Effect of high night temperature and CO2 on yield and seed quality of summer greengram (Vigna radiata) under soil plant atmospheric research (SPAR)

An experiment was designed in Coimbatore, Tamil Nadu during two successive summer seasons, 2021 and 2022, to investigate the effects of high night temperature (HNT) (ambient minimum temperature+3°C) and CO2 (600ppm at night) on the yield and seed quality parameters of greengram under ten treatments in SPAR (Soil Plant Atmospheric Research) and ambient conditions. The objective of this research was to (i) quantify the short-term effects of HNT and CO2 on yield contribution factors and (ii) quantify seed quality parameters employing biochemical analysis. Greengram yield and quality parameters were significantly reduced under HNT and CO2 when compared to ambient conditions. Pooled data from two successive summer seasons revealed that when stress was imposed from (i) 43 to 49 DAS (Day After Sowing), the number of flowers dropped per plant significantly increased by 41.3% (ii) 29 to 35 DAS, pod setting percentage decreased by 18.5% (iii) 36 to 42 DAS, grain yield and biomass/plant decreased by 26.9 % and 29.3% respectively. In aspects of seed quality parameters, data revealed that under stress (i) Seed protein decreased by 20.5% from 50 to 56 DAS. (ii) Total sugars, polyphenols, calcium and iron decreased by 17.7, 19.9, 19.9 and 37.3%, respectively from 43 to 49 DAS. (iii) Seed moisture was reduced by 19.7% during 57 to 63 DAS (iv) The levels of proline and phytic acid increased by 64.3 and 33.8%, respectively, from 50 to 56 DAS and 43 to 49 DAS. Overall, greengram yield was adversely affected on three treatments from 35 to 56 DAS (flower initiation stage to pod filling stage) and seed quality parameters such as protein, total sugars, polyphenols, seed moisture, proline, phytic acid, calcium and iron were reduced under HNT and CO2 from 50% flowering to pod development stage (42 to 56 DAS).