Foliar brassinosteroid analogue (DI-31) sprays increase drought tolerance by improving plant growth and photosynthetic efficiency in lulo plants

The use of agronomic alternatives such as plant hormone sprays has been considered a tool to mitigate drought stress. This research aimed to evaluate the use of foliar brassinosteroid analogue DI-31 (BRs) sprays on plant growth, leaf exchange and chlorophyll a fluorescence parameters, and biochemical variables in lulo (Solanum quitoense L. cv. septentrionale) seedlings grown under drought stress conditions. Seedlings were grown in plastic pots (3 L) using a mix between peat and sand (1:1 v/v) as substrate. Lulo plants were subjected to drought stress by suppressing 100% of the water needs at 30-37 and 73-80 days after transplanting (DAT). Foliar BRs analogue (DI-31) sprays were carried out at four different rates (0, 1, 2, 4, or 8 mL of analogue per liter) at different times (30, 33, 44, 60, 73, and 76 DAT). Drought stress caused a reduction in the F-v/F-m ratio, leaf gas exchange properties, total biomass, and relative water content. Foliar DI-31 sprays enhanced leaf photosynthesis in well-watered (WW) (similar to 10.7 mu mol m(-2) s(-1)) or water-stressed plants (WS) (similar to 6.1 mu mol m(-2) s(-1)) when lulo plants were treated at a dose of 4 and 8 mL.L-1 compared to their respective controls (0 mL.L-1 for WW: 8.83 mu mol m(-2) s(-1) and WS: 2.01 mu mol m(-2) s(-1)). Also, DI-31 sprays enhanced the photochemical efficiency of PSII, and plant growth. They also increased the concentration of photosynthetic pigments (TChl and Cx thorn c) and reduced lipid peroxidation of membranes (MDA) under drought conditions. The results allow us to suggest that the use of DI-31 at a dose of 4 or 8 mL.L-1 can be a tool for managing water stress conditions caused by low water availability in the soil in lulo-producing areas to face situations of moderate water deficit at different times of the year.

Automated summary

This research evaluated the effects of foliar brassinosteroid analogue DI-31 sprays on lulo seedlings under drought stress conditions, showing that the sprays enhanced leaf photosynthesis, PSII efficiency, pigment concentration, and reduced lipid peroxidation.