Silicon foliar application attenuates the effects of water suppression on cowpea cultivars

Abstract

Silicon and proline play important physiological, metabolic and functional roles in plants, especially under water deficit conditions. Their application can mitigate the adverse effects of stress in crops by increasing water use efficiency and antioxidant activity. The objective of this study was to evaluate silicon (Si) as attenuator of the effects of water deficit on cowpea cultivars, through physiological, biochemical and growth indicators. The experimental design was randomized blocks with four cultivars (BRS Guariba, BRS Itaim, BRS Aracê and BRS Rouxinol) and four irrigation treatments associated or not with Si application (W100 - 100% ETo; W50 - 50% ETo; W50+100Si and W50+200Si, with 100 and 200 mg L-1 silicon, respectively), in a 4 x 4 factorial scheme, with five replicates. Leaf water potential, proline concentration, antioxidant enzymes and growth indicators were evaluated in cowpea plants. Under water deficit conditions, all cultivars showed reductions in leaf water potentials, which compromised plant growth. However, Si applications of 200 mg L-1 in the cultivar BRS Guariba and 100 and 200 mg L-1 in the cultivar BRS Itaim minimized the effects of stress, by increasing leaf water potential and the activity of the enzyme ascorbate peroxidase, in both cultivars, besides increasing proline concentration in the former and reducing proline concentration in the latter, which ensured the maintenance of growth. Despite the no contribution to the increase in water potential, Si applications of 100 and 200 mg L-1 in BRS Rouxinol and BRS Aracê, respectively, reduced the deleterious effects of the stress on their growth by regulating the enzymatic metabolism and proline.

Hydrogen sulfide, potassium phosphite and zinc sulfate as alleviators of drought stress in sunflower plants

“…The proline (Pro) leaf concentration was higher in the WD condition and differed only as a function of FC (Figure 1d). The general strategy of plants for maintaining water in WD conditions is an osmotic adjustment, due to the accumulation of osmolytes (Chaumont;Tyerman, 2014;Nawaz et al, 2016;Silva et al, 2019). However, there was no differential osmotic adjustment due to the spraying of KPhi, NaHS, and ZS in the present study, which was observed in the results of osmotic potential (Ψ S ) ( Figure 1c), with only an effect of the imposed water regimes.…”

Water restriction in cowpea plants [Vigna unguiculata (L.) Walp.]: Metabolic changes and tolerance induction

“…Proline accumulation is compatible with osmoprotective strategies, that is, it is regulated between source and sink organs in the plant similarly, regardless of the genotype (Zegaoui et al, 2017). In cowpea under water restriction, proline synthesis induction can increase the osmolyte concentration by more than 100% (Silva et al, 2019;Andrade et al, 2021), which confirms its importance in maintaining the cell water status of this species.…”

“…In cowpea, the water potential of tissue is reduced under water deficit conditions, which decreases cell turgor (Goufo et al, 2017;Merwad et al, 2018;Silva et al, 2019). During water stress, the decline of leaf water potential alters the permeability and sustainability of the membranes and interferes with the regular plants' functions mainly due to osmotic and redox system imbalance, which causes losses in the developing organs during the growth stage (Silva et al, 2019). As a result of the oxidative stress, an increment in lipid peroxidation is observed in cowpea under water restriction, mainly due to the overproduction of hydrogen peroxide (H 2 O 2 ).…”

“…•-) into H 2 O 2 , ascorbate peroxidase (APX, EC 1.11.1.11) and catalase (CAT), which act in hydrogen peroxide (H 2 O 2 ) removal. In addition, guaiacol peroxidase (POX, EC 1.11.1.7) and glutathione reductase (GR, EC 1.6.4.2) control ROS levels, at suitable concentrations for cellular function, and promote important changes in the water deficit tolerance mechanism (Dutra et al, 2017;Carvalho et al, 2019;Silva et al, 2019;Andrade et al, 2021) (Figure 1).…”

“…It is important to highlight that the non-enzymatic components, such as flavonoids and proline, have antioxidant activities in cowpea under water deficit, becoming an integral part of the adaptive response, rather than just indicators of stress (Goufo et al, 2017;Silva et al, 2019;Andrade et al, 2021). Proline accumulation is compatible with osmoprotective strategies, that is, it is regulated between source and sink organs in the plant similarly, regardless of the genotype (Zegaoui et al, 2017).…”