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Anatomy of Flowering Plants – CBSE NCERT Study Resources

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11th

11th - Biology

Anatomy of Flowering Plants

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Overview of the Chapter

This chapter explores the internal structure and organization of flowering plants (angiosperms). It covers the different types of tissues, their functions, and the anatomical features of roots, stems, and leaves. The chapter also discusses secondary growth in plants, which leads to an increase in girth.

Tissues in Flowering Plants

Meristematic Tissue: Composed of actively dividing cells responsible for plant growth. It is classified into apical, lateral, and intercalary meristems based on location.

Permanent Tissue: Consists of differentiated cells that have lost the ability to divide. It includes simple tissues (parenchyma, collenchyma, sclerenchyma) and complex tissues (xylem and phloem).

Anatomy of Root, Stem, and Leaf

Root

The root has distinct regions: root cap, meristematic zone, elongation zone, and maturation zone. The internal structure includes epidermis, cortex, endodermis, pericycle, and vascular bundles.

Stem

The stem consists of nodes and internodes. The internal structure includes epidermis, cortex, vascular bundles (arranged in a ring in dicots and scattered in monocots), and pith.

Leaf

The leaf has a dorsiventral structure with upper (adaxial) and lower (abaxial) surfaces. The internal structure includes epidermis, mesophyll (palisade and spongy parenchyma), and vascular bundles.

Secondary Growth in Plants

Secondary growth occurs due to the activity of lateral meristems (vascular cambium and cork cambium). It results in the thickening of stems and roots, forming secondary xylem (wood) and secondary phloem (bast).

Differences Between Dicot and Monocot Plants

  • Dicots have taproots, while monocots have fibrous roots.
  • Dicot stems have vascular bundles arranged in a ring, whereas monocot stems have scattered bundles.
  • Dicot leaves show reticulate venation, while monocot leaves exhibit parallel venation.

All Question Types with Solutions – CBSE Exam Pattern

Explore a complete set of CBSE-style questions with detailed solutions, categorized by marks and question types. Ideal for exam preparation, revision and practice.

Very Short Answer (1 Mark) – with Solutions (CBSE Pattern)

These are 1-mark questions requiring direct, concise answers. Ideal for quick recall and concept clarity.

Question 1:
Define meristematic tissue in plants.
Answer:
Definition: Meristematic tissue is undifferentiated tissue responsible for plant growth.
Question 2:
Name the two types of simple permanent tissues.
Answer:
  • Parenchyma
  • Collenchyma
Question 3:
What is the function of phloem?
Answer:

Phloem transports organic nutrients from leaves to other plant parts.

Question 4:
Identify the tissue that provides mechanical support in stems.
Answer:
Sclerenchyma provides mechanical support.
Question 5:
What are lenticels?
Answer:
Definition: Lenticels are porous structures facilitating gas exchange in woody stems.
Question 6:
Which tissue forms the epidermis in plants?
Answer:
Epidermal tissue forms the epidermis.
Question 7:
Name the components of xylem.
Answer:
  • Tracheids
  • Vessels
  • Xylem parenchyma
  • Xylem fibers
Question 8:
What is the role of cambium?
Answer:

Cambium produces secondary xylem and phloem for lateral growth.

Question 9:
Differentiate between apical and lateral meristem.
Answer:

Apical meristem increases length, lateral meristem increases girth.

Question 10:
What is secondary growth?
Answer:
Definition: Secondary growth is the increase in plant thickness due to lateral meristems.
Question 11:
Name the dead element of phloem.
Answer:
Phloem fibers are the dead element.
Question 12:
Which tissue stores food in plants?
Answer:
Parenchyma stores food.
Question 13:
What is the function of guard cells?
Answer:

Guard cells regulate stomatal opening for gas exchange.

Question 14:
Give an example of complex permanent tissue.
Answer:
Xylem is a complex permanent tissue.
Question 15:
What is the function of parenchyma in plants?
Answer:

Parenchyma stores food and performs photosynthesis.

