MAIZE INTERNODE ELONGATION PATTERNS

During maize (Zea mays L.) growth, the stalk elongates in a sigmoidal pattern. This overall pattern arises from the variable growth rates of individual internodes comprising the maize stalk. To discern differences in growth rate among internodes of the stalk, individual elongation rates and patterns were determined in a single-cross hybrid. When each of 12 aboveground internodes (7 through 18) of growth-chamber-grown plants reached approximately 10 mm in length, they were dotted along their lengths with black acrylic paint at 1-mm intervals and photographed daily over 35 d. Full-scale photographs documented that all internodes elongated sigmoidally, in a basipetal direction. Elongation began slowly and uniformly throughout the length of the undeveloped internode during the first 2 to 3 d, increased in rate and shifted basipetally from the upper internode region toward the middle, and later, toward the basal region of the enlarging internode. Elongation decelerated in the intercalary meristem region during the final days of internode lengthening. Internodes 8 through 12 elongated similarly with the greatest daily growth rates. Internodes 13 and 14, which supported developing ears, had the longest elongation periods but slower growth rates and shorter final lengths than other internodes. Internode 15 had a rapid rate of growth like 18 through 12, but an elongation pattern similar to 113 and 14. Evidence from this study indicates that the relative position of internodes in the emerging stalk hierarchy and the functional role of internodes in stalk development influences individual internode growth rate, elongation period, and developmental pattern.