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

Sulfeto de hidrogênio, fosfito de potássio e sulfato de zinco como aliviadores do estresse por seca em plantas de girassol

ABSTRACT

Drought is the most harmful environmental factor crop productivity. Some chemicals are used in agriculture to mitigate the damage from this stress on plants. Therefore, we examined whether the spraying of zinc sulfate (ZS), potassium phosphite (KPhi) and the hydrogen sulfide (H₂S) donor sodium hydrosulfide (NaHS) would mitigate the deleterious effects of water deficit on sunflower plants by analyzing physiological and biometric characteristics. The experiment was carried out in a greenhouse using a randomized block design with five replications. The treatments were arranged in a 4 x 2 factorial scheme: [Factor A (Alleviators)] - spraying of KPhi (0.5 L ha^-1), ZS (3.2 kg ha^-1), NaHS (1.2 g ha^-1), and water; [Factor B (substrate humidity, SH)] - 100% (well irrigated) and 30% (water deficit, WD) of field capacity. Under WD conditions, alleviators led to the maintenance of higher values of water potential (Ψ_W), a lower content of leaf malonaldehyde (MDA), and increased activity of the antioxidant enzyme peroxidase (POX), except for ZS. However, leaf osmotic potential, proline concentration, variables related to gas exchange and chlorophyll a fluorescence, and biometric characteristics differed only according to the SH factor. The results of Ψ_W and MDA for sunflower plants under WD are indicative of the mitigating capacity of ZS, KPhi, and H₂S. Thus, the spraying of these compounds on sunflower plants mitigates the effects of WD, acting specifically in physiological processes related to antioxidant responses and in the maintenance of water in leaf tissues.

Index terms:
Photosynthesis; water deficit; malonaldehyde; leaf water potential; mitigating substance