Question 16:
Name the tissue responsible for secondary growth in dicots.
Answer:

Lateral meristems (cambium).

Question 17:
Which complex tissue transports water in plants?
Answer:

Xylem.

Question 18:
What is the epidermis covered with to reduce water loss?
Answer:

Cuticle.

Question 19:
Define collenchyma.
Answer:

Flexible mechanical tissue with unevenly thickened walls.

Question 20:
Which meristem increases stem length?
Answer:

Apical meristem.

Question 21:
What are stomata guarded by?
Answer:

Guard cells.

Question 22:
Name the dead element of phloem.
Answer:

Phloem fibers.

Question 23:
What replaces epidermis in older stems?
Answer:

Periderm.

Question 24:
Which tissue provides mechanical support to growing organs?
Answer:

Collenchyma.

Question 25:
What is the function of sclerenchyma?
Answer:

Provides rigidity and strength.

Question 26:
Name the living cells in xylem.
Answer:

Parenchyma and xylem fibers.

Question 27:
What is the composition of cork?
Answer:

Suberin and dead cells.

Question 28:
Which tissue forms the vascular bundle?
Answer:

Xylem and phloem.

Question 29:
Name the tissue responsible for secondary growth in dicot stems.
Answer:

The cambium (specifically vascular cambium and cork cambium) is responsible for secondary growth in dicot stems. It adds girth by producing secondary xylem (wood) and phloem.

Question 30:
What is the function of parenchyma cells in plants?
Answer:

Parenchyma cells perform multiple functions:

  • Storage of food (e.g., starch in potatoes)
  • Photosynthesis (chlorenchyma)
  • Gas exchange (aerenchyma in aquatic plants)
  • Wound healing and regeneration

Very Short Answer (2 Marks) – with Solutions (CBSE Pattern)

These 2-mark questions test key concepts in a brief format. Answers are expected to be accurate and slightly descriptive.

Question 1:
What is the function of collenchyma tissue in plants?
Answer:

Collenchyma provides mechanical support to growing plant parts like stems and leaves. It is flexible, allowing elongation, and contains unevenly thickened cellulose walls.

Question 2:
Name the two types of complex permanent tissues in plants.
Answer:

The two types are:
Xylem (conducts water and minerals)
Phloem (transports organic nutrients).

Question 3:
Why are sclerenchyma cells dead at maturity?
Answer:

They deposit a rigid lignin wall, which makes them impermeable to water and nutrients, leading to cell death. Their primary role is structural support.

Question 4:
What is the role of companion cells in phloem?
Answer:

Companion cells assist sieve tube elements by providing metabolic support (e.g., ATP, proteins) as sieve tubes lack nuclei and organelles.

Question 5:
How does secondary growth occur in dicot stems?
Answer:

It occurs due to:
1. Vascular cambium activity (forms secondary xylem/phloem)
2. Cork cambium activity (forms cork and bark).

Question 6:
List two features of monocot roots.
Answer:

1. Polyarch xylem (many bundles)
2. Pith is large and well-developed.

Question 7:
What are lenticels? State their function.
Answer:

Lenticels are porous structures in bark that allow gas exchange (O2/CO2) in woody stems.

Question 8:
Why is endodermis called a checkpoint in roots?
Answer:

It has Casparian strips (suberin deposits) that regulate water/mineral entry into the stele, preventing backflow.

Question 9:
Name the four types of xylem elements.
Answer:

1. Tracheids
2. Vessels
3. Xylem fibres
4. Xylem parenchyma.

Short Answer (3 Marks) – with Solutions (CBSE Pattern)

These 3-mark questions require brief explanations and help assess understanding and application of concepts.

Question 1:
Explain the significance of meristematic tissue in plants.
Answer:

Meristematic tissue is responsible for the growth and development of plants. It consists of undifferentiated cells that continuously divide, leading to the formation of new cells.

