Agriculture Reference
In-Depth Information
can contribute to a reduction of the energy consumption by 80-90 % and operate a
greenhouse with minimum CO
2
-emissions.
The Influence of Temperature on Plant Growth
and Product Quality of Greenhouse Horticultural Plants
General
The “greenhouse effect” may have a positive effect on plants at higher latitudes;
however, a negative effect on plant growth and development is also possible due
to high temperatures in these latitudes. In general, the speed of all biochemical
processes is temperature dependent and the reaction rate of different biological pro-
cesses increases with increasing temperature. Afterwards, enhanced exposition du-
ration and temperature intensity, the reaction rate decreases, because most enzymes
lose their effectiveness or have been damaged resulting in reduced plant growth
and development. Temperatures are highly affected by light intensity and to a lesser
extent, by CO
2
-concentration together with seasonal growth pattern and plant stage
also needed to be considered (Gruda
2005
).
Numerous studies have revealed optimum temperature range requirements for
various plant species.
The optimum air temperature, regulation of the minimum air temperature and
the commencement of cooling measures are three important aspects concerning air
temperature regulation and control in protected cultivation. An optimum air tem-
perature is crucial, due to regulation of the setting point of day temperature. As it
was mentioned above, optimum temperature has to be regulated according to the
particular plant species and/or cultivars and their subsequent development stages.
Thus recommended temperatures for the germination of vegetables are higher than
those for seedlings, transplants or for further cultivation. Optimum air tempera-
tures are dependent on existing light intensity in protected cultivation. Plants grown
under high radiant energy and low thermal energy become stocky, but grow and
develop more slowly (Liu and Heins
2002
). By contrast, plants grown under low
radiant energy and high thermal energy grow and develop rapidly but become thin
and weak. Moccaldi and Runkle (
2007
) reported that the flowering rate of salvia
(
Salvia splendens
) and marigold (
Tagetes patula
) was primarily controlled by tem-
perature within the experimental conditions provided with flowering decreasing
from 42 to 24 days as temperature increased from 15 to 25 °C. Similarly, Blanchard
et al. (
2011
) found the same trend for two petunia cultivars. (
Petunia
×
hybrida
).
Although the flowering rate increased with temperature, plant quality parameters
decreased, especially when the daily light integral (DLI) was low (Moccaldi and
Runkle
2007
).
In order to balance plant growth and development, during the European winter
period, the optimum day temperatures in greenhouses have to be lower than in the
