Spermine reduces the harmful effects of drought stress in Tropaeolum majus

Abstract

Drought stress is one of the main causes of low crop productivity due to disturbances in plant growth, physiology and biochemical processes. Spermine application is an alternative to mitigate the harmful effects of this stress on plants. Nasturtium (Tropaeolum majus L.) is an ornamental, medicinal and edible plant cultivated and consumed in several countries. This plant has medicinal properties (among them the presence of glucosinolates and phenolic compounds), in addition to being appreciated in cooking. Thus, the objective of this work was to evaluate the effects of spermine application on growth, gas exchange and antioxidant metabolism of T. majus grown under drought stress. Growth (stem diameter, number of leaves, number of flowers, number of buds, total dry mass and leaf area), gas exchange (gs, A, E and Ci), relative water content, free amino acids, phenolic compounds, reducing and non-reducing sugars, lipid peroxidation and enzymatic activity (CAT, POD and APX) were evaluated. Spermine reduced the harmful effects of severe drought stress on the relative water content, reducing sugars and non-reducing sugars. Spermine reduced the harmful effects of moderate drought stress on the relative water content, amino acids, reducing sugars and non-reducing sugars. Spermine application decreased lipid peroxidation (MDA) of T. majus under severe and moderate drought stress and in plants without stress. Spermine increased the activity of POD and APX in plants under severe drought stress and of CAT, POD and APX in plants under moderate drought stress. Spermine application increases the drought tolerance of T. majus by increasing morphology, gas exchange, relative water content, amino acids, reducing and non-reducing sugars, CAT, POD and APX enzymes, and decreasing lipid peroxidation. Spermine (1 mM) can be used to mitigate the harmful effects of drought stress in T. majus.