Observation on the successive development of surface structure in unhulled rice.

Abstract

The surface of unhulled rice has a complicated structure. Therefore, simple observation of a matured hull from outside is not enough to clarify its structure. In order to obtain further information materials were collected over a long period of. development. The surface structure of these samples was then examined by scanning electron microscopy. In outer epidermis, elongation of macrohairs and differentiation of microhairs started 15 days before heading. The stoma-like cells were observed 1) in the lemma near the hooking portion with palea, 2) at the tips of both glumes and 3) in the awn. These cells were identified as stomata by their morphology and distribution. There were one or two linear rows of stomata in the lemma near the hooking portion, and in these rows few microhairs were observable. Examination of the inner epidermal layer showed many stomata around the veins co-existing with the microhairs. In the lateral veins (lemma) and central veins, the stomata and microhairs coexist in the same rows. Around the hooking portion, stomata and microhairs separately exist in different rows, and the former were located closer to the hooking portion. We have concluded that the stomata and hairs perform an important function in the water metabolism of the hull.