5. Essential Minerals of Plants Mineral nutrients are essential chemical elements that plants
extract from the soil in the form of inorganic ions Macronutrients are needed in relatively large amounts
Nitrates supply nitrogen Phosphates supply phosphorus Sulfates supply sulfur Ca2+, Mg2+, K+
Generally function as components of macromolecules eg. Mg2+ is a component of chlorophyll; K+ functions in water balance
Micronutrients are needed in very small amounts Ionic forms of chlorine, iron, manganese, boron, zinc, copper, nickel,
and molybdenum Often function as enzyme cofactors, components, or to activate
enzymes Macronutrients and micronutrients are essential elements
because they are required for a plant to complete its life cycle Without the proper nutrients, mineral deficiencies occur
6. Obtaining Nutrients Figure 37.2! Carbon dioxide enters the plant
through the stomata in the leaf Water, mineral nutrients and oxygen
are absorbed through the roots Water and oxygen exit the plant
through the leaf, while carbon dioxide is expelled from the roots
Plants are net producers of oxygen and net consumers of carbon dioxide and water 80-90% of a plant’s wet weight is
water The bulk of a plant’s dry mass is
derived from carbon dioxide
The Role of Bacteria in Symbiotic Nitrogen Fixation Symbiotic relationships with
nitrogen-fixing bacteria provide certain plants with a source of fixed nitrogen Usually plants in the legume
family eg. Peas, soybeans, peanuts, alfalfa and clover
The bacteria, such as Rhizobium, live in swellings on the roots called nodules that consist of plant cells with the bacteria in the form of bacteroids located in vesicles
Mycorrhizae and Plant Nutrition Mycorrhizae (“fungus roots”) are modified roots consisting of
mutualistic associations of fungi and roots The fungus benefits from a steady supply of sugar donated by the host
plant The fungus increases the surface area for water uptake by the root, and
selectively abosrbs phosphates and other minerals from the soil and supplies them to the plant
Occur in most plant species, and probably represent an early adaptation to a terrestrial environment
Unusual Nutritional Adaptations of Plants
Epiphytes, parasitic plants and carnivorous plants use other organisms in unusual nonmutualistic ways Epiphytes nourish themselves but grow on other plants
They obtain water and minerals through leaves, from rain Parasitic plants absorb sugars and minerals from their hosts
Some are photosynthetic, some not Roots may function as haustoria, nutrient-absorbing projections
into the host plant Carnivorous plants obtain nitrogen and minerals by killing and
digesting small animals such as insects They are photosynthetic, but live in acid bogs and other mineral-
poor soils