Diurnal patterns of canopy net photosynthetic rates (jPií), evapotranspiration (£) and
water use efBciency (WŤJE = P^^E) of field grown irrigated wheat (Triticum
aestivum L. cv. WH 147) were studied fi'om tillering to maturity at Haryana
Agricultural University Farm, Hisar, India. Hie maximum photosynthetic rates
(^N, max) increased fi'om tillering to anthesis and declined at a rapid rate thereaňer till
maturity. Relatively high £'mav but low WUE„ax were recorded at tillering, milk ripe
and dough stages of growth. Diumally foUowed die course of photosynthetícaUy
active radiation (PAR) fiom tillering to wateiy ripeness but it declined at high PAR at
latter reproductive stages of growth. E was curvilinearly related to air temperature.
There was a lag of about 2 h between ^N, „lax (12.00 h) and E„,ax (14.00 h) during
the day. WUE was high fi-om 07.30 to 10.00 h, depressed during midday and a
slightly increased fi^om 15.00 to 16.00 h.Diurnal patterns of canopy net photosynthetic rates (jPií), evapotranspiration (£) and water use efBciency (WŤJE = P^^E) of field grown irrigated wheat (Triticum aestivum L. cv. WH 147) were studied fi'om tillering to maturity at Haryana Agricultural University Farm, Hisar, India. Hie maximum photosynthetic rates (^N, max) increased fi'om tillering to anthesis and declined at a rapid rate thereaňer till maturity. Relatively high £'mav but low WUE„ax were recorded at tillering, milk ripe and dough stages of growth. Diumally foUowed die course of photosynthetícaUy active radiation (PAR) fiom tillering to wateiy ripeness but it declined at high PAR at latter reproductive stages of growth. E was curvilinearly related to air temperature. There was a lag of about 2 h between ^N, „lax (12.00 h) and E„,ax (14.00 h) during the day. WUE was high fi-om 07.30 to 10.00 h, depressed during midday and a slightly increased fi^om 15.00 to 16.00 h.