Diurnal and seasonal trends in net photosynthetic rate (P N ), stomatal conductance (g), transpiration rate (E), vapour pressure deficit, temperature, photosynthetic photon flux density , and water use efficiency (WUE) were compared in a two-year-old Dalbergia sissoo and Hardwickia binata plantation. Mean daily maximum P N in D. sissoo ranged from 21.40±2.60 µmol m -2 s -1 in rainy season I to 13.21±2.64 µmol m -2 s -1 in summer whereas in H. binata it was 20.04±1.20 µmol m -2 s -1 in summer and 13.64±0.16 µmol m -2 s -1 in winter. There was a linear relationship between daily maximum P N and g s in D. sissoo but there was no strong linear relationship between P N and g s in H. binata. In D. sissoo, the reduction in g s led to a reduction in both P N and E enabling the maintenance of WUE during dry season thereby managing unfavourable environmental conditions efficiently whereas in H. binata, an increase in g s causes an increase of P N and E with a significant moderate WUE.Additional key words: net photosynthetic rate; photosynthetic photon flux density; species differences; stomatal conductance; temperature; transpiration rate; vapour pressure deficit; water use efficiency.