Growth and Development of Horticultural Crops (1+1)

Symptoms of Fruit Ripening

1.Texture (Softening of fruit)

• The changes in the texture of fruit result due to changes in the structure and composition of their cell walls.
2.Colour

• The factors responsible for changes in colour of fruit during ripening may be due to changes in pigments localized in chloroplasts or those which are stored outside chloroplasts in vacuoles.
(a) Colour changes due to conversion of chloroplasts into chromoplasts – The carotenoids.

• A major factor in the colour changes of fruit ripening is the transition from chloroplasts which are rich in green pigment chlorophyll into chromoplasts which are rich in red or yellow carotenoid pigments.
• Carotenoids are important constituents of chloroplasts and are present in green fruit tissues even before maturation. Maturation does not always involve accumulation of carotenoid pigments. For instance, yellowing in many varieties of apples, pears, grapes, olives and mature bananas results from pre-existing carotenoids which are unmasked due to disappearance of chlorophyll.
• A large number of other fruits such as citrus, tomato, capsicum etc., accumulate large amounts of carotenoids which are biosynthesized during later stages of maturation. The complement of carotenoid pigments in these fruits, however, differs greatly from one species to another. In tomatoes, the carotenoid pigments are dominated by lycopene and β-carotene.
(b) Colour changes due to pigments stored outside chloroplasts (i.e., in vacuole)-The anthocyanins.

• Anthocyanins are water soluble phenolic pigments which accumulate in vacuole and impart red, blue and purple colors to many fruits such as ripening fruits of apple, grape, strawberry etc. Anthocyanins exist as complex conjugates of parent aglycones called as anthocyanidins.