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Effect of Change in Time of Flowering, Induced by Altering Photoperiod or Temperature, on Attributes Related to Yield in Maize¹

Flowering date of maize (Zea mays L.) was advanced, by increasing temperature or decreasing photoperiod, in order to study the effect of a decrease in length of vegetative phase on leaf area at flowering, number of female florets, and length of grain-filling period. Plants of two single-crnss hybrids were grown at temperatures of 20 or 25 C, combined with 10- or 15-hour photoperiods, until ears started developing, and then transferred to a single regime of a 14 hour photoperiod and 23/19 C light/dark temperature.

Increased temperature shortened the intervals from sowing to start of ear initiation and from ear initiation to silking. Decreased photoperiod shortened only the first period. Total leaf area per plant decreased as temperature increased, because leaves were smaller, and as photoperiod decreased, because fewer leaves were formed. Change in temperature altered total leaf area and time between sowing and silking by proportionately similar amounts, but change in photoperiod altered leaf area proportionately more than it did time to silking. Number of florets per ear row was little affected by temperature or photoperiod; apparent rate of floret initiation was unaffected by photoperiod but increased with temperature. Some plants died prematurely, evidently because of insufficient assimilate to maintain plant tissues. The black layer, denoting grain maturity, formed sooner in the kernels of these plants than in those of the remaining plants. In the latter, number of days from silking to black layer formation was decreased slightly by an increase in either temperature or photoperiod during the period before ear initiation.

Key Words: Zea mays L. • Duration of vegetative and grain-filling phases • Leaf area • Floret number • Senescence

² Department of Agriculutre, Univ. of Rhodesia, Salisbury, Rhodesia (present address: S. A. Sugar Assoc. Exp. Stn., Mount Edgecombe, Natal, South Africa) and Dep. of Crop Science, Univ of Guelph, Ontario.

Received for publication November 17, 1977.