Morpho-physiological adaptation of Jatropha curcas L. to salinity stress

Abstract

The aim of the current study is to assess the growth response, biochemical changes, photosynthetic pigments content and gas exchanges of physic nut (Jatropha curcas) grown under natural saline conditions. The experiment was arranged in a completely randomized design based on the following soil electrical conductivities: 0.29 dS.m-1 (control), 1.76 dS.m-1 (moderate salt concentration), 2.61 dS.m-1 (high salt concentration), 3.79 dS.m-1 (very high salt concentration). Physic nut plants were kept under saline conditions for 19 days in greenhouse. Plant growth analyses were performed on a weekly basis. Plant biomass allocation was quantified at the end of the experiment. Leaf gas exchange, stomatal conductance, Fv/Fm and quantum yield were quantified 102 days after planting. Photosynthetic pigments, amino acids, proline and carbohydrates in fresh leaf tissue were also quantified. The leaf antioxidant enzymes catalase (CAT) and ascorbate peroxidase (APX) were quantified. Although there was no alteration in biomass allocation, the initial growth of J. curcas was gradually reduced by increasing salt concentration, which was observed through reduced plant height, stem diameter, and total number of leaves. Soil electrical conductivity 3.79 dS.m-1 was lethal to seedlings. Seedlings exposed to salt stress had their photosynthesis, stomatal conductance, transpiration and effective photochemical efficiency reduced, and their catalase and ascorbate peroxidase enzyme activity increased. Amino acids, proline and carbohydrate concentrations increased due to salt stress, whereas there was decrease in the chlorophyll content. J. curcas is sensitive to soil salinity at electrical conductivity levels higher than 1.76 dS.m-1. To some extent, salinity effects can be relieved by osmolyte accumulation and by greater antioxidant activity; however, these factors were not sufficient to keep plant growth within normal rates.