Plant pigments — biochemical basis of flower colour The visible colour of many flowers is primarily due to which cellular components or pigments?

Introduction / Context:
Flower colours attract pollinators and are central to angiosperm reproduction. Multiple pigments contribute to the palette, but two sources dominate in petals: plastid-based carotenoids and vacuolar anthocyanins.

Given Data / Assumptions:

• We are concerned with the main determinants of petal colour.
• Chromoplasts house carotenoids (yellow to red/orange).
• Anthocyanins in vacuoles provide red, purple, blue hues depending on pH and metal chelation.

Concept / Approach:

Chromoplasts are specialized plastids that accumulate carotenoids, creating yellow and orange colours. Anthocyanins are water-soluble flavonoids stored in vacuoles; their colour shifts with vacuolar pH, co-pigments, and metal ions. Chlorophyll is typically degraded in petals; xanthophylls are carotenoids but the term alone ignores anthocyanins. “Florigen” is a historical term for flowering signal, not a pigment.

Step-by-Step Solution:

Verification / Alternative check:

Plant biochemistry and horticulture references consistently attribute petal colours to carotenoids and anthocyanins, with betalains in certain families as exceptions.

Why Other Options Are Wrong:

Chlorophyll is a leaf pigment, not typically giving petal colour. Xanthophylls are a subset of carotenoids but the answer must include anthocyanins. Florigen is not a pigment. Cellulose is structural and colourless.

Common Pitfalls:

Overgeneralizing carotenoids as “xanthophylls only,” or assuming chlorophyll colours petals. Petal pigments are specialized.

Final Answer:

Chromoplasts or anthocyanin pigments