These tissues are found in regions like the apical meristem (tips of roots and shoots) and lateral meristem (cambium), enabling primary and secondary growth.

Without meristematic tissue, plants would not be able to grow taller, produce new leaves, or increase in girth.

Question 2:
Differentiate between parenchyma, collenchyma, and sclerenchyma tissues based on their structure and function.
Answer:
  • Parenchyma: Thin-walled, living cells with large intercellular spaces. Functions include photosynthesis, storage, and secretion.
  • Collenchyma: Thickened at corners, living cells. Provides mechanical support to growing parts like stems and leaves.
  • Sclerenchyma: Thick-walled, dead cells with lignin. Offers rigid support and protection to mature plant parts.
Question 3:
Describe the structure and function of xylem in flowering plants.
Answer:

Xylem is a complex permanent tissue responsible for water and mineral transport from roots to other plant parts.

It consists of four cell types: tracheids, vessels, xylem parenchyma, and xylem fibers.

Tracheids and vessels are dead cells with lignified walls, forming long tubes for water conduction.

Xylem parenchyma stores food, while xylem fibers provide structural support.

Question 4:
What is the role of phloem in plants? Name its components.
Answer:

Phloem transports organic nutrients (like sucrose) from leaves to other plant parts, a process called translocation.

Its components include:

  • Sieve tube elements (main conducting cells)
  • Companion cells (support sieve tubes)
  • Phloem parenchyma (stores food)
  • Phloem fibers (provide strength)

Question 5:
Explain the internal structure of a dicot root with a labeled diagram.
Answer:

A dicot root has the following layers from outside to inside:

1. Epidermis: Outer protective layer with root hairs for absorption.
2. Cortex: Stores starch and facilitates water movement.
3. Endodermis: Contains Casparian strips to regulate water entry.
4. Pericycle: Gives rise to lateral roots.
5. Vascular bundles: Xylem (star-shaped) and phloem alternate in a radial arrangement.

(Diagram to be drawn showing these layers.)

Question 6:
How does the secondary growth in dicot stems increase their girth?
Answer:

Secondary growth occurs due to the activity of lateral meristems (vascular cambium and cork cambium).

1. Vascular cambium produces secondary xylem (wood) inward and secondary phloem outward.
2. Cork cambium forms the periderm (bark) for protection.

This process leads to an increase in stem thickness, providing mechanical strength and allowing the plant to grow taller.

Question 7:
Differentiate between parenchyma and collenchyma tissues based on their structure and function.
Answer:

Parenchyma and collenchyma are simple permanent tissues with distinct features:

  • Parenchyma: Composed of thin-walled, living cells with large intercellular spaces.
    Function: Storage, photosynthesis (chlorenchyma), and secretion.
  • Collenchyma: Contains unevenly thickened cell walls (due to pectin) and lacks intercellular spaces.
    Function: Provides mechanical support to growing plant parts.

Key difference: Parenchyma is involved in metabolic activities, while collenchyma offers flexibility and support.

Question 8:
Explain the significance of casparian strips in the endodermis of roots.
Answer:

The casparian strip is a band of suberin present in the radial and transverse walls of endodermal cells. Its significance includes:

  • Prevents apoplastic movement of water and minerals, forcing them to pass through the selectively permeable membrane of endodermal cells.
  • Ensures controlled absorption and prevents harmful substances from entering the stele.
  • Maintains root pressure by regulating ion transport.

Thus, it acts as a checkpoint for nutrient uptake.

Question 9:
Describe the structure and function of phloem in flowering plants.
Answer:

Phloem is a complex tissue responsible for translocation of organic nutrients. Its components are:

  • Sieve tube elements: Enucleated, tubular cells with sieve plates for transport.
  • Companion cells: Metabolically active cells supporting sieve tubes.
  • Phloem parenchyma: Stores starch and resins.
  • Phloem fibers: Provides mechanical strength.

Function: Transports sucrose and other nutrients from leaves (source) to growing regions (sink) via pressure flow hypothesis.

