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to which plants must acclimatise and adapt in order to thrive.
Abiotic components of an ecosystem include temperature, soil,
water, humidity, light and wind, while biotic components of an
ecosystem include parasitic and herbivorous pests, competition
from other plants, and favourable (symbiotic) relationships with
other organisms along with human (agricultural) operations. All
these factors (abiotic and biotic) influencing the yield and qual-
ity parameters of MAPs are discussed in detail in the following
sections of this chapter.
12.4 Abiotic factors
temperature
Mean surface air temperatures of the Earth have increased
0.68°C during the last century, and global circulation models
project a global warming of 1.4-5.88°C by 2100 (Houghton
et  al., 2001). Numerous studies have examined the effects of
elevated temperatures on plants (Berry and Bjorkman, 1980;
Morison and Lawlor, 1999; Rustad et al., 2001). Elevated tem-
peratures reduce stomatal conductance and, subsequently,
reduce photosynthesis and growth of many plant species (Berry
and Bjorkman, 1980). The photochemical efficiency of pho-
tosystem II also decreases at elevated temperatures, indicat-
ing increased stress (Gamon and Pearcy, 1989; Maxwell and
Johnson, 2000). When plants are stressed, secondary metabo-
lite production may increase because growth is often inhibited
more than photosynthesis, and the carbon fixed not allocated to
growth is instead allocated to secondary metabolites (Mooney
et  al., 1991). Several studies have examined the effects of
increased temperatures on secondary metabolite production
of plants, but most of these studies have contradictory results.
Some report that secondary metabolites increase in response to
elevated temperatures (Litvak et al., 2002), while others report
that they decrease (Snow et al., 2003).
For the last 5-10 years, climate change in Europe has caused
an abrupt transition from winter to summer with temperatures in
April and May that are more typical for summer temperatures.
This has resulted in severe damages; for example, throughout
Europe the spring planting of chamomile ( Matricaria recutita ,
Asteraceae) has been disastrous with an average yield loss of
80% (Cavaliere, 2009).
Total alkaloid content of Datura metel L. has been shown
to peak in the hot dry season and is at its lowest during the
rainy season in Ibadan (Cavaliere, 2009). To model the effects
of the environmental factors, especially temperature, on yield
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