Concurrent Change in Photosynthetic Parameters in Kinnow Leaves under Integrated Nutrient Application

Seasonal changes in photosynthetic characteristics, relative water content, canopy volume, leaf nutrient content in Kinnow leaves in response to integrated nutrient sources were investigated in Jhalawar district of South Eastern Rajasthan state of India during 2012-13. Interaction effect of nitrogen and vermicompost were significantly superior over other treatments in terms of better photosynthetic efficiency parameters of Kinnow mandarin plants during gestation period of 3 years age viz. photosynthesis rate, transpiration rate, stomatal conductance, photosynthetic active radiation, internal CO2 concentration, vapour pressure deficit, leaf temperature, relative humidity. Out of all treatment combinations, T15 (nitrogen @ 350 g/plant + vermicompost @ 20 kg/plant) proved significantly superior over most of treatment combinations including control in photosynthetic efficiency parameters of Kinnow mandarin plants. The photosynthetic efficiency of Kinnow mandarin plants was found maximum under T15 (6.97) treatment. The better stomatal conductance, transpiration rate, relative humidity percentage of leaves, internal CO2 concentration and leaf temperature attained optimal values at higher PAR. The application of 350 g nitrogen along with 20 kg vermicompost per plant in two split doses in Kinnow mandarin at gestation phase may improve the plant growth, developmental and photosynthetic efficiency parameters which are pre-requisite for strong framework and higher yield along with improvement in the soil health. In order to define Pn of the tree, it is necessary to consider not only photosynthetic response of the single leaf but also the overall canopy structure (leaf area index, total leaf area, leaf orientation towards radiation flux) which varies considerably according to environmental conditions. The canopy structure influences the overall Pn of the tree. Further studies on the carbon balance in relation to nutrition may contribute to growth and developmental improvement in the plants.