Panicle inclination influences pollination stability of rice (Oryza sativa L.)

Abstract

Rice pollination occurs when pollen grains fall by gravity from the anther onto the stigma and has been thought to be assured under suitable conditions. However, the position of the stigma relative to the anther pores may affect pollination. The inclination of panicle, that is quite usual in agricultural scene, may change the relative position of anther and stigma. We investigated the effect of panicle inclination on pollination stability. Pots of rice at flowering stage were tilted at one of the four inclinations (0°= control, 15°, 30°, and 45°). We assessed pollination (numbers of total and germinated pollen grains on the stigma) and morphology of dehisced anthers. Inclination significantly affected the number of total and germinated pollen grains on the stigma: as it increased from 0°to 45°, the percentage of florets with <20 total pollen grains on the stigma (TP20) increased from 36.6% to 59.9%, and that of florets with <10 germinated pollen grains on the stigma (GP10) increased from 26.6% to 58.9%. Both an increase in TP20 and a decrease in the rate of pollen germination were major causes of the increase in GP10. Inclination did not affect anther morphology. A panicle inclination of ≥30°could greatly reduce rice production because rice fertilization requires >10 germinated pollen grains on the stigma. Uprightness of the panicle at flowering should be an important objective in rice breeding and production.Abbreviations: TP20: percentage of florets with <20 total pollen grains on the stigma; GP10: percentage of florets with <10 germinated pollen grains on the stigma ARTICLE HISTORY

How panicle angle and panicle position in the canopy determine pollination and seed set in rice (Oryza sativa L.)

“…However, we found that small panicle inclination reduced pollination stability in isolated pot-grown rice probably by changing the relative position between anther and stigma, and delaying pollen release (Win et al, 2020). Panicle inclination of 30°increased percentage of florets having less than 10 germinated pollen grains on the stigma after flowering by 24%.…”

“…From each floret, we randomly selected four anthers to observe at 80× magnification under a digital microscope (KH-7700, Hirox Co., Ltd., Tokyo, Japan). We measured the lengths of dehiscence formed at basal and apical parts of anther (Win et al, 2020).…”

Continuous Heavy Rainfall and Wind Velocity During Flowering Affect Rice Production

“…According to Matsui, Kobayasi, Yoshimoto, Hasegawa, & Tian (2020), strong wind causes the ideal position of the panicle for pollination to decrease. Previously, Win et al (2020a;2020b) noted that pollination success in rice decreased by increasing panicle inclination.…”

Drought-Induced Changes in The Flowering Capacity, Anthesis Quality and Seed Set in Rice (Oryza sativa L.)

“…In addition, failure of anther dehiscence was also reported to be responsible for low spikelet fertility in drought stressed rice at pre-anthesis stage (Liu et al 2006). Failure of anther dehiscence would certainly prevent stigma from receiving pollen grains for the pollination process (Win et al 2020). Above all, spikelet opening during flowering was a prerequisite for anthesis process to occur in rice (Ekanayake et al 1993).…”