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The aim of this study was to examine the environmental regulation of flower initiation and subsequent development in heliotrope (Heliotropium aborescens L. cv. Marine). Five experiments were conducted, two examined whether flowering could be advanced by cool temperatures. The duration of cool temperature required to induce rapid flowering was also investigated. The final three experiments examined the effects of light integral, photoperiod and temperature on flower initiation and development. It was found that plants grown for 9 days at 108C and than transferred to 208C flowered significantly earlier (first flowering recorded after 55 days) than plants held constantly at 208C (65.9 days to flowering). Plants grown at a constant temperature of 208C had significantly more leaves than all other treatments. This suggested that ‘cool’ temperatures, prior to initiation, advanced flowering. In a transfer experiment, plants were moved from 10 to 208C at 3 days intervals postpinching. Earliest flowering (by 20 days compared to the 208C constant treatment) occurred when plants were exposed to 108C for 9 days and then transferred to 208C. Photoperiod was shown to have no effect on either flower bud initiation or development (postinitiation). Both temperature and light integral strongly influenced flower development post-flower bud initiation. However, the response to temperature plotted in terms of the reciprocal of days to flowering was non-linear. # 2000 Elsevier Science B.V. All rights reserved. |
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