ABSTRACT
Salt stress hampers the growth and physiology of nasturtium (Tropaeolum majus), due to biochemical, physiological, and anatomical disruptions. The application of salicylic acid stands as an alternative to alleviate the detrimental effects of salt stress, but studies on nasturtium are scarce. Thus, the aim of present study was to assess the effects of foliar application of salicylic acid on nasturtium cultivated under salt stress. The experiment followed a completely randomized design in a 3 x 3 factorial scheme, with 0 (no stress), 50 (moderate salt stress), and 100 (severe salt stress) mM of NaCl, and application of 0, 0.5, and 1 mM of salicylic acid, each with six replications. Growth (plant height, stem diameter, and number of leaves), gas exchange (stomatal conductance, photosynthesis, transpiration, internal CO2 concentration, intrinsic water use efficiency, instantaneous water use efficiency, and intrinsic carboxylation efficiency), as well as chlorophyll indices and chlorophyll a fluorescence were evaluated. Salt stress affected the variables analyzed in this study. The application of salicylic acid had a positive effect on mitigating the effects of severe salt stress, resulting in a significant increase in the number of leaves. The most effective dose was 1 mM, also leading to notable improvements in water use efficiency and photochemical efficiency. However, other combinations of salinity and salicylic acid reduced growth and gas exchange in nasturtium plants.
Key words:
nasturtium; phytohormone; salinity; Tropaeolaceae
HIGHLIGHTS:
Salicylic acid reduces the impacts of salt stress in nasturtium.
Application of 1 mM salicylic acid increases photosynthetic capacity of salt-stressed plants.
Salicylic acid improves plant growth under severe salt stress.
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Means followed by the same letters do not differ according to the Tukey’s test (p ≤ 0.05). The values are expressed as mean ± standard deviation (n = 5)
Means followed by the same lowercase letters do not differ for salicylic acid, and those with the same uppercase letters do not differ for salt stress according to the Tukey’s test (p ≤ 0.05). The values are expressed as mean ± standard deviation (n = 5)
Means followed by the same lowercase letters do not differ for salicylic acid, and those with the same uppercase letters do not differ for salt stress according to the Tukey’s test (p ≤ 0.05). The values are expressed as mean ± standard deviation (n = 5)
Ci- internal CO2 concentration, E- transpiration, gs- stomatal conductance, A- net photosynthesis, WUE- instantaneous water use efficiency, iWUE- intrinsic water use efficiency, iCE- instantaneous carboxylation efficiency, PH- plant height, SD- stem diameter, NL- number of leaves, Chla- chlorophyll a, Chlb- chlorophyll b, tChl- total chlorophyll, Chla/b- chlorophyll a/b, F0- initial fluorescence, Fm- maximum fluorescence, Fv- variable fluorescence, Fv/Fm- quantum yield of photosystem II, Fv/F0- conversion of absorbed energy, S- salicylic acid, N0S0- plants without stress and without salicylic acid application, N0S0.5 and N0S1- plants without stress and with salicylic acid application, N50S0- plants with moderate stress and without salicylic acid application, N50S0.5 and N50S1- plants with moderate stress and salicylic acid application, N100S0- plants with severe stress and without salicylic acid application, N100S0.5 and N100S1- plants with severe stress and salicylic acid application
Ci- internal CO2 concentration, E- transpiration, gs- stomatal conductance, A- net photosynthesis, WUE- instantaneous water use efficiency, iWUE- intrinsic water use efficiency, iCE- instantaneous carboxylation efficiency, PH- plant height, SD- stem diameter, NL- number of leaves, Chla- chlorophyll a, Chlb- chlorophyll b, tChl- total chlorophyll, Chla/b- chlorophyll a/b, F0- initial fluorescence, Fm- maximum fluorescence, Fv- variable fluorescence, Fv/Fm - quantum yield of photosystem II, Fv/F0 - conversion of absorbed energy. (n = 5)