Tea [Camellia sinensis (L.) O. Kuntze] is an aluminum (Al) hyperaccumulator plant and is commercially important due to its high content of antioxidants. Although Al induced growth is well-known for the plants growing in acid soil, yet the cause underlying the stimulatory effect of Al has not been fully understood. To investigate the possible role of Al in growth induction, we studied morphological, physiological as well as biochemical changes of tea plant under different Al concentrations (0-4,000 μM). In hydroponics, Al (15 μM), enhanced shoot and root growth, but at higher concentrations, it caused oxidative damage which culminated in a cascade of biochemical changes, Al content increased concurrently with the maturity of the leaf as well as stem tissues than their younger counterparts. Hematoxylin staining indicated that Al accumulation started after 6 h of exposure in the tips of young roots and accumulation was dose dependent. The physiological parameters such as pigments, photosynthetic rate, transpiration and stomatal conductance were declined due to Al toxicity. Alteration in activated oxygen metabolism was also evidenced by increasing lipid peroxidation, membrane injury, evolution of superoxide anions and accumulation of H(2)O(2). Contents of phenols initially exhibited an acceleration which gradually plummeted at higher levels whereas total sugar and starch contents decimated beyond 15 μM of Al concentration. Activities of antioxidant defense enzymes were increased with the elevated concentration of Al. Expression of citrate synthase gene was up-regulated in the mature leaves, young as well as old roots simultaneously with increased concentration of Al in those parts; indicating the formation of Al-citrate complex. These results cooperatively specified that Al concentration at lower level promoted growth but turned out to be a stressor at elevated stages indicating the sensitivity of the cultivar (T-78) to Al.

Zinc is the most widespread deficient micronutrient in the tea growing soils of India which affects growth of the plants. In order to investigate the structural, physiological, and biochemical changes under Zn stress (i.e. both deficient and excess supply) of tea [Camellia sinensis (L.) O. Kuntze cv. T-78] plants, we treated young plants with ZnSO 4 at 0 (deficiency), 0.3, 3 (optimum), and 30 µM (toxic) concentrations for 8 weeks. Zn deficiency and excess resulted in considerable decrease in shoot and root fresh and dry masses, and transmission electron microscopy (TEM) revealed disorganization of some cellular organelles. Further, Zn-stress decreased net photosynthetic rate (P N ), transpiration rate (E), stomatal conductance (g s ), and content of chlorophylls a and b. On the other hand, content of superoxide anion, malondialdehyde, hydrogen peroxide, and phenols, and electrolyte leakage were elevated in stressed plants. The activities of ascorbate peroxidase, catalase, superoxide dismutase, and peroxidase as well as expression of respective genes were up-regulated under Zn-stress. Nevertheless, antioxidant system as a whole did not afford sufficient protection against oxidative damage.

An alternative protocol for in vitro propagation of Picrorhiza scrophulariiflora is described using bavistin and adenine sulphate. The explants differentiated into multiple shoot buds on MS supplemented with various concentrations of bavistin and adenine sulphate ranging from 0 -400 mg/l either alone or in combination. Maximum number of multiple shoots were obtained on MS containing the combination of bavistin (100 mg/l) and adenine sulphate (100 mg/l). In this combination as high as 28 shoots per explant was achieved and also vetrification of the cultures were not recorded. This study also demonstrates that the bavistin has stronger cytokinin-like activity than adenine sulphate. For instance, it was observed that bavistin alone in the concentration of 300 mg/l produced as high as 24 shoots per explant, however, adenine sulphate (100 mg/l) could produce a maximum of 18 shoots per explant. Moreover, higher or lower concentration did not improve the shoot multiplication. The microshoots were separated from the multiple shoots and transferred to MS containing various concentrations of auxins. Among them, NAA (1 mg/l) produced as high as 6 roots per explant. The regenerated plantlets were hardened in plastic cups (6 x 8 cm) containing 9 : 1 virgin soil and soil at Kyongnosla nursery and acclimated for four weeks. A 90% survival rate of the plants was recorded after 60 days.

No abstract

A reproducible in vitro regeneration system for Nepalese kutki (Picrorhiza scrophulariiflora Pennell) was developed from in vitro leaf derived callus. Induction of more than seven shoot buds per explant was achieved on Woody plant medium (WPM) supplemented with 0.53 μM α-napthaleneacetic acid (NAA) and 0.23 μM kinetin (KIN). The shoots were elongated on WPM supplemented with 0.44 μM 6-benzylaminopurine (BAP) and rooted on WPM supplemented with 5.3 μM NAA within 2 weeks. The random amplified polymorphic DNA (RAPD) analysis indicated genetic uniformity of the micropropagated plants with its donor plants.