VARIATION OF ACTIVE CHEMICALCONSTITUENTS IN RUMEX VESICARIUS UNDER- ENVIRONMENTAL STRESS AND MODE OF PROPAGATION

Abstract

Rumex vesicarius L. is a medicinal plant of a pharmacological importance. The present study was undertaken to evaluate the influence of salinity and water stress on the growth, yield, and accumulation of medicinally important secondary metabolites. Also, to evaluate the tissue culture technique as an alternative method for propagation and active constituent's production. Results showed that salinity and water stress adversely affected growth and yield of R. vesicarius under open greenhouse conditions. Relative growth rate, inflorescence number and number of fruits produced per individual plant during all growth stages were found generally higher in control plants than in plants exposed to water deficit or excess salinity. The accumulation of total flavonoids attained no change at low NaCl concentration (42.74 mM NaCl) in comparison with the control plants. At higher salt concentrations values declined significantly from 1005.60 )lg lg f. wt in control plants to 183.44, 107.18, and 104.15 )lg lg f. wt in plants treated with 85.47, 128.21, and 170.94 mM NaCl, respectively. Exposure of plants to different water stress treatments did not significantly affect their quercetin and kaempferol content, while the effects of salinity stress on quercetin and kaempferol content acted in destructive manner, and the two phytochemicals have not been detected in all NaCl treatments. Simple protocol for the micropropagation and acclimatization of R.

vesicarius was established. Tip and node segments were used as starting material for in vitro proliferation and multiplication of adventitious shoots. The developed rooted plantlets were successfully acclimatized to ex vitro conditions and exhibited normal development. The hypocotyl and cotyledon segments from two week-old R. vesicarius seedlings were used as explants for callus initiation. Callus maintenance and response of callus to increased NaCl concentration were reported. Callus mean fresh weight and mean dry weight values in general were not significantly affected by the presence ofNaCl concentrations below or equal to 170.94 mM. The higher level of salt stress led to reduction in mean fresh and mean dry weight yield, while the quercetin and kaempferol contents of cultured cells were enhanced. Kaempferol values for hypocotyl and cotyledonary derived calli increased from 14.39 and 18.38 (respectively) in control calli to 142.75 and 35.50 in calli treated with 128.21 mM NaCl.

The present study demonstrates that there is no clear correspondence between the physiological behavior for flavonoids accumulation at whole plant level and corresponding callus cultures. This may be due to the stepwise increase ofNaCl concentration applied to callus culture. Further studies are thus required in order to gain complementary information on these properties.

Keywords: Hommad, Rumex vesicarius, Salinity, Water stress, Falvorioids, Quercetin, Kaempferol, Callus, Micropropagation, Growth regulators.