosynthetic pigments when the plants received the H 2 O 2 concentration of 15 µM Dantas et al (2022). …”

Use of hydrogen peroxide in acclimatization of melon to salinity of irrigation water

“…The salinity levels were based on the threshold water salinity of melon (2.2 dS m -1 ) (Ayers & Westcot, 1999), selecting a low salinity level and another level above the threshold. Due to the absence of research on H 2 O 2 in melon, the concentrations used in the present assay were based on studies carried out with zucchini (Dantas et al, 2022) with adaptations.…”