Leaf Orientation, Light Reception, and Growth of Winter Wheat1

Abstract

A major goal of crop scientists is to develop methods of harnessing solar energy. Efficient utilization of direct‐beam radiation is one method. Therefore, it is important to determine radiation received on the inclined and horizontal surfaces of leaves. The objective of the present study was to determine if, and to what extent, two cultivars of winter wheat (Triticum aestivum L. ‘KanKing’ and ‘Ponca’) received different amounts of direct‐beam radiation. The wheat was planted at two locations on the border between an Eudora silt loam (Fluventic Hapludolls, coarse‐silty, mixed, mesic) and a Muir silt loam (Cumulic Haplustolls, fine‐silty, mixed, mesic). During fall, winter, and spring months, values of I/I0 (ratio of intensity of received direct‐beam radiation to intensity of incident direct‐beam radiation) were calculated from solar‐noon sun angles, leaf orientation, and leaf angle. Leaf length, leaf width, leaf area, plant height, dry weight of tops, and grain yield also were determined. A majority of KanKing's leaves faced north and south and a majority of Ponca's leaves faced east and west. KanKing had more horizontal leaves than did Ponca, and KanKing's leaves appeared to receive a greater amount of direct‐beam radiation than the more erect leaves of Ponca. In general, KanKing had longer leaves, wider leaves, a larger leaf area, a higher dry weight of tops, and was taller than Ponca. Grain yields of the two cultivars were similar. The results showed that radiation reception of the two cultivars varied because they had different leaf orientations.