Plant Form And Stem Cells

Question 1

What are the main developmental differences between plants and animals?

Answer 1

Animals have determinate development, little developmental plasticity, and are less regenerative. Plants have indeterminate development, high developmental plasticity, and are very regenerative.

Question 2

What constitutes a module of a plant shoot?

Answer 2

A module of a plant shoot includes a leaf, bud, and internode.

Question 3

What are the three phases of plant development?

Answer 3

1. Embryogenesis. 2. Vegetative phase. 3. Reproductive phase.

Question 4

What are the two primary meristems in plants?

Answer 4

1. Shoot apical meristem (SAM). 2. Root apical meristem (RAM)

SAM RAMs mary’s house DOWN

Question 5

What are the two lateral meristems in woody plants?

Answer 5

1. Vascular cambium. 2. Cork cambium.

Question 6

What is the function of meristems?

Answer 6

Meristems contain stem cells that renew themselves while producing new cells that differentiate via asymmetric cell division.

Question 7

What is phyllotaxy, and what are its types?

Answer 7

Phyllotaxy refers to the arrangement of leaves (and branches) around the stem. Types include: 1. Alternate. 2. Spiral. 3. Opposite. 4. Whorled.

Question 8

What is the significance of spiral phyllotaxy?

Answer 8

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.

Question 9

How does the hormone auxin influence early plant development?

Answer 9

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.

Question 10

What are the main zones of the shoot apical meristem?

Answer 10

1. 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)

Question 11

What are the L1, L2, and L3 layers in the shoot apex, and what do they produce?

Answer 11

L1: Divides anticlinally to form the epidermis. L2 and L3: Produce internal tissues, with L3 often forming the vasculature.

Question 12

What are the three major tissue types in plants and their functions?

Answer 12

1. Epidermis: Protection, light reflection, water/gas exchange.
2. Ground Tissue: Fills the interior; functions vary by location.
3. Vascular Tissue: Transports water and nutrients (xylem and phloem, primary by SAM , secondary by vascular cam)

Question 13

What are the three types of venation patterns in plants?

Answer 13

1. Dichotomous
2. Parallel ( monocots mainly )
3. Reticulate.

Question 14

What are the key take-home points about plant development?

Answer 14

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.

Question 15

Why are trees ‘bottom heavy’?

Answer 15

It provides stability and ensures efficient access to gases for transpiration.

Question 16

What are the key differences between plant and animal development?

Answer 16

Plants: Indeterminate development, high developmental plasticity, sessile, and regenerative.
Animals: Determinate development, little plasticity, mobile, and less regenerative.

Question 17

Why are auxillary buds important in plants ID?

Answer 17

They determine what is a real leaf (presence indicates a real leaf) and are critical for branching and lateral growth.

Question 18

What does viviparous mean in plants?

Answer 18

It describes seeds that germinate while still attached to the mother plant.

Question 19

What are the three phases of plant development?

Answer 19

1. Embryogenesis: Formation of the embryo.
2. Vegetative Phase: Includes juvenile and adult sub-phases; development is indeterminate.
3. Reproductive Phase: Development becomes more determinate, leading to flowering and seed production.

Question 20

What is the difference between cambium cells and meristem cells?

Answer 20

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).

Question 21

What is the difference between anticlinal and periclinal cell divisions?

Answer 21

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.

Question 22

Why does the Fibonacci sequence frequently appear in plants?

Answer 22

It ensures optimal packing, space utilization, and light capture, improving structural and functional efficiency.

Question 23

How does auxin influence plant development phases? Where is it produced?

Answer 23

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.

Question 24

How does auxin affect shoot growth?

Answer 24

1. Promotes Growth at Shoot Tips: Stimulates cell elongation and division in the apical meristem.
2. Inhibits Lateral Growth: Maintains apical dominance by suppressing axillary bud growth.
3. Reduction of Apical Dominance: Pruning the shoot tip reduces auxin, allowing lateral buds to grow.

Question 25

What are primordia in plants?

Answer 25

Early-stage structures that develop into specialized organs like leaves, roots, or flowers.

Question 26

How do vascular bundles differ between stems and roots?

