Studies on Vessel Elements of Rice Shoots Grown on Border and in the Inner Part of Paddy Fields.

[摘要] Rice plants grown on the border of paddy fields show a strong resistance to lodging. This phenomenon may, in part, be attributed to the elasticity of plant. With this view in mind, the authors have carried out investigations on metaxylem vessel elements, in various organs of rice shoots, which may play an important role in making the plants more elastic. Observations were mainly made on rice shoots taken just before heading stage from the border as well as from the interior of the actual paddy field at Ookusamachi, Chiba City. Each organ of the shoots was macerated separately with Jeffrey's method and vessel elements (metaxylem II, according to the previous paper were examined under the ordinary microscope. It was found that there is a clear difference in the size, form and type of pitting of lateral wall of vessel elements between plants grown on the border and those grown in the interior of a field. This difference is most conspicuous in the basal elongated internodes and gradually becomes indistinct in the upper parts of the shoots, especially in the leaf blades. The morphological characteristics of vessel elements of the shoots grown on the border of a field were as follows, as compared with those of the shoots grown in the interior; vessel elements are shorter in length with larger diameters, their end walls tend to be simple transverse, and the lateral walls show a tendency of increasing alternate pitting. From evolutional point of view, it is generally believed that the morphological characteristics of vessel elements are specific for species. But our results suggest that, even if the species is the same, they are changed within some limits by ecological conditions. It is assumed that the factors controlling the water balance of plants may be most important, as suggested by Maximov and others. Our experience in actual paddy fields shows that degree of effectiveness of these factors acting on the border and in the interior of the field are likely to be different.

[学科分类] 农业科学（综合）