Studies on Wind Damage of Rice Plant

Abstract

This study was made in 1959 to clarify the effect of strong wind before the flowering stage upon the morphological character and the physiological function of the reproductive organs of rice plant. Norin 35 of paddy rice, grown in square pots, were used for this purpose. The plants were exposed to an artificial wind with varying velocities (9, 12, and 15 metres per second)for five hours on different days (0, 3, 6, 9, 12, and 15 days before flowering) as shown in Table 1.1. Strong wind at 15 days before flowering resulted in abnormal anthers of smaller than the standard anther or of irregular form (Figure 1 and Table 2). The time of this treatment seemed to be the iniation or early developing stage of anthers and it is a little earlier than the sensitive stage when the tapatum cells of anther occur in the case of cool air and cold water treatments which had been reported by Sakai (1937 and 1947) and Shimazaki (1949).2. Abortive pollens also were the result when plants were exposed to wind at 15 days before flowering, especially at 15 metres per second as shown in Table 2. But the abortive pollens were comparatively less than the values which were imaginated from both of atrophied spikelets (Tsuboi and Hitaka; 1962) and abnormal anthers.3. Regarding pollination and germination of pollen grains in spikelets which bloomed under normal conditions, as in the case of plants used as standard, significant differences were not found between those of treated and untreated plants (Table 3).4. During the few days following the wind treatments, many spikelets were found to have accelerated blooming as an after effect of the treatments (Table 4), and such spikelets did not at all receive pollen grains or received only very few pollen grains on the stigmas, thereby resulting sterile kernels (Table 5). However, the pollination and pollen germination in the spikelets which bloomed at the normal times did not differ so much from those of standard plants.5. Wind treatments before the heading or flowering stage resulted in the occurrence of discoloured dead and empty grains and in the reduction of the proportion in the formation of complete grains.The most harmful effect on ripening was recognized when the spikelets were exposed to wind just at the flowering date, as reported already by many investigators Matsuo (1942), Togari (1940), Tsuboi and Hitaka (1958) and etc. (Table 6).6. The colour of the glumes changed from normal to brown or grey when the plants were exposed to strong winds at the flowering stage, because the spikelets received physical bruises or rubs and physiological dessication by the wind treatments. The grains in discoloured glumes became coloured under the drying conditions caused by the kernels not being locked perfectly by the inner and outer glumes, as suggested by Tsuboi (1961) and may be easily attacked by fungus as reported by Matsuo (1942). Influence of discoloured glumes on the occurrence of coloured grains was about 3.5 times larger in the case of discoloured grey than in the case of discoloured brown (Table 7).