Question

Suggest a reason why plants contain lightabsorbing pigments in addition to chlorophylls \(a\) and \(b\)

Short answer

Plants contain additional pigments to absorb a broader spectrum of light and to protect chlorophyll from damage.

Step-by-step solution

Understand Chlorophylls

Chlorophylls are the primary pigments in plants that absorb light for photosynthesis. They mainly absorb light in the blue and red parts of the spectrum but not green, which is why plants appear green.

Role of Additional Pigments

Plants also contain other light-absorbing pigments such as carotenoids and phycobilins. These pigments absorb light in parts of the spectrum that chlorophylls do not, such as the green and yellow parts.

Optimize Light Absorption

By having a range of pigments, plants can absorb a broader spectrum of light. This helps in maximizing the energy they obtain from sunlight, enhancing photosynthesis efficiency.

Protect the Plant

Some accessory pigments also play a role in protecting the plant from harmful UV radiation by dissipating excess energy as heat, thus preventing damage to chlorophyll molecules.

Key concepts

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Chlorophylls are essential for photosynthesis, acting as the primary pigments in plants. These molecules, designated chlorophyll a and chlorophyll b, absorb light most effectively in the blue (430-450 nm) and red (640-680 nm) parts of the spectrum. This absorption powers the production of chemical energy. However, chlorophylls reflect green light, giving plants their characteristic color and leaving a gap in potential light absorption.

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Carotenoids are accessory pigments found in plants alongside chlorophyll. These pigments absorb light primarily in the blue and green parts of the spectrum (400-550 nm). By capturing light in these ranges, carotenoids complement chlorophyll’s absorption capabilities.

Carotenoids also play a protective role by quenching reactive oxygen species produced during photosynthesis. This protects plants from oxidative damage and further improves photosynthetic efficiency.

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Phycobilins are another group of pigments that absorb light in wavelengths not covered by chlorophyll. These pigments, prevalent in cyanobacteria and red algae, absorb light mainly in the orange and red spectrum (520-620 nm).

By extending the range of absorbed light, phycobilins allow these organisms to harvest sunlight more effectively, especially in deeper or shaded aquatic environments where light penetration reduces.

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Light absorption is crucial for photosynthesis, the process by which plants convert light energy into chemical energy. Various pigments absorb different wavelengths, broadening the spectrum of available light energy. The combination of pigments like chlorophyll, carotenoids, and phycobilins ensures that plants can utilize light across a wider range of the spectrum.

• Chlorophylls absorb mainly blue and red light
• Carotenoids capture blue and green light
• Phycobilins absorb orange and red light

This comprehensive absorption enables plants to maximize their light energy intake, driving effective photosynthesis.

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Photosynthesis efficiency is optimized when plants use a broad spectrum of light. Accessory pigments like carotenoids and phycobilins complement chlorophyll by capturing additional light energy and protecting the plant. This synergy enables plants to:

• Increase their overall energy absorption
• Enhance photosynthesis under diverse light conditions
• Reduce damage from intense light and UV radiation

Thus, having various pigments improves the plant's ability to thrive in different environments, ensuring robust growth and survival.