Introduction:

Brassinosteroids and their analogues are compounds that have been successfully used in the tolerance induction to abiotic stresses in plants, at international level. The main objective of this research was to determine the effect that the exogenous application of brassinosteroids and their analogues exerted on the tomato seedling tolerance to high temperature stress and the role of brassinosteroid homeostasis and oxidative stress in this tolerance. The effects that brassinosteroids and their analogues exerted on rice plant growth under saline stress and the main physiological and biochemical mechanisms associated with this response, were also determined.

Methods:

An experiment was carried out in which different genotypes were used. They were characterized by genetic changes that produce different endogenous levels of castasterone. In order to combine the theoretical interest with the practical one, experiments with genotype Amalia were conducted. This crop is widespread in Cuba. So as to determine the influence of treating the seeds with BR and their analogues during the growth of rice seedlings in a saline environment, several experiments were run in semi-controlled conditions.

Results:

The performed experiments demonstrated that the thermotolerance of tomato seedlings depends on kinase domain activity of the brassinosteroid tBRI1 receptor, as well as the participation of oxidative stress in the BR-induced thermotolerance. Furthermore, MH-5 analogue was more effective in protecting Amalia tomato seedlings from thermal shock than BB-6. Regarding the rice plant protection from salt stress, for the first time, in an integral manner, the physiological and biochemical responses associated with 24-epibrassinolide (EBL) and Biobras-16 induced protection are reported; it allowed for proposing an EBL action model in rice plants under these conditions. It was demonstrated that both compounds protected the plants; however, the physiological and biochemical responses associated with this protection are different.

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