Browsing by Author "Shivashankar, S."

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    Ammonium enhances the nitrate induced nitrate reductase activity in coconut (Cocos nucifera L.) leaves
    (2007-02-08) Shivashankar, S.; Kasturi Bai, K.V.
    Induction of nitrate reductase (NR) activity by nitrate in leaves of low and high yielding coconut palms was markedly different, requiring different levels of nitrate for optimum induction. Ammonium enhanced induction of NR activity by nitrate, under both light and dark conditions. Nitrate uptake was also enhanced in the presence of ammonium in the induction medium. It is postulated that ammonium might bring about the activation of NR by binding to an allosteric site on the enzyme in addition to its role in inducing NR synthesis.
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    Biochemical changes and leaf water status of coconut genotypes differing in drought tolerance
    (2007-02-08) Shivashankar, S.; Nagaraja, K.V.; Voleti, S.R.; Kasturi Bai, K.V.
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    Biochemical changes during fruit maturation in coconut
    (2007-02-08) Shivashankar, S.
    Literature relevant to the biochemical changes occurring in the endosperm of the developing fruit, from the time of fertilization to maturity, is reviewed. The biosynthesis and utilisation of the major fruit components at various growth stages and the interrelationships among them are discussed. It is pointed out that the discovery of the involvement of a D- galactosidase in the formation of normal endosperm and in the control of germination is of major importance and should lead to more work on the mutant Maka-puno for a better understanding of the control mechanisms. Comparative studies of several coconut genotypes during fruit development are recommended in order to enhance their utility in the food industry and in the manufacture of other products. Some of the major areas for future work are listed.
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    Characterisation of drought tolerance in coconut
    (1993) Rajagopal, V.; Shivashankar, S.; Kasturi Bai, K.V.
    Coconut palms experience moisture stress of different magnitudes depending upon the extent of dry spell. Investigations on drought tolerance centred around the morphological observations on leaf and inflorescence characters, the physiological parameters like stomatal regulation and water potential components and biochemical aspects such as epicuticular wax and assay of certain sensitive enzymes. Out of the 23 genotypes screened, ten were found to possess desirable traits to withstand moisture stress. These included high stomatal resistance with low transpiration rate, high leaf water potential, high leaf-wax content, and relatively stable enzyme activities during moisture stress. Based on the above features, the released hybrids like LO x GB, LO x COD, WCT x COD are classified as drought tolerant. A rapid screening method has been developed to evaluate a large number of samples.
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    Chlorophylls and nitrate reductase activity in relation to heterosis in coconut seedlings
    (1985) Shivashankar, S.; Rajagopal, K.; Ramadasan, A.
    The F1 progeny of Chowghat Dwarf Orange (CDO) and West Coast Tall (WCT) cross tend to be highly heterozygous with respect to the colour of petiole and seedling vigour. The study indicated that the greenish brown coloured vigorous plants had higher chlorophyll (a + b) content and nitrate reductase (NR) activity compared to the orange coloured vigorous plants and the dwarfs. The greenish brown seedlings were also characterized by a larger leaf area and shoot d. wt. The results provide biochemical evidence in support of the morphological criteria being used at present in the selection of hybrid coconut seedlings.
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    Chlorophylls and Nitrate reductase activity in relation to Heterosis in coconut seedlings
    (2007-02-08) Shivashankar, S.; Rajgopal, K.; Ramadasan, A.
    The F1 progeny of Chowghat Dwarf Orange (CDO) and West Coast Tall (WCT) cross tend to be highly heterozygous with respect to the colour of petiole and seedling vigour. The study indicated that the greenish brown coloured vigorous plants had higher chlorophyll (a+b) content and nitrate reductase (NR) activity compared to the orange coloured vigorous plants and the dwarfs. The greenish brown seedlings were also characterized by a larger leaf area and shoot d. wt. The results provide biochemical evidence in support of the morphological criteria being used at present in the selection of hybrid coconut seedlings.
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    Comparative physiological studies on the drought tolerance of three hybrids of coconut
    (2007-02-08) Shivashankar, S.; George, K.M.; Rajagopal, V.; Voleti, S.R.
