Articles
INFLUENCE OF EXOGENOUS FACTORS ON THE QUALITY AND CHEMICAL COMPOSITION OF VEGETABLES
Quality standards depend largely on the purpose for which the produce is used, differing standards being applied to the same plant material according to the particular use for which it is destined, e.g. quality standards for table potatoes differ from those for starch production.
Whatever the required quality standards, they are related to physiological and biochemical processes which, in turn, are influenced by exogenous factors.
This paper discusses some of the chief physiological relationships between exogenous factors and plant processes relevant to quality characteristics.
Exogenous factors include plant nutrients, temperature, light intensity and the water supply to crops.
Relationships between these factors are often of great importance for the production of chemical constituents and also determine the physical properties of plant material relevant to quality.
For the purpose of a general physiological discussion, it is convenient to divide the great range of plant species used as vegetables, which show a great range of properties and quality standards, into three groups:
- Vegetables grown mainly for their leaves and stems (vegetative plant material), such as lettuce, spinach, rampion.
- Vegetables grown for their vegetative storage organs such as beetroot, radish, onion, celery, potatoes and some brassica species.
- Vegetables grown for their fruits or seeds.
In this group fruits like tomatoes and cucumbers have to be distinguished from legumes like peas and beans.
This paper is not concerned with specific mineral deficiencies producing characteristic deficiency symptoms, which limit growth and yield and result in poor quality.
Examples of these conditions are whiptail in cauliflower caused by Mo deficiency and heart rot of beet and celery due to boron deficiency.