Effects of temperature and light on growth, flowering and corm formation in Freesia

ScopeWhen Freesias are planted throughout the year several problems arise. In some months, flowers are produced too rapidly and abundantly, with a corresponding loss in quality; in other months, flower production is limited and too slow. Simultaneously, there is a great variation in stem length, in number and shape of the flowers and in corm production.This study was undertaken to establish the effect of the two major inveronmental factors, temperature and light, on the characteristics mentioned, from the moment of planting to the harvest of the corms.ConclusionsFrom this study on the effect of temperature and light on the development of the Freesia plant, the following conclusions could be drawn:Effects of temperature in the range of 9-24°C:1. Sprouting of the corms was promoted by high temperature (experiments 1,4,19).2. The number of leaves was reduced (i.e., Rower initiation was promoted) by low temperature, and increased by high temperature, especially 21° and 24°C (experiments 1, 3, 4, 5, 19). There was a further reduction by a pretreatment at 5°C during 4 weeks (experiment 7). There was no specific effect of day or night temperature (experiment 4).3. The number of days to flowering reached a minimum at 18' (experiments 1, 3, 5, 19, 20; in experiment 4 the optimal temperature was 15°C and in experiment 2 it was 21°C. The night temperature was especially important (experiments 4, 5). There was a further reduction in the number of days to flowering by a pretreatment at 5°C for 3 or 4 weeks (experiment 7).4. The number of flowers in the main inflorescence was increased by high temperature (experiments 1-5, 19, 20; in experiment 3 there was a reduction at 24°C but it was also increased by a pretreatment at 5°C during 1 or 2 weeks (experiment 7).5. The number of lateral stems was reduced by high temperature; the greatest number was formed at 12°C (experiment 3) or 15°C (experiments 1, 2). A low night temperature was especially important (experiment 5).6. Stem length reached an optimum at 21 °C (experiments 1- 5, 19, 20); 24°C was unfavourable, especially in later stages (experiment 3). The effect of day temperature was much stronger than that of night temperature (experiments 4, 5). Stem length increased after a pretreatment at 5' during 1-2 weeks, but 4 weeks 5° led to stunted growth (experiment 7).7. Corm dry weight increased with the temperature (experiments 1, 2, 4, 19). The effect of day temperature was stronger than that of the night temperature (experiment 4, 5). Corm weight was reduced after a pretreatment at 5° during 3 or 4 weeks (experiment 7).8. The number of cormlets was decreased by high temperature (experiments 1-4, 19). A pretreatment of 1-2 weeks at 5°C increased it, but 4 weeks 5°C led to a decrease (experiment 7).Effects of the photoperiod in the range of 8 to 16 hrs:9. Leaf number was reduced (i.e. flower initiation was promoted) by short day (experiments 8, 12, 13, 19). The cultivar 'Sonata' was more responsive than 'Rijnveld's Golden Yellow' (experiment 15).10. The development of the inflorescence was strongly promoted in the early stages by short day (experiments 12, 13, 19) but later stages were promoted by long day, although not as strongly (experiments 11, 12).11. The number of flowers in the main inflorescence was reduced by long day (experiments 8, 10, 14), especially in the later stages (experiment 15). Long day also reduced the percentage of open flowers (experiments 9-12).12. The number of lateral stems decreased with the daylength (experiments 8-14) which was especially effective in later stages (experiment 15).13. There were no unequivocal effects of photoperiod on stem length experiments 9, 12, 15).14. Corm dry weight was proportional to daylength (experiments 8, 10, 12, 14), although it was sometimes lower again in the longest photoperiod (experiments 9, 11).15. The number of cormlets was greatest in short day (experiments 8-13).Effect of light intensity:16. Light intensity had little effect on the number of leaves (experiments 10, 13, 17), but low light intensity delayed flower initiation (experiments 13, 14), flower development (experiments 10, 13, 14, 17). It also reduced the number of flowers in the main inflorescence (experiments 13, 14, 17) and the precentage of open flowers (experiment 17). High light intensity increased the number of lateral stems (experiment 13). Stem length was usually slightly promoted by low light intensity (experiment 14, 17). Corm dry weight was proportional to light quantity (experiment 13, 14, 16, 17). The number of cormlets was reduced by low light intensity (experiment 10).Comparison of effects on light and temperature:17. Within the given ranges of these two factors the effect of temperature was usually greater than that of light. Only the number of lateral stems was determined primarily by the light conditions. As a rule, a higher temperature had a similar effect as a longer photoperiod (experiments 19, 20).Effect of planting date (experiment 21):18. The greatest number of leaves (and also the longest time to flower initiation) was found after planting in May and June, the smallest number of leaves after planting in February. The minimum number of days to flower initiation occurred after planting between November and January.19. The minimum number of days between planting and flowering occurred after planting in January and February; plants started in May took the longest time to flower.20. The number of flowers on the main inflorescence reached a maximum after planting in May and June and a minimum after planting between October and February.21. The number of lateral stems was high in plants started in June and low after planting in November and April.22. Stem length and plant height were greatest after planting between June and August and smallest after planting in February and March.23. Corm and cormlet dry weight were highest after planting in summer and low after planting in winter; the number of days between planting and harvest showed the opposite trend.Effect of planting density (experiment 21):24. In comparison to plants at a small distance, those at a wider distance were shorter, had more lateral stems and more flowers, a greater corm dry weight and more cormlets.25. The number of days to flowering was not affected by the planting density when the plants were started between November and March. Plants started between March and August flowered earlier when at a smaller distance; those started between September and November, however, flowered slightly earlier when at a greater distance.