    Drought tolerance of three hybrid crosses developed at CPCRI, Kasaragod were compared using physiological and morphological indices. Leaf water potential, stomatal resistance and specific leaf weight measured during stress and pre-stress periods indicated that MYD x WCT possessed better ability to conserve moisture. Morphological parameters also gave similar results. Based on the data, the three hybrids could be ranked for drought tolerance in the order, MYD x WCT > MOD x WCT > COD x WCT
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    Comparative study of coconut genotypes for components of photosynthesis and respiration
    (2007-02-08) Shivashankar, S.; Kasturi Bai, K.V.; Ramadasan, A.
    The three coconut genotypes, West Coast Tall (WCT), Chowghat Dwarf Orange (CDO) and the hybrid WCTxCDO (TxD) were com-pared for the rate of apparent photosynthesis, dark respiration, chlorophylls a and b, total carotenoids, relative assimilation rate (RAR), leaf area, and stomatal frequency. With die exception of WCT, the rate of photosynthesis was not correlated with yield, There was significant difference in the rate of photosynthesis between TxD and WCT. CDO exhibited higher dark respiration as compared to WCT and TxD. TxD had significantly higher amounts of total chlorophylls than WCT and CDO. Stomatal frequency was not related with the rate of photosynthesis. The total leaf area of T x D was the highest followed by WCT and CDO. The results indicate that the total leaf area might be an important factor determining productivity.
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    Comparison of physiological and biochemical parameters of coconut hybrid seedlings
    (2007-02-08) Voleti, S.R.; Shivashankar, S.; Rajagopal, V.
    Annual rate of leaf production, leaf area, leaf dry weight, increase in height and girth of four year old seedlings of MYD x WCT were higher than those of COD x WCT and MOD x WCT. Activities of enzymes such as nitrate reductase and malate dehydrogenase was higher in MYD x WCT whereas that of acid phosphatase and glutamic-oxalic acid transaminase more in COD x WCT. Thus under irrigated conditions, the superiority of MYD x WCT hybrid from nursery stage is being maintained over the other two hybrids.
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    Diurnal Rhythm in Nitrate Reductase Activity of Cocos nucifera L. Leaves
    (1983) Shivashankar, S.; Rajgopal, K.
    Nitrate reductase (NR) activity in the leaves of Cocos nucifera L. exhibited a strong diurnal rhythm with a peak at 2 p.m. This rhythm was maintained under permanent dark or light conditions indicating the endogenous control of the rhythm. The NR activity was independent of tissue nitrate level. The study suggested a possible regulatory role of sugars on leaf NR activity.
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    Embryo culture of coconut: The CPCRI protocol
    (2007-02-08) Anitha Karun; Sajini, K.K.; Shivashankar, S.
    The field collection of embryos from mature nuts (9 months onwards), which can be easily identified for its hard eye and thick kernel, is done by means of a surface-sterilized cork borer. From the endosperm plug thus scooped out, the embryo is separated by using knife. The collected embryos are placed in distilled water. Once all the embryos are extracted, they are subjected to surface sterilization with 50% chlorine water for 20 minutes. The embryos are washed thoroughly in sterile water 4-5 times and inoculated individually into screw-cap bottles containing 2-5 ml sterile water (pH 5.7). The entire operation is to be done in surface-sterilized (absolute alcohol) inoculation hood (portable). The field-collected embryos are then transferred to Y3 solid medium within 2 months. The medium is supplemented with 30 g/1 sucrose and 1 g/1 charcoal for embryos of tall types and 60 g/ 1 sucrose and 2.5 g/1 charcoal for dwarf types. For the 8 months old nuts, embryos being small in size (1.5 to 4 mm), surface sterilization was done for 10 minutes. These embryos can be stored in half-strength Y3 medium for 1 month. Initially these embryos are inoculated in Y3 medium supplemented with 60 g/1 glucose and 2.5 g/1 charcoal. After 1 month, on attaining the full size, the embryo were transferred to regular retrieval medium. Cultures in the retrieval medium are initially kept in dark room till germination and later transferred to the illuminated room. Periodical sub-culturing was followed at monthly intervals. Once the plants attain the length of 5-7 cm, they were transferred to liquid medium. For rhizogenesis, the medium was supplemented with 1BA (5 ppm) and NAA (1 ppm). For pot establishment, sterilized sand, soil and coir dust in equal proportion were used as the potting mixture. The humidity was controlled in the initial stage of ex vitro establishment and macro nutrients were provided.
