Function of long basal dehiscence of the theca in rice (Oryza sativa L.) pollination under hot and humid condition

MATSUI T. 2005. Function of long basal dehiscence of the theca in rice (Oryza sativa L.) pollination under hot and humid condition. - Phyton (Horn, Austria) 45 (4): (401)-(407). Anticipated global warming is expected to increase floret sterility in rice (Oryza sativa L.). For selection of-genotypes tolerant to high temperatures during the flowering period, it is important to identify the morphological traits controlling tolerance to temperature stress. We investigated the relationship between the length of dehiscence at the basal part of thecae and the viability of pollination in japonica type cultivars of rice subjected to a hot and humid condition (37/25 degrees C, day/night, > 90% relative humidity) for three days at flowering. Control plants were left under the ambient conditions in a semi-cylindrical house covered with cheesecloth (30% shading; temperature range: 24-35 degrees C). The length of basal dehiscence of thecae and the number of pollen grains on the stigmata were examined with a light microscope after flowering. The percentage of florets with more than 20 pollen grains closely correlated with the length of basal dehiscence under the high-temperature treatment (r = 0.906, significant, P < 0.0001) and the percentage of florets with more than 80 pollen grains correlated with the length of the basal dehiscence of thecae under the control condition (r = 0.745, significant, P < 0.01). The length of basal dehiscence under the high-temperature treatment was highly correlated with that in the control (r = 0.911, significant, P < 0.0001). We concluded that the long basal dehiscence of the theca helps the pollen grains to fall from the theca onto the stigmata and increases the stability of the pollination under hot and humid conditions as well as normal conditions. We also concluded that we can estimate the tolerance of the variety to high temperature by measuring the basal dehiscence under a normal condition.