Partitioning of photosynthetic carbohydrates in leaves of salt-stressed olive plants

Abstract

Changes in photosynthetic carbon partitioning were determined, during 14CO2 pulse-chase experiments, in fully-expanded leaves of olive (Olea europaea L. cv. Frantoio) plants treated in containers with 100 mM NaCl for 5 weeks and compared with partitioning in leaves of untreated plants. Salt stress caused an increase in the radioactivity partitioned into mannitol and a decrease of that recovered as glucose. The radioactivity in sucrose was significantly reduced in salt-treated plants after 19.5 min of chase. There was no difference between the two treatments in the radioactivity found in fructose and galactose, whereas a significant decrease in the radioactivity found in stachyose and raffinose of salt-treated leaves was observed after 19.5 min chase. The radioactivity incorporated into starch was 11 and 16% of the total in control and salt-treated leaves respectively. There were no significant differences in the leaf pools of soluble carbohydrates over the chase period, except for mannitol which increased in the leaf tissue of salt-treated plants. Over the course of the diurnal period, and under high irradiance conditions, the leaf mannitol content increased more markedly in salt-treated plants than in the controls. In contrast, contents of other nonstructural carbohydrates were not affected by the 100 mM NaCl treatment.