Plant Form And Stem Cells Flashcards
What are the main developmental differences between plants and animals?
Animals have determinate development, little developmental plasticity, and are less regenerative. Plants have indeterminate development, high developmental plasticity, and are very regenerative.
What constitutes a module of a plant shoot?
A module of a plant shoot includes a leaf, bud, and internode.
What are the three phases of plant development?
- Embryogenesis. 2. Vegetative phase. 3. Reproductive phase.
What are the two primary meristems in plants?
- Shoot apical meristem (SAM). 2. Root apical meristem (RAM)
SAM RAMs mary’s house DOWN
What are the two lateral meristems in woody plants?
- Vascular cambium. 2. Cork cambium.
What is the function of meristems?
Meristems contain stem cells that renew themselves while producing new cells that differentiate via asymmetric cell division.
What is phyllotaxy, and what are its types?
Phyllotaxy refers to the arrangement of leaves (and branches) around the stem. Types include: 1. Alternate. 2. Spiral. 3. Opposite. 4. Whorled.
What is the significance of spiral phyllotaxy?
Spiral phyllotaxy follows a golden angle of 137.5° between successive leaves. Leaves are arranged along an equiangular spiral, with numbers corresponding to the Fibonacci sequence.
How does the hormone auxin influence early plant development?
Auxin accumulation dynamics regulate organ formation and positional patterns. Local auxin maxima induce organ primordia formation. Auxin drainage into primordia explains organ positioning patterns and phyllotaxi.
What are the main zones of the shoot apical meristem?
- Central Zone: Contains stem cells. 2. Peripheral Zone: Produces organs like leaves and flowers, where the auxiliary meristem are located ( aux mer are part of SAM)
What are the L1, L2, and L3 layers in the shoot apex, and what do they produce?
L1: Divides anticlinally to form the epidermis. L2 and L3: Produce internal tissues, with L3 often forming the vasculature.
What are the three major tissue types in plants and their functions?
- Epidermis: Protection, light reflection, water/gas exchange.
- Ground Tissue: Fills the interior; functions vary by location.
- Vascular Tissue: Transports water and nutrients (xylem and phloem, primary by SAM , secondary by vascular cam)
What are the three types of venation patterns in plants?
- Dichotomous
- Parallel ( monocots mainly )
- Reticulate.
What are the key take-home points about plant development?
Plants have indeterminate development driven by four types of meristems. They are modular and consist of three different tissue types. Final anatomy and morphology are highly plastic, responding to environmental conditions. The hormone auxin regulates many growth and developmental events.
Why are trees ‘bottom heavy’?
It provides stability and ensures efficient access to gases for transpiration.
What are the key differences between plant and animal development?
Plants: Indeterminate development, high developmental plasticity, sessile, and regenerative.
Animals: Determinate development, little plasticity, mobile, and less regenerative.
Why are auxillary buds important in plants ID?
They determine what is a real leaf (presence indicates a real leaf) and are critical for branching and lateral growth.
What does viviparous mean in plants?
It describes seeds that germinate while still attached to the mother plant.
What are the three phases of plant development?
- Embryogenesis: Formation of the embryo.
- Vegetative Phase: Includes juvenile and adult sub-phases; development is indeterminate.
- Reproductive Phase: Development becomes more determinate, leading to flowering and seed production.
What is the difference between cambium cells and meristem cells?
Meristem Cells: Undifferentiated cells that contribute to both primary (lengthening) and secondary (thickening) growth.
Cambium Cells: A type of lateral meristem specifically responsible for secondary growth, producing xylem, phloem, and cork (bark). Divide periclinally (parallel to increase girth).
What is the difference between anticlinal and periclinal cell divisions?
Anticlinal: Division is perpendicular to the surface, increasing the number of cells in a layer.
Periclinal: Division is parallel to the surface, increasing the thickness of the tissue.
Why does the Fibonacci sequence frequently appear in plants?
It ensures optimal packing, space utilization, and light capture, improving structural and functional efficiency.
How does auxin influence plant development phases? Where is it produced?
Auxin regulates leaf shapes, phyllotaxis, and transitions between development phases (vegetative to reproductive). It is produced in the root apical meristem SAM and young leaves and primordia and transported through the vascular system.
How does auxin affect shoot growth?
- Promotes Growth at Shoot Tips: Stimulates cell elongation and division in the apical meristem.
- Inhibits Lateral Growth: Maintains apical dominance by suppressing axillary bud growth.
- Reduction of Apical Dominance: Pruning the shoot tip reduces auxin, allowing lateral buds to grow.
What are primordia in plants?
Early-stage structures that develop into specialized organs like leaves, roots, or flowers.
How do vascular bundles differ between stems and roots?
Stem: Vascular bundles are arranged in a circle.
Root: Vascular bundles are concentrated in the center.
What are the primary functions of the epidermis in plants?
Protects against water loss.
Reflects light and helps with surface cleaning by rolling off water and dust.
