POSSIBLE ROLE OF ALTERNATIVE RESPIRATION IN TEMPERATURE RISE OF WATER-STRESSED PLANTS

Role of alternative respiration, a thermogenic pathway, was evaluated in temperature rise of water stressed plants. Transpiration rate, plant temperature and respiratory dynamics were monitored in field grown irrigated and unirrigated sorghum (Sorghum vulgare Pers.) hybrid CSH 6 and pearl miller (Pennisetum typhoides (Burm. f.) Stapt and Hubbard) val. J 104 for 22 days. Transpiration rate of irrigated plants was always higher than the unirrigated plants. But the plant temperature and the alternative respiration activity of irrigated plants was always lower than unirrigated plants. The reduction in transpiration rate of unirrigated pearl miller was more as compared to unirrigated sorghum. Nonetheless, alternative respiration activity was higher in unirrigated sorghum as compared to unirrigated pearl miller. Temperature of unirrigated sorghum plants increased by 10.4 degrees C during 22 days and it was 8.0 degrees C higher than irrigated sorghum at day 22, Stressed pearl miller showed an increase of 3.9 degrees C during 22 days and it was 2.9 degrees C higher than the irrigated pearl millet at day 22. It is suggested that the heat released because of the alternative respiration activity also contributes towards temperature rise of water stressed plants.