Potential Role of Foliage Applied Strigolactone (GR24) on Photosynthetic Pigments, Gas Exchange Attributes, Mineral Nutrients and Yield Components of Zea mays (L.) Under Saline Regimes

Phytohormones are plant growth regulators, temporally or spatially produced by plants in response to varying environmental conditions. A pot experiment was conducted in Old Botanic Garden, the University of Agriculture, Faisalabad, Pakistan to evaluate the effect of foliage applied GR24 on physiological, mineral nutrients, and yield attributes of maize under salt stress. Seeds of two maize lines PB-ProA-2018 and PB-ProA-2019 were sown in thoroughly washed sand-filled pots. Each pot has been nourished with two full litter strength Hoagland nutrient medium solutions as mineral supplementation. Salt stress i.e. non-saline and 100 mM was applied after 28 days of sowing. GR24 was applied as a foliage spray at concentrations of non-spray, water spray, 0.001, 0.01, and 0.1 mg/L after 14 days of salinity treatment. Results showed that salt stress prominently decreased all photosynthetic pigments, gas exchange, yield attributes, and shoot and root K⁺ and Ca²⁺ of maize while increasing C_i, C_i/C_a ratio, and shoot and root Na⁺. GR24 as foliage spray considerably enhanced photosynthetic pigments while partially upgraded gas exchange attributes. Foliar applied GR24 increased cob diameter, a number of grains/cob, shoot and root K⁺ while decreased root Na⁺. GR24 level 0.01 mg/L performed better than other concentrations. Among both maize lines, PB-ProA-2019 behaved better than PB-ProA-2018. A completely randomized design of experiment with four replicates was implicated.