VARIABLE SEED GERMINATION AND SEEDLING GROWTH RESPONSES OF HIPPOPHAE RHAMNOIDES AND H. SALICIFOLIA TO CADMIUM

Abstract

The phytotoxic effects of heavy metals (HMs) and metalloids in crop plant species are well documented. There is, however, a dearth of information concerning HM toxicity in wild plants of medicinal and economic importance particularly those from high altitude regions. Here, we have assessed the effects of a range of Cd concentrations on seed germination, seedling growth and certain associated metabolic parameters of Hippophae salicifolia (Kinnaur) and two populations of H. rhamnoides namely, Kinnaur and Lahaul (Himachal Pradesh, India). The stated Hippophae (seabuckthorn) species, distributed in Himalayan states of India including Himachal Pradesh, possess tremendous medicinal value, fix atmospheric nitrogen and reduce soil erosion. Higher Cd concentrations differentially suppressed the seed germination of the tested Hippophae species/populations with the lowest effect being in case of H. salicifolia. The lower Cd concentrations stimulated the germination in H. salicifolia and H. rhamnoides Kinnaur. The seedling growth was suppressed by Cd with organ- and species/population specific differences. The magnitude of root growth inhibition was invariably greater than that of shoot and H. salicifolia proved more tolerant to Cd than both the H. rhamnoides populations. The TTC reduction ability of embryos excised from Cd treated seeds was marginally suppressed by Cd while α-amylase activity was substantially inhibited. Due to Cd treatment, the MDA contents, activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) and proline contents increased in the seedling tissue. No marked species/population specific differences were evident in these parameters except that MDA contents did not change due to lower Cd concentration in H. salicifolia. The relative Cd tolerance of H. salicifolia has implications for its better survival in an HM-contaminated scenario.