In a phytotron experiment, two hybrids of maize (LG 11 and Bastion) were exposed to different levels of temp., heat around noon, photoperiod and water supply at certain stages of development. Treatment influenced the flowering biology, but hardly affected leaf number. High temp. from tassel initiation until grain set increased the rate of development, but shortened the duration of pollen shedding; the interval between pollen shedding and silking was much longer. Thus the exposure of silks to pollen was curtailed. Grain set in the uppermost ear was hampered. The effect of extra heat from tassel emergence until grain set was minor. Long days from tassel initiation to tassel emergence delayed silking more than anthesis, thus increasing the desynchronization. Long photoperiods shortened the duration of the pollination period, but increased the number of female spikelets and the numbers of grains. Drought from tassel emergence until grain set delayed anthesis by 1-2 d and silking by 4 d. Drought did not consistently reduce the duration of pollen shedding, but impeded grain set. Many interactions between environmental factors and/or hybrid proved to be significant. Variation in number of female florets was partly explained by desynchronization of inflorescences. There was a highly significant (rsuperscript 2 = 0.64; n = 32) simple positive correlation between relative grain set and duration of the period of pollination of the silks by the plant's own pollen. The scatter around this relationship was mainly due to the effects of water availability on the functionality of male and female florets. The final number of grains was correlated closely with the desynchronization, although this relationship depended on hybrid and photoperiod. The environmental effects that influence flowering of maize are summarized in a simplified model of the dynamics of anthesis and silking. (Abstract retrieved from CAB Abstracts by CABI’s permission)