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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.

The long‐term effect of organic recycling on some aspects of quality in a lowland rice soil of an Indian plateau region was studied. The experiment was set up at the agricultural experimental farm of the Indian Statistical Institute, Giridih, Bihar, India. Two rice cultivars, and treatments with four organic supplements (cowdung manure, Leuceana leaves, decomposed farm residue and Sesbania), chemical fertilizers (urea, superphosphate and muriate of potash) and no input were arranged in a factorial randomized block design. Organic supplements improved soil quality parameters such as water holding capacity, total organic C, microbial biomass C, urease and acid phosphatase activities of soils in comparison to chemical fertilizers and no input. Among the organic supplements, cowdung manure gave significantly higher organic C (1.39%), microbial biomass C (276.46 μg g−1 dry soil), urease activity (32.79 and 21.22 μg urea hydrolized g−1 dry soil h−1 at 37 °C by the buffer and non‐buffer method, respectively) and acid phosphatase activity (1.99 μmol p‐nitrophenol released g−1 dry soil h−1 at 37 °C) than the others. The conversion of organic C into biomass C (2.46%) was highest in Leuceana‐treated soil.

The effect of organic sources of nutrients and inorganic fertilizers, was studied on grain yield of lowland rice and some aspect of soil quality parameters in a field experiment at Agricultural Experimental Farm of Indian Statistical Institute, Giridih, situated at eastern plateau region of India, during consecutive years 1997-2002. Chemical fertilizers and various organic matters were applied to two rice cultivars, Sabita and Subarna. The highest mean grain yield was 3.53 t ha )1 and maximum agronomic efficiency was 60.3 % with the application of inorganic fertilizer followed by cow dung, where 3.47 t ha )1 grain yield was recorded with an agronomic efficiency of 57.5 %. Grain yield of rice recorded under organic sources of nutrients was not significantly different from that of inorganic fertilization though there was improvement in soil quality parameters under organic sources. Soil organic carbon (0.72 %), microbial biomass-C (279.23 lg g )1 dry soil), urease activity with buffer (33.54 lg urea hydrolyzed g )1 oven-dry soil) and nonbuffer (21.97 lg urea hydrolyzed g )1 of oven-dry soil) methods and acid phosphatase activity (2.24 lg paranitrophenol released g )1 of oven-dry soil) analysed following the harvest of the crop were highest under cow dung manure treatment; the most efficient organic source under the experiment. Mean grain yield of rice was significantly higher in Sabita cultivar over Subarna. The regression analyses among the variables have shown that there was linear relationship among soil parameters and grain yield of rice.

BackgroundThe control and prevention of dengue largely depends on vector control measures, environmental management, and personal protection. Dengue control programmes are facing great challenges due to development of insecticide resistance among vector mosquitoes. Information on susceptibility status to different insecticides is important for national programmes to formulate vector control strategies.MethodsWe have studied the larval susceptibility of Aedes albopictus to temephos and adult susceptibility to 4% DDT, 0.05% deltamethrin, and 5% malathion as per WHO protocols in the northern districts of West Bengal. Polymorphisms in the VGSC gene were studied by direct sequencing of PCR products.ResultsThe Ae. albopictus larval population showed sensitive [Resistance Ratio (RR99)<3] to moderate levels of resistance (510) to temephos at different study sites. Adult bioassay results revealed that Ae. albopictus was highly resistant to DDT [Corrected Mortality (CM) < 90%] in all the study sites and susceptible to deltamethrin and malathion (CM > 98%), except in Dhupguri where a low level of resistance to deltamethrin (CM = 96.25%) was recorded. None of the six important kdr mutations (S953P, I975M/V, L978, V980G, F1474C, D1703Y) were found in the VGSC of studied mosquitoes, but we identified 11 synonymous and 1 non-synonymous mutation in the VGSC gene.ConclusionThe higher susceptibility level to deltamethrin and malathion, along with the absence of important kdr mutations indicates that these two insecticides are still effective against Ae. albopictus in the study areas. The susceptibility status of temephos should be monitored closely as low to moderate levels of resistance were observed in few sites. A similar study is recommended for monitoring and early detection of insecticide resistance in other parts of the country.

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