What are Plants?
Plants are multicellular eukaryotic organisms with cell walls made of cellulose. Plant cells also have chloroplasts. In addition, plants have specialized reproductive organs. These are structures that produce reproductive cells. Male reproductive organs produce sperm, and female reproductive organs produce eggs. Male and female reproductive organs may be on the same or different plants.
How Do Plants Obtain Food?
Almost all plants make food by photosynthesis. Only about 1 percent of the estimated 300,000 species of plants have lost the ability to photosynthesize. These other species are consumers, many of them predators. How do plants prey on other organisms? The Venus fly trap in Figure below shows one way this occurs.
Venus fly trap plants use their flowers to trap insects. The flowers secrete enzymes that digest the insects, and then they absorb the resulting nutrient molecules.
What Do Plants Need?
Plants need temperatures above freezing while they are actively growing and photosynthesizing. They also need sunlight, carbon dioxide, and water for photosynthesis. Like most other organisms, plants need oxygen for cellular respiration and minerals to build proteins and other organic molecules. Most plants support themselves above the ground with stiff stems in order to get light, carbon dioxide, and oxygen. Most plants also grow roots down into the soil to absorb water and minerals. And, of course, we need the energy stored in plants through photosynthesis to survive. Life as we know it would not be possible without plants.
- cellulose: Carbohydrate component of cell walls; characteristic of eukaryotic cell walls.
- cell wall: Rigid layer that surrounds the plasma membrane of a plant cell; helps support and protect the cell; also characteristic of many prokaryotes.
- chloroplast: Organelle in the cells of plants and algae; site of photosynthesis.
- photosynthesis: Process of using the energy in sunlight to make food (glucose).