Anatomical Study on the Epicotyl of Etiolated Seedlings of Stizolobium hassjoo

The epicotyl of etiolated seedlings of Stizolobium hassjoo was anatomically studied, and it was compared with that of normally-grown seedlings. This work serves as the basis of physiological and biochemical studies on the etiolated epicotyl, especially concerning of the callus formed on its cut surface, reported by Komamine et al.1-4)In both etiolated and normally-grown plants, the course of differentiation of the procambium in the shoot as well as that of phloem elements is acropetal in connection with the leaf development. The tracheary elements show discontinuous sequence in their differentiation. The lignification of tracheary elements and bundle cap is more prominent in the normally-grown epicotyl than in the etiolated one.At the levels slightly below the plumular hook in the etiolated epicotyl, primary tissues of the stem are almost differentiated and the seriated cells of the procambium are parenchymatized. The cambium begins to differentiate at the level 3.5 or 4.5cm below the plumular hook. The procambial and cambial activities of the normally-grown epicotyl are continuously transformed from upper to lower levels. Problems on cambium differentiation were discussed in comparing the developmental processes of the etiolated epicotyl with those of the normally-grown one.It was certified that the callus does not appear on the cut surface of the etiolated epicotyl at the level, where the procambium is declining or parenchymatized, but appearing at the level where the cambium is differentiating or differentiated.