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    Enzymes as indicators of water stress in coconut
    (2007) Shivashankar, S.
    The study was conducted on West Coast Tall (WCT) palms growing under rainfed and irrigated conditions in the Institute farm. Activities of the following enzymes extracted -from leaves, viz: Peroxidase (PEROX), Poly Phenol oxidase (PPO) , Acid Phosphatase (APH),Glutamic oxalacetic trans aminase (GOT) and Malate dehydrogenase (MDH) were measured from Dec 85 to May 86 at an interval of one month. The levels of APH, GOT and MDH increased with the development of stress in the rainfed palms while they were consistently low in the irrigated palms. The activities of PPO and PEROX were highly variable. The soluble protein content in leaves of rainfed palms was also significantly lower. When the leaves were artificially stressed in PEG-6000 medium for 24 hours, two additional fast-moving isoenzymes of PPO were noticed on polyacrylamicle gel£ in the case of DxT and TxD while there was no change in the pattern of PPO isoenzymes in WCT and CDO, The results suggest that these enzymes could serve as useful indicators of stress in coconut.
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    Field collection and in vitro germination of coconut embryos
    (2007-02) Anitha Karun; Shivashankar, S.; Sajini, K.K.; Saji, K.V.
    A method for collection and inoculation of coconut embryos directly in the field was investigated. Embryos collected from 8-11 months old nuts were surface sterilized and cultured in liquid nutrient medium, inside a portable hood made of plexiglass. The cultures were maintained at room temperature for 3 to 5 days after which they were transferred to fresh medium and stored inside the culture room. The extent of contamination at the time of shoot production was very low. These shoots formed a number of lateral roots in Y-3 medium supplemented with N A A and IB A. The study highlights the possibility of employing the field technique for successful collection of coconut germplasm as zygotic embryos and their retrieval in vitro.
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    Heritability of seedling vigour in coconut palm
    (2007-02) Ramadasan, A.; Kasturi Bai, K.V.; Shivashankar, S.; Vijayakumar, K.
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    Impact of dry spells on the ontogeny of coconut fruits and its relation to yield
    (2007-02) Rajagopal, V.; Shivashankar, S.; Jacob Mathew
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    Influence of Vesicular—Arbuscular Mycorrhiza on Growth and Nitrate Reductase Activity of Black Pepper
    (2007-02) Shivashankar, S.; Rohini Iyer
    Supplementation of the pots with soil containing spores of Glomus fasciculatum (Thaxter sensu Gerdemann) Gerdemann and Trappe enhanced the root infection from 55 per cent in the control to 98 per cent at the end of five months in black pepper plants. The growth of plants varied directly in proportion with the percentage of root infection. The phosphate levels used in the study did not adversely affect the mycorrhizal population. Mycorrhizal plants showed statistically significant increase in the tissue N, P and leaf nitrate reductase activity over the control. The nitrate compensation point (NCP) was lower in mycorrhizal plants than in the control.
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    Leaf Water Potential as an Index of Drought Tolerance in Coconut (Cocos nucifera L.)
    (1988) Rajagopal, V.; Shivashankar, S.; Kasturi Bai, K.V.; Voleti, S.R.
    Leaf water potential as an index of drought tolerance in coconut (Cocos nucifera L.). Rajagopal V, Shivishankar S, Kasturibai K V, and Voleti S R. (PI. Physiol. & Biochem. Divn., Central Plantation Crops Res. Inst., Kasaragod 670 124, India). PI Physiol. & Biochem. 15(1) : 80-86, 1988—Coconut genotypes were screened for drought tolerance using the leaf water potential (