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102 Cards in this Set
- Front
- Back
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Tissue |
A group of cells consisting of several cell types that together form a specialized function |
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Three basic plant organs |
Roots, Stems, Leaves
All basic plant organs contain vascular tissue |
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Basic plant organ systems |
Shoot system = stems + leaves Root system = roots
All basic plant organs contain vascular tissue |
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Root system - functions |
Anchors into the ground Absorbs minerals and water Stores carbohydrates/other resources
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Taproot system |
Common in dicots Primary root (first to emerge) grows long & thick, helps to anchor plant in ground; branches laterally over time Allows the plant to be taller Can be specialized for food storage |
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Fibrous Root System |
Common in monocots Primary root (first to emerge) eventually dissolves completely, and smaller roots emerge from stem into the soil All smaller roots can branch laterally many times Adventitious roots = roots that extend directly from the stem/leaves |
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Root hairs |
Extension of root epidermal cells, which increase root surface area enormously Responsible for most absorption of water and minerals; occur near the end of elongating roots |
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Mycorrhizal Associations |
Symbiotic relationships between plant roots and soil fungi which increase a plant's ability to absorb minerals |
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Shoot system - Functions |
Above ground, plants take in CO2 and light and carry out photosynthesis to produce sugars + other products for the plant |
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Synchronicity between plant systems |
Vascular plans rely on both root & shoot systems for survival: - Roots are not photosynthetic and will starve without products of photosynthesis from shoot system - Shoot system depends on water and minerals absorbed from the soil |
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Lecture example: Horseshoe Lake |
- CO2 is highly abundant in the air in this area, and trees are suffering/dying - Remember that roots carry out cellular respiration, and shoots carry out both photosynthesis and respiration - Diatomic oxygen produced in photosynthesis is lighter than CO2, doesn't fill soil spaces and reach the roots - Heavier CO2 doesn't diffuse into the air and reach the leaves; so, the plant dies |
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Prop roots |
Prop roots on corn plant (Maize) Grow downward from the node, then bury into the ground |
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Buttress roots |
Large roots on all sides of shallowly rooted tree Grow upwards as "plates" Give architectural support to tree trunks |
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Strangling aerial roots |
- Plant sends out small root-like structures which are aerial and strangle the host - Can be parasitic and kill their host plant |
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Storage roots |
Many plants store products of photosynthesis in modified, fleshy root structures - Shown: Storage root structure of sweet potato |
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Stems |
Plant organ which bears leaves and buds. - Consists of nodes, internodes, axila, axillary buds, apical bud - Chief function is to elongate the plant and orient leaves in a position that maximizes photosynthesis |
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Nodes |
- The points on a stem at which leaves are attached - Leaf attachment consists of the axil and axillary bud |
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Axil |
- The upper angle formed by each leaf and the stem - Contains an axillary bud, which can form a lateral branch, a thorn, or a flower |
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Internodes |
- The stem segment between nodes |
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Apical bud |
- Growing shoot tip; causes elongation of the shoot system |
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Rhizome |
- Modified stem; spongy, underground mass with small roots extending |
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Pneumatophores |
- Specialized root structures that grow out from the water surface and allow access to air for trees growing in swamp habitats (eg. mangroves) |
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Stolons |
- Horizontal stem which sits on the ground, produces adventitious roots which can support a new plant - Mode of asexual reproduction for plants |
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Leaf |
- Main photosynthetic organ of most vascular plants - Functions: capturing photons, gas exchange, dissipation of heat, protection from herbivory - Consist of blade, petiole, veins - Can be simple or compound |
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Blade |
- Main, photosynthetic surface area of the leaf which is attached to the stem by a petiole and contains veins |
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Petiole |
- Stalk attached to the blade of the leaf, which attaches the leaf to the stem at a node, forming an axil |
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Primary vs. Secondary Metabolism in Plants |
- Primary metabolism = glycolysis, photosynthesis, etc. -> produces nutrients and chemicals vital for life - Secondary metabolism = production of different secretory or internal products which benefit the plant in some way (ex. production of cinnamon in some plants for anti-herbivorous purposes) |
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Veins; Monocot vs. Dicot venation |
- Vascular tissue of the leaf - Leaves have different venation patterns: In monocots, veins are arranged parallel to each other; in dicots, they are arranged branching out of a main vein (midrib) which runs down the center of the leaf |
