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Plants, like
animals, need
minerals for healthy
growth and to
function normally, but plant nutrition is very different from animal
nutrition in several ways. In a plant high-energy
food (for example,
carbohydrate) is made inside the plant by
photosynthesis, mineral salts
from the environment are absorbed from soil water by the
roots (see
root
hair cell) while animals get theirs from their
food. Mineral salts are
taken up in soluble form. When mineral salts dissolve in water they
separate into particles called ions. Some of the ions travel by
diffusion into the root; others are
absorbed by active transport. The
minerals required in the greatest amounts by plants (also called
macroelements) are those containing the elements
potassium,
phosphorous
and in particular nitrogen, (For example nitrate ions or nitrates are
used by plants in the production of proteins such as
enzymes, so they
are important for plant growth) The mineral salts are often in short
supply in the soil, which is why
inorganic fertilizers are required.
Plants also require magnesium in order to make
chlorophyll, the green
chemical that absorbs the energy of sunlight for
photosynthesis. A
microelement is a mineral salt required only in tiny amounts , such as
calcium,
iron, zinc,
copper etc. |