Question 10:
How does the secondary growth in dicot stems increase their girth? Explain with steps.
Answer:

Secondary growth occurs due to the activity of lateral meristems (vascular cambium and cork cambium):


1. Vascular cambium forms a ring and produces secondary xylem (wood) inward and secondary phloem outward.
2. The stem expands as secondary xylem accumulates, pushing primary tissues outward.
3. Cork cambium replaces epidermis with periderm (bark) for protection.

Result: Increased girth due to continuous deposition of secondary tissues.

Question 11:
Compare the anatomy of a dicot and monocot leaf with respect to their vascular bundles.
Answer:

Differences in vascular bundles of dicot and monocot leaves:

  • Dicot leaf: Vascular bundles are arranged in a reticulate pattern with a prominent midrib.
    Bundle sheath may be parenchymatous or sclerenchymatous.
  • Monocot leaf: Vascular bundles are parallel and scattered, with no midrib.
    Bundle sheath is typically sclerenchymatous for support.

Note: Dicots show differentiation into palisade and spongy parenchyma, while monocots lack this.

Question 12:
What is the role of pericycle in roots? Mention its additional functions.
Answer:

The pericycle is a layer of cells located just inside the endodermis. Its roles include:

  • Forms lateral roots through mitotic activity, aiding in absorption.
  • In dicots, contributes to secondary growth by generating cork cambium.
  • Helps in vascular cambium formation during secondary growth.

Additional function: Stores nutrients and provides structural support to the root.

Long Answer (5 Marks) – with Solutions (CBSE Pattern)

These 5-mark questions are descriptive and require detailed, structured answers with proper explanation and examples.

Question 1:
Explain the secondary growth in dicot stems with reference to the roles of vascular cambium and cork cambium.
Answer:
Theoretical Framework

Secondary growth increases the girth of dicot stems through the activity of lateral meristems. Our textbook shows that vascular cambium produces secondary xylem (wood) and phloem, while cork cambium forms the protective periderm.

Evidence Analysis
  • Vascular cambium arises from interfascicular and intrafascicular regions, creating concentric rings.
  • Cork cambium replaces epidermis with cork cells, preventing water loss.
Critical Evaluation

This process is absent in monocots due to scattered vascular bundles. Example: Banyan trees develop thick bark via cork cambium.

Future Implications

Understanding secondary growth aids in forestry management and wood production.

Question 2:
Compare the anatomy of dicot and monocot roots with emphasis on vascular bundles and pith.
Answer:
Theoretical Framework

We studied that dicot roots have radial vascular bundles with a distinct pith, while monocot roots show polyarch bundles and reduced pith.

Evidence Analysis
  • Dicots: Xylem is exarch (2-4 patches); pith stores starch.
  • Monocots: 8+ xylem poles (polyarch); pith is sclerenchymatous.
Critical Evaluation

Example: Pea (dicot) shows tetrarch bundles, whereas maize (monocot) has 12-20 poles. This adaptation supports varied soil anchorage needs.

Future Implications

Differences influence crop breeding for drought resistance.

Question 3:
Describe the structure of stomata and its significance in transpiration and gas exchange.
Answer:
Theoretical Framework

Stomata are epidermal pores flanked by guard cells containing chloroplasts. Our textbook shows they regulate transpiration and CO2 uptake.

Evidence Analysis
  • Guard cells swell (turgid) to open stomata via K+ influx.
  • Example: Sunken stomata in xerophytes reduce water loss.
Critical Evaluation

Stomatal density varies; C4 plants like maize have higher density for efficient photosynthesis.

Future Implications

Research on stomatal mutants may enhance crop water-use efficiency.

Question 4:
Analyze how xylem and phloem differ in structure and function, citing two examples each.
Answer:
Theoretical Framework

Xylem conducts water/minerals upward (dead cells), while phloem transports sugars bidirectionally (living sieve tubes).

