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Composition and Quality of Wheat Grown Under Different Shoot and Root Temperatures During Maturation

¹Department of Agronomy, Throckmorton Hall, Kansas State University, Manhattan, KS 66506. ²Corresponding author. E-mail: guedira@ksu.edu Phone: (785) 532-7235. Fax: (785) 532-6094. ³Department of Grain Science and Industry, Shellenberger Hall, Kansas State University, Manhattan, KS 66506-5501.

Diminished quality of wheat (Triticum aestivum L.) from high temperature during maturation is usually attributed to direct effects of the stress on the shoots or grain. However, the upper soil temperature approaches the air temperature, and roots are highly sensitive and interact profoundly with other plant parts. The objective of this study was to determine the effect of differential shoot and root temperatures on quality of hard red spring wheat (cv. Len). Plants were grown in hydroponic containers at 15/10°C day/night until 10 days after anthesis, when shoot/root treatments of 15/15°C, 15/30°C, 30/15°C, and 30/30°C were imposed until the grain ripened. Both high shoot and high root temperature affected quality of the grain. Kernel size and weight were diminished more by high root than by high shoot temperature, but flour yield was decreased significantly only by the 30/30°C treatment. The percentage of starch in B granules was reduced by high shoot temperature, and the diameter of A granules was decreased by all heat treatments. Amylose concentration was increased by high temperatures of both shoot and root, resulting in decreased pasting characteristics. Flour protein increased after all heat treatments, but high shoot temperature decreased the polymer-to-monomer ratio and unextractable polymeric protein and it affected dough mixing. We concluded that stress on roots directly affects properties of the grain that are important for milling and baking.