Browsing by Author "Laxman, R.H."

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    Day time fluctuations in photosynthetic parameters and water relations in juvenile coconut palms grown under rainfed and irrigated conditions
    (2007-02-08) Rajagopal, V.; Naresh Kumar, S.; Kasturi Bai, K.V.; Laxman, R.H.
    Day time (7 h to 18 h) fluctuations in photosynthetic parameters (net photosynthetic rate, Pn; stomatal conductance, gs; internal CO2 concentration, Ci); water relations (leaflet water potential, Yiear; transpiration rate, E) and weather parameters (photosynthetically active radiation, PAR; leaflet temperature, Tleaff; air vapor pressure deficit, VPD) were estimated in juvenile palms of coconut grown under rainfed and irrigated conditions. Variations in values and day time fluctuations in photosynthetic parameters and water relations were observed between palms grown under rainfed and irrigated conditions, Pn, E and gs were maximum between 09:00 and 11:30 and 15:00 and 16:00 h. Ci and ψie,r were least during mid-day. Mid-day slump in Pn and gs was observed. Tleaf, PAR and VPD were maximum between 09:00 and 16:00 h. E and VPD were positively correlated. Rainfed palms had higher Tleaf, Ci, CilCa and leaf to ambient temperature difference (∆T) and lower Pn, ψr and E compared to the irrigated palms. Instantaneous and intrinsic water use efficiency increased under mild water-deficit conditions. It is apparent that under rainfed conditions the carbon assimilation efficiency was low compared to irrigated condition. VPD and Ar influenced gs and water relations during day time which predominantly determined the variations in photosynthetic efficiency of coconut under irrigated and rainfed conditions.
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    Factors contributing to female flower production and button shedding in coconut
    (2007-02) Kasturi Bai, K.V.; Laxman, R.H.; Ratnambal, M.J.; Srinivasa Reddy, D.V.
    Influence of various factors viz., varietal difference, irrigation, leaf area and dry matter production, on female flower production and shedding of buttons in coconut have been reported in this paper. Among the 16 varieties, comprising both Tails and Dwarfs, varietal difference was found to exist in female flower production and nut setting. However, between Tails and Dwarfs no significant difference in button shedding was observed. Although, increased female flower production was observed in the irrigated palms as compared to rainfed palms, the variation in button shedding between the two was not significant. Seasonal changes were found to influence the button shedding. Leaf area and dry matter production did not influence the button shedding. However, an indirect relation has been observed between leaf area and shedding of buttons via female flower production. The observations clearly indicated that shedding of buttons is directly related to the number of female flowers produced in a bunch. An attempt has been made to check the button shedding by spraying salicylic acid and encouraging results have been obtained. This needs to be further investigated before coming to a conclusion.
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    Photosynthetic Characteristics and Water Relations in Coconut Palms under Drip Irrigation Levels on Sandy and Laterite Soils
    (2007-02) Naresh Kumar, S.; Maheswarappa, H.P.; Dhanapal, R.; Laxman, R.H.; Rajagopal, V.
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    Photosynthetic Characteristics and Water Relations in Coconut Palms Under Drip Irrigation on Sandy and Laterite Soils
    (2002) Naresh Kumar, S.; Rajagopal, V.; Laxman, R.H.; Dhanapal, R.D.; Maheswarappa, H.P.
    Plants response to irrigation depends on various internal and external factors. The leaf moisture status and its photosynthetic efficiencies are interrelated and largely influence the final economic yield.To assess the extent of this influence on yield, coconut (Cocos nucifera L.) palms, grown on sandy and laterite soils were given different levels of irrigation through drip {sandy-66,100 and 133% of open pan evaporation (Eo); laterite - 33,66 and 100% of Eo} and basin (100% of Eo). Control palms without irrigation were maintained. The data on source parameters (photosynthetic and chlorophyll fluorescence (PSII) characteristics, besides water relations) were recorded during 1995-96 and 1996-97. Sink parameters such as female flower production, nut yield and nut retention were recorded during the experimental period. Photosynthetic rate, Y leaflet and PS II efficiency varied with the irrigation level and soil type. Instantaneous WUE increased markedly with irrigation and time. Palms receiving irrigation also showed marked improvement in female flower production and their retention to produce higher nut yields. Three types of physiological conditions in source and sink were observed in the palms based on the type of irrigation treatment they were subjected to. Results indicated that the drip irrigation provided conditions for better physiological efficiency of source and sink for high WUE and yield.They also indicated that the drip irrigation increased WUE at field and at plant and leaflet level.