Evidence Analysis
  • Xylem: Tracheids (gymnosperms) and vessels (angiosperms).
  • Phloem: Companion cells (dicots) and albuminous cells (gymnosperms).
Critical Evaluation

Example: Oak wood (xylem) shows annual rings; sugarcane phloem has high sucrose transport rates.

Future Implications

Understanding aids in developing drought-resistant crops.

Question 5:
Explain the periderm formation in woody plants and its protective role with reference to lenticels.
Answer:
Theoretical Framework

Periderm replaces epidermis in secondary growth, comprising cork cambium, phellem, and phelloderm. Lenticels facilitate gas exchange.

Evidence Analysis
  • Cork cells are suberized, making them impermeable.
  • Example: Potato tubers develop periderm to prevent pathogen entry.
Critical Evaluation

Lenticels appear as raised pores (e.g., cherry bark) and contain complementary cells for O2 diffusion.

Future Implications

Research on periderm can improve post-harvest storage techniques.

Question 6:
Compare the anatomy of dicot and monocot stems with labeled diagrams. Highlight key structural differences.
Answer:
Theoretical Framework

We studied that dicot stems have a distinct arrangement of vascular bundles in a ring, while monocot stems show scattered vascular bundles. The presence of cambium in dicots allows secondary growth.


Evidence Analysis
  • Dicot stems: Cortex, endodermis, and pith are clearly differentiated.
  • Monocot stems: Lack cambium and show sclerenchymatous hypodermis.
[Diagram: Cross-section of dicot and monocot stems]
Critical Evaluation

Our textbook shows that dicots (e.g., sunflower) adapt for strength, while monocots (e.g., maize) prioritize flexibility.

Question 7:
Explain the secondary growth in dicot stems with emphasis on the roles of vascular cambium and cork cambium.
Answer:
Theoretical Framework

Secondary growth increases stem girth via vascular cambium (produces secondary xylem/phloem) and cork cambium (forms periderm).


Evidence Analysis
  • Vascular cambium: Generates annual rings in trees like neem.
  • Cork cambium: Replaces epidermis with bark, as seen in banyan trees.

Critical Evaluation

Our textbook highlights how this adaptation supports long-term survival in perennial plants.

Question 8:
Describe the internal structure of a dorsiventral leaf with reference to photosynthesis and transpiration.
Answer:
Theoretical Framework

Dorsiventral leaves (e.g., mango) have palisade (upper) and spongy (lower) mesophyll for optimized light absorption and gas exchange.


Evidence Analysis
  • Palisade tissue: Tightly packed chloroplasts for photosynthesis.
  • Stomata: Lower epidermis regulates transpiration.
[Diagram: T.S. of dorsiventral leaf]
Critical Evaluation

We observed how this structure balances CO2 intake and water loss.

Question 9:
Analyze the adaptive significance of xylem and phloem in flowering plants. Provide two examples of specialized cells in each.
Answer:
Theoretical Framework

Xylem transports water/minerals (dead cells), while phloem transports sugars (living cells). Both show cellular specialization.


Evidence Analysis
  • Xylem: Vessels (e.g., oak) and tracheids for vertical transport.
  • Phloem: Sieve tubes (e.g., pumpkin) and companion cells for bidirectional flow.

Critical Evaluation

Our textbook confirms these adaptations enable long-distance resource distribution.

Question 10:
Discuss the economic importance of plant tissues with examples of commercial products derived from sclerenchyma and parenchyma.
Answer:
Theoretical Framework

Sclerenchyma (e.g., jute fibers) provides mechanical strength, while parenchyma (e.g., potato starch) stores nutrients.


Evidence Analysis
  • Sclerenchyma: Used in ropes (coir from coconut).
  • Parenchyma: Source of sugar (sugarcane) and medicines (aloe vera).

Critical Evaluation

We studied how tissue properties directly influence their industrial applications.

