Effect of drought, flood and heat at flowering stage on canopy cooling related traits in rice

Standing water is an important contributor for yield formations and physiological activities at flowering stage of the rice crop. It may help to maintain tissue temperature below the critical level by transpiration cooling. Drought and heat stress arising from late planting may affect on transpiration cooling, resulting in high canopy temperature. Canopy temperature can be used as a selection criteria for drought tolerant variety screening. Thus, it is important to study the importance of canopy temperature related traits and trait diversity on heat and drought stress. This field trial was conducted at the Field Crops Research and Development Institute, Mahailluppallama, to investigate the changes of pattern and distribution of morphological traits across eight rice varieties under four management conditions (i.e., early planting flood, late planting flood, early planting drought and late planting drought), to identify the transpiration cooling related traits. Morphological traits were subjected to factor analysis across the management conditions. Factor coefficients of each selected trait were used as an explanatory variable for regression on canopy temperature. Factor one highly correlated with plant height and panicle length. Tiller angle and number of tillers were highly correlated with Factor two. Pollen fertility was highly correlated with Factor three. Factor one negatively and Factor two positively correlated with canopy temperature across flooded, drought stress and heat stress conditions. Thus, canopy angle, pollen fertility index, plant height and tiller angle are important characters in variety selection for drought and heat stress. The variety Bg 366, Pachchaperumal and Kaluheenati have high transpiration cooling ability among the tested varieties.