MORPHOLOGICAL STUDIES ON THE DEVELOPMENT AND COLD RESISTANCE OF THE WINTER BUDS OF ZIZANIA CADUCIFLORA HAND.-MAZZ.

The internodal transverse vascular tissues are extraordinary overwintering vascular structures formed in the development period of winter buds of Zizania caduciflora Hand. -Mazz.. They originate in about the 5th internode from the shoot apex. The initial cells are formed by dedifferentiation of a layer of parenchyma cells next to the ring of surrounding vascular bundles The internodal transverse vascular tissues possess well-developed xylems which are not V-shaped They play an important role in enhancing the transport of water and solutes during development period of winter buds in the next early spring. A series of cytological changes occurring in the shoot apex and young leaves of winter buds during their development period can be summerised as following: ① The activity of cell division decreases gradually and stops finally; ② The light rings of the nucleoli become smaller gradually and disappear nearly at last. ③The starch grains accumulated in cells get much more and much bigger. ④The phenomenon of the plasmolysis generally appears in the cells during the period of dormancy. These cytological changes can be served as efficient basis in determinating the cold resistance of the winter buds of Z. caduciflora.