The Direction of Growth of Seminal Roots of Triticum aestivum L. and Experimental Modification Thereof

Abstract

The seminal root system of wheat (Triticum aestivum L.) consists of a primary seminal root and the first and second pair of seminal roots, counting upwards. These roots are plagiotropic. The direction of growth was estimated as the angle from the vertical for each of the three types of seminal roots that protruded from a hemispherical, soil-filled basket buried in the field. The angle of growth varied with cultivar. It was smallest in the primary seminal root and largest in the second pair of roots in all 12 cultivars grown in the field. Attempts to modify the angle of growth were made under controlled environmental conditions. When the grain was sown with its embryo face down, the angle of growth of the first pair of roots became smaller in the cultivars with inherently larger angles. The excision of the primary seminal root affected the first pair of roots and the excision of the first pair affected the second pair. These effects comprised a decrease in the angle of growth and an increase in root diameter. These changes in the angle of growth caused by root excision is interpreted as a kind of compensatory growth. The direction of root growth and its impact on shaping wheat root system is discussed.