2.2. Plastids

What is the most salient feature that we immediately associate with plants? Obviously, it is the color green. We also link the term photosynthesis with plants. The green coloration of leaves is because of the light-harvesting organelle called the chloroplast. Chloroplast is a sub-type of an organelle broadly termed Plastid and has distinctive structural features evolutionarily tailored for photosynthesis. Other types of plastids include leucoplasts (often found in root cells) and chromoplasts (often found in flower petals), but we shall exclusively focus on chloroplasts. 

Chloroplasts have specific molecules called chlorophylls that capture energy from mostly the blue and red part of the visible light spectrum, reflecting off the green light - hence the green coloration of the leaves. During photosynthesis, carbon dioxide from the atmosphere and water taken up from the soil via roots are synthesized to form carbohydrates. In the next few pages we will explore chloroplasts, and shall encounter them again later when we take a closer look at the leaves.