Genecological studies on Japanese lawn grass (Zoysia japonica Steud.) with special reference to the seed propagation characteristics, 5: Some morphological attributes of seeds in relation to germinability and early growth of seedlings

We discussed the variability in some eco-physiological properties related to the seed propagation in local clones of Japanese lawn grass (Zoysia japonica Steud.) in our previous papers. In this report, we dealt with the variation in morphological attributes of seeds in relation to the seed germinability and seedling vigor. As to the seed morphology, 100-seed weight of fertile grain (caryopsis+hull) and sterile grain (hull only) were measured using the seeds produced from 56 clones selected for their germinability based on the previous reports. After that, caryopsis weight and hull ratio in weight were obtained. Further, the thickness of hull (mainly lemma) and caryopsis was measured directly using soft X-ray pictures of fertile grains produced from 18 selected clones belonging to the contrastive germinability groups (about 30 grains each). In parallel with these measurements, seed germinability of the 56 clones was tested using the previously reported procedure. Seeding growth under controlled conditions was observed for about 6 weeks using the seeds produced from 20 of the 56 clones. In this case, germination of seeds from which the seedlings originated was synchronized by pretreatment. The seed attributes mentioned above, as well as the germinability and seedling growth, showed a great variation between clones tested. In connection with the seed germinability, hull ratio in weight showed a significant negative correlation of r=-0.40 (p0.01) with percent germination of seeds. Thickness of hulls and its ratio to caryopses also significantly between clone groups, that is, the seeds from the difficult germinability group tended to have thicker hulls. Concerning seedling vigor, the caryopsis weight showed a fairly high correlation of r