The effect of elevated root zone temperature (24, 28, 30, and 35ºC) on carbon partitioning and growth rates of wheat plants growing at constant air temperature (24ºC) was investigated. Air temperatures are typically held constant in controlled environment chambers aboard spacecraft, however root zone temperatures are typically not controlled because of power limitations. The root zone temperature treatments were not initiated until after 5 days after planting. The effects of increased root zone temperature on C partitioning and development were determined from growth analysis of destructive harvests at 7, 15, 22 and 28 days after planting. Plant height, mass, leaf area index and stomatal conductance were affected by root zone temperatures above 28ºC. The 35ºC root zone temperature treatment resulted in severe decreases in plant growth rates.