Variations of yield, biochemical and antioxidative responses in sesame with silicon and cytokinin treatments under drought stress

Drought is one of the major limiting factors for crops that severely reduce plant growth and productivity. The appli­cation of cytokinin (Ck) and silicon (Si) fertilizers can help increase tolerance to drought stress in sesame plants. The present study aimed to evaluate the effects of Ck and Si fertilizers on seed yield, malondialdehyde (MDA) content, proline content, and antioxidant enzyme activities in sesame plants under drought-stress conditions. The experiment was conducted as a split plot-factorial in a randomized complete block design with three replications at Firuzkandeh Agricultural Research Station during two crop years of 2020 and 2021. The main plot was three drought stress levels: control, moderate drought stress (MDS), and severe drought stress (SDS), whereas the subplots were three Si appli­cation levels: control or non-use of Si, calcium silicate and nano-Si, and two Ck application levels: control or non-use of Ck, Ck application. The results indicated that the sesame seed yield was reduced by 9.3% under MDS and by 32.7% under SDS when compared with control conditions. The highest MDA content and proline accumulation were observed when the plants were subjected to SDS, whereas the higher activity of antioxidant enzymes occurred under MDS. Higher activity of antioxidant enzymes and reduction of MDA content was observed in the plants treated by combined application of Si and Ck under MDS. However, the higher seed yield, greater proline content, and higher antioxidant enzyme activities were obtained from plants treated by nano-Si than calcium silicate. Overall, the results of the present study revealed that the foliar application of nano-Si + Ck can be a promising option for mitigating the negative impacts of drought stress and improving sesame seed yield.