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

Nieman, R. H., Clark, R. A., Pap, D., Ogata, G. and Maas, E.V. 1988. Effects of salt stress on adenine and uridine nucleotidepools, sugar and acid-soluble phosphate in shoots of pepperand safflower.-J. exp. Bot. 39: 301–309. Pepper (Capsicum annuum cv. Yolo wonder) and safflower (Carthamustinctonus L. cv. Gila) were grown hydroponically and subjectedto a salt stress (51 mol m^–3 NaCl plus 25.5 mol m^–3CaCl₂). Mature photosynthetic source leaves and shoot meristematicsinks (young pepper leaves and safflower buds) were analyzedfor nucleotides by high performance liquid chromatography andfor hexose and acid-soluble P—pepper was still vegetativewhereas safflower had switched to flower bud formation—thesalt stress reduced the fresh shoot yield of pepper by nearlytwo-thirds and of safflower by half. It reduced the ATP pooland ATP/ADP ratio in the source leaves of both species and alsoin the young pepper leaves. It had little or no effect on ATPor other nucleotide pools in safflower buds. The UDPG pool wasnot affected in source leaves or safflower buds, but in theyoung pepper leaves it was reduced by half, along with UTP.These reductions were accompanied by over a 3-fold increasein 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 pepperbecause it reduced assimilation of photosynthate, possibly aconsequence of reduced UDPG, UTP, and ATP pools in the growingleaves. Salt stress did not so markedly affect assimilationof photosynthate in the more tolerant safflower. Key words: Growth suppression, energy charge, UDPG