Question 11:
Describe the internal structure of a dicot stem with the help of a well-labelled diagram. Highlight the roles of different tissues in providing mechanical strength and conducting water and nutrients.
Answer:

The internal structure of a dicot stem consists of several distinct layers, each performing specialized functions. A cross-section reveals the following tissues:

  • Epidermis: The outermost protective layer covered with a cuticle to reduce water loss.
  • Cortex: Composed of parenchyma, collenchyma, and sclerenchyma cells, providing mechanical support.
  • Endodermis: The innermost layer of the cortex, often containing starch grains.
  • Pericycle: A layer of cells that may form part of the vascular bundle.
  • Vascular Bundles: Arranged in a ring, each bundle contains xylem (for water conduction) and phloem (for nutrient transport), with cambium in between for secondary growth.
  • Pith: Central region made of parenchyma cells for storage.

Mechanical Strength: Collenchyma and sclerenchyma in the cortex and vascular bundles provide rigidity. Conduction: Xylem transports water and minerals upward, while phloem distributes organic nutrients. A well-labelled diagram should show all these layers clearly.

Question 12:
Explain the secondary growth in dicot stems. How does it contribute to the increase in girth of the plant? Include the roles of vascular cambium and cork cambium.
Answer:

Secondary growth in dicot stems involves the activity of two lateral meristems: vascular cambium and cork cambium, leading to an increase in girth.

Vascular Cambium:
1. It originates from undifferentiated cells between xylem and phloem in vascular bundles.
2. Forms a continuous ring and produces secondary xylem (wood) inward and secondary phloem outward.
3. This process thickens the stem over time.

Cork Cambium (Phellogen):
1. Develops in the outer cortex and produces cork (phellem) outward and secondary cortex (phelloderm) inward.
2. The cork cells are dead and suberized, providing protection and reducing water loss.

Contribution to Girth:
The combined activity of both cambia results in:
- Accumulation of secondary xylem (wood), adding bulk.
- Formation of bark (cork + secondary phloem), protecting the expanding stem.

This process ensures structural support and sustained nutrient transport as the plant grows older and larger.

Question 13:
Describe the internal structure of a dicot stem with the help of a well-labelled diagram. Explain the roles of vascular bundles and cambium in secondary growth.
Answer:

The internal structure of a dicot stem consists of several distinct layers, each with specific functions. A transverse section reveals the following regions:

  • Epidermis: The outermost protective layer covered with a cuticle to reduce water loss.
  • Cortex: Comprises parenchyma, collenchyma, and sclerenchyma cells, providing mechanical support.
  • Endodermis: The innermost layer of the cortex, often rich in starch grains.
  • Pericycle: A layer of cells that may form part of the vascular bundles.
  • Vascular Bundles: Arranged in a ring, each bundle contains xylem (inner) and phloem (outer) separated by cambium.
  • Pith: Central region for storage and support.

Vascular bundles are crucial for transport: xylem carries water and minerals upward, while phloem transports organic nutrients. The cambium is a meristematic tissue responsible for secondary growth, producing secondary xylem (wood) and phloem (inner bark), increasing stem girth.

For full marks, a well-labelled diagram should include all layers and highlight the vascular bundles and cambium.

Question 14:
Describe the internal structure of a dicot stem with the help of a well-labelled diagram. Explain the functions of each tissue layer.
Answer:

The internal structure of a dicot stem consists of several distinct tissue layers, each performing specific functions. Below is a detailed explanation along with a diagrammatic representation:


1. Epidermis: The outermost protective layer covered with a cuticle to reduce water loss. It may have trichomes or stomata for gaseous exchange.


2. Cortex: Located beneath the epidermis, it has three sub-layers:

  • Hypodermis: Collenchyma cells provide mechanical support.
  • General Cortex: Parenchyma cells store food and perform photosynthesis if chloroplasts are present.
  • Endodermis: Also called the starch sheath, it stores starch and regulates material movement.


