ISHS Acta Horticulturae 174: Symposium Greenhouse Climate and its Control
GROWTH OF YOUNG CUCUMBER PLANTS UNDER DIFFERENT DIURNAL TEMPERATURE PATTERNS |
| Authors: | H. Challa, P. Brouwer |
| Abstract:
In the present study the question was investigated whether growth of young cucumber plants responded similar to the same temperature integral irrespective of the diurnal temperature pattern. Our results obtained by means of growth analysis show that this is not the case. Alternating high (25 °C) and low (15 °C) temperatures within the night resulted in relatively fast growth of young cucumber plants if the periods were 2 or 4 h, but if the same temperature integral was obtained with alternating nights of 25 °C and 15 °C growth was reduced. In another series of experiments with young cucumber low night temperature affected plant growth much less when applied after a dull day than after a bright day. In both cases the difference in relative growth rate could be attributed largely to differences in leaf area ratio (LAR), the ratio of leaf area and plant dry weight. The magnitude of these differences in LAR were comparable to the effect brought away by a difference in constant night temperature of approximately 3 °C, under our growing conditions. Our results strongly suggest that the effect of temperature on plant morphogenesis depends on growth rate. The positive effect of fluctuating temperatures as compared to constant average temperatures might be explained by the double role of temperature which besides controling the rate of growth on a short term also affects the morphological characteristics of the plant. When cool periods of slow growth are alternated with warm periods of fast growth, morphology of the plant will be affected relatively more by the higher temperature than would be predicted by the exposure time alone. Because this phenomenon is important in greenhouse culture, where temperature can be controlled from moment to moment, emphasis should be given to a proper quantitative description in plant growth models, in particularly those that are designed as a basis for temperature control in greenhouses. | |
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