Ch 7 Flashcards
Radicle
the main root of a seed; it is the direct continuation of the embryonic stem
Taproot system with lateral roots
fleshy roots that are the plants main site of carbohydrate storage during the winter; fine lateral roots growing but removed before they are sold; carrots, beets, turnips
Fibrous root system
many similarly sized roots in most monocots and some eudicots
Adventitious roots
roots that form on leaves, nodes or cuttings rather than on another root; an organ that forms in an unusual place; increase the absorptive and transport capacity of the root system
Root cap
a thick layer of cells that protects the root apical meristem
Mucigel
a complex polysaccharide which lubricates passage of the root through the soil secreted by the dictyosomes of root cap cells
Apical meristem
regular files of cells that originate in the meristem and extend into regions of mature root tissues
Quiescent center
mitotically inactive central region
Zone of elongation
just behind the root cap and root apical meristem only a few mm long within which the cells undergo division and expansion
Protoderm
any immature epidermal cell
Protoxylem
the part of the primary xylem that differentiates early, while adjacent cells are still elongating
Protophloem
the part of the primary phloem that differentiates early, while adjacent cells are still elongating
Ground tissue
The tissue of a plant other than the epidermis, periderm, and vascular tissues, consisting primarily of collenchyma, parenchyma, and sclerenchyma. Cortex and pith are types of ground tissue
Zone of Maturation/ root hair
root hairs grow outward, which increases the absorption of water and minerals
Epidermis with root hairs
epidermal cells extend out as narrow trichomes; root hairs form only part of the root that is not elongating, otherwise they would be shorn off
Epidermis with Casparian strips
layer of impermeable lignin and suberin in the walls of endodermal cells, preventing diffusion of material through that portion of the wall
Cortex
primary tissue located between the epidermis and the phloem
Metaxylem
the part of the primary xylem that differentiates late, after adjacent cells have completed their elongation
Metaphloem
the part of the primary phloem that differentiates late, after adjacent cells have completed their elongation
Pericycle
an irregular band of cells in the root, located between the endodermis and the vascular tissue
Mature root
continued maturation of the endodermis is the formation of a watertight sheath around vascular tissues to keep water in; underlying cortex and epidermis often die and are shed from the root
Xylem
the water and mineral conducting portion of vascular tissues. containing either tracheids or vessel elements or both
Phloem
involved in conducting sugars and other organic compounds along with some water and minerals
Lateral roots
initiated by cell divisions in the pericycle
Storage roots
store carbohydrates; in biennial species and many perenials roots are the only organ
Prop roots
transport additional water and minerals to the stem after they come in contact with the soil; they place some tension on the stem and act as stabilizers; strong supports; adventitious roots that extend to the soil
Buttress roots
upper side grows more rapidly than the underside of the root; brace the trunk from being blown over by wind
Aerial roots
orchids; roots dangle freely because the orchid lives attached to branches of trees; roots have a waterproof barrier
Contractile roots
after roots extend through the soil and firmly attach the uppermost portions begin to contract; stem is pulled downward; contraction caused by changes in the shape of cortex cells
Mycorrhizae
fungi that forms a symbiotic relationship with roots, usually of benefit to plants because they provide phosphorus
Ectomycorrhizae
a type in which the fungi invade only the outermost cells of the root
Endomycorrihizae
a type in which the fungi invade all cells of the root cortex
Root Nodules
in the root’s inner cortex where adjacent cortical cells undergo mitosis and form root nodules
N-fixation
chemical conversion of atmospheric nitrogen into usable compounds; nitrogen scarcity is one of the main growth-limiting factors for plants
Parasitic haustoria
the structure by which a parasite enters and draws nutrients from a plant; in fungi it is hypha; in mistletoes and similar parasites it is a modified root
Strangler figs
roots of strangler figs cling to bark of host tree branch and grow downward; they absorb nutrients from rainwater that runs down the host tree; when the roots finally hit the soil the roots branch and encircle host tree until it does or rots
