Soil and Plant Nutrition
31.1 Nutritional Requirements of Plants
Plants meet their nutritional needs for growth by absorbing soil nutrients, water, and carbon dioxide, in addition to the required sunlight.
The Chemical Composition of Plants
Plants are composed of water, carbon-containing organics, and non-carbon-containing inorganic substances such as potassium and nitrogen.
Approximately 20 macronutrients and micronutrients are deemed essential nutrients to support all the biochemical needs of plants.
31.2 The Soil
Soil is a mix of varying amounts of inorganic matter, organic matter, water, and air.
Soil formation is the result of a combination of five factors: parent material, climate, topography, biological factors, and time.
Physical Properties of the Soil
Soils are made up of combinations of four distinct layer types or horizons: O horizon, A horizon, B horizon, and C horizon.
31.3 Nutritional Adaptations of Plants
Nitrogen Fixation: Root and Bacteria Interactions
Plants cannot extract the necessary nitrogen from soil, so they form symbiotic relationships with rhizobia that can fix it as ammonia.
Mycorrhizae: The Symbiotic Relationship between Fungi and...
Many plants form associations called mycorrhizae with fungi that give them access to nutrients in the soil, protecting against disease and toxicities.
Nutrients from Other Sources
Many species of plants are unable to make their food via photosynthesis and must acquire nutrients in a variety of additional ways.