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Simple vs. Compound Leaves |
- Simple leaf = single, undivided blade - Compound leaves = multiple leaflets attached to a single petiole; a leaflet has no axillary bud at its base |
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Spines |
- Modified anti-herbivory leaves; also help prevent water loss - Photosynthesis is carried out in spines |
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Tendrils |
- Tendrils can be modified leaves or modified stems - Grab/wrap around more solid objects for support |
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Storage leaves |
- Modified to store sugar products - All bulbs (ex. onion) are storage leaves |
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Reproductive leaves |
- "Mother of thousands" - small structures which can fall off and reproduce asexually |
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Plant tissue systems |
- All major plant organs consist of all three tissue systems - Tissue systems are continuous throughout the plant and consist of different tissues working together - Ground, vascular, dermal tissue systems |
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Dermal Tissue System |
- In nonwoody plants = epidermis + cuticle - In woody plants = periderm replaces the epidermis in older stem/root regions - Specialized functions in different organs: • In roots; water/minerals enter through root hairs (extensions of the epidermis) • In shoots, epidermal guard cells open/close the stomata • Trichomes; outgrowths of the shoot epidermis, help prevent water loss |
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Cuticle |
- A waxy epidermal coating which helps to prevent water loss |
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Epidermis |
- A layer of tightly packed cells surrounding the outside of plant shoots and roots; functions like a human skin for protection of the entire plant body - Cell types present: Ground cells, guard cells, tricomes, sclerenchyma cells
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Vascular Tissue System |
- Facilitates the transport of materials through the plant - Two main tissues: xylem and phloem - Vascular system is collectively called the stele |
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Stele Arrangements |
- In the root, the stele is a single solid vascular cylinder - In the shoot system, the stele is made up of bundles of xylem and phloem |
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Ground Tissue System |
- Tissues that are neither dermal nor vascular - Ground tissue internal to vascular tissue is pith; ground tissue external to vascular tissue is - Ground tissue can be modified for support or storage |
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Periderm |
- Protective tissue on woody plants; replaces the epidermis with age - Types of cells present: Cork cells, parenchyma cells, sclerenchyma cells |
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Xylem |
- Responsible for transfer of water and dissolved minerals from the roots to the shoots - Cell types present: Tracheids, vessel elements, sclerenchyma cells, parenchyma cells |
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Phloem |
- Responsible for transfer of photosynthesis products (sugars) from sources to sinks - Cell types present: Sieve cells, companion cells, parenchyma cells, sclerenchyma cells |
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Parenchyma (Cell wall, alive/dead, location, function) |
- Cell wall: Primary or secondary, may be lignified - Alive at maturity - Located: Throughout plant in cortex and pith, xylem and phloem (most ground tissue is parenchyma) - Function: Respiration, digestion, photosynthesis, storage, healing; can differentiate into anything (wound repair/growth) |
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Collenchyma (Cell wall, alive/dead, location, function) |
- Cell wall: Primary only; unevenly thickened - Alive at maturity - Location: Beneath epidermis in growing/young parts of plants - Function: Provides flexible support in new plant parts without restraining growth - Ex: Celery strings |
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Fibers |
- Very long, thin - Cell wall: Primary + secondary (lignified) - Dead at maturity - Location: Xylem, phloem, monocot leaves - Function: Rigid support, storage |
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Lignin |
- Relatively indigestible strengthening polymer; present in all vascular plants as a key ingredient of secondary cell walls |
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Sclerids (Cell wall, alive/dead, location, function) |
- Shorter than fibers, round/squat - Cell wall: Primary + secondary (lignified) - Living or dead at maturity - Location: Throughout some plants - Function: Protection, mechanical support - Ex: "Grit" in pears |
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Tracheids (Cell wall, alive/dead, location, function) |
- Shape: Elongated, tapered; have pits but not perforations - Cell wall: Primary + secondary (lignified) - Dead at maturity - Location: Xylem - Present in gymnosperms + angiosperms |
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Vessel elements (Cell wall, alive/dead, location, function) |
- Shape: Elongated, tapered; have pits and perforations, shorter than tracheids, often assembled end to end - Cell wall: Primary + secondary (lignified) - Dead at maturity - Location: Xylem - Present in angiosperms only |
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Sieve-tube membera (Cell wall, alive/dead, location, function) |
Shape: Elongate, tapered Cell wall: Primary Living at maturity Location: Phloem Food conduction - Note perforated sieve plate |
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Companion cells (Cell wall, alive/dead, location, function) |
Shape: Variable, usually elongated Cell wall: Primary Living at maturity Location: Phloem Movement of food into and out of sieve tube members |
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Indeterminate growth |
- Most perennial plants grow continuously due to the presence of meristem |
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Determinate growth |
