Ch 8 Flashcards
Fusiform initials
in a vascular cambium, the long cells with tapered ends that give rise to axial cells of the secondary xylem and secondary phloem; produce the elongate cells of wood (tracheids, vessel elements and fibers)
Periclinal wall
a wall that is parallel to a nearby surface, especially the outer surface of the plant; produces two elongate cells; one continues to be a fusiform initial and the other differentiates into a cell of secondary xylem or secondary phloem
Anticlinal wall
a wall perpendicular to a nearby surface, especially the outer surface of the plant; divides longitudinally thereby increasing the number of cambial cells
Ray Initials
similar to fusiform initials except they are short and more or less cuboidal; undergo periclinal cell divisions, one of the daughters remains a cambial ray initials and the other differentiates into either xylem parenchyma if it is the inner cell or phloem parenchyma if it is the outer cell; produce short cells, mostly storage parenchyma and in gymnosperms, albuminous cells
Axial system Secondary Xylem
derived from the fusiform initials; always contains tracheary elements (tracheids or vessel elements or both) which carry out longitudinal conduction of water through the wood; also usually gives wood strength and flexibility
Radial systems (Rays) Secondary Xylem
develops from the ray initials; woody angiosperms contains only parenchyma, arranged as uniserate, biserate or multiserate masses called rays; ray parenchyma cells store carbohydrates and other nutrients during dormant periods and conduct material over short distances radially in wood
Hardwoods
dicot trees and shrubs’ wood, because in general dicot wood contains fibers
Softwoods
gymnosperms’ wood because few gymnosperms have any fibers in their wood
Growth rings
in secondary xylem, the set of wood, usually early wood and late wood, produced in one year; AKA annual ring
Early wood
AKA spring wood; in secondary xylem, the wood formed early in the season, usually with an abundance of vessels in angiosperms or with wide tracheids in gymnosperms
Late wood
AKA summer wood; in secondary xylem, the wood formed late in the season, usually with few or no vessels in angiosperms, or with narrow tracheids in gymnosperms
Heartwood (tylosis)
the colored, aromatic wood in the center of a trunk or branch; all the wood parenchyma cells have died and no water conduction is occuring
Sapwood
the light-colored, light-scented outermost wood of a trunk or branch; conduction is still occurring and many wood parenchyma cells are alive
Reaction wood
wood formed in response to mechanical stress; tension wood: the reaction of wood dicots, formed on the upper side of a branch; compression wood: the reaction wood of gymnosperms, formed on the lower side of a branch
Axial System Secondary Phloem
conduction up and down the stem or root; contains sieve tube members and companion cells in angiosperms or sieve cells in gymnosperms; fibers and nonconducting parenchyma are also usually present
Radial System Secondary Phloem
consist only of parenchyma cells; used for storage; in gymnosperms albuminous cells are ray cells
Cork Cambium (AKA Phellogen)
a layer of cells that produces the cork cells of bark
Cork cells
a subterranean, vertical stem that is thick and fleshy and has only thin papery leaves; example: gladiolus
Periderm
technical term for bark; consists of cork, cork cambium, and any enclosed tissues such as secondary phloem
Outer bark
the outermost dead layers of bark, from the surface to the innermost cork cambium
Inner bark
the innermost, living layer of bark, located between the vascular cambium and the innermost cork cambium
Lenticel
in bark, a region of cork cells with intercellular spaces, permitting diffusion of oxygen into inner tissues
Anomalous Secondary Growth
alternative cambria that produce secondary bodies that differ from the common type
Secondary growth in roots of sweet potatoes
dramatic increase in the amount of storage parenchyma, numerous vascular cambia arise around individual vessels or groups of vessels; rate of cell production is important b/c root must become very large very quickly; multiple cambia functioning simultaneously speed the production of storage capacity
Secondary growth in monocots
a vascular cambium arises just outside the outermost vascular bundles and produces only parenchyma; conducting cells absent; some parenchyma cells differentiate into secondary vascular bundles; the ones that don’t divide form secondary ground tissue
Primary growth in palm trees
trunks do not taper at the tips and they do not branch; palm trunk is all primary tissue consisting of vascular bundles distributed throughout ground tissue; each bundle has primary phloem and xylem derived from shoot apical meristem; no vascular cambium; no true wood, no secondary phloem; vascular bundle enclosed in a sheath of strong, heavy fibers
Establishment growth
increase in width and addition of adventitious roots in palms which is a form of primary growth
