INFLUENCE OF HUMIDIFICATION AND DEHUMIDIFICATION ON GREENHOUSE CLIMATE AS WELL AS WATER RELATIONS AND PRODUCTIVITY OF CUCUMBER - II - INFLUENCES ON PLANTS

The influence of humidification and/or dehumidification on water relat ions as well as growth and fruit production of cucumbers (May planting s) were investigated in two year experiments. The vapour pressure defi cits (vpd) achieved in the treatments (FRICKE and KRUG 1997) resulted in different transpiration rates of the plants. But with ample water s upply by permanent fertigation the plants aid not show significant mor phogenetic effects and no water stress. With restricted water availabi lity in dry soil leaf growth rate was reduced and transpiration was st rictly reduced, but it still increased linear with decreasing relative humidity and there was no break down at noon. The quantity of yield w as not significant influenced. In humidified treatments, however, frui t reduced. Contrary to common expectations, less infection with Botryt is cinerea occurred in humidified treatments. Summarizing it can be st ated, that in the range tested with sufficient water supply humidifica tion and/or dehumidification measures are not necessary for a summer c ucumber crop. With insufficient water supply or possibly for reducing fungus infection humidification can secure production.