| Abstract: | During periods of water depletion the water supply of plants from saline soils is reduced due to the simultaneous decrease of the soil osmotic and the soil matric water potential. Common models on the water uptake from saline soils assume a similar depressing effect of osmotic and matric water potentials on the water uptake by plants. As plants differ in their ability to overcome salt stress and soils differ in their water retention curves there is some doubt for the general validity of this assumption. The paper presents results of an experiment with rape grown in a sandy and a silty soil at three salinity levels. The transpiration rate of the plants was determined during a period of 34 hours and related to the total water potential of the two soils. In case of the silty soil, the transpiration was related to the total soil water potential at all salinity levels. In the sandy soil, however, the transpiration was much more affected by decreasing soil matric potential than by equivalent decreases of the soil osmotic potential. The results show that the effect of both potentials on the water supply of plants is not the same and has to be treated separately. |
