38 KINGDOM PLANTAE Part 2: SEEDLESS PLANTS A. Introduction: All plants share many features with their green algal (Class Charophyceae) ancestors. They possess chlorophyll a and b, carotenoids, and xanthophylls. Their cell walls are predominantly composed of cellulose, and photosynthetic products are stored as starch. However, in contrast to their algal predecessors, most are terrestrial organisms. There are many differences between water and land as environments for plant growth. In an aquatic environment, water is available to all cells and also acts as a supportive medium. All of the oxygen, carbon dioxide and minerals required by a photosynthetic organism are in solution and thus, most cells are capable of photosynthesis. In terrestrial habitats, light, oxygen and carbon dioxide are readily available, but water is often limiting, and when present, is mostly found in the soil. As a result, photosynthesis and nutrient absorption are often separated in terrestrial photosynthetic organisms. As you examine the plant material provided for you in
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