Biological Pigments in Plants: Definition, Types and Examples

Edited By Irshad Anwar | Updated on Jul 02, 2025 06:57 PM IST

What Are Pigments?

In simple terms, these are any of the naturally occurring compounds that absorb and reflect wavelengths of light to give colour and make different physiological functions within living organisms possible. The pigments play a fundamental role in photosynthesis in plants by capturing the energy from light and then storing it in the form of chemical energy.

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What Are Pigments?
Types Of Biological Pigments
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The paper discusses different types of biological pigments, such as chlorophylls, carotenoids, and phycobilins, in connection to their role in the health functions of plant pigment. Their contribution to the effectiveness of photosynthesis via absorption and photoprotection shall also be discussed.

Types Of Biological Pigments

The green chromophores compose the general category of chlorophylls whose basic structure includes a porphyrin ring bound to the central magnesium ion.

Chlorophyll

The details for chlorophyll are given below:

Structure and Types

The most widely distributed forms are chlorophyll a, which plays a part in electron transfer during the realisation of light-dependent reactions in photosynthesis, and chlorophyll b, which captures light energy and extends the spectrum of absorbed light. Such forms as chlorophyll c, d, and e are well spread in certain algae. Their function is the same as in the above cases, only adapted to some other light conditions.

Role in Photosynthesis

Chlorophylls absorb light energy emanating from the blue-violet and red ends of the visible spectrum and convert light energy into chemical energy. The chemically converted form of light energy gets stored and put to use again in the synthesis of glucose from carbon dioxide and water.

Distribution in Plant Cells

Chlorophylls are found in plant cells. In plant cells, they are mainly distributed in the chloroplasts and more clearly in the thylakoid of the chloroplast where light reactions take place.

Carotenoids

The details for carotenoids are given below:

Types

There are two types of carotenoids. They are carotenes( ex; β-carotene ), and xanthophylls( ex; lutein ).

Role in Photosynthesis and Photoprotection

They absorb bluish-green light, which is not absorbable by chlorophyll itself, and then transfer the energy to the chlorophyll. Also, they serve to protect the photosynthetic apparatus from too much harmful light energy by scavenging it and dissipating it as heat.

Examples (β-Carotene, Lutein)

One such carotenoid is beta-carotene, which is a naturally occurring precursor to vitamin A, important in nutrition. Another is lutein, which protects the tissue of the plant from light damage.

Anthocyanins

The details for anthocyanins are given below:

Chemical Structure and Variability

The anthocyanins are a water-soluble group of pigments having the general structure of a glycosylated flavonoid. It underlies the colour in the red, purple, and blue colours in plants. Herein, the precise chemical structure of the individual anthocyanins and also its specific glycosylation pattern are variable.

Role in Plant Defense and Attraction

The colours of anthocyanins are bright, playing a double role in defending the plant against herbivores and again attracting pollinators.

Distribution in Plant Tissues

They occur in different tissues of the plants like fruits, flowers, and leaves. Being part of the pigment system, they colour the plants and interact with the environment.

Other Pigments

The other pigments are described below:

Flavonoids

These are pigments implicated in plant pigmentation, UV protection, and signalling. The subtypes, such as flavonols and flavones, are implicated in the defence mechanisms of the plant and in attracting pollinators.

Phytochromes

Light receptor pigments control the response of plants to the presence or absence of light. This response includes seed germination and time of flowering.

Cryptochromes

Another pigment, which acts as a receptor of blue light. It is controlling growth and developmental processes in response to changes in light.

Role and Distribution in Plants

The pigments are differentially distributed in plant tissues and result in differential functioning concerning light perception, development, and protection against environmental stresses.

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Frequently Asked Questions (FAQs)

1. What are the main types of pigments found in plants?

Chlorophyll, carotenoid, and anthocyanin are the major types.

2. How do plant pigments contribute to photosynthesis?

In photosynthesis, light energy is absorbed by the chlorophyll and carotenoid and is transformed into chemical energy.

3. What roles do anthocyanins play in plants?

Anthocyanins participate in plant defence, UV protection, and pollinator attraction.

4. How does light intensity affect pigment production in plants?

Light intensity regulation for the synthesis and accumulation of chlorophyll pigments and carotenoids.

5. What are the industrial uses of plant pigments?

Plant pigments are used in foods as natural dyes, by their function as antioxidants.

6. What is the role of carotenoids in photosynthesis?

Carotenoids play several roles in photosynthesis: 1) They act as accessory pigments, absorbing light energy and transferring it to chlorophyll for photosynthesis. 2) They protect chlorophyll from photooxidation by dissipating excess light energy. 3) They help stabilize photosynthetic membranes. 4) Some carotenoids are precursors for plant hormones like abscisic acid.

