Estudio de diferentes aspectos agronómicos, fisiológicos y moleculares de la aplicación de H2S en plantas de Brassica oleracea CV. BRONCO

Abstract

In chapter 1, the potential effects of hydrogen sulfide on the biomass of the aerial part, the nutritional quality and the antioxidant capacity of Brassica oleracea were investigated, through the application of increasing doses of NaHS (NaHS as a donor of H2S; 0.5, 1, 2.5 and 5 mM). The results showed that the treatments 0.5 and 1 mM of NaHS increased the biomass and the nutritional quality of the 'Bronco' cabbage (that is, chlorophylls, carotenoids, anthocyanins, flavonols, total phenols and sinigrin). On the other hand, there was an increase in lipid peroxidation and hydrogen peroxide content after the application of doses above 2.5 mM NaHS. Therefore, we selected the doses of 0.5 and 1 mM NaHS as optimal for the plants of Col. The application of 2.5 and 5 mM NaHS produced an excessive peroxidation of lipids, decreases in the biomass of the plants and losses of chlorophylls, being all of them considered negative effects, and clear evidence of stress in the plants. In terms of practical applications, this study suggests that the exogenous application of NaHS as a donor of H2S at 0.5 and 1 mM can be useful as a biostimulant to increase the yield and healthpromoting composition of the cabbage plant (Brassica oleracea L. 'Bronco'). Given the intimate relationship between the processes of assimilation of N and S in plants, in chapter 2, the effects of different doses of hydrogen sulfide in the form of NaSH (0, 0.5, 1,2,5 and 5 mM) on the formation and assimilation of NH4 + in plants of Brassica oleracea L. 'Bronco' were studied. According to our results, the 0.5 and 1 mM NaSH treatments increased the biomass while decreasing the NO3 - concentration. In the 0.5 mM NaSH treatment, NH4 + accumulation decreased with the stimulation of GS activity, resulting in a higher content of certain amino acids (AAs) and soluble proteins, which could be related to the higher biomass found in this treatment. However, the 2.5 and 5 mM NaSH treatments induced the formation and accumulation of NH4 +, as well as photorespiration. This excessive accumulation of NH4 + could be responsible for the lower biomass in these treatments (2.5 and 5 mM NaSH). Therefore, in this chapter we conclude that the excessive accumulation of NH4 + may be responsible for the decrease in biomass in the 2.5 and 5 mM NaSH treatments. On the other hand, we conclude that the application of 0.5 mM of NaSH could be a beneficial strategy to improve the processes involved in the assimilation of N, accompanied by an increase in the biomass of cabbage crops. Next, in Chapter 3, we investigated how the application of hydrogen sulfide (0.5 mM NaHS) in Brassica oleracea L. 'Bronco' influences the processes involved in glutathione homeostasis and alkali stress tolerance (50 mM NaHCO3:Na2CO3). According to our results, alkaline stress increases the O2 .- content, lipid peroxidation and the activities of the enzymes glyoxalase I (Gly I) and glyoxalase II (Gly II) which detoxify methylglyoxal (MG) while decreasing the biomass, superoxide dismutase (SOD) activity, the activity of the enzymes involved in glutathione (GSH) synthesis and in the AsA-GSH cycle, as well as the reduced glutathione content and the different forms of ascorbate (AsA) On the other hand, the application of NaHS improved the antioxidant response, inducing SOD activity and improving the processes involved in glutathione homeostasis, boosting the reduced glutathione (GSH) content as well as the activity of key enzymes in glutathione synthesis and the AsA-GSH cycle. Consequently, the application of H2S in the form of NaHS at a concentration of 0.5 mM could strengthen the tolerance of Brassica oleracea L. 'Bronco' to alkaline stress. Finally, in Chapter 4 it was investigated how the application of hydrogen sulfide (50 μM NaHS) in Arabidopsis thaliana L. plants influenced the relative expression of genes involved in sulfur assimilation, glutathione homeostasis and the involvement of these genes in alkali stress tolerance (50 mM NaHCO3:Na2CO3). According to our results, the application of H2S (NaHS) mitigated the harmful effect of alkaline stress evidenced by the reduction in biomass loss of 31% after applying H2S to plants subjected to alkaline stress. On the other hand, no significant specific increases were observed in response to the application of H2S on the relative expression of genes involved in the biosynthesis of enzymes and isoenzymes key to the regulation of SO4 2- (Serat 1,1) assimilation processes; OAS TL, OAS TL B; OAS TL C; ATPS ; ATPS 2, ATPS 3; ATPS 4 and APR 1) and glutathione homeostasis (GMPase; GDPME; L-GAL PPase; LGALDH; L-GLDH; SOD 1;SOD 2; APX; MDHAR; GR2; GR 1; gsh 1; gsh 2 and GPX) under alkaline stress conditions.