- Most animals, annual plants, and and some plant organs (ex. leaves, thorns, and flowers) undergo stop growing after they reach a certain size |
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Meristems |
- Perpetually dividing, unspecialized tissues that divide when conditions permit - New cells created by meristem elongate and become specialized |
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Two main types of meristems |
Apical: Located at the tips of roots and shoots; associated with primary (vertical) growth Lateral: Add thickness to woody plants through secondary (thickening) growth • Two main types: vascular and cork cambium |
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Vascular cambium |
In secondary growth, adds layers of vascular tissue called secondary xylem (wood) and secondary phloem |
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Cork cambium |
Replaces the epidermis with periderm, which is thicker and tougher |
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Flowering plant categories (based on life cycle) |
Annuals = complete life cycle in a year or less Biennials = require two growing seasons Perennials = live for many years |
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Primary Growth of Roots |
- A root cap of dead cells is present at the root tip to protect the root apical meristem as it pushes down through the soil - Growth occurs behind the root tip in three zones of cells: zone of cell division, elongation, and differentiation/maturation
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Vascular Stele arrangement in Monocot Roots |
- Stele exists as a single central cylinder - Parenchyma core (pith) is present, surrounded by a ring of xylem and phloem |
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Vascular Stele arrangement in Dicot Roots |
- Stele exists as a single central cylinder - Stele appears as a lobed core ("star shape") of xylem surrounded by phloem |
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Cortex |
The region between the vascular cylinder and the epidermis - mostly ground tissue (parenchyma) |
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Endodermis |
A cylinder one cell thick that forms the boundary between the cortex and the vascular cylinder Selective barrier, regulates passage of substances from the soil into the vascular cylinder |
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Pericycle/ lateral growth in roots |
The outermost layer of the vascular cylinder from which lateral root growth can occur Emerging lateral roots push through the cortex and epidermis |
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Primary growth of shoots |
- Shoot apical meristem = present at the tip of the stem - Leaves develop from leaf primordia along the sides of the apical meristem - Other types of meristematic tissue are present slightly further down the stem |
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Plant meristematic tissues |
- Protoderm --> Epidermal tissue - Procambium --> Vascular tissue - Ground meristem --> Ground tissue - Axillary bud meristem = present near the leaf primordia |
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Apical dominance |
- The closer an axillary bud is to an apical bud, the more growth is inhibited - Axillary buds are released from dominance if the apical bud is removed or shaded - This is due to chemical communication by plant hormones |
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Tissue Organization of Eudicot Stems |
- Vascular bundles arranged in a ring around the pith - Vascular bundles have a fiber cap - Phloem towards the outside, xylem towards the inside |
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Tissue Organization of Monocot Stems |
- Vascular bundles scattered throughout the ground tissue, which is not differentiated into a pith or cortex |
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Tissue Organization of Leaves |
- Epidermis, interrupted by stomata - Ground tissue, called mesophyll, separated into palisade and spongy layers - Vascular tissue organized into veins |
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Stomata |
- Pores that allow CO2 and O2 exchange and evaporative loss of water - Each stoma is flanked by two guard cells which can open and close the pore |
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Mesophyll |
- Ground tissue in a leaf, responsible for photosynthesis - Two layers: • Palisade mesophyll (upper part of the leaf) • Spongy mesophyll (lower part of the leaf) |
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Veins |
- Vascular tissue in the leaf has the same structure as within the stem - Veins also function as the leaf's skeleton - Veins are surrounded by protective bundle-sheath cells |
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Secondary growth: Definition |
- Increases the diameter of stems/roots in woody plants; common in gymnosperms and eudicots but not monocots - Growth in thickness produced by lateral meristems (vascular/cork cambium)
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Secondary growth: Process --> Vascular cambium |
- Vascular cambium is present outside of primary xylem, inside of primary phloem - Vascular cambium forms from parenchyma cells and produces secondary xylem to the inside and secondary phloem to the outside - Secondary xylem (dead) accumulates as wood |
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Early vs. Late Wood |
- Early wood, formed in the spring, has thin cell walls to maximize water delivery - Late wood, formed in the late summer, has thick cell walls to contribute to stem support - Tree rings are formed where early & late wood meets |
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Heartwood vs. Sapwood |
- As a tree or woody shrub ages, the older/innermost layers of secondary xylem (heartwood) no longer transport water/minerals - The outer/newer layers (sapwood) still transport - Older secondary phloem (outermost) sloughs off and does not accumulate |
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Secondary Growth: Process --> Cork cambium |
- Cork cambium produces cork cells, which deposit suberin into their walls and then die - Cork functions as protection for the plant |
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Periderm & Bark |
