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Partition of photosynthates between shoot and root in spring wheat (Triticum aestivum L.) as a function of soil water potential and root temperature
Authors:Xiaomeili Li  Yongsheng Feng  Larry Boersma
Institution:(1) Soils Branch, Environmental Enhancement, Alberta Environmental Centre, T9C 1T4 Vegreville, Alberta, Canada;(2) Department of Soil Science, University of Alberta, T6G 2E3 Edmonton, Alberta, Canada;(3) Department of Crop and Soil Science, Oregon State University, 97331 Corvallis, OR, USA
Abstract:Low soil water potential and low or high root temperatures are important stresses affecting carbon allocation in plants. This study examines the effects of these stresses on carbon allocation from the perspective of whole plant mass balance. Sixteen-day old spring wheat seedlings were placed in a growth room under precisely controlled root temperatures and soil water potentials. Five soil water potential treatments, from −0.03 MPa to −0.25 MPa, and six root temperature treatments, from 12 to 32°C were used. A mathematical model based on mass balance considerations was used, in combination with experimental measurements of rate of net photosynthesis, leaf area, and shoot/root dry masses to determine photosynthate allocation between shoot and root. Partitioning of photosynthates to roots was the lowest at 22–27°C root temperature regardless soil water potential, and increased at both lower and higher root temperatures. Partitioning of photosynthates to the roots increased with decreasing soil water potential. Under the most favourable conditions, i.e. at −0.03 MPa soil water potential and 27°C root temperature, the largest fraction, 57%, of photosynthates was allocated to the shoots. Under the most stressed conditions, i.e. at −0.25 MPa soil water potential and 32°C root temperature, the largest fraction, more than 80%, of photosynthates was allocated to roots.
Keywords:photosynthate partitioning  root temperature  turgor potential  water potential  water stress
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