Journal of Environmental Biology

Diurnal photosynthesis, water use efficiency and light use efficiency of wheat under Mediterranean field conditions

Fatih Evrendilek*¹, Jiftah Ben Asher² and Mehmet Aydin³

¹Department of Environmental Engineering, Faculty of Engineering and Agriculture, Abant Izzet Baysal University,

Golkoy Campus, 14280 Bolu, Turkey

²Department of Dryland Agriculture, Institute for Desert Research, Ben-Gurion University of the Negev,

Sede Boqer Campus, 684993, Israel

 ³Department of Soil Science, Mustafa Kemal University, Antakya-Hatay, 31034, Turkey

(Received: July 27, 2006; Revised received: November 02, 2006; Accepted: December 15, 2006)

Abstract: Photosynthesis and transpiration rates of wheat leaves (Triticum aestivum L.) were measured at 30 min intervals under Mediterranean field conditions, using Photosynthesis Monitor system (PM-48M). The dynamics of net photosynthetic rate (P_N), transpiration rate (E_T), water use efficiency (WUE), light use efficiency (LUE), stomatal conductance (g_s), photosynthetically active radiation (PAR), air temperature (T), relative humidity (RH), and atmospheric CO₂ concentration (C_atm) were quantified at five rainfed wheat sites with the same stages of development (midflowering) along south-to-north and east-to-west transects for eight days in April. Diurnal P_N (3.6 to 6.6 µmol m^-2 s^-1), PAR (392 to 564 µmol m^-2 sec^-1), LUE (0.006 to 0.015) and WUE (0.0001 to 0.011) did not vary significantly across all five wheat sites (p>0.05). P_N and E_T were strongly coupled and highly correlated with PAR (p<0.001). Best multiple linear regression (MLR) models accounted for 92% of variations in P_N as a function of PAR and E_T, and 90% in E_T as a function of PAR and RH (p<0.001). P_N exhibited a peak at mid-morning, and a photosynthetic midday depression under the limiting effects of high evaporative demand. Diurnal variations in WUE and LUE showed a bimodal behavior with the maximum values in early morning and late afternoon.  As the impacts of global climate change become increasingly felt, continuous measurements of climate-crop-soil-management interactions under natural conditions play a pivotal role not only in exploring changes in ecophysiological properties of strategic crops for food security such as wheat but also in devising preventive and mitigative management practices to ensure sustained agricultural productivity.

Key words:   Photosynthesis, Light use efficiency, Transpiration, Water use efficiency, Wheat

PDF of full length paper is available with author (fevrendilek@yahoo.com)

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