Articles
DISCUSSION OF POSTERGROUP D: GREENHOUSE CLIMATE AND CROP RESPONSE
The temperature effect will depend on the crop, the time of the year, and the growth phase.
The 24-hour mean temperature has been shown to be important for some growth reactions such as flowering, fruit production and leaf and stem growth.
For other growth responses such as stem lenght, specific day/night temperatures seem to be more important.
For photosynthesis or dry weight gain it is most important to have higher day than night temperatures, but the type of temperature schedule used will mostly depend on the crop to be sold.
For Spray Chrysanthemums where quality is expressed as the number of flowers per stem, night temperature is important.
Also the effect of temperature on morphology was discussed.
The effect of temperature on morphology is dependent on the irradiance and temperature levels.
The day temperature may be affecting the growth rate at night; in the winter when light levels are low and the nights long, this effect becomes more complicated to interpret.
Crop growth responses to sudden temperature changes may be due to differences in internal water content.
With increasing temperature the differences in root and air temperature increase.
The root temperature does not follow sudden increases in air temperature.
In some cases reported with tomato sudden increases in temperature from 17 to 22 degrees, or from 22 to 27 degrees resulted in a 30% decrease in photosynthesis.
After approx. two days the plants were adapted to the change of temperature.
It was suggested that this reaction was due to stomatal resistance.