Naresh Kumar, S.Kasturi Bai, K.V.2014-07-152014-07-152009Indian J. Plant Physiol., Vol. 14, No. 3, (N.S.) pp. 215-223 (July-Sept., 2009)http://hdl.handle.net/123456789/4097The details about the gas exchange parameters in leaves of coconut canopy in three different types of canopy shapes, viz. (i) oval shaped (ii) X- shaped and (iii) semi circle shape under rainfed and irrigated conditions are discussed. Mean photosynthesis rate (Pn), stomatal conductance (gs), internal CO2 concentration (Ci) and transpiration rate (E) were significantly higher in irrigated palms. However, rainfed palms had significantly higher WUE. The Pn rates were higher in leaves from 2nd to 10th leaf from top and then gradually declined with increase in age of the leaf. Similar trends were observed for gs and E. The relationship between the deviations of Ci/gs and Pn indicated two types of relationship, (i) asymptotic negative relationship in irrigated condition and (ii) low relationship under rainfed conditions. The Pn rates positively correlated with specific leaf weight in irrigated condition while negatively in rainfed conditions. Four general types of leaves were found in coconut canopies, viz. (i) leaves with higher Pn and WUE than mean performance of canopy leaves, (ii) leaves with higher Pn and lower WUE, (iii) leaves with lower Pn and higher WUE and (iv) leaves with lower Pn and lower WUE (lower leaves). Oval shaped canopy is more suitable for higher photosynthesis efficiency, WUE and productivity as compared to X-shaped and semi circle shaped canopies. These results indicate that canopy shape plays a role in the overall performance of photosynthesis and water use efficiencies and productivity in coconut. Results also indicate coconut as a source-limited plant.enCanopycoconutgas exchange charactersphotosynthetic rateswater use efficiencyArticle