Effects of Salt Stress on Adenine and Uridine Nucleotide Pools, Sugar and Acid-Soluble Phosphate in Shoots of Pepper and Safflower

Abstract

Nieman, R. H., Clark, R. A., Pap, D., Ogata, G. and Maas, E. V. 1988. Effects of salt stress on adenine and uridine nucleotide pools, sugar and acid-soluble phosphate in shoots of pepper and safflower.—J. exp. Bot. 39: 301-309. Pepper (Capsicum annuum cv. Yolo wonder) and safflower (Carthamus tinctorius L. cv. Gila) were grown hydroponically and subjected to a salt stress (51 mol m~3 NaCl plus 25-5 mol m~3 CaCl2). Mature photosynthetic source leaves and shoot meristematic sinks (young pepper leaves and safflower buds) were analyzed for nucleotides by high performance liquid chromatography and for hexose and acid-soluble P—pepper was still vegetative whereas safflower had switched to flower bud formation—the salt stress reduced the fresh shoot yield of pepper by nearly two-thirds and of safflower by half. It reduced the ATP pool and ATP/ADP ratio in the source leaves of both species and also in the young pepper leaves. It had little or no effect on ATP or other nucleotide pools in safflower buds. The UDPG pool was not affected in source leaves or safflower buds, but in the young pepper leaves it was reduced by half, along with UTP. These reductions were accompanied by over a 3-fold increase in hexose and a large decrease in ester phosphate. In safflower, on the other hand, salt stress had little or no effect on UDPG, hexose, or ester phosphate in either source leaves or buds. The results suggest that salt stress reduced the growth of pepper because it reduced assimilation of photosynthate, possibly a consequence of reduced UDPG, UTP, and ATP pools in the growing leaves. Salt stress did not so markedly affect assimilation of photosynthate in the more tolerant safflower.