PHYSIOLOGICAL RESPONSE AND RECOVERY OF Zoysia japonica Steud. (Family: Poaceae) TO DROUGHT STRESS

The purpose of this research was to understand the effects of mild, moderate and severe drought stress and subsequent recovery in zoysia grass (Zoysia japonica). Mild drought (60%~70% of field capacity), moderate drought (45%~55% of field capacity), and severe drought (25%~35% of field capacity) were maintained for 16 days. Recovery was determined after 2 to 6 days of re-watering. At the end of the experiment, all treatments had reduced aboveground and belowground fresh and dry weights relative to the control treatments. Leaf chlorophyll concentration in three treatments from day 5 to 16 was significantly lower compared with controls, with the greatest affect observed in the severe drought stress treatments. The net photosynthetic rate in plants exposed to either moderate or severe drought treatments was significantly lower than that of control. SOD activity significantly increased in plants exposed to mild and moderate drought at 7 to 13 days, and was significantly lower in plants exposed to severe drought at 1 to 10 days. POD and CAT activity increased in all treatments, and with the greatest effect observed in the severe drought stress treatments. MDA concentration in plants exposed to either moderate or severe drought at 4 to 13 days was higher than that in control plants. Leaf proline concentration significantly increased in all treatments at 7 to 13 days. The chlorophyll concentration, POD and CAT activity, MDA and proline concentration in leaves of plant reached the control level after the recovery, even in plants exposed to severe drought. These data collectively suggest that zoysia grass possesses excellent drought tolerance.