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Wheat Growth Related to Rhizosphere Temperature and Oxygen Levels¹

Although extensive research has been conducted on the separate effects of various soil-temperature levels and various soil-oxygen levels on wheat growth, little work has been done on the interaction of soil-temperature and soil-oxygen levels upon wheat response. Mexican semi-dwarf wheat (Triticum aestivum L. em Thell cv Yecora) was grown in soil at regulated temperatures under greenhouse conditions to measure response to varying combinations of root zone oxygen levels and soil temperatures. Components of dry weight production, tillering, leaf area, stomatal aperature, and leaf xylem tension were measured.

Decreasing soil-oxygen levels reduced total, root, and top dry weight components and root/shoot ratios, reduced leaf area, and retarded tillering. Soil temperature of 15 C generally favored higher total, shoot, and root dry weight, and a lower root/shoot ratio, increased leaf area, and increased the number of tillers per plant at harvest compared to 9 and 21 C. Stomatal closure (as measured by a diffusion porometer) occurred at very low soil-oxygen levels, but no consistent aeration or temperature effect on leaf water potential was observed. Low soil temperature and low soil oxygen levels interacted to retard shoot development pointing to a dependence of shoot development on root metabolism.

The data underscore the need to characterize both soil temperature and soil oxygen availability when considering either parameter separately in order to fully understand the relative oxygen status of plant roots.

Key Words: Soil aeration • Soil temperature • Leaf difussive resistance • Plant water potential • Roots

² Former research assistant (presently postdoctoral research associate, Dep. of Agronomy, Univ. of Arkansas) and professor of soil phys:.cs, Dep. of Soil Science and Agricultural Engineering, and associate professor of plant physiology, Dep. of Plant Sciences, respectively, Univ. of California, Riverside, CA 92502.

Received for publication August 30, 1974.