Field Investigations of the Relationships of Leaf Angle in Corn (Zea mays L.) to Grain Yield and Apparent Photosynthesis1

Abstract Field investigations were conducted at Urbana, III., concerning the relationship of leaf angle and canopy shape to grain yield and apparent photosynthesis of Zea mays L. A backcross‐derived isogenic single cross hybrid (‘C103’ ✕ ‘Hy’) carrying the lg 2 gene for erect leaf produced 40% more grain than its counterpart with normal (horizontal) type leaf, when compared in rows 51 cm wide at 59,304 plants/ha. Mechanical manipulation of the leaves of a widely grown commercial hybrid. ‘Pioneer 3306’ into a more upright nature resulted in grain yields above that produced by the same hybrid in its normal leaf orientation and canopy shape. Apparent photosynthesis measurements on individual corn leaves showed the relative efficiency of CO 2 fixation/unit of incoming sunlight to steadily increase as the leaf angle decreased. The results strongly support corn breeding programs in the area of plant geometry and crop canopy.