Submergence inhibits photosynthesis by terrestrial wetland plants, but less so in species that possess leaf gas films when submerged. Floodwaters are often supersaturated with dissolved CO2 enabling photosynthesis by submerged terrestrial plants, although rates remain well-below those in air. This important adaptation that enhances survival in submerged conditions is reviewed.

The present investigation was undertaken to mass propagate Cymbidium mastersii, an ornamental orchid of Northeast India by in vitro propagation method. This approach could also help for the conservation as well as commercialization of C. mastersii and other threatened and ornamental orchids.

Tea is the oldest, most popular, non-alcoholic caffeine containing beverage in the world. Tea plants are prone to the attack of many diseases which can be controlled by the treatment of pesticides. These pesticides contain heavy metal which prolonged accumulation can lead to the damage of crop yield both in quantity and quality. In the present study, we observed the effects of high concentration of Cu stress on physiological and biochemical parameters. The tea cultivars (S 3 A 3 and TS-491) were collected from the Rosekandi Tea Estate, Silchar, Assam. The accumulation of Cu in the different parts of the tea plants had a positive correlation with the Cu stress. The accumulation of Cu was higher in roots than in leaves and also the new stems. The results show gradual decrease in the photosynthetic activity with the increase in the concentration of the Cu stress in both the cultivars. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) increased with the increase in the Cu concentration but remarkably in different manner in both the cultivars. The activities of antioxidants ascorbate peroxidase (APX), CAT, SOD and POD in cultivar S 3 A 3 increased up to 500 µM and at 600 µM showed a low rate of increase whereas TS-491was tolerant up to 400 µM. The responses in the oxidative stress were characterized by an accumulation of malondialdehyde (MDA). Phenol content has also positive correlation with increase in the concentration in both the cultivars up to 500 µM. Finally it was concluded that Cu is tolerant to the cultivars of tea plant to some extent (specifically at lower concentration), but at higher concentration (beyond 400 µM) of Cu with exposure time, tea plant had a strong inhibition of growth by damaging the normal metabolism.

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