Overview
This lecture introduces plant pigments, their roles in coloration and photosynthesis, and provides a brief overview of major pigment categories in plants.
What Are Plant Pigments?
- Pigments are organic compounds that give color to living things and often serve other functions.
- In plants, pigments color leaves, flowers, and fruits, and are involved in processes like food production.
Types of Plant Pigments
Chlorophyll
- Chlorophyll is the main pigment involved in photosynthesis.
- Three types: chlorophyll a, b, and c.
- Chlorophyll molecules are large and contain a cyclic part that binds magnesium.
- Similar in structure to hemoglobin, but hemoglobin contains iron instead of magnesium.
- Chlorophyll reflects green light and absorbs red, yellow, and blue light.
- Excited electrons in chlorophyll initiate photosynthesis.
Carotenoids
- Carotenoids give plants red, yellow, and orange colors.
- They act as accessory pigments, assisting chlorophyll in capturing light energy.
- Carotenoids are responsible for colors in autumn leaves and vegetables like carrots.
Flavonoids
- Flavonoids are pigments mostly found in plant cell vacuoles.
- The most common flavonoids are anthocyanins, which produce bright red colors in flowers, fruits, and stems.
- Anthocyanins contribute to the red color in autumn leaves.
Phytochrome
- Phytochrome is a pigment that absorbs light to trigger plant growth and developmental events.
- It is not directly responsible for visible color but controls processes like seed germination, stem growth, and flowering.
Key Terms & Definitions
- Pigment — Organic compound that imparts color to living organisms.
- Chlorophyll — Green pigment essential for photosynthesis in plants.
- Carotenoids — Accessory pigments that provide red, yellow, and orange color and assist in light absorption.
- Flavonoids — Pigments, particularly anthocyanins, that provide red coloration and are found in vacuoles.
- Phytochrome — Plant pigment that senses light to control growth and development processes.
Action Items / Next Steps
- Review photosynthesis mechanisms, focusing on the role of pigments.
- Prepare for the next topic: the different kinds of plants on Earth.