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  1. Vol. 23 No. 3, p. 457-460
     
    Received: Sept 7, 1982
    Published: May, 1983


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doi:10.2135/cropsci1983.0011183X002300030004x

A Photoperiod and Temperature Sensitive Period for Leaf Number of Maize1

  1. M. Tollenaar and
  2. R. B. Hunter2

Abstract

Abstract

The heat unit concept, e.g. Growing Degree Days, is used extensively to account for temperature effects on maize (Zea mays L.) development in models which attmept to predict crop development and yield. Environmental effects on rate and duration of leaf initiation, which determine final leaf number, have received much less attention in such models, although leaf number and the period from planting to silking are highly correlated for maize. Photoperiod and temperature are two environmental variables known to affect leaf number. The objective of this study was to delineate the sensitive period during which leaf number of the short-season maize hybrid, Guelph GX 122, is influenced by photoperiod and temperature. Periods during which leaf number was influenced by temperature and photoperiod were determined by transferring plants to different photoperiod/temperature regimes at various stages of vegetative development. Leaf number was determined at tassel emergence and, in two of three experiments, leaf stage at which tassel initiation occurred was estimated by dissection of plants at regular intervals. AH experiments were conducted in the environmentally controlled growth cabinets of the University of Guelph. Results of these experiments indicate that initiated leaf number of Guelph GX 122 was influenced by temperature between the five- and the seven-leaf stage and by photoperiod betweenthe four- and the seven-leaf stage. The transition from vegetative to reproductive development (i.e., tassel initiation) occurred a leaf stage which was numerically equal to 50% of final leaf number. Photoperiod and temperature effects on leaf number were additive for Guelph GX 122 grown under the conditions of these experiments.

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