Comparison of sodium uptake by and transport in detached plant parts among several crops

Abstract

Na+ uptake by and transport in detached petiole or leaf sheath (DP) and detached petiole or leaf sheath with leaf blade (PLB) were investigated among several crops. DP and PLB were cultured in a nutrient solution containing 40 mM NaCI, then the time-dependent movement of22Na+ within tissues was investigated. Results obtained were as follows: 1) The Na+ transport to the xylem was in the following order: rice > cucumber > field bean > soybean = adzuki bean > maize > pumpkin. 2) The relationship between the transpiration and22Na+ uptake varied among the crops. Since the value of the transpiration stream concentration factor of Na+ was less than 1, only mass flow could not account for the Na+ transport in detached plant parts. 3)22Na+ taken up from the xylem of petioles or leaf sheaths, was transported to the leaf blade in 2 gramineous crops, 3 leguminous crops, and cucumber, and the ability of Na+ exclusion from the leaf blade was in the following order: maize > field bean = cucumber > soybean = adzuki bean > rice. 4) In pumpkin,22Na+ could not penetrate into the xylem, and was retained in the lower part of the petiole. Therefore22Na+ was not transported to the leaf blade, suggesting that pumpkin has a special mechanism to retain Na+ in the lower part of the petiole. © 1999, Taylor & Francis Group, LLC.