7. What are biological pigments in plants and why are they important?

Biological pigments in plants are colored molecules that absorb specific wavelengths of light. They are crucial for photosynthesis, protection against UV radiation, and attracting pollinators. The most important pigments are chlorophylls, carotenoids, and anthocyanins, each serving unique functions in plant survival and growth.

8. How do chlorophylls differ from other plant pigments?

Chlorophylls are green pigments that primarily absorb red and blue light, reflecting green. Unlike other pigments, chlorophylls are directly involved in the light-dependent reactions of photosynthesis, converting light energy into chemical energy. Other pigments like carotenoids and anthocyanins serve accessory roles in light absorption and photoprotection.

9. How do anthocyanins protect plants?

Anthocyanins protect plants in several ways: 1) They act as a "sunscreen," absorbing harmful UV radiation and protecting cellular components. 2) They function as antioxidants, neutralizing free radicals produced during stress. 3) They help regulate osmotic pressure in cells during drought stress. 4) In some plants, they deter herbivores by making leaves less palatable.

10. Why do leaves change color in autumn?

Leaves change color in autumn due to the breakdown of chlorophyll as days shorten and temperatures cool. As chlorophyll degrades, it reveals other pigments like carotenoids (yellow and orange) and anthocyanins (red and purple) that were present but masked by the green chlorophyll. This process, called senescence, helps trees conserve energy and nutrients before winter.

11. What is the relationship between pigment structure and its absorption spectrum?

A pigment's structure, particularly its system of conjugated double bonds, determines which wavelengths of light it absorbs. More extensive conjugation allows absorption of longer wavelengths. For example, chlorophyll a has a more extensive conjugated system than chlorophyll b, allowing it to absorb light at slightly longer wavelengths. This relationship between structure and absorption is crucial for understanding pigment function in photosynthesis.

12. How do different pigments contribute to the absorption spectrum of a leaf?

Different pigments absorb light at specific wavelengths, creating a unique absorption spectrum for a leaf. Chlorophylls absorb strongly in the blue and red regions, carotenoids in the blue-green region, and anthocyanins in the green-yellow region. The combination of these pigments allows plants to utilize a broader range of the light spectrum for photosynthesis and other functions.

13. Why are some plants variegated, and how does this affect their photosynthetic efficiency?

Variegated plants have leaves with areas lacking chlorophyll, often appearing white or yellow. This is usually due to genetic mutations or viral infections affecting chloroplast development. Variegated plants typically have lower photosynthetic efficiency because they have less chlorophyll overall. However, they may compensate by increasing chlorophyll content in green areas or adjusting leaf morphology.

14. How do pigments contribute to photosystem organization in chloroplasts?

Pigments play crucial roles in organizing photosystems within chloroplast membranes. Chlorophyll a forms the reaction centers of both Photosystem I and II. Accessory pigments like chlorophyll b and carotenoids surround these reaction centers in light-harvesting complexes, capturing light energy and funneling it to the reaction centers. This organization optimizes light capture and energy transfer in photosynthesis.

15. Why do some algae appear red even though they contain chlorophyll?

Some algae, particularly red algae (Rhodophyta), appear red despite containing chlorophyll because they also contain high levels of red pigments called phycobilins, specifically phycoerythrin. These pigments mask the green color of chlorophyll. Phycobilins allow these algae to absorb green light, which penetrates deeper into water, enabling them to photosynthesize at greater depths where other organisms cannot.

16. What is the xanthophyll cycle, and how does it protect plants from excess light?

The xanthophyll cycle is a photoprotective mechanism involving the interconversion of specific carotenoids (violaxanthin, antheraxanthin, and zeaxanthin). In high light conditions, violaxanthin is converted to zeaxanthin, which can dissipate excess light energy as heat. This process helps prevent damage to the photosynthetic apparatus from excess light, a condition known as photoinhibition.

17. What is chlorophyll fluorescence, and how is it used to study plant health?

Chlorophyll fluorescence occurs when excited chlorophyll molecules release energy as light instead of using it for photosynthesis. By measuring this fluorescence, scientists can assess photosynthetic efficiency and plant stress. Increased fluorescence often indicates stress or damage to the photosynthetic apparatus. This non-invasive technique is widely used to monitor plant health in agriculture and ecological studies.

18. How do plants balance the production of different pigments?

Plants balance pigment production through complex regulatory mechanisms involving genetics, environmental sensing, and hormonal control. For example, light quality and intensity influence the ratio of chlorophyll a to b. Stress conditions can trigger anthocyanin production. Nutrient availability affects overall chlorophyll content. This balance ensures optimal light absorption while providing necessary photoprotection and other pigment functions.

