In vitro carbohydrate stress: salicylic acid increases soluble invertase activity in Pistacia vera L. in vitro plantlets

The action of salicylic acid (SA) has been well investigated in plant resistance against pathogen attacks but its role may be extended to a more global anti-stress plant cell strategy. The expression of defense-related functions may be also enhanced by elevated hexose levels. To verify if there exists a relation between these two defense programs, SA effect on soluble acid invertase (EC 3.2.1.26) activity was investigated in in vitro grown Pistacia vera plantlets from isolated embryonic axes, at different doses of exogenous sucrose. For this purpose embryonic axes were cultivated on Murashige and Skoog medium containing 10, 20, 30, 40 and 50 g.L-1 sucrose (control range) with 50 µM SA. After one month of growth, roots and shoots were used for analysis separately. SA treatment significantly enhanced the soluble invertase activity in tissues. The increase was more remarkable in root tissues. Sucrose limitation (10 g.L-1) SA-treated plantlets and sucrose osmotic stressed (50 g.L-1) SA-treated plantlets have shown very important increases in invertase activity and this was accompanied with a significant raise of total protein in spite of growth reduction. The implication of soluble invertase in the anti-stress strategy of these tissues seems to be important. It is likely that hexose signaling of defense expression may be related to the action of salicylic acid on soluble invertase activity.