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ISHS Acta Horticulturae 515: XXV International Horticultural Congress, Part 5: Culture Techniques with Special Emphasis on Environmental Implications Chemical, Physical and Biological Means of Regulating Crop Growth in Ornamentals and Other Crops

EFFECTS OF DIURNAL TEMPERATURE STRATEGIES ON CARBOHYDRATE CONTENT AND FLOWER QUALITY OF GREENHOUSE ROSES

Authors:   J.V.M. Vogelezang, J. De Hoog Jr, N. Marissen
Keywords:   Rosa hybrida, carbohydrates, DIF, flower quality, greenhouse roses, keepability, starch, sugars, temperature, vase life
Abstract:
Diurnal temperature strategies may have an influence on the pattern of carbon export from source leaves to developing rose shoots, through which flower (bud) quality might improve. A rise of temperature during the first night hours is a popular climate strategy in The Netherlands. Effectiveness was studied in relation to other temperature strategies such as DIF (difference between day and night temperature) and the application of supplementary lighting.

Three months old plants of Rosa hybrida First Red ‘Pekoujenny’ were placed in climatized daylight chambers and grown for two production cycles. Four temperature strategies were applied (constant, DIF +5, DIF -5, temperature rise of 4 hrs 24°C after sunset), all treatments having the same 24-hour mean temperature of 19°C. The control and the temperature rise treatment were also combined with supplementary lighting during the period of temperature rise. CO2 was held at 700 ppm during daylight and lighting hours.

Samples of plant material for carbohydrates were taken at two crop stages (3–4 cm shoots, harvestable stems) at three moments during the 24-hour period. The amount of starch in leaves gradually deceased during the night, whereas the amount of sucrose in the flower bud increased. The temperature rise treatment did not affect levels of sugars or starch, irrespective of the lighting treatment. The amount of starch was significantly affected by supplementary lighting, as the positive DIF treatment also did. However, this increase in starch level did not affect flower quality at harvest (bud length, bud disorders) or keeping quality. Stem length and bud length was slightly reduced by the temperature rise treatment compared to the control. Number of roses with petal-blueing was noticeable high in the temperature rise treatment without supplementary lighting.

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