The effect of temperature on inflorescence initiation, differentiation and development of Lachenalia cv. 'Romelia'

Abstract

Inflorescence initiation and differentiation of Lachenalia cv. 'Romelia' corresponded with that of a typical bulb. There was, however, a difference between La.chena,lia and most other bulbs with regard to the morphological development of the vegetative bud. The vegetative apex of Lachenalia do not produce additional leaves during storage before it transform into a reproductive apex. Temperature affected the time of flower initiation and differentiation. Flowering size bulbs were stored for different periods at different temperatures. Flower initiation is promoted at 20 and 25 °C. Fifteen and 30 °C retarded flower initiation and at 5, 10 and 35 °C no flowers were initiated. Further flower differentiation and elongation proceeded most rapidly at 15 ° C while 30 ° C retarded this process. Storage temperature during flower differentiation influence inflorescence quality. The best quality was obtained when flower differentiation occurred at 25 ° C for at least 4 weeks. Compact inflorescences with a high floret number and firm peduncles were produced at this treatment. The storage temperature also influenced the number of secondary inflorescences. More secondary inflorescences were produced after storage at high temperatures, than at low temperatures. Peduncle length was also influenced by the storage temperature. Storage at 15 ° C resulted in significantly longer peduncles than the other temperatures. Light intensity, however, played the major role in this regard. High light intensity generated short peduncles. Keeping ability of the inflorescence was not determined by the storage temperature, but by the environmental conditions that prevailed during flowering. The flowering date of Lachenalia cv. 'Romelia' was retarded by storing the bulbs at 10 °C, since flower initiation was totally inhibited at this temperature. When these bulbs were transferred to an incubator at optimum initiation temperature, an after inhibition effect was noticed. This after-effect prevented the commencement of flower initiation for up to 20 weeks. The duration of the after-effect depended on the period at 10 ° C. This aftereffect must be considered when the flowering date is manipulated, since it has a major effect on the flowering date. When bulbs that were stored at 10 ° C were planted in a glasshouse, this after-effect was shortened. The environmental effect that was responsible for this shortened time period was probably the provision of water. From this study it was clear that prolonged storage at 10 ° C does not have any negative effect on flower quality, provided that flower differentiation occurred at the optimum temperature. Good quality inflorescences were produced when flower differentiation commenced at 22 ° C after the bulbs were stored at 10 ° C.