Diurnal and seasonal trends in photosynthetic performance of Dalbergia sissoo Roxb. and Hardwickia binata Roxb. from a semi-arid ecosystem

Abstract

Diurnal and seasonal trends in net photosynthetic rate (PN), 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 PN 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 PN and gs in D. sissoo but there was no strong linear relationship between PN and gs in H. binata. In D. sissoo, the reduction in gs led to a reduction in both PN and E enabling the maintenance of WUE during dry season thereby managing unfavourable environmental conditions efficiently whereas in H. binata, an increase in gs causes an increase of P N and E with a significant moderate WUE. © 2008 Institute of Experimental Botany, ASCR.