Factors Affecting Leaf Area Development in Husk Leaf of Flint Corn

Some corn (Zea mays L.) genotypes produce husk leaves (laminae extending from the husk) that on a per unit area basis, contribute more photosynthate to grain production than culm leaves. Furthermore, a high correlation between husk leaf area and dry weight has been observed, but little is known about the changes in cell components during development of husk leaves. A field experiment was conducted to quantify methanol (MeOH)‐soluble fraction (cytosol) and incorporation of 13C‐labeled photosynthate in cell walls from 9 d before silking (DBS) to silking. The ear leaf of flint corn (F1 of N‐19 by X‐15) was subjected to 13CO2 eight DBS. Leaf area, dry weight, and photosynthetic activity of the husk leaves, and sugar content of various cell components were measured continuously during the 9‐d period. The husk leaf attained one‐half of its maximum apparent photosynthetic rate (Po) when it had 8% of its maximum leaf area at 4 DBS. At 9 DBS, neutral sugars in the MeOH‐soluble fraction accounted for most of nonstarch carbohydrates within the husk leaf (68%), while hemicellulose and cellulose fractions accounted for <10%. At silking, however, sugars in the hemicellulose and cellulose fractions increased by 23 and 56%, respectively. Results of 13CO2 labeling suggest that during rapid husk leaf development, MeOH‐soluble fraction decreases, while the hemicellulose fraction fluctuates, and cellulose fraction increases.