19. What is the role of phytochrome in relation to plant pigments?

Phytochrome is a photoreceptor pigment that exists in two interconvertible forms: Pr (absorbs red light) and Pfr (absorbs far-red light). While not directly involved in photosynthesis, phytochrome plays a crucial role in plant development and pigment production. It regulates processes like seed germination, flowering, and shade avoidance. Phytochrome also influences the production of other pigments, such as anthocyanins, in response to light conditions.

20. What is the connection between chlorophyll degradation and nitrogen recycling in plants?

Chlorophyll degradation, particularly during leaf senescence, is closely linked to nitrogen recycling in plants. Chlorophyll molecules contain nitrogen, an essential nutrient. As leaves age or as plants prepare for winter, they break down chlorophyll and other proteins, transporting the nitrogen to other parts of the plant for storage or new growth. This process is crucial for nutrient conservation and overall plant fitness.

21. How do pigments contribute to plant thermotolerance?

Pigments contribute to plant thermotolerance in several ways: 1) Anthocyanins can act as antioxidants, neutralizing reactive oxygen species produced under heat stress. 2) Some carotenoids, through the xanthophyll cycle, help dissipate excess energy as heat, preventing damage to photosynthetic apparatus. 3) Certain pigments may alter leaf optical properties, reflecting more light and reducing leaf temperature. These mechanisms help plants cope with high-temperature environments.

22. What is the relationship between anthocyanins and plant cold tolerance?

Anthocyanins contribute to plant cold tolerance in several ways: 1) They act as antioxidants, neutralizing reactive oxygen species produced during cold stress. 2) They may help stabilize cell membranes, preventing damage from ice crystal formation. 3) Their red color can absorb more heat, potentially warming leaves. 4) They may play a role in osmotic adjustment, helping cells retain water under freezing conditions. These functions help explain why many plants produce anthocyanins in response to cold.

23. What is the role of pigments in plant-pollinator interactions?

Pigments play a crucial role in plant-pollinator interactions, primarily through flower coloration. Different pigments create various colors that attract specific pollinators. For example, bees are attracted to blue and yellow flowers, while birds often prefer red. Some flowers have pigments that absorb UV light, creating patterns visible to insects but not humans. These "nectar guides" direct pollinators to the flower's reproductive parts, facilitating pollination.

24. What is the significance of chlorophyll d and f in cyanobacteria?

Chlorophyll d and f are unique pigments found in some cyanobacteria. Chlorophyll d absorbs far-red light (700-750 nm), while chlorophyll f absorbs even longer wavelengths (700-800 nm). These pigments allow certain cyanobacteria to perform oxygenic photosynthesis using far-red light, which is abundant in specific habitats like underwater or under other organisms. This adaptation expands the range of environments where photosynthesis can occur and has implications for understanding the evolution of photosynthesis.

25. What is the difference between primary and accessory pigments?

Primary pigments, like chlorophyll a, are directly involved in the light reactions of photosynthesis, converting light energy into chemical energy. Accessory pigments, such as chlorophyll b, carotenoids, and phycobilins, absorb light at different wavelengths and transfer that energy to primary pigments, expanding the range of light used for photosynthesis.

26. How do marine algae differ in their pigment composition compared to land plants?

Marine algae have evolved different pigments to adapt to underwater light conditions. While they contain chlorophyll a like land plants, many also have chlorophyll c instead of b. Additionally, red algae contain phycobilins (red and blue pigments), and brown algae have fucoxanthin (a brown carotenoid). These pigments allow algae to absorb the blue-green light that penetrates deeper into water.

27. How do plants adjust their pigment composition in response to different light environments?

Plants can adjust their pigment composition through a process called chromatic adaptation. In low light, they may increase chlorophyll b relative to chlorophyll a to capture more green light. In high light, they might increase carotenoids for photoprotection. Some plants can even produce new pigments, like anthocyanins, in response to stress or changing light conditions.

28. How do betalains differ from anthocyanins, and in which plants are they found?

Betalains are red and yellow pigments found in certain plant families, most notably the Caryophyllales (e.g., beets, cacti). Unlike anthocyanins, which are flavonoids, betalains are tyrosine-derived compounds. Betalains and anthocyanins are mutually exclusive in plants; species that produce betalains do not produce anthocyanins. Betalains serve similar functions to anthocyanins, including attracting pollinators and protecting against stress.

29. What is the evolutionary significance of different pigment compositions in plants?

The diversity of pigment compositions in plants reflects evolutionary adaptations to various environments. For example, the evolution of different chlorophyll types and accessory pigments in aquatic plants and algae allowed them to exploit different underwater light environments. The development of photoprotective pigments like carotenoids and anthocyanins enabled plants to colonize high-light and stressful terrestrial environments.

