On the Cracking of Abscission Layer in Asian Rice Cultivar (Oryza sativa L.)

Abstract

Using 10 aman varieties, 11 aus varieties, 6 boro varieties, 8 bulu varieties, 8 tjereh varieties, 100 Korean paddy rice varieties and 16 Japanese paddy rice varieties, degree of grain shedding (breaking tensile strength) and morprology of abscission region in longitudinal sections of pedicel at harvest time were examined. The results obtained were summarized as follows. 1. Breaking tensile strength was weakest in both aus and boro, followed in ascending order by aman, tjereh, Korean paddy rice, Japanese paddy rice, and bulu (Table 1). 2. All the varieties belonging to aman, aus, boro, bulu and tjereh had abscission layer. In aman, aus, boro and tjereh varieties, parenchymatous cells presented in the abscission layer had completely cracked (Table 2 and Fig. 1-A). The parenchymatous cells of bulu varieties, however, had not cracked (Table 2 and Fig. 1-C). On the other hand, in both Korean and Japanese paddy rices, one group of varieties had abscission layer of bulu type and the other had not abscission layer (Table 2 and Fig. 1-C and D). Therefore, from the viewpoint of cracking of abscission layer, bulu varieties appeared to be situated closely to Korean and Japanese paddy rices.