iron - needed in several of the electron transport substances of the cell (ferredoxin, cytochromes)
iron - can occur in soils with high or low pH
micronutrients - vitamins and minerals that are needed in small amounts
micronutrients:
boron
copper
iron
chloride
manganese
molybdenum
zinc
boron - deficiency results in abnormally dark foliage, growth abnormalities, and malformations
zinc- required for the production of amino acid tryptophan
zinc - indirectly required for the production of auxins
zinc - Deficiency produces small leaves and stunted stems owing to short internodes.
zinc - poisonous to plants
manganese - required as a cofactor for enzymes in oxidative metabolism and in photosynthetic oxygen production.
manganese - Its deficiency produces a mottled, characteristic form of chlorotic leaf yellowing.
chlorine - required for ionic balance and maintenance of cellular membrane potentials
chlorine - its deficiency results in very small leaves and slow growth. Leaves become wilted, chlorotic, or even necrotic and may eventually become bronze-colored.
molybdenum - needed as part of the denitrifying and nitrogen-fixing enzymes of microorganisms
copper - component of some enzymes and cytochromes.
copper - deficiency results in a lowered rate of protein synthesis and sometimes in chlorosis
specialized absorptive structures:
root hairs
root nodules
mycorrhizae
root hairs – slender extensions of specialized epidermal cells that greatly increase the surface area available for absorption.