3. Storage of energy or food - usually in the form of tubers
4. Propogation in some species
Approximately how big is the root system of a plant?
The root system ranges from 1/4 to 1/3 of the entire dry weight of any plant
What are the three types of root systems?
Taproot, fibrous, adventitious
Taproot
A dominant main root that is larger and grows faster than branch roots (ex: carrots, turnips, oaks, alfalfa)
Fibrous root
Root system that branches in many directions and includes radicle, nodal, and seminal roots
What are the three parts of a fibrous root system?
Radicle, nodal, and seminal roots
Radicle root
Primary root of fibrous root systems that develops from the seed
Nodal root
Root of the fibrous root system that develops from lower stem nodes
Seminal root
Root part of a fibrous root system that develops from the first root node
What are the two parts of a tap root system?
A taproot that develops from the radicle and branch roots that grow from the taproot after being triggered by hormones
Adventitious root
A root that forms on any part of the plant other than the radicle of a germinating seed (ex: stem, leaf petioles, leaf blades...think of propagating succulents)
Root hair
Hair-like outgrowth of the epidermis of a plant root that increases surface area to absorb water and minerals from soil
What are the four zones of the root?
Zone of maturation, zone of elongation, meristematic region, and root cap
Root cap
End portion of the root that acts as a protective layer as the root forces its way through the soil
What slippery, mucus-like substance does the root produce to help it glide through soil?
Mucigel, which is produced by the golgi apparatus
What are the two zones of root growth?
Elongation and maturation zone
Elongation zone
"Site of cell division that propels the root tip through soil as much as 0.8"" per day"
Maturation zone
Region of the root where root hairs are developed
Epidermis
Outermost layer of cells (tissue) in the root
Cortex
Tissue of the root comprised of three layers: the exodermis, ground tissue, and endodermis
Exodermis
Layer of cortex tissue that acts to prevent water loss
Ground tissue
Layer of cortex tissue that contains parenchyma cells and thus acts mainly for the storage of starch
Endodermis
Layer of cortex tissue that regulates root uptake of mineral nutrients and contains the caspian strip
Caspian strip
Layer of water-impermeable cells that regulate water and mineral uptake by roots
Stele
Collective term for tissue within the endodermis that includes the pericycle, vascular tissue, and pith
Pericycle
Meristematic tissue within the endodermis that is the origin of branch roots
What are the names of the two vascular tissue structures?
Xylem and phloem
Pith
Only in some plants, the dead portions
What two organisms are involved in symbiotic nitrogen fixation?
Legumes and rhizobia bacteria
What does rhizobia bacteria do?
Takes in atmospheric nitrogen from legumes and converts it into ammonia
Rhizobia
Free-living soil bacteria that are attracted to the roots of legumes and are involved in nitrogen fixation