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The Growth of the Shoot Apex in Maize: External Features

E. C. Abbe and B. O. Phinney
American Journal of Botany
Vol. 38, No. 9 (Nov., 1951), pp. 737-744
Stable URL: http://www.jstor.org/stable/2437922
Page Count: 8
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The Growth of the Shoot Apex in Maize: External Features
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Abstract

The following terminology is used in describing the vegetative growth of the shoot apex in maize: shoot apex, that portion of the apical meristem which is distal to the youngest recognizable leaf primordium; plastochron, the time interval between the initiation of successive leaf primordia; and shoot apex stage, that portion of the ontogeny of the shoot apex which falls within the time limits of the corresponding plastochron. The average external dimensions of the shoot apex of maize are reported for stages 7-14. Apparently a linear relationship exists between the dimensions of the shoot apex in successive stages. The shoot apex in the strain of maize examined in this study closely approximates an ellipse in median sagittal section and on this basis the volume of each shoot apex was calculated. From these individual volumes, average volume for each stage has in turn been calculated. The average volumes of shoot apex stages 7-14 appear to increase by a constant amount from stage to stage. The data lend themselves to an analysis of the rate of leaf initiation. This phenomenon is acceleratory in this strain of maize. The values for the plastochron were calculated from the data for the rate of initiation of leaf primordia. The duration of successive plastochrons decreases markedly from shoot apex stage 7-14, the sequence thus obtained conforming to a simple exponential sequence.

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