Production Practices and Quality Assessment of Food Crops. Vol. 1

Effects of Agronomic Practices 41
6. INFLUENCE OF AGRONOMICAL PRACTICES
The cultivation method is another factor affecting the contents of tomato ingredients.
Regarding the carotenoids, tomatoes grown on an open field were compared
to those grown under glass or under plastic foil (Cabibel and Ferry, 1980).
Figure 3 shows the two carotenoids β-carotene and lycopene in tomatoes of five
maturity stages for these three cultivation methods.
For all maturity stages, both carotenoids showed significantly higher contents
in field grown tomatoes compared to the in-house grown tomatoes. Lycopene
contents in red tomatoes grown under foil were slightly higher than those ripened
under glass. These differences have to be further investigated (Cabibel and Ferry,
1980).
In another study, irrigation with water at electrical conductivity of 4.4 dS/m
led to a 40% increase of the lycopene content without decrease of the yield. In
contrast, fertilisation with different nitrogen sources did not affect the carotenoid
content (Fogliano et al., 2001).
Heavy metals in the soil led to an increase of those metals in the tomato leaves
but did not affect the contents of carotenoids and total phenolics in tomato fruits
(Schicketanz et al., 1999). Thus, heavy metal stress did not induce changes in
secondary plant products of the tomato fruit. In contrast to these results, a mechanical
wounding led to a 10-fold increase of the contents of the two phenolic
compounds E-feruloyl-tyramine and E-p-coumaroyl-tyramine conjugates. These
results support a role for hydroxycinnamate-tyramine conjugates as part of the
defence system of the plant (Pearce et al., 1998).
Figure 3. Contents of β-carotene and lycopene in five maturity stages of tomatoes grown in field,
under glass or under plastic foil (modified from (Cabibel and Ferry, 1980))