THE EFFECT OF LEAF POSITION ON THE PHYSIOLOGICAL RESPONSES IN POPLAR LEAVES (CLONE S7C15) IRRIGATED WITH FLUORIDE-LADEN WATER

摘要

In the present study, a Skewed model was developed and compared with the existing Gaussian model to describe the physiological parameters of poplar leaves (Populus deltoides L. clone S7C15) under irrigation with fresh water with no fluoride (control) and fluoride-laden (100-500 mg/L) water. The models fitted well with the experimental data and the calculated physiological responses were in close agreement with the observed values. The average root mean square deviations of the calculated photosynthetic CO2 assimilation (P-N), the stomatal conductance (g(s)), and a chlorophyll fluorescence variable per maximum yield (F (v)/F-m), under fresh water irrigation, were found to be 1.92, 1.73, and 1.65%, respectively, with the Skewed model, and 4.23, 5.69 and 1.29%, respectively, with the Gaussian model. With fluoride-laden water irrigation, the corresponding values for the P-N, g(s), and F-v/F-m were 3.54, 4.09, and 1.83% with the Skewed model and 8.02, 8.46, and 2.87% with the Gaussian model. The use of the models was illustrated with a solved example by calculating the total CO2 assimilation of a field plantation. The Skewed model was found to be superior to the Gaussian model in explaining the physiological responses of leaves positioned over a stem-branch with irrigation with both fresh and fluoride-laden water and is recommended for further application.