Roots
External structure of roots
Internal structure of roots #
Origin and development of lateral roots
Root modification and its types
Organization of root system
Structure of individual roots
Mature portion of roots
Zone of Elongation
Root apical meristem
Root cap
Zone of Maturation
Mycorrhizae
Contractile roots
Root nodules and Nitrogen fixation
Aerial roots of orchids
Roots of strangler figs
Prop roots
Parasitic flowering plants
Storage roots
3 major function of roots
Absorbing water and minerals
Producing hormones
Anchoring the plant firmly to a substrate
Stem, leaf, flower and fruit are oriented towards sun, pollinators or food distributors
Provide stability
Root hair cells are responsible
Absorb water by osmosis
Cytokinin and Gibberellin responsible for shoot growth and development
Hormones helps to control the size of its root
Tap root system
Fibrous root system #
Lateral roots
Branch roots
Grows from embryonic root called radicle
Examples-: Sunflower, carrot, Dandelion
Does not arise from radicle, in aged plants roots are called adventitious roots
Adventitious root increase absorptive and transport capacities
Examples-: Wheat, Rice, Maize, Banana
Individual root is simple, without leaves, leaf scars, buds.
Apical meristem helps in longitudinal growth
Apical meristem is protected by root cap
Cells are small and meristematic
Provide effective protection for root apical meristem
Mitotically inactive central reason is called Quiescent center, only works if apical meristem or root cap is damaged
Helps in longitudinal growth of plants
Most cells expand and enlarge
cell differentiate into visible patterns
Tissues here are quite permeable, minerals penetrate deep into root through apoblast
Root hair function only several day and they die and degenerate
Casparian stripes called passage cells are found in mature portion
Root hairs grow outward, increase absorption of water and minerals
Root cells differentiates into specialized cell types
Cell division occurs here
Root hairs are present in this area
cross section of root
Dicot root #
Monocot root
Formation and organization of Primordium helps in cell division
Stimulated by auxin and other growth regulators #
Initiated by cell division in pericycle
Extend horizontally from primary root and serves as anchor
Branches also helps in conduction of water and minerals
Carrots, beets, sweet potatoes
Banyan tree, different grass have aerial roots outside soil
Orchids and bromeliads
Lily, Dandelion
Beech, willow, pine, oak,
Cannabaceae
Australian Christmas tree, and yellow rattle.
Weeping figs