Effect of salt stress on growth and contents of organic and inorganic compounds in noni (Morinda citrifolia L.)

Abstract

Salinity is one of the abiotic stresses that most affect agricultural prodn., esp. in arid and semi-arid regions; however, among species there are large differences in salt tolerance. In this study, the effects of salinity on the growth and accumulation of org. and inorg. solutes were evaluated in 'noni' seedlings at 1, 10, 20, 30 and 40 days of salt stress in a 5 x 2 completely randomized exptl. design. Seedlings of 'noni' were grown in the nutrient soln. at two salinity levels (0 and 100 mM sodium chloride). Plant height, no. of leaves, stem diam. and dry matter of leaves, stems and roots, the allocation of biomass and the contents of org. and inorg. solutes were detd. in the different plant organs. Salinity reduced all growth variables, being less expressive in stem diam. The biomass allocation in leaves was higher than in roots, regardless of treatment or time considered. The contents of org. and inorg. solutes varied according to the plant part and the time of exposure to salinity. In general, salinity increased the contents of sodium ion (Na+), chloride ion (Cl-) and reduced potassium ion (K+), nitrogen (N) and phosphorus (P). Sol. carbohydrates and free amino acids were the main org. solutes contributing to osmotic potential of noni to salt stress. The salinity increased proline content in roots more than in leaves, but the proline content in the leaves was, on av. 17 and 6 times higher than that of roots of plants under control and stressed conditions, resp. Quant., proline does not contribute substantially to the osmotic potential of noni, however its increase suggests that it plays a role in the salt stress acclimation or is an indicator of salt-induced metabolic disorders. [on SciFinder(R)]