Respostas de fitohormônios atenuantes do estresse salino no crescimento e desenvolvimento do gergelim.
Palavras-chave:
Fatores abióticos, morfologia, mudanças climáticas, produtividade, salinidade.Resumo
Plants face significant challenges due to biotic and abiotic factors, with climate change and salinity being critical environmental concerns impacting agricultural productivity. This study aims to investigate the impact of exogenous application of phytohormones in mitigating the effects of salinity on the morphological and growth characteristics of sesame. The experiment was conducted in a greenhouse at the Universidade Federal Rural do Semi-Árido (UFERSA), Mossoró-RN, with a semi-arid climate. Sesame seeds, cultivar Anahí, were sown in 21.5-liter pots and thinned at 10 days. The pots were filled with a layer of gravel and a mixture of soil and bovine manure in a 2:1 ratio. Initial irrigation was performed with campus water, followed by saline irrigation 23 days after sowing. Salinity stress levels were induced with sodium chloride (NaCl) at concentrations of 0.5 dS.m⁻¹ (control), 2.5 dS.m⁻¹, and 4.5 dS.m⁻¹. Four treatments (control, methyl jasmonate, melatonin, putrescine) at 1 mM were applied weekly to mitigate the effects of salinity stress. The experimental design was a randomized block design with a 3 x 4 factorial scheme, totaling 12 combinations with 48 experimental plots. Variables analyzed included plant height, stem diameter, number of leaves, and dry mass of leaves, stems, and roots. Data were subjected to analysis of variance and compared using Tukey's test (p<0.05) with R software. The increase in salinity significantly affected the growth of sesame plants, resulting in reductions in plant height, stem diameter, and leaf number. Plants grown under 4.5 dS/cm of NaCl showed a 41% decrease in height and a 43% decrease in the number of leaves compared to the control (0.5 dS/cm). The attenuators demonstrated limited effectiveness, with melatonin maintaining relatively stable leaf dry mass up to 2.5 dS/cm but showing a sharp 71% decrease at 4.5 dS/cm. The dry mass of roots and stems also progressively decreased with increasing salinity, while the attenuators did not significantly alter these parameters. These results indicate that although attenuators may offer some protection at moderate salinity levels, their effectiveness is substantially reduced under high salinity conditions, highlighting the need for additional strategies to mitigate the negative effects of salinity on sesame cultivation.