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Roots (mature portions of the root. (root hairs function only for several…
Roots
mature portions of the root.
root hairs function only for several days.
absorption of water and minerals in this area is then greatly reduced.
continued maturation in which a layer of suberin is applied over all radial surfaces.
passage cells because they were once thought to represent passageways for the absorption of minerals.
the powerful absorption of water, and a water pressure called root pressure.
three primary functions of the root
anchoring the plant firmly to a substrate
absorbing water and minerals
producing hormone
Zone of Maturation/Root Hair Zone
Root hairs grow outward, greatly increasing absorption of water and minerals.
on some a thin cuticle appears to be present on root epidermal cells.
in the zone of maturation, minerals do not have free access to the vascular tissue because of endodermis.
other type of roots and root modification
storage roots
contractile roots
mycorrhizae
symbiotic relationship in which both benefit
ectomycorrhizal and endomycorrhizal
External structure of Roots
organization of root system
taproot develops from the embryonic root, called the radicle.
structure of individual roots
simple, no leaves or leaf scars.
root tip, where growth in length occurs by discrete apical meristems.
root apical meristem is protected by thick layer of cells, the root cap.
most monocots and some eudicots have a mass of many similarly sized roots constituting a fibrous root system.
Dictyosomes of root cap cells secrete a complex polysaccharidecalled mucigel.which lubricates passage of the root through the soil.
zone of elongation present behind the root cap and root apical meristem .
root hairs form only in a part of the root that is not elongating.
internal structure of roots
root cap
to remain in place and provide effective protection for the root apical meristem.
must have a specific and growth pattern.
cells are small and meristematic when first formed at the base of the root cap.
Root Apical Meristem
produces, regular files of cells can be seen to originate in the meristem and extend into the regions of mature root tissues.
Mitotically inactive central region is known as the quiescent center.
root is more orderly than the shoot.
origin and development of lateral roots.
lateral roots are initiated by cell divisions in the pericycle.
