Regulation by kinetin and abcisic acid of correlative senescence in relation to grain maturation,source-sink relationship and yield of rice (Oryza sativa L.)

When kinetin was applied to the source organ (flag leaf) of rice (Oryza sativa L. cv. Ratna), foliar senescence was delayed and grain yield per plant (as evidenced by grain weight, grain/straw weight ratio and 1,000 grain growth) was increased through the increase of sink activity (increase in dry weight of the grains/plant), duration of sink capacity as well as photosynthetic ability of the glumes (as determined by the chlorophyll content of the glumes of the developing grains). However, application of kinetin to the sink organs (fruits), promoted senescence of the source but increased the yield by increasing the sink capacity and 1,000 grain growth mostly at the earlier stage of reproductive development. Lower sterility percentage was associated with higher grain yield of the plant by kinetin treatments. ABA applied either to the source or the sink promoted leaf senescence and reduced the grain yield by reducing the sink activity, harvest index, sink capacity duration and increasing the sterility percentage. Thousand grain dry weight at harvest did not vary significantly amongst the treatments. It was concluded that nutrient drainage was associated with the correlative influence of fruit on the monocarpic senescence of rice plant and that a competetion for differential allocation of cytokinin and ABA in the source and sink organs initiates this senescence syndrome.     

Effect of calcium on water-stress-induced biochemical changes and yield of field-grown rice

Three different treatments by calcium (10²M), namely seed treatment, foliar spraying and their combination were applied on field-grown rice (Oryza sativa L. cv. Ratna) under both water stressed and non-stressed conditions in the course of plant development. The relative water content and leaf water potential decreased with increase in age of stressed and non-stressed plants. Pretreatment of seeds with Ca improved the water status of the plants most prominently at the vegetative stage but the effect gradually faded away with plant development. The foliar spraying by Ca was more effective in improving the water status of the plants at the reproductive stage. The combined Ca treatment significantly improved water status of the plants both at the vegetative and reproductive stages. The contents of chlorophyll and protein decreased and the activities of protease and RNase increased in the course of plant development in both non-stressed and even more in stressed plants. Ca treatments of seeds or plants or their combination inhibited the decline in chlorophyll and protein contents and the rising trends of protease and RNase activities, the combined treatment being most effective. During plant development free proline content increased significantly more in water stressed plants. In non-stressed plants there was a marked increase in the free proline content at the mature fruit stage. Ca treatment inhibited the rise of free proline in stressed plants. A significant reduction in yield components and yield of the crop in water stressed plants was increased by Ca treatment.     

Effect of corticosterone on adrenal 5-ene-3 beta-hydroxysteroid dehydrogenase in estrogen-treated rats

Treatment of adult male rats with estradiol-17 beta for 7 days results in adrenal hyperplasia, increased level of serum ACTH along with reduction in serum level of alpha 2u-globulin and inhibition of adrenal 5-ene-3 beta-hydroxysteroid dehydrogenase (5-ene-3 beta-HSD) activity. Administration of corticosterone in estrogen-treated rats reverses the effects of estrogen while in normal rats corticosterone treatment reduces adrenal weight, serum ACTH and adrenal 5-ene-3 beta-HSD activity. In vitro experiments show that alpha 2u-globulin fails to change adrenal 5-ene-3 beta-HSD activity in corticosterone pretreated rats while in normal and estrogen pretreated rats alpha 2u-globulin increases 5-ene-3 beta-HSD activity.     

Transformation-deficient mutants of piliated Neisseria gonorrhoeae

Seven transformation-deficient mutants of piliated, competent Neisseria gonorrhoeae were isolated by screening them for their inability to be transformed by chromosomal DNA after chemical mutagenesis. Three distinct classes of mutants were obtained, each of which was piliated, as determined by electron microscopy. One class exhibited abnormal colony morphology and was unable to take up DNA into a DNase-resistant state. A second class was morphologically normal and took up DNA into a DNase-resistant state normally, but was deficient in both chromosomal and plasmid transformation; mutations in these mutants may affect entry of DNA into the cell proper. A third class was similar to the second but was fully competent for plasmid transformation, suggesting that there was a defect in a late stage of chromosomal transformation.