Heat stress is one of the most important constraints for crop production. Temperature beyond the optimum level leads to heat stress and causes irreversible damage to the growth and development of chickpea. Biomass partitioning is highly responsive to environmental stimuli affecting seed yield under sub-optimal conditions. Plant growth regulator application is a viable option to alter biomass partitioning, optimizing seed yield under heat stress conditions. Therefore, an experiment was conducted to identify effective plant growth regulators for biomass partitioning in chickpeas under high-temperature stress conditions. The investigation comprises two chickpea genotypes viz., JG 14 (heat tolerant cultivar) and JG 36 with two dates of sowing viz., timely sown (18th November) and late (20th December) sown for exposing the crop to high temperature and nine sub-sub treatments viz., control (no spray), water spray, foliar spray of plant growth regulator viz., thiourea (100ppm, 200 ppm, 400 ppm and 600 ppm) and salicylic acid (200 ppm, 400 ppm am 600 ppm) at anthesis stage. Delayed sown high-temperature stress condition reduces biomass partitioning in leaves, main stem, and secondary branches, with an increase in pods. Heal tolerant variety JG 14 exhibited enhanced biomass partitioning in leaves, main stems, secondary branches, and pods compared to JG 36. Under timely sown conditions at the physiological maturity stage (90 DAS), salicylic acid @ 200 ppm and 400 ppm efficiently increased biomass partitioning in pods and main stem, respectively. Pulse, a source-limited crop, is desired to enhance source activity under heat-stress conditions. In the present study, under high-temperature stress conditions, source activity or biomass partitioning in source tissue (leaves) was enhanced by foliar application of salicylic acid @ 400 ppm, while thiourea @ 600 ppm enhances biomass partitioning in the main stem and secondary branches.

Biomass partitioning, plant growth regulator, heat stress, late sowing, heat tolerance, salicylic acid, thiourea

The dry matter partitioning towards leaves, secondary branches, and main stem decreases as the phenology progresses from flowering to maturity under timely and high-temperature stress conditions. In contrast, dry matter partitioning towards pods increases with the progression of growth duration under both timely and high-temperature stress conditions. Late sown high-temperature stress reduces dry matter partitioning of leaves, secondary branches, and main stem, whereas an increase in dry matter partitioning towards pods was observed. Heat tolerant chickpea variety, JG 14, reflected an increase in biomass partitioning towards leaves, secondary branches, and main stem compared to the JG 36 chickpea variety. Under the timely sown condition, at the post-flowering stage, salicylic acid @ 600 ppm, 200 ppm, and thiourea @ 200 ppm enhanced dry matter partitioning towards leaves, secondary branches and main stem. In the seed filling stage, at 75 DAS, water spray enhances dry matter partitioning towards leaves, secondary branches and main stem. In contrast, salicylic acid@400ppm enhances dry matter partitioning towards pods in timely sown condition. Under the timely sown condition, during physiological maturity at 90 DAS, salicylic acid @ 200 ppm and 400 ppm efficiently increased dry matter partitioning towards pods and main stem, respectively (Fig. 4). Pulse being a source-limited crop, seed yield is drastically affected due to a reduction in source size and strength. Therefore, pulse yield under high-temperature stress can be increased by enhancing source strength. In the present study, Plant growth regulator salicylic acid @ 400 ppm proves its potential by enhancing biomass partitioning towards source tissues (leaf), main stem, and secondary branches (Fig. 3). Plant growth regulator salicylic acid @ 400 ppm can mitigate high-temperature stress effect on yield through enhancing biomass partitioning towards source tissue (leaf), main stem, and secondary branches.

Supriya Debnath, R. Shiv Ramakrishnan, Rohit K. Kumawat, Mrunal Ghogare, Parikha P. Singh, Ashish Kumar, Stuti Sharma, Radheshyam Sharma, Preeti S. Nayak, Gyanendra Tiwari and R.K. Samaiya (2022). Plant Growth Regulators Application on Biomass Partitioning in Source and Sink Tissues under Timely Sown and high Temperature Stress Condition in Chickpea. Biological Forum – An International Journal, 14(4a): 318-327.