Chapter 35 Flashcards
A vascular plant consists of
Root system
Anchors the plant
Used to absorb water and ions from the soil
Shoot system
Consists of supporting stems, photosynthetic leaves, and reproductive flowers.
Repetitive units consist of internode, node, leaf, and axillary bud.
Roots, shots, and leaves contain 3 basic tissue types
Dermal – outer protective cover.
Ground – function in storage, photosynthesis, and secretion.
Vascular – conducts fluids and dissolved substances.
Tissue systems
each of these tissue types extends through root and shoot systems
Distinguishing plant cell types based on
Size of vacuoles.
Whether they are living or not at maturity.
Thickness of secretions found in their cellulose cell walls.
Some cells have only a primary cell wall of cellulose, synthesized at the protoplast (cell membrane).
Some cells have more heavily reinforced cell walls with multiple layers of cellulose.
Meristems
Clumps of small cells with dense cytoplasm and large nuclei.
Act as stem cells do in animals.
One cell divides producing a differentiating cell and another that remains meristematic.
Extension of shoot and root produced by apical meristems.
Lateral meristems produce an increase in shoot and root diameter.
Apical Meristems
Located at tips of stems and roots
Give rise to primary tissues which are collectively called the primary plant body
Apical meristems composed of delicate cells that need protection
Root cap protects root apical meristem.
Leaf primordia shelter shoot apical meristem.
Apical meristem gives rise to the three tissue systems by first initiating primary meristems
3 primary meristems.
Protoderm – forms epidermis.
Procambrium – produces primary vascular tissue.
Ground meristem – differentiates into ground tissue.
Some plants have intercalary meristems.
Arise in stem internodes
Add to internode length
Grow rapidly
Lateral Meristems
Found in plants that exhibit secondary growth
Give rise to secondary tissues which are collectively called the secondary plant body
Woody plants have two types
Cork cambium produces outer bark.
Vascular cambium produces secondary vascular tissue.
Secondary xylem is the main component of wood.
Three main types of tissue
Dermal.
On external surfaces that serves a protective function.
Ground.
Forms several different internal tissue types and can participate in photosynthesis, serve a storage function, or provide structural support.
Vascular.
Conducts water and nutrients.
Dermal Tissue
Forms the epidermis
One cell layer thick in most plants
Forms the outer protective covering of the plant
Covered with a waxy cutin layer constituting the cuticle
Contains special cells, including guard cells, trichomes, and root hairs
Guard Cells
Paired sausage-shaped cells
Flank a stoma (pl. stomata) - epidermal opening
Passageway for oxygen, carbon dioxide, and water vapor.
Stomatal patterning genes reveal a coordinated network of cell–cell communication that informs cells of their positions relative to other cells and determines cell fate
Trichomes
Cellular or multicellular hairlike outgrowths of the epidermis
Occur frequently on stems, leaves, and reproductive organs
Reduce evaporation by covering stomatal openings
Protect leaves from high-intensity light and ultraviolet radiation
Can buffer against temperature fluctuations
May be a single cell or multicellular
Some are glandular, secreting substances that deter herbivory
Glandular Trichomes
The trichomes with tan, bulbous tips on this tomato plant are glandular trichomes. These trichomes secrete substances that can glue insects to the surface of the plant.
Root Hairs
Tubular extensions of individual epidermal cells
Greatly increase the root’s surface area and efficiency of absorption
Should not be confused with lateral roots
Ground Tissue 3 cell types
3 cell types
Parenchyma
Function in storage, photosynthesis, and secretion.
Collenchyma
Provide flexible support and protection.
Sclerenchyma
Provide rigid support and protection.
Parenchyma
Most common type of plant cell
Living protoplasts – may live many years
Function in storage, photosynthesis, and secretion
Most have only primary cell walls
Less specialized than other plant cells
Parenchyma Cells
Only primary cell walls are present in these parenchyma cells of a grass plant. Note the thin cell walls and abundant chloroplasts.
Collenchyma
Provide flexible support for plant organs
Allow bending without breaking
Living protoplasts – may live many years
Lack secondary cell walls
Collenchyma Cells
Thickened primary cell walls are seen in these collenchyma cells from a young branch of elderberry, Sambucus. In other kinds of collenchyma cells, the thickened areas may occur at the corners of cells.
Sclerenchyma Cells
Tough thick walls
Usually lack living protoplasts at maturity
Secondary cell walls often contain lignin
Two general types – both strengthen tissues
Fibers – long, slender cells that are usually grouped in strands.
Sclereids – variable shape, often branched, may occur singly or in groups.
Sclereids
Clusters of sclereids (“stone cells”) are stained red in this preparation. The surrounding thin-walled cells, stained green, are parenchyma. Sclereids are one type of sclerenchyma tissue; another type is fibers.
Xylem
Conducts water and dissolve minerals throughout plant.
Phloem
Conducts a solution of carbohydrates – mainly sucrose – used by plants for food.
Also transports hormones, amino acids, and other substances necessary for plant growth.
Xylem Cells
Two types of water conducting cells
- Vessels
Continuous tubes of dead cylindrical cells arranged end-to-end.
- Tracheids
Dead cells that taper at the end and overlap one another.
Vessels tend to be shorter and wider than tracheids.
In addition to conducting cells, xylem typically includes fibers and parenchyma cells (ground tissue cells)
Phloem Cells
Contains two types of elongated food-conducting cells
Sieve cells (seedless vascular plants and gymnosperms) and sieve tube members (angiosperms).
Living cells that contain clusters of pores called sieve areas or sieve plates.
Sieve-tube members are more specialized (more efficient).
Associated with companion cells, which carry out some of the metabolic functions needed to maintain the sieve-tube member.
Roots
Simpler pattern of organization and development than stems
Four regions are commonly recognized:
Root cap.
Boundaries not clearly defined.
Zone of cell division.
Zone of elongation.
Zone of maturation.
Root Cap
No equivalent structure in stems
Contains two types of cells that are formed continuously by the root apical meristem
Columella cells – inner.
Root cap cells – outer and lateral.
Functions mainly in protection of the delicate tissues behind it
Also in the perception of gravity
Zone of Cell Division
Derived from rapid divisions of the root apical meristem
Contains mostly cuboidal cells, with small vacuoles and large central nuclei
Daughter cells of apical meristem.
A group of cells in the center of the root apical meristem (the quiescent center) divides very infrequently
Apical meristem daughter cells soon subdivide into the three primary tissues
Protoderm, procambium, and ground meristem.
Control of the Zone of Cell Division
Patterning of these tissues begins in this zone
WEREWOLF (W E R) gene
Suppresses root hair development.
SCARECROW (S C R) gene
Necessary for differentiation of endodermal and ground cells.
Zone of Elongation
Roots lengthen because cells become several times longer than wide
Width also increases slightly
No further increase occurs above this zone
Mature parts of the root, except for increasing in girth, remain stationary for the life of the plant
