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Roots (Other types of roots and modifications (Butress roots (large, wide…
Roots
Other types of roots and modifications
Storage roots
such as carrots, beets, and sweet potatoes
They usually grow underground as protection from plant-eating animals
specially modified for storage of starch and water
Prop roots
Any of the modified roots that arise from the stem of certain plants
develop at successively higher levels as the stem elongates
maize plant
Butress roots
large, wide roots on all sides of a shallowly rooted tree
they are found in nutrient-poor rainforest soils
do not penetrate to deeper layers
prevent the tree from falling over
gathering more nutrients
Aerial roots of Orchids
rapidly absorb water and nutrients
dangle their roots in the air and absorb moisture
Contractile Roots
these pull bulbs or corms of monocots
hyacinth and lily, and some taproots, such as dandelion
deeper in the soil through expanding radially
contracting longitudinally
They have a wrinkled surface
Mycorrhizae
symbiotic association between a fungus and the roots of a vascular host plant
refers to the role of the fungi in the plants' rhizosphere, its root system
exchange nutrients between their surroundings and their host plant
increase in root surface area
the protection they offer to the plant's roots
able to acquire a lot of nutrients for its host
Roots of Strangler figs
its own root system forced to compete with that of the strangling fig
develop roots from their branches and send them straight down through the air
External structure of roots
taproot
develops from embryonic root called the radicle
not functional
lateral roots
also referred to as branch roots
become swollen
highly branched shoot system
fibrous root system
mass of many similarly sized roots
caused by the radicle dying
root primordia
become more relevant when the plant is older
functional
adventitous roots
increase absorption
increase transport
Structure
root cap
protects the growing tip
mucigel
lubricates passage of root
zone of elongation
where cells undergo division and expansion
root hair zone
where epidermal cells extend
root hairs
form in part not elongating
Internal root structure
Root cap
provides protection for root apical meristem
cells are small and meristematic
develop dense starch grains
Root apical meristem
relationship to root tissues it produces
more orderly than the shoot
quiescent center
Zone of elongation
behind the root apical meristem
cells expand greatly
some meristematic activity continues
permeable
Zone of Maturation
root hairs grow outward
increases absorption of water
thin cuticle present
merges gradually with zone of elongation
no boundary cells
minerals don't have access to vascular tissues
endodermis
Casparian strips
control minerals that pass through
Pericycle
between vascular tissues and endodermis
lateral roots produced here
Mature portion
passage cells
called also transfusion cell
often opposite the protoxylem strands
represent passage for minerals
root pressure
powerful absorption of watering water pressure
