EN
The physiological responses pertaining to influence of fluoride-contaminated irrigation water (100–500 ppm) on 6-week-old seedlings of Populus deltoides, a fast growing tree crop in northern India are investigated. It is observed that the various fluoride concentrations in irrigation water are directly proportional to the changes in the physiological responses. The reduction in stomatal conductance is found higher (~57 %) in relation to photosynthetic CO2 assimilation (~38 %) and chlorophyll fluorescence yield (~12 %) in fluoride-contaminated (100 ppm) irrigation. Similarly, impaired values for g s (75 %), P N (55 %), and F v/F m (18 %) are also triggered by higher level of fluoride-contaminated (200 ppm) irrigation. Further higher dose of fluoride (500 ppm) contaminated irrigation water could severely minimize the physiological responses viz., g s, P N and F v/F m ca. 86, 65, and 36 %. A mathematical model developed based on the changes in rates of stomatal conductance (Δg s/ΔC), photosynthetic CO2 assimilation (ΔP N/ΔC) and chlorophyll fluorescence yield (ΔF v/F m/ΔC), which has shown straight line relationship, and was verified with average deviations from 1.86 to 5.87 %. The calculated physiological responses influenced by fluoride irrigation on poplar seedlings are also verified with developed model. The governing equation suggests the existence of functional relationship between physiological responses and applied fluoride treatment doses. Hence, the cultivation of poplar crop may be designed precisely in fluoride affected areas to boost and sustain agro-socio economy.