Do brassinosteroids alleviate water stress in seedlings of Handroanthus serratifolius?

Abstract

Limited water availability in reforestation areas can compromise plant growth and development, especially for plants at early stages. In this context, the exogenous application of growth regulators, such as brassinosteroids (BRs), can be used to mitigate the negative effects of water restriction. The aim of this study was to evaluate the effect of the application of BRs (90% brassinolide + a brassinosteroid) on initial growth, gas exchange, leaf water potential and leaf anatomy in yellow Ipê (Handroanthus serratifolius), under water restriction conditions. Throughout the experimental period, plants were maintained in two different water regimes: WR1-plants maintained at 100% of the pot capacity; WR2-plants rehydrated with 50% of the evapotranspiration from the previous day. BRs were applied on three occasions during the experimental period, in five concentrations: C1, 0 g/L (application of distilled water); C2, 0.25 g/L; C3, 0.5 g/L; C4, 0.75 g/L; and C5, 1.00 g/L. The dry mass, root:shoot ratio, water status and leaf anatomy traits were evaluated at the end of the experimental period and were analysed in two-level factorial scheme (2WR  5BRs concentrations). The plant height, number of leaves, gas exchange and leaf chlorophyll content were evaluated four times during the experimental period and were analysed in a split-split-plot design (two WR  five BRs concentrations  four evaluation times). The differences between the means were evaluated by analysis of variance (ANOVA). Pairs of means were separated using the standard error of the difference between the means (SED) and the Fisher's protected least significant difference test (LSD) at p < .05. In addition, all variables were subjected to regression analysis, being the variables evaluated over time, analysed through a two-stage modelling approach. The results obtained indicate that the water deficit led to reductions in growth and gas exchange parameters, regardless of the exogenous application of the regulator; therefore, higher concentrations (C4 and C5) were the most harmful for the maintenance of metabolic and photosynthetic activity. The exogenous application of BRs in H. serratifolius plants attenuated the effects of water limitation on the leaf water potential, but was not able to mitigate for the negative effects in growth, gas exchange and leaf anatomy.

Arbuscular Mycorrhizal Fungi Promote Physiological and Biochemical Advantages in Handroanthus serratifolius Seedlings Submitted to Different Water Deficits

“…However, Vieira et al [ 27 ] did not observe any influence of water deficit on leaf development in H. serratifolius . In our study, the total leaf area and the number of leaves were not influenced by the water deficit due to the short period of time of exposure to stress.…”

24‐Epibrassinolide alleviates drought effects in young Carapa guianensis plants, improving the hydraulic safety margin, gas exchange and antioxidant defence

“…Vieira et al . (2022) evaluated the effect of BR application on Handroanthus serratifolius under conditions of water restriction and also reported increased Ψ W .…”

“…Moreover, antioxidant defence was stimulated after pretreatment with EBR, as these responses are regulated by the SOD, CAT, APX and POX, representing an efficient mechanism against ROS overproduction during water deficit. Vieira et al (2022) evaluated the effect of BR application on Handroanthus serratifolius under conditions of water restriction and also reported increased Ψ W .…”