The Photoperiod Sensitive Interval in Maize
1983
Kiniry, J. R. | Ritchie, J. T. | Musser, R. L. | Flint, E. P. | Iwig, W. C.
In order to apply photoperiodic response functions developed in controlled environments to field grown maize (Zea mays L.), the timing of photoperiod sensitivity must be known. The timing of photoperiod sensitivity is also necessary for defining effective photoperiods for determining the effect of latitude and planting date on development of photoperiod- sensitive maize cultivars. The objective of this study was to determine the time when maize is sensitive to photoperiod. Two photoperiod sensitive cultivars of maize were grown in controlled environment chambers at the Duke Univ. Phytotron in photoperiods of 10, 12.5, 15, and 17.5 h. A third cultivar was grown in 12.5 and 17.5 h photoperiods. Plants were moved at different times between chambers having different photoperiods. Time from seedling emergence to tassel emergence was recorded. The length of this development interval was compared to the same interval for control plants that remained in a constant photoperiod for the entire time. The timing of photoperiod sensitivity was determined by knowing when the plants were moved and assessing which photoperiod affected them. Plants were insensitive to photoperiod immediately after seedling emergence. They remained insensitive until 4 to 8 days prior to the date of tassel initiation in short photoperiods. The insensitive, juvenile phase, therefore ended at least 4 days prior to tassel initiation in short photoperiods. The sensitivity continued until tassel initiation or shortly thereafter. The photoperiod affecting development in the field, considering the slow rate of change of photoperiod, is the value at the time of tassel initiation.
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