Four temperature treatments were studied in the climate controlled growth chambers of the Georgia Envirotron: 25/20, 30/25, 35/30, and 40/35 °C during 14/10 h light/dark cycle. For the first growth stage (V3-5), the highest net photosynthetic rate (P N) of sweet corn was found for the lowest temperature of 28-34 μmol m-2 s-1 while the P N for the highest temperature treatment was 50-60 % lower. We detected a gradual decline of about 1 P N unit per 1 °C increase in temperature. Maximum transpiration rate (E) fluctuated between 0.36 and 0.54 mm h-1 (≈5.0-6.5 mm d-1) for the high temperature treatment and the minimum E fluctuated between 0.25 and 0.36 mm h-1 (≈3.5-5.0 mm d-1) for the low temperature treatment. Cumulative CO2 fixation of the 40/35 °C treatment was 33.7 g m-2 d-1 and it increased by about 50 % as temperature declined. The corresponding water use efficiency (WUE) decreased from 14 to 5 g(CO 2) kg-1(H2O) for the lowest and highest temperature treatments, respectively. Three main factors affected WUE, P N, and E of Zea: the high temperature which reduced P N, vapor pressure deficit (VPD) that was directly related to E but did not affect P N, and quasi stem conductance (QC) that was directly related to P N but did not affect E. As a result, WUE of the 25/20 °C temperature treatment was almost three times larger than that of 40/35 °C temperature treatment.
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*Corresponding author; fax: +972 8 6472821, e-mail: email@example.com Acknowledgement: The authors thank Stanley M. Thain, Samuel Wright, and Ian Flitcroft for their technical assistance during the study. The study was partially supported by a grant from the Ministry of Science, Israel, the Bundesministerium für Bildung und Forschung (BMBF), by State and Federal funds allocated to Georgia Agricultural Experiment Stations Hatch project GEO01654, and by a special grant from the U.S. Department of Agriculture-Cooperative State Research, Education, and Extension Service (USDA-CSREES).
- Transpiration rate
- Vapor pressure deficit
- Water use efficiency
- quasi stem conductance