Chapter 23 Flashcards
Apical meristems
Found at the tips of all roots and stems and are involved primarily w/ extension of the plant body
Initials
Cells that maintain the meristem as a continuing source of new cells
They divide and one of the sister cells remain in the meristem while the other becomes a new body cell or derivative
Differentiation
Process by which cells with identical genetic constitution become different from one another and from the meristematic cells from which they originated, behind while cell is still enlarging
Depends on gene expression
3 tissue systems
Ground or fundamental tissue system: Parenchyma, Collenchyma, Sclerenchyma
Vascular tissue system: Xylem and Phleom
Dermal tissue system: epidermis and periderm
Initiated during the development of embryo
Totipotent
Cells with the Ability to become embryonic cells and to develop into an entire plant
Collenchyma Tissue
Occurs in discrete strands or as continuous cylinders beneath the epidermis in stems and petioles(strings in celery)
Supporting tissue of growing stems, leaves, and floral parts and of most herbaceous organs that undergo little or no secondary growth
Absent in roots stems and monocot leaves
Sclerenchyma cells
Fibers: long, slender cells, that occur in strands or bundles
Sclereids: variable in shape and often branched and short cells; make up seed coat, shell of nuts, and endocarp
Xylem
Conduct minerals, water, and food storage
In primary plant body it derives from procambium
In secondary plant body derives from vascular cambium
Primary conducting cells of xylem are tracheary elements
Tracheary elements
Tracheid and vessel elements, both are elongated cells that have secondary walls and lack protoplasts at maturity, may have pits
Vessel elements contain prefrontations: areas lacking primary and secondary walls, more efficient but less safe
Tracheid: lacks perforations, found in most seedless vascular plants and gymnosperms
Phloem
Food conducting tissue of vascular plants, amino acids, lipids, micronutrients, hormones, the floral stimulus, and proteins and RNAs
Long distance signaling
Route for plant viruses
Conducting cells are sieve elements
Sieve elements
Sieve cells: only type of food conducting cell in gymnosperms, the sieve areas are uniform in structure on all walls, overlap long slender sieve cells
Sieve tube elements: some walls have larger pores than those on other walls of the same cell
P-protein
Originated in young sieve element in the form of discrete bodies, during late stages of differentiation they elongate and disperse along walls
Accumulate at sieve plates called slime plugs
Serves to seal sieve plate pores if wounded
Forisomes
Large P-protein that does not disperse during later stages of maturation
Undergo rapid and reversible calcium controlled changes from the rest stage to disperse stage
Epidermis
The dermal tissue system of leaves, floral parts, fruits, and seeds—- stems and roots until secondary growth occurs
Site of the light perception involved in circadian leaf movement and photoperiodic induction
Guard cells of epidermis
Regulate small pores or stomata, movement of gases
Associates with subsidiary cells
