Vol. 17 No. 3
Canopy temperature depression as influenced by various osmoprotectants in late sown irrigated wheat (Triticum aestivum L.)
Abstract: A field experiment was conducted during rabi season of 2019-20 and 2020-21in late sown irrigated wheat under eastern sub-Himalayan plains of West Bengal to assess the effect of various osmoprotectants on grain yield and canopy temperature depression (CTD)as a means of alleviating terminal heat stress. The experiment was laid out in randomized block design (RBD) with seven treatments, each replicated thrice. The treatments were consisted of five osmoprotectants viz., thiourea @ 750ppm(T1); salicylic acid @ 1.0mM (T2); potassium nitrate @ 2.0% (T3); trehalose@ 1.5mM (T4) and sodium nitroprusside(SNP) @ 800 µg ml-1 (T5) along with water @ 450 l ha-1 (T6)and no spray (control) (T7).All the osmoprotectants (except trehalose) including water were sprayed twice, at active tillering and anthesis stages, while trehalose was sprayed at weekly interval starting from 48 hours before heat stress and continued during entire stress period. It was revealed that foliar spray of SNP recorded the highest aerial biomass production (9.38 and 6.76 t ha-1during 2019-20 and 2020-21, respectively) vis-à-vis grain yield (3.54 and 2.58 t ha-1during 2019-20 and 2020-21, respectively), being at par with trehalose and potassium nitrate during both the years. Canopy temperature depression (CTD) did not vary significantly during pre-anthesis and anthesis stages in both the years under various osmoprotectant treatments. However, during grain filling stage, maximum CTD was recorded with SNP treatment (8.3 and 5.2°C in 2019-20 and 2020-21, respectively) followed by potassium nitrate (7.4°C) and trehalose (7.1°C) in 2019-20, being at par with each other. However, SNP treatment was statistically superior to other osmoprotectants in terms of CTD during 2020- 21 which is evident through significant positive correlation (r=0.596)between grain yield and CTD at grain-filling. Amongst the osmoprotectants, SNP showed its superiority in terms of CTD and grain yield signifying its potentiality in alleviating terminal heat stress.
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