Die Invloed van temperatuur op bloeiwyse-inisiasie en -differensiasie van Ornithogalum Thyrsoides Jacq

Abstract

No literature could be found covering the subject of developmental morphology of the inflorescence of OrnithogaZuthyrsoides. This study filled the existing gap in the literature. The development (differentiation) is discussed fully and is illustrated with photographic figures, from the beginning of differentiation (flattening of the growth point) up to differentiation of floral parts of the individual flowers. Because of the specific morphology and chemical composition of the flower bulb, many problems were experienced with dehydration and wax infiltration. Complete dehydration and wax infiltrati-0n were obtained by altering the standard procedures. Tertiary butyl alcohol was replaced with xylol and intermediary steps of liquid paraffin, prior to the final step (wax at 55°C), were included in the final procedure. According to the literature, temperature is probably the most important single factor with a direct influence on inflorescence initiation and - differentiation. According to the results of this study, there is a negative correlation between storage temperature and the developmental rate (differentiation rate), with the result that the flowering date is retarded, as the storage temperature increases. From the results of this study, it is clear that the flowering date is directly correlated with storage temperature. Storage of the flower bulbs at 5°C for 14 weeks, resulted in the earliest flowering date. With every 5°C increase in storage temperature up to a maximum of 30°C the flowering date was progressively retarded with a number of days. There are no meaningful statistical differences between the results of the 30°C - and 35°C treatments. The mechanism involved in inflorescence initiation and - differentiation is probably a temperature-controlled growth inhibitor. This inhibitor does not only have an influence on the commencement of differentiation, but probably has an influence on the rate of differentiation as well. The inhibitor could also have an influence on the second inflorescence which differentiates after planting. The low storage temperature (5°C) has a disadvantageous effect on flowering characteristics, whereas the high storage temperatures (30°C and 35°C) have an advantageous effect. There is a prominent difference in the total number of flowers which differentiate and tn the total length of the inflorescence in the above-mentioned treatments. Flower bulbs of OrnithogaZwn thyrsoides can be put in storage for prolonged periods (6 months) at 35°C, without detrimental effects on the flowering characteristics. The fact that differentiation commences immediately at 5°C storage. in a phenomenon with practical application in the flower bulb industry: With this - a very early flowering date can be achieved. A further practical inhibitory effect of storage temperatures between 30°c and 35°C. With this - flowering dates can be regulated so that flowers can be produced for a 3-month period after the natural flowering date. There are particular aspects in this study which justify further research. Especially the minimum~ and maximum storage temperatures, can be looked into in more detail. The developmental morphology of micro - and macro sporogenesis is another aspect that needs attention to conclude with work done in this study.