Answer 26

**Stem**: Vascular bundles are arranged in a circle. **Root**: Vascular bundles are concentrated in the center.

Question 27

What are the primary functions of the epidermis in plants?

Answer 27

Protects against water loss. Reflects light and helps with surface cleaning by rolling off water and dust.

Question 28

What are the differences between reticulate and parallel venation?

Answer 28

**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.

Question 29

What are the main types of phyllotaxis?

Answer 29

**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.

Question 30

What is indole acetic acid (IAA), and why is it significant?

Answer 30

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).

Question 31

What does the vascular cambium produce?

Answer 31

It produces **xylem** (water-conducting tissue) and **phloem** (nutrient-conducting tissue), contributing to secondary growth.

Question 32

Why is the golden angle (137.5°) significant in spiral phyllotaxis?

Answer 32

It ensures optimal space utilization and light capture, aligning with the Fibonacci sequence.

Question 33

How is apical dominance maintained in plants?

Answer 33

High concentrations of auxin at the shoot tip suppress axillary bud growth, focusing resources on upward growth.

Question 34

What is modular plant development?

Answer 34

It refers to the way plants grow by producing repeated units (modules) like leaf, bud, internode, allowing continuous and flexible growth.

Question 35

What are the key features of modular plant development?5

Answer 35

1. Repetitive unit formation: Plants grow in modules that include leaves, stems, and buds. 2. Indeterminate growth: Plants grow continuously under favorable conditions. 3. Plasticity: Plants adapt growth patterns to environmental factors, like light or nutrients. 4. Clonal propagation: Detached modules can form new plants (e.g., runners in strawberries). 5. Self-repair: New modules replace lost or damaged parts.

Question 36

What is secondary growth in plants?

Answer 36

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.

Question 37

What does the cork cambium (phellogen) produce?

Answer 37

Cork (phellem): Forms the protective outer bark. Phelloderm: Provides inner protection beneath the cork.

Question 38

What is the role of lenticels in plants?

Answer 38

Lenticels are horizontal slits in the bark that enable gas exchange between the plant and the atmosphere.

Question 39

How can you differentiate a compound leaf from a branch with multiple leaves?

Answer 39

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.

Question 40

How does root architecture adapt to environmental conditions?

Answer 40

Roots branch more where water and nutrients are abundant. Roots grow towards water and avoid obstacles like rocks (plasticity) Strigalactones aid this.

Question 41

What is the function of root hairs in plants?

Answer 41

Root hairs increase surface area for water and nutrient absorption and are cost-efficient extensions of epidermal cells.

Question 42

What is heterophylly in plants (3 types)?

Answer 42

The presence of different types or shapes of leaves on the same plant. It can be: 1. Developmental: Changes with the plant's age. 2. Environmental: Adapts to conditions like water availability. 3. Habitual: Naturally occurs in some plants.

Question 43

What 3 ways does auxin influence plant growth?

Answer 43

Auxin regulates cell elongation at the shoot tip. Apical dominance by suppressing lateral buds. Root formation and leaf shape development.

Question 44

What is the effect of mechanical loading on wood formation?

Answer 44

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.

Question 45

What is grafting, and why is it useful?

Answer 45

Grafting joins tissues from two plants, allowing nutrient exchange and the combination of desirable traits. Cambial connection is crucial for success.

Question 46

What is clonal propagation, and how is it achieved?

Answer 46

Clonal propagation involves creating identical plants from parts like stolons, rhizomes, or cuttings. It can also be done through meristem cultures to exclude viruses.

Question 47

What is totipotency in plants?

Answer 47

The ability of a single plant cell to regenerate into a complete plant, enabling cloning and regeneration.

Question 48

How is cell fate determined in plants?

Answer 48

In plants, cell fate depends on the cell’s position in the tissue, not its lineage, allowing flexibility and adaptation during growth.

Question 49

How does auxin maintain apical dominance?

Answer 49

Auxin produced in the shoot apex suppresses lateral bud growth, prioritizing upward growth.

Question 50

How does modular growth benefit plants?

Answer 50

Enables flexible adaptation to the environment. Supports self-repair after damage. Allows indefinite growth by adding new modules.

Question 51

Summary of Meristems and Their Contributions:

Answer 51

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.