Response of Tamarindus indica seedlings to salt stress

摘要

Tamarind (Tamarindus indica L.) seedlings were grown in sand culture under greenhouse conditions in order to examine the responses of growth, leaf mineral concentration and leaf gas exchange to increasing salinity levels. Four-months-old seedlings were exposed to a 10-week treatment, either with 0 (control), 40, 80 or 160 mM NaCl. Plant growth (fresh and dry weight) was slightly affected by 40 and 80 mM NaCl, but was markedly reduced on the 160 mM NaCl treatment. The root/shoot ratio increased by 24 when the NaCl concentration in the irrigation solution increased from 0 to 160 mM. With increasing salinity levels, leaf moisture content also increased, indicating a salt-induced leaf succulence. In plants treated with 160 mM NaCl, the concentrations of Na+ and Cl- in the leaf dry matter reached 0.91 and 0.92 mM g(-1), respectively. Leaf K+ decreased with higher salinity level, leading to higher Na+/K+ ratios. CO2 assimilation rate (A) diminished both with time of exposure and increasing salinity. T indica seedlings tolerated a salinity level of 80 mM NaCl, probably as the result of their ability to avoid excess ion accumulation through increased leaf volumes associated with succulence.