Polyamines mitigate the harmful effects of salt stress on the growth and gas exchange of nasturtium

ABSTRACT Abiotic stresses are one of the major reasons for low crop productivity owing to the disturbances caused by them. Polyamines can be applied to mitigate the harmful effects of stress in plants. Nasturtium (Tropaeolum majus L.) is an ornamental, medicinal, and edible plant that is found in many countries. The objective of this work was to evaluate the effect of polyamines application and salt stress on the growth and leaf gas exchange of T. majus. The treatments to induce salt stress were as follows: 0 mM NaCl (no stress), 40 mM NaCl (moderate stress), 80 mM NaCl (severe stress), 40 mM NaCl + spermine (Spm), 40 mM NaCl + spermidine (Spd), 40 mM NaCl + putrescine (Put), 80 mM NaCl + Spm, 80 mM NaCl + Spd, and 80 mM NaCl + Put. Polyamines were applied every week for four weeks. The applications of Spd and Spm attenuated the harmful effects of moderate salt stress on plant height and leaf fresh mass. The application of Spm attenuated the harmful effects of moderate salt stress on stem diameter. The application of Spd attenuated the harmful effects of moderate salt stress on the number of buds, the stem fresh mass, and total fresh mass. The application of Spm attenuated the harmful effects of severe salt stress on stomatal conductance and transpiration rate and attenuated the harmful effects of moderate salt stress on stomatal conductance, net photosynthesis, and transpiration. The application of Spd attenuated the harmful effects of moderate salt stress on instantaneous water use efficiency and intrinsic water use efficiency. The applications of Spm and Spd application can attenuated the harmful effects of moderate salt stress on the growth and leaf gas exchange of nasturtium.