A Preliminary Report on Tolerance of Vetiver to Submergence

摘要

To date, there are still no ideal bio-or eco-measures protecting or stabilizing inner slopes of rivers, reservoirs, and lakes, as plants established on the inner slopes are almost all drowned by the elevated water level in rainy season. Thereby, the key is screening out strongly tolerant plant species to submergence in order to effectively stabilize and vegetate the 'wet' slopes. A comparative study on the tolerance of eight grasses to submergence was conducted. The selected eight grasses were vetiver grass ( Vetiveria zizanioides Nash), bahia grass (Paspalum notatum Flugge), aciculate chrysopogon (Chrysopogon aciculatus Trin. ), Bermuda grass ( Cynodon dactylon Pars.), common centipedegrass (Eremochloa ophiuroides Hack.), St. Augustine (Stenotaphrum secundatum Kuntze.), carpet grass ( Axonopus compressus Beauv.), and sour paspalum (Paspalum conjugatum Bergius). They are all excellent plant species for soil and water conservation in southern China. The tested plants were raised in pots first and then put into a cement tank filled with water to investigate their tolerance to complete submergence. Through 3 years of observation, it was found that vetiver and Bermuda grass could tolerate the longest time of submergence, at least up to 100 days and were probably more than that; bahia grass ranked second, up to 60 - 70 days, followed by carpet grass, up to 32 - 40 days and then aciculate chrysopogon and sour paspalum, up to 25-32 days; St. Augustine was penultimate, up to 18 - 32 days; the poorest species to resist submergence was centipede grass, only 7-10 days. Moss seemed to be an environmental factor influencing the tolerance of plants to submergence, inferring that muddy or polluted water kills plants more easily than clear water. A further experiment, including the final tolerance of vetiver and Bermuda grass and the tolerant mechanisms of the 8 species, is still ongoing.