Salinity Effects on Growth Characteristics, Biomass Accumulation and Some Physiological Changes of Torpedograss (Panicum repens L.)

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The effects of NaCl concentrations (0, 50, 100, 200 and 400 mM) on the growth parameters, dry matter production, water content, stomata number, mineral content and proline content of torpedograss (Panicum repens L.) were evaluated to elucidate the salt tolerance mechanism of the plant. The values of all the growth parameters of torpedograss decreased with increasing concentrations of NaCl. Water content in the plants decreased from 84.5 to 68.0% under a salt stress of 400 mM. The contents of Na⁺, K⁺ and Ca²⁺ in the plants increased with increasing salt concentrations at 28 days after treatment (DAT). Shoot dry matter production was negatively correlated with the increase of Na⁺ content in shoots at 14 (r = -0.95) and 28 DAT (r = -0.93). Proline content increased by 10 and 100 fold under the salt stress of 200 and 400 mM, respectively, compared to that in the control plants. Positive correlation was observed between the proline content and Na⁺ content in shoots at 14 (r = 0.82) and 28 DAT (r = 0.94). Although torpedograss survived under a 200 mM NaCl stress, the plants grown under a 400 mM NaCl stress accumulated a high level of Na⁺ in cells at the early stage, which was severely toxic and led to the plant death at 21 DAT. The present study indicated that torpedograss maintained an adequate water content (about 68%), and accumulated higher levels of K⁺, Ca²⁺ and proline for maintaining the ion balance and osmoregulatory activities in cells to survive under NaCl stress conditions.