This thesis presents the biotic and abiotic stress factors that have a significant impact on
the growth and quality of vegetables in organic production. In organic production, due
to the limitations of the permitted pesticides and fertilisers, plants are more exposed to
stress. The causes of stress include soil salinity, high temperatures, drought, pest and
disease infestation and weed pressure. Exposure to stress leads to morphological,
physiological and biochemical adaptations in vegetables, often resulting in slower plant
growth. In addition to slowing growth and reducing yield, stress factors also affect the
accumulation of antioxidants and secondary metabolites such as ascorbic acid, phenolic
compounds, glucosinolates and terpenes. Plants form these molecules to protect
themselves from reactive oxygen species, to maintain cell turgor and to maintain lipid
and protein conformations. Antioxidants and secondary metabolites are key to
maintaining homeostasis and repairing or preventing damage to plant tissues under
stress conditions. These molecules also play an important role in human nutrition, as
they have many beneficial effects on human health. Comparisons between organic and
conventional or integrated vegetable production have shown that organically produced
vegetables often contain more antioxidants and secondary metabolites, which also
supports the thesis that organic vegetables are more exposed to stress. This thesis also
describes some of the products that are allowed in organic production to alleviate the
negative effects of stress and to increase the quantity and quality of yields.
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