What are the differences between reticulate and parallel venation?
Reticulate: Branching veins form loops, allowing nutrient bypass if a main vein is damaged.
Parallel: Veins run side-by-side; damage can leave parts nutrient-less.
What are the main types of phyllotaxis?
Alternate: Common in monocots (e.g., grasses, iris).
Spiral: Most prominent; follows the golden ratio.
Opposite: Seen in plants like mint.
Whorled: Seen in sticky weed.
What is indole acetic acid (IAA), and why is it significant?
IAA, also known as auxin, is a plant hormone that regulates cell elongation, phyllotaxis, and the balance between shoot and root growth. It plays a crucial role in promoting cell elongation, root development, tropisms (e.g., phototropism and gravitropism), and apical dominance (the suppression of lateral bud growth by the main shoot). It plays a crucial role in promoting cell elongation, root development, tropisms (e.g., phototropism and gravitropism), and apical dominance (the suppression of lateral bud growth by the main shoot).
What does the vascular cambium produce?
It produces xylem (water-conducting tissue) and phloem (nutrient-conducting tissue), contributing to secondary growth.
Why is the golden angle (137.5°) significant in spiral phyllotaxis?
It ensures optimal space utilization and light capture, aligning with the Fibonacci sequence.
How is apical dominance maintained in plants?
High concentrations of auxin at the shoot tip suppress axillary bud growth, focusing resources on upward growth.
What is modular plant development?
It refers to the way plants grow by producing repeated units (modules) like leaf, bud, internode, allowing continuous and flexible growth.
What are the key features of modular plant development?5
- Repetitive unit formation: Plants grow in modules that include leaves, stems, and buds.
- Indeterminate growth: Plants grow continuously under favorable conditions.
- Plasticity: Plants adapt growth patterns to environmental factors, like light or nutrients.
- Clonal propagation: Detached modules can form new plants (e.g., runners in strawberries).
- Self-repair: New modules replace lost or damaged parts.
What is secondary growth in plants?
Secondary growth is the increase in thickness or girth of stems and roots, primarily in woody plants, driven by the vascular cambium and cork cambium.
What does the cork cambium (phellogen) produce?
Cork (phellem): Forms the protective outer bark.
Phelloderm: Provides inner protection beneath the cork.
What is the role of lenticels in plants?
Lenticels are horizontal slits in the bark that enable gas exchange between the plant and the atmosphere.
How can you differentiate a compound leaf from a branch with multiple leaves?
Compound leaves have leaflets without axillary buds at their base, and all leaflets attach to one petiole. A branch has multiple leaves, each with its own axillary bud.
How does root architecture adapt to environmental conditions?
Roots branch more where water and nutrients are abundant. Roots grow towards water and avoid obstacles like rocks (plasticity) Strigalactones aid this.
What is the function of root hairs in plants?
Root hairs increase surface area for water and nutrient absorption and are cost-efficient extensions of epidermal cells.
What is heterophylly in plants (3 types)?
The presence of different types or shapes of leaves on the same plant. It can be:
- Developmental: Changes with the plant’s age.
- Environmental: Adapts to conditions like water availability.
- Habitual: Naturally occurs in some plants.
What 3 ways does auxin influence plant growth?
Auxin regulates cell elongation at the shoot tip.
Apical dominance by suppressing lateral buds.
Root formation and leaf shape development.
What is the effect of mechanical loading on wood formation?
Mechanical stress (e.g., wind, gravity) can cause: Stem thickening for stability. Reaction wood to counter tilting or bending. Changes in wood density and fiber structure.
What is grafting, and why is it useful?
Grafting joins tissues from two plants, allowing nutrient exchange and the combination of desirable traits. Cambial connection is crucial for success.
What is clonal propagation, and how is it achieved?
Clonal propagation involves creating identical plants from parts like stolons, rhizomes, or cuttings. It can also be done through meristem cultures to exclude viruses.
What is totipotency in plants?
The ability of a single plant cell to regenerate into a complete plant, enabling cloning and regeneration.
How is cell fate determined in plants?
In plants, cell fate depends on the cell’s position in the tissue, not its lineage, allowing flexibility and adaptation during growth.
How does auxin maintain apical dominance?
Auxin produced in the shoot apex suppresses lateral bud growth, prioritizing upward growth.
How does modular growth benefit plants?
Enables flexible adaptation to the environment. Supports self-repair after damage. Allows indefinite growth by adding new modules.
Summary of Meristems and Their Contributions:
SAM (Shoot Apical Meristem): Primary growth (elongation), produces epidermis, vascular tissue, ground tissue.
RAM (Root Apical Meristem): Primary growth (root elongation), produces epidermis, vascular tissue, ground tissue.
Vascular Cambium: Secondary growth (girth increase), produces secondary xylem (wood) and phloem.
Cork Cambium: Secondary growth (bark formation), produces cork and phelloderm.
