ABSTRACT
The anatomy of the mature leaf's petioles of one-year-old Bruguiera gymnorrhiza seedlings cultured in greenhouse was studied in this paper. The results are as follows: (1) Most of the vessel elements of the petioles of B. gymnorrhiza are of scalariform. Helical vessels and their transition type only account for a small portion of the total vessels. However, there is a notable increase in the number of helical vessels and their transition type with increasing salinity. (2) The length of petioles, diameter and length of scalariform vessel elements, and bar number of a scalariform perforation plate all exhibit of parabolic relationship with substrate salinity. They maximized at salinity between 20 g/L and 30 g/L. (3) It is new phenomenon that there are two scalariform perforation plates, facing differently, at the polar of the vessel element of the petioles in the seedlings under 10 g/L treatment. (4) Under low salinity, the changes in the structure of vessel elements had the tendency to promote the transportation of water with increasing salinity. While under high salinity, it tended to raise the reliability of the water transportation. The adaptive significance of the morphological characteristics of vessel elements in the petiole was discussed.
