POL sections 24.1, 25.3, 25.4, and Campbell section 7.4 Flashcards
Sessile
Stationary
Progression of plants
Aquatic Ancestors -> Simple Land Plants -> Vascular Plants
Angiosperms
Flowering plants
Plant organs are organized into ____ systems:
two; root system and shoot system
Root system
Anchors plant in place
Roots
Absorb water and dissolved minerals and store the products of photosynthesis; extreme branching of roots and their high surface area-to-volume ratios
Shoot system
Cconsists of the stems, leaves, and flowers
Leaves
Chief organs of photosynthesis
Stems
Hold and orient the leaves to the sun and provide connections for the transport of materials between roots and leaves
Phytomer
Consists of a node carrying one or more leaves; an internode, which is the interval of stem between two nodes; and one or more axillary buds, each of which forms in the angle where the leaf meets the stem
Bud
undeveloped shoot that can produce another leaf, a phytomer, or a flower
Monocots
narrow-leaved plants such as grasses, lilies, orchids, and palms
Eudicots
broad-leaved plants such as soybeans, roses, sunflowers, and maples
four processes that govern the development of all organisms
determination, differentiation, morphogenesis, growth
Determination
the commitment of an embryonic cell to its ultimate fate in the organism
differentiation
the specialization of a cell
morphogenesis
the organization and spatial distribution of cells into tissues and organs
growth
increase in body size
Meristems
capable of producing new roots, stems, leaves, and flowers throughout the plant’s life, enabling the plant to continue growing
In plants, differentiated cells are _______ and most are ___________
pluripotent, totipotent
Apical-basal axis
the arrangement of cells and tissues along the main axis from root to shoot
Radial axis
the concentric (circular) arrangement of the tissue systems
Formation of Plant Embryo Steps
- Mitotic division of the zygote that gives rise to two daughter cells. Asymmetrical plane of cell division results in smaller, apical daughter cell (produces embryo proper) and larger daughter cell (produces supporting structure, suspensor). Establishes apical-basal axis
2.
In eudicots, the initially globular embryo develops into the characteristic heart stage as the cotyledons (“seed leaves”) start to grow (FIGURE 24.5, STEP 3). Further elongation of the cotyledons and of the apical–basal axis of the embryo gives rise to the torpedo stage, during which some of the internal tissues begin to differentiate (FIGURE 24.5, STEP 4). Between the cotyledons is the shoot apical meristem; at the other end of the axis is the root apical meristem. These meristems contain undifferentiated cells that will divide to give rise to the shoot and root systems.
As shown in Figure 24.5, step 2, the plant embryo is first a sphere and later a cylinder. The root and stem retain a generally cylindrical shape throughout the plant’s life. You can see this most easily in the trunk of a tree. By the end of embryogenesis, the radial axis of the plant has been established. The embryonic plant contains three tissue systems, arranged concentrically, that will give rise to the tissues of the adult plant body.
Tissue
organized group of cells that have features in common and that work together as a structural and functional unit
all vascular plants are constructed from three tissue systems:
dermal, vascular, and ground
Dermal tissue system
forms the epidermis, or outer covering, of a plant, which usually consists of a single cell layer
Stomata
pores for gas exchange in leaves
Trichomes
leaf hairs, which provide protection against insects and damaging solar radiation
Root hairs
greatly increase root surface area, thus providing more surface for the uptake of water and mineral nutrients
Protective extracellular cuticle
Secreted by aboveground epidermal cells; consists of cutin (a polymer composed of long chains of fatty acids), a complex mixture of waxes, and cell wall polysaccharides; limits water loss
In stems and roots of woody plants, epidermis is shet and replaced by _____
periderm
ground tissue system
virtually all tissue lying between dermal and vascular tissue; contains three cell types: parenchyma, collenchyma, sclerenchyma
Parenchyma cells
most abundant ground tissue cells. They have large vacuoles and relatively thin cell walls. They perform photosynthesis (in the shoot) and store protein (in seeds) and starch (in roots)
Collenchyma cells
elongated and have unevenly thickened primary cell walls. They provide support for growing tissues such as stems
Sclerenchyma cells
Have very thick secondary walls reinforced with the polyphenol polymer **lignin; **undergo programmed cell death (apoptosis); two types: fibers and sclereids;
Elongated fibers provide relatively rigid support to wood and other parts of the plant, within which they are often organized into bundles
Sclereids occur in various shapes and may pack together densely, as in a nut’s shell or in some seed coats
Vascular Tissue system
plant’s plumbing or transport system—the distinguishing feature of vascular plants. Its two constituent tissues, the xylem and phloem, distribute materials throughout the plant
Xylem
distributes water and mineral ions taken up by the roots to all the cells of the roots and shoots. It contains two types of conducting cells—tracheids and vessel elements
tracheids
spindle-shaped cells, with thinner regions in the cell wall called pits through which water can move with little resistance from one tracheid to its neighbors
Vessel elements
larger in diameter than tracheids. They meet end-to-end and partially break down their end walls, forming an open pipeline for water conduction
Phloem
transports carbohydrates (primarily sugars) from sites where they are produced (called sources) to sites where they are used or stored (called sinks). Sources are often photosynthetic organs (such as leaves) but also include nonphotosynthetic storage organs (such as tubers and seeds) when they are drawn on to supply sugars to other parts of a plant. Sinks include growing tissues, roots, and developing flowers and fruit. The characteristic cells of the phloem are sieve tube elements
Sieve tube elements
sieve tube elements are connected by plasmodesmata, which form a set of pores called a sieve plate. Although still alive, mature sieve tube elements have lost much of their cellular contents
companion cells
adjacent, fully functional to sieve tube elements; perform many of the phloem’s metabolic functions
Membrane Potential
Voltage across a membrane, ranging from -50 to -200 mV
Electrochemical gradient
Combination of chemical force (concentration gradient) and electrical force (membrane potential)
Electrogenic pump
Transport protein that generates voltage across a membrane
Cotransport
Mechanism in which a single ATP-powered pump that transports a specific solute can indirectly drive the active transport of several other solutes
Apoplast
consists of the cell walls, which lie outside the cell membranes, and intercellular spaces (spaces between cells), which are common in many plant tissues. The apoplast is a continuous meshwork through which water and solutes can flow without ever having to cross a membrane
Symplast
passes through the continuous cytoplasm of the living cells connected by plasmodesmata. The selectively permeable cell membranes of the root cells control access to the symplast, so movement of water and solutes into the symplast is tightly regulated
Casparian Strip
Waxy, suberin-impregnated region of the endodermal cell wall forms a hydrophobic belt around each endodermal cell where it is in contact with other endodermal cells. The Casparian strip acts as a seal that prevents water and ions from moving through spaces between the endodermal cells
Transpiration–cohesion–tension theory
Transpiration: evaporation of water from cells within the leaves
Cohesion of water molecules in the xylem sap as a result of hydrogen bonding
Tension on the xylem sap resulting from transpiration
Guard cells
Specialized epidermial cells that control the opening and closing of each stoma
Translocation
Movement of carbohydrates and other solutes through the plant in the phloem
Source
organ (such as a mature leaf or a storage root) that produces (by photosynthesis or by digestion of stored reserves) more carbohydrates than it requires
Sink
organ (such as a root, flower, developing fruit or tuber, or immature leaf) that consumes carbohydrates for its own growth and storage needs
____ surrounds _______
phloem; xylem
Pressure Flow Model
Two steps in phloem translocation require metabolic energy
Transport of sucrose and other solutes from sources into companion cells and then into the sieve tubes; called “loading”
Transport of solutes from the sieve tubes into sinks; called “unloading”
