INFLUENCE OF FLUORIDE-CONTAMINATED IRRIGATION WATER ON PHYSIOLOGICAL RESPONSES OF POPLAR SEEDLINGS (POPULUS DELTOIDES L. CLONE-S7C15)

When exposed to 100-500 ppm fluoride-contaminated irrigation water for six weeks, six-week old poplar (Populus deltoides L. clone-S7C15) seedlings showed decreases in the following physiological characteristics: growth, leaf expansion, photosynthetic CO2 assimilation, stomatal conductance, chlorophyll fluorescence yield, plant biomass, and harvest index. An enhanced electrolyte leakage triggered susceptibility of the seedlings to loss in the harvest index. The 500-ppm F level induced marked inter-vein chlorosis, leaf-margin necrosis, and leaf-curl on younger leaves with a xerophytic condition for rhizosphere that altered the tree habit of poplars in scrub vegetation. With increasing F concentration's, the harvest index and other growth parameters were successively reduced.