Effects of salinity and relative humidity on growth and ionic relations of plants


  • M. SALIM

    1. School of Biological Sciences, University of Sydney, Australia-2006
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      Land Resources Section, National Agricultural Research Centre, Park Road, Islamabad, Pakistan.


Growth and ionic relations of mung bean (Vigna radiate L.), sunflower (Helianthus annuus L.), red kidney bean (Phaseolus vulgaris L.), tomato (Lycopersicum esculentum L.) and Atriplex spongiosa L. were studied with three concentrations of NaCl up to 100 mM in the root medium and at either 30% or 90% relative humidity (RH). Two harvests (7 days apart) of all five plant species were taken. Increase in root zone salinity and relative humidity significantly decreased the transpiration rates of all except A. spongiosa. Fresh weight/dry weight ratios of the shoots were unaffected by salinity, except in mung bean, whereas increased RH generally increased the ratios. Shoot/root ratios of mung bean and A. Spongiosa plants were unaffected by both salinity and humidity but increased salinity decreased these ratios in the other three species. In sunflower and tomato greater RH increased the shoot/root ratios at all salt levels. Generally, increased salinity decreased the relative growth rates of mung bean, red kidney bean and sunflower whereas increased RH improved the relative growth rates of mung bean. A. Spongiosa and sunflower.

In most of the species, concentrations of [K + Na] and Cl in the shoot tissue water increased, and those of Ca and Mg decreased, with increase in NaCl concentration in the root medium up to 100 mM. However, in some cases, the concentrations of inorganic ions in the shoot tissue water decreased at all levels of NaCl when the RH in the growth cabinet was increased up to 90%. Concentrations of K in root tissue water of all five species decreased and their Na and Cl concentrations generally increased with increasing salinity of the root medium. Although rates of Na transport relative to that of K through the roots of all the species significantly increased with salinity, red kidney bean roots conducted more Na relative to K under low RH compared with high RH. Similarly the roots of sunflower and A. spongiosa conducted more Cl relative to [K + Na] when the RH was decreased. Higher rates of net ion transport from roots to shoot of mung bean and A. spongiosa plants resulted in higher concentrations of K, Na and Cl in their shoot tissue water when the RH was decreased from 90% to 30%.