Duration of the grain-filling period in maize is not affected by photoperiod and incident PPFD during the vegetative phase

Total number of initiated leaves and duration from sowing to silking increases when photoperiod is increased during the photoperiod-sensitive phase in maize (Zea mays L.). Little is known, however, about possible other effects of photoperiod and incident photosynthetic photon flux density (PPFD) on rate of development and duration of life cycle. A study was undertaken to quantify effects of photoperiod and incident PPFD from sowing to the 15-leaf stage on rate of leaf appearance and duration of the grain-filling period. The short-season maize hybrid Pioneer 3902 was grown in growth cabinets from sowing to the 15-leaf stage with either (i) a 10 h photoperiod at high PPFD (650 μmol m⁻² s⁻¹), (ii) a 20 h photoperiod consisting of 10 h of high PPFD followed by 10 h of low PPFD (5–50 μmol m⁻² s⁻¹), or (iii) a 20 h photoperiod of high PPFD. From the 15-leaf stage to maturity the plants were placed under a 16 h photoperiod in a growth room. Increasing photoperiod from 10 to 20 h increased final number of initiated leaves and delayed silking but did not affect rate of leaf appearance. Doubling incident PPFD to a value similar to that under Ontario field conditions during the summer resulted in a 16% increase in rate of leaf appearance and in a significant increase in total number of initiated leaves. Differences in final number of initiated leaves and in rate of leaf appearance from sowing to the 15-leaf stage among treatments resulted in a 4-day difference in silking date between the 10 h photoperiod treatment and the two 20 h photoperiod treatments. Duration of the grain-filling period did not differ among the three treatments.