| Summary: | 碩士 === 國立中興大學 === 農業經濟學系 === 84 === In Taiwan, Zoysia spp. from different ecotopes significantlly varied in
the ability of salt tolerance. The clones of Zoysia spp. with higher salt
tolerance could survive in the solution with 7.5% NaCl, about 2.5 times of
sea water concentration. Those with lower salt tolerance could also tolerate
with the salinity about half to equal concentration of sea water. Thus Zoysia
spp. could be defined as halophytes. Under highly saline environment, Zoysia
spp. not only challenged to the ionic toxicities, but also adapted to the
osmotic stress which was caused by the high concentration of salt ions. Zoysia
spp. owned both morphological and physiological characters of draught
tolerance for adapting to the osmotic stress. In the view of morphological
features, stomata on the adaxial epidermis were surrounded by several ball-
shape structures and subsided. In some clones, stomata on abaxial epidermis
were more than that on the adaxial epidermis. The abaxial epidermis was not
covered with wax, while the adaxial epidermis was covered with wax. The stomata
of some clones were covered with wax. These structural characteristics could
help reduce water loss and increase drought tolerance. In the view of physio-
logical features, Zoysia spp. could accumulate solutes to lower osmotic
potential and maintain turgor pressure in the cell through osmotic adjustment
to reduce the damages. The accumulated solutes consisted of the out-coming
inorganic ion such as Na+, and the synthesized products such as soluble sugar
and proline. Among the total solutes, the Na+ played the most important role
to osmotic adjustment among the solutes. For adapting ionic toxicities,
Zoysia spp. could extrude salt by the salt glands which were located on the
adaxial epidermis to reduce the salt accumulation and damages. The clones of
Zoysia spp. with higher salt tolerance had much more salt glands on the
adaxial epidermis and were more active in salt-excreting than those with lower
salt tolerance. Further, the membrane system of Zoysia spp. with higher salt
tolerance was more stable to maintain the regular selective permeability to
prevent the cell from leaking under high concentration of Na+ accumulated.
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