Studies on the Chilling Injury in Wheat Plants : III. Cytological studies on the sterile injury caused by the chilling.

Abstract

The abnormal pollens which have empty cytoplasm were never observed somewhat before the heading stage of Norin No. 39 at the region of Shigarami in 1957, but were remarkably observed after the heading stage. Cytological studies on the injured ears produced by artificial induction were performed in 1962. 1) The abnormality of pollen similar to that in injured ears at the region of Shigarami was found out also in the injured ears induced by the artificial low temperature. 2) Types of the abnormal pollen could be mainly classified into two kinds, immature pollen and degenerated pollen. The immature pollen tended to arise, when the injurious low temperature was relatively severe. 3) The anthers in the injured florets contained the abnormal pollen generally in proportion of more than 50 %. 4) It seemed that the pollen abnormality is caused by gradual physiological processes acompanied with a decrease in the function of the anther, and neither from direct and quick actions of low temperature at the heading stage, nor from chromosomal aberrations at the PMC stage, and nor from abnormal swelling of the tapetum. 5) It was thought to be difficult to express the sensitive stage to low temperature with the cytological stage of pollen, but to be better to express it with the anther stage. The development of ovary in the injured glume stopped suddenly after the flowering stage, although it was normally performed until just before the flowering stage. All the injured glumes were re-opened in a few days after the flowering stage. And it was clear by the observation in use of the microscope that the injured grains were not fertilized. The injured grains induced by the refrigerator was nonfertilized ones similar to those induced by the natural conditions at the region of Shigarami.