30. How do pigments contribute to non-photosynthetic functions in plants?

Beyond photosynthesis, plant pigments serve various functions: 1) Anthocyanins and carotenoids in flowers and fruits attract pollinators and seed dispersers. 2) Some pigments act as antioxidants, protecting plants from oxidative stress. 3) Certain pigments deter herbivores through visual or taste cues. 4) Some pigments, like carotenoids, are precursors for plant hormones involved in growth and development.

31. How do pigments contribute to photoperiodism in plants?

Pigments, particularly phytochrome, are central to photoperiodism - the response of plants to day length. Phytochrome exists in two forms that interconvert based on the ratio of red to far-red light, which changes at dawn and dusk. This allows plants to measure day length and trigger responses like flowering or dormancy. Other pigments may also play roles in fine-tuning these responses to seasonal light changes.

32. How do plants produce chlorophyll, and what factors can limit its production?

Chlorophyll synthesis is a complex process occurring in chloroplasts. It requires light, iron, magnesium, and several enzymes. The process begins with the amino acid glutamic acid and involves multiple steps. Factors that can limit chlorophyll production include: 1) Lack of light (etiolation). 2) Nutrient deficiencies, especially iron or magnesium. 3) Genetic mutations affecting chlorophyll synthesis enzymes. 4) Environmental stresses like extreme temperatures or drought.

33. What is the difference between constitutive and inducible pigments in plants?

Constitutive pigments are always present in plants, regardless of environmental conditions. These include chlorophylls and most carotenoids, which are essential for basic plant functions. Inducible pigments are produced in response to specific environmental stimuli or stresses. Many anthocyanins are inducible, produced in response to high light, cold temperatures, or other stresses. This distinction allows plants to balance energy use with protective needs.

34. What is the role of pigments in C4 and CAM photosynthesis?

In C4 and CAM photosynthesis, pigments play similar roles as in C3 plants, but their distribution and regulation may differ. In C4 plants, chlorophyll and other pigments are concentrated in bundle sheath cells, optimizing CO2 fixation. In CAM plants, pigment activity is temporally regulated, with most light absorption occurring during the day while CO2 fixation happens at night. These adaptations help these plants photosynthesize efficiently in hot, dry environments.

35. How do pigments in variegated leaves affect plant energy balance?

Variegated leaves, with areas lacking chlorophyll, present a unique energy balance challenge for plants. The white or yellow areas reflect more light, potentially reducing heat absorption but also decreasing photosynthetic capacity. To compensate, plants may increase chlorophyll concentration in green areas, alter leaf thickness or orientation, or adjust overall leaf size. This balance between aesthetics and function demonstrates the complex adaptations in plant pigment systems.

36. How do pigments in deep-sea algae differ from those in surface-dwelling species?

Deep-sea algae have evolved specialized pigments to capture the limited light available at depth. While surface algae rely primarily on chlorophylls and carotenoids, deep-sea species often contain additional pigments like phycoerythrins, which absorb blue-green light that penetrates to greater depths. Some deep-sea algae can even detect and use very low levels of light for photosynthesis, demonstrating extreme adaptations in pigment systems.

37. How do pigments contribute to plant defense against herbivores?

Pigments contribute to plant defense against herbivores in several ways: 1) Some pigments, like certain anthocyanins, make leaves unpalatable or even toxic to herbivores. 2) Red pigments in young leaves may mimic autumn foliage, deterring insects that avoid mature leaves. 3) Some pigments create visual patterns that mimic insect eggs, discouraging further egg-laying. 4) Pigments can signal the presence of other defense compounds, warning potential herbivores.

38. How do pigments contribute to the phenomenon of shade avoidance in plants?

Pigments, particularly phytochrome, play a key role in shade avoidance. When plants are shaded, the ratio of red to far-red light changes, as leaves absorb more red light than far-red. This shift is detected by phytochrome, triggering a series of responses including stem elongation, reduced branching, and accelerated flowering. Other pigments may also be involved in fine-tuning this response, allowing plants to compete effectively for light in crowded environments.

39. What is the role of pigments in photoprotection during leaf development?

During leaf development, pigments play crucial photoprotective roles: 1) Anthocyanins often accumulate in young leaves, acting as a "sunscreen" to protect developing photosynthetic apparatus. 2) Carotenoids are produced early in leaf development to prevent photooxidative damage. 3) The ratio of chlorophyll a to b changes as leaves mature, optimizing light capture. These mechanisms ensure that developing leaves are protected while they establish their full photosynthetic capacity.

40. How do pigments contribute to the circadian rhythm in plants?

Pigments, especially phytochrome and cryptochrome, are key to plant circadian rhythms. These photoreceptors detect daily light cycles, entraining the plant's internal clock. This clock then regulates numerous processes, including the expression of genes relate