The Use of Red Shade Nets Improves Growth in Salinized Pepper (Capsicum annuum L.) Plants by Regulating Their Ion Homeostasis and Hormone Balance

Abstract

The actual climate crisis scenario is aggravating the abiotic stress episodes that crop plants have to face. Salinity is one of the most important abiotic stresses directly impairing plant growth and productivity. Several strategies have been developed to minimize the negative effects of salinity in agricultural industry, mainly at the plant level, while management strategies, such us the control of microclimate conditions and light quality over plant canopy, have also been used. Indeed, shading plants with photoselective nets has been considered an efficient management strategy to modulate solar radiation to improve crop productivity. The aim of this work was to gain insights about the physiological factors underlying the salinity-alleviating effect of using red shading nets. For that, pepper plants (Capsicum annuum L.) were grown under control (0 mM NaCl) and moderate salinity (35 mM NaCl) conditions, with half of the plants covered with a red net (30% shading). The shoot growth impairment provoked by salinity was in part minimized by shading plants with red nets, which can be explained by their higher capacity to exclude Na+, control of K+ homeostasis and regulation of hormonal balance. Indeed, the concentrations of the most active cytokinin in pepper, trans-zeatin, as well as its metabolic precursor, zeatin riboside, increased in shaded plants, associated to shoot growth recovery and photosynthetic rate maintenance under salinity. Furthermore, the stress-related hormone abscisic acid (ABA) increased with salinity but in a lower extend in the plants shaded with red nets, suggesting a fine tune of stomata opening by ABA which, in crosstalk with salicylic acid increment, improved plant water relations. Likewise, the concentrations of gibberellins and the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid, also changed during salinity stress in shaded plants but those changes were uncoupled of growth responses as indicated by the principal component analysis and thus they seem to play a minor role. Our data demonstrate that shading pepper plants with red nets is an efficient management strategy to modulate microclimate conditions at crop level thus controlling the ion homeostasis and hormonal balance of the plant to cope with salinity stress. This is especially important due to the actual and expected changes of the global climatic conditions.

Physiological responses of the beet crop under agricultural environment and saline stress

“…Similar results were found by Gálvez et al (2020), in peppers shaded with red screens and not shaded under salt stress, where they found an increase in net photosynthetic rate under salinity conditions in shaded pepper plants.…”

“…The increase in A/E in water use in plants irrigated with low salinity water in the protected environment is possibly related to quantitative effects of water in the leaf and qualitative effects on osmotic potential, because the shaded plants are not directly exposed to the external environment (Gálvez et al, 2020). Furthermore, Fernandes et al (2016) describe that in saline environments, the A/E increase is a strategy of moderately tolerant crops, which aims to decrease high salt concentrations in the plant area.…”

“…Cultivation in a protected environment mitigates seasonal variations in production, reduces the adverse effects of excess rainfall, high incidence of radiation, and extremes of air temperature (Reis et al, 2012). The shading, partial or total, emerges as an alternative to minimize the damaging effects caused by salts on plants, due to the maintenance of photosynthetic mechanisms, CO2 assimilation and increased chlorophyll content (Aras et al, 2021;Gálvez et al 2020). Similarly, Nojosa Lessa et al (2022 on passion fruit and Pinho et al (2022) in the culture of Anadenanthera colubrina (Vell.)…”

Quantitative and qualitative responses of Euphorbia milii and Zamioculcas zamiifolia exposed to different levels of salinity and luminosity

“…Shading allows the modulation of a microclimate at the crop level, leading to lower water demand by the plant with the reduction of evapotranspiration, which results in lower salt stress, thus supporting the hypothesis raised in the present study by the results obtained. Shading also promotes control of ionic homeostasis and hormonal balance of the plant to cope with salt stress (GÁLVEZ et al, 2020).…”

The Interaction between Hydromulching and Arbuscular Mycorrhiza Improves Escarole Growth and Productivity by Regulating Nutrient Uptake and Hormonal Balance

“…Various studies have shown the implication of gibberellins (GAs) in the arbuscule formation in plant roots [ 18 ], while other early reports suggested that AMF are involved in the upregulation of GAs in tomato plants [ 19 ]. Cytokinins (CKs) have been considered an important hormone class related to growth enhancement in horticultural crops [ 20 , 21 ]. In this regard, it has been reported that a stronger increase in the shoot CK content was accompanied by elevated root CK levels associated with a positive plant growth response to AM symbiosis [ 22 , 23 ].…”