Tamarindus indica L. seedlings are moderately salt tolerant when exposed to NaCl-induced salinity

To study the salt tolerance of tamarind trees (Tamarindus indica L.), the effect of salinity on growth, photosynthesis, leaf chlorophyll concentration and mineral uptake of seedlings was investigated. Four-week-old seedlings were grown in a sand culture and were treated with different salt solutions for a period of 20 weeks. Treatments were prepared by adding 0, 20, 40, 60 and 80 mM NaCl to the nutrient solution. Plant growth was slightly affected by 20 and 40 mM NaCl but was markedly reduced on the 60 and 80 mM NaCl treatment. Foliar injuries (chlorosis) appeared only within the 60 and 80 mM variant. It was interesting that with increasing salinity concentration, leaf water content increased, indicating a salt-induced leaf succulence. This phenomenon was accompanied with an upward cupping of the leaflets. Increased NaCl salinity decreased the net photosynthesis rate from 5.6 to 0.5 mumol CO2 m(-2) s(-1) in 80 mM treatment compared with the control. Chlorophyll was also decreased with increasing salinity. Raising NaCl in the irrigation solution increased Na+ and Cl- concentration in the plant tissue. The uptake of the cations Ca2+ and K+ to the leaves was successfully maintained in the salt-stressed plants. The results indicate that T. indica seedlings tolerated a salinity concentration of up to 40 mM NaCl. Therefore, in the seedling stage, tamarind can be characterised as a moderate salt tolerant fruit tree species. (C) 2004 Elsevier B.V. All rights reserved.