Periderm = Cork cambium + cork (cork cambium and all tissues it produces) Bark = Secondary phloem + periderm (all tissues external to the vascular cambium) |
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Lenticels |
Holes in the periderm allowing for gas exchange between living stem/root cells and the outside air |
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Development |
The process through which cells form specialized tissues, organs, and organisms - Consists of growth, morphogenesis, and cell differentiation |
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Developmental plasticity |
The effect of the environment on development |
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Growth |
An irreversible increase in size |
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Morphogenesis |
Development of body form and organization Gives a tissue, organ, or cell its shape and determines its function |
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Cell differentiation |
The process by which cells with the same genes become different from each other |
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Cell Division vs. Cell Expansion |
- By increasing the number of cells via division, a plant increases the potential for growth; however, most growth is caused by enlargement of cells |
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Plane and Symmetry of Cell Division (Preprophase band) |
- New cell walls form perpendicularly to the direction of cell expansion - The cytoskeleton gathers into a preprophase band which predicts the future direction of cell division; this determines the plane on which the cell divides • Planes of cell division: transverse/longitudinal |
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Leaf growth & TANGLED-1 |
- Leaf growth results from a combination of transverse and longitudinal divisions - In TANGLED-1, it was shown that the plane of division does not affect the leaf form; rather, symmetry of division determines form |
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Symmetry of Division |
- The distribution of cytoplasm between the two daughter cells - Asymmetrical cell division (unequal division of cytoplasm) signals a key event in development - Asymmetrical cell division plays a key role in establishing polarity; the first cell division in plants is likely asymmetrical
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Formation of guard cells |
- Involves asymmetrical cell division and a change in plane of cell division - Cell asymmetrically divides to form smaller "mother cell", then changes plane of division to transverse to form guard cells |
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Polarity |
The condition of having structural or chemical differences at opposite ends of an organism Ex. Root and shoot ends on plants |
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Orientation/Method of Cell Expansion |
- Plant cells expand rapidly and "cheaply" by taking in and storing water in vacuoles - Plant cells expand along the plant's main axis (longitudinally) - Cellulose microfibrils in cell wall restrict the direction of expansion (cell expands perpendicular to the microfibrils, which do not stretch) |
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Pattern formation (two hypotheses) |
- The development of specific structures in specific locations - Explained by two hypotheses • Position-based hypothesis: cell fate is determined by the final position (plants) • Lineage-base hypothesis: cell fate is determined early on and passed on to daughter cells (animals) |
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KNOTTED-1 and Hox |
- A plant homolog to Hox genes (which cause the expression of entire structures like limbs and eyes and can affect number/placement of structures) known as KNOTTED-1 exists - However, KNOTTED-1 does not affect the placement or number of plant organs; supporting the idea that plant cells have position-based pattern formation, unlike animals - The expression of KNOTTED-1 in greater-than-usual quantity in tomato plants causes its leaves to become "super-compound" |
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Gene Expression and the Control of Cell Differentiation |
- Despite sharing a common, complete genome, cells within an organism synthesize different proteins and differ in structure and function - This control of gene expression is largely position-based and controlled by interactions between cells |
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GLARBA-2 |
- Example of gene expression controlled by position: Arabidopsis root cells form root hairs or don't depending on how many cortical cells that are touching (whether or not they are on the outer edge of the root) - If GLARBA-2 is expressed, a root hair will not grow |
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Phase changes |
- Plants pass through developmental phase changes from a juvenile to adult phase - These changes occur within the shoot apical meristem and are paired with morphological changes, often in leaf shape or size |
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Genetic Control of Flowering/ Meristem Identity Genes |
- Flower formation involves a phase change from vegetative -> reproductive growth - This change is triggered by environmental and internal signals, and is flipped "on" by meristem identity genes |
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Organ Identity Genes/MADS-box genes |
- Organ identity genes help to regulate the formation of flowers/development of floral pattern - Each primordium develops into a whorl depending on its order of emergence - Mutations in these genes can cause abnormal flower development |
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ABC Hypothesis for Organ Identity Genes |
- There are three classes of organ identity genes for flowers: A, B, and C - These genes direct the formation of the four types of floral organs - Research of mutants lacking certain genes has been consistent with this hypothesis for formation • For example, A forms the sepals, and A + B forms the petals; plants lacking A have mutated sepals and petals |
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Organ |
Several types of tissue that together carry out particular functions |
