Factors Affecting the Flowering of Andropogon gayanus Kunth. Responses to Photoperiod, Temperature and Growth Regulators

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Abstract
Andropogon gayanus is a short-day plant with a critical daylength for flowering between 12 and 14 h. Flowering is more intense as the daylength is shortened from 12 h to 8 h, initiation is also accelerated by increasing durations of short-day treatment. Plants flower more readily with increasing age. The maximum flowering response can be induced by short-day exposure of only one expanding leaf. A fixed number of short days distributed among different groups of leaves on the plant gave less flowering than the same number given to only one group. Approximately 25°C was optimal for flowering. Root removal treatments in short day reduced both growth and flowering responses. Application of the growth regulators indol 3yl-acetic acid, abscisic acid, gibberellic acid or dimethylaminosuccinamic acid (B9) was inhibitory to flowering in all cases but gibberellic acid and B9 applied simultaneously had no inhibitory effect. Growth hormone treatments failed to stimulate flower development in long day. These results are discussed in relation to the internal mechanisms controlling growth and flowering.