Dependence of pollination and fertilization in rice (Oryza sativa L.) on floret height within the canopy

We examined changes in rice (Oryza sativa L.) floret sterility and pollination as a function of vertical position of florets in the canopy at anthesis in paddy fields to clarify the ideal panicle height. Flowering pot-grown rice plants were placed in the rice canopy at different heights to position their florets at different depths below the canopy surface. The percentage of floret sterility was approximated as Y = 0.000335 X-1(2) + 0.0296 X-1 - 0.0451 X-2 + 0.0152 X1X2 - 0.0468 (R-2 = 0.921), where Y is the logic-transformed floret sterility (%), X-1 is floret depth at anthesis (cm), and X-2 is wind speed above the canopy (m s(-1)). The percentage of florets with fewer than 20 pollen grains on the stigma after flowering was approximated well by Y = 0.000554 X-1(2) - 0.235 X-2(2) + 0.5346 (R-2 = 0.892), where Y is the logic-transformed percentage. The floret sterility (%) was correlated with the percentage of florets with < 10 germinated pollen grains and with the percentage with < 20 total pollen grains. Thus, there exists an optimal flowering depth and an ideal panicle position with respect to the canopy surface that stabilizes pollination and fertilization, and the optimal position for fertilization deepens with increasing wind strength.