Studies on Morphogenesis in Rice Plant : IX. On the structure of vascular bundles and phloem transport in the spikelet

[摘要] Climbing from the pedicel up into the rachilla, the vascular bundle of the rice spikelet swells in bowl-shape and subsequently piller-shape, branching off the bundles of spikelet organs (Fig. 1 and 3). In the swelling bundle of the rachilla, ramificated xylem and phloem are thrown in confusion, in which tracheids, sieve elements, parenchyma cells and thick-walled cells elaborate a formidable mosaic structure(Figs. 2, 4, 5, 6, 7, 9 and 10). It may be supposed on this structure that, by metabolic activity of the parenchyma cells, water in the sieve elements is extracted out and exuded actively into the tracheids in order to be transpired from the lemma and palea, so that the numerous sieve elements with reduced turgor pressure pump up the sieve current from the pedicel and pump it out toward the dorsal bundle of the ovary. It the dorsal bundle, large xylem sits on the main passway of assimilates from phloem via nucellar projection into endodermis (Fig. 12 and 13), but barium chloride absorbed by the roots does not go up via the vessels of this xylem in normal outdoor condition. This structure might present us with a suggestion that the vessels function in normal condition as drainpipes in order to control the turgor pressure of the ovary and the sieve elements (Fig. 14).

[学科分类] 农业科学（综合）