3. Pericycle: A few layers of sclerenchyma cells forming a hard bast for strength.


4. Vascular Bundles: Arranged in a ring, each bundle is conjoint, collateral, and open, with:

  • Xylem: Transports water and minerals; has vessels, tracheids, fibers, and parenchyma.
  • Phloem: Transports organic nutrients; consists of sieve tubes, companion cells, phloem fibers, and parenchyma.
  • Cambium: Meristematic tissue for secondary growth.


5. Pith: Central parenchymatous region for storage and sometimes photosynthesis.


Diagram: A cross-section of the dicot stem showing all layers with labels (epidermis, cortex, vascular bundles, pith, etc.).


Value-added note: The dicot stem shows secondary growth due to cambium activity, unlike monocots. This adaptability allows dicots to thrive in diverse environments.

Question 15:
Describe the internal structure of a dorsiventral leaf with the help of a labelled diagram. Discuss the role of each tissue in photosynthesis and transpiration.
Answer:

The internal structure of a dorsiventral leaf (dicot leaf) consists of three main regions: epidermis, mesophyll, and vascular bundles. Below is a detailed explanation along with their roles in photosynthesis and transpiration:


1. Epidermis:
- Upper epidermis: A single layer of tightly packed cells with a thick cuticle to reduce water loss.
- Lower epidermis: Contains numerous stomata (guard cells) for gaseous exchange and transpiration.
- Role: Protects inner tissues, regulates transpiration, and allows CO2 entry for photosynthesis.


2. Mesophyll:
- Palisade parenchyma: Tightly packed, elongated cells below the upper epidermis, rich in chloroplasts.
- Spongy parenchyma: Loosely arranged cells with air spaces for gas diffusion.
- Role: Palisade cells perform maximum photosynthesis; spongy cells aid in gas exchange and storage.


3. Vascular Bundles:
- Xylem: Transports water and minerals to the leaf.
- Phloem: Transports organic nutrients (sugars) from the leaf.
- Role: Supports leaf structure and facilitates transport for photosynthesis and transpiration.


Diagram (Labelled):
- Draw a cross-section showing upper/lower epidermis, palisade/spongy mesophyll, and vascular bundles (xylem above phloem).


Value-Add: The air spaces in the spongy mesophyll enhance CO2 diffusion, while the cuticle minimizes water loss, balancing photosynthesis and transpiration efficiently.

Question 16:
Describe the internal structure of a dicot stem with the help of a well-labelled diagram. Highlight the functions of each tissue layer.
Answer:

The internal structure of a dicot stem consists of several distinct tissue layers, each performing specialized functions. Below is a detailed explanation along with their roles:


1. Epidermis: The outermost protective layer covered with a cuticle to reduce water loss. It may bear trichomes or stomata for gaseous exchange.


2. Cortex: Located beneath the epidermis, it has three sub-layers:

  • Hypodermis: Collenchymatous cells provide mechanical support.
  • General Cortex: Parenchyma cells store food and perform photosynthesis if chloroplasts are present.
  • Endodermis: Innermost layer with starch grains, also called the starch sheath.


3. Pericycle: Composed of sclerenchyma patches, it provides strength and may form part of the vascular cambium during secondary growth.


4. Vascular Bundles: Arranged in a ring, each bundle is conjoint, collateral, and open (with cambium).

  • Xylem: Conducts water and minerals; has vessels, tracheids, fibers, and parenchyma.
  • Phloem: Translocates organic food; consists of sieve tubes, companion cells, phloem fibers, and parenchyma.


5. Pith: Central parenchymatous region for storage and sometimes disintegration to form a hollow stem.


Note: A labelled diagram should show all layers clearly, including epidermis, cortex, vascular bundles, and pith. The cambium (between xylem and phloem) is responsible for secondary growth.

Question 17:
Describe the internal structure of a dicot stem with the help of a well-labelled diagram. Highlight the roles of different tissues in providing mechanical strength and conduction.
Answer:

The internal structure of a dicot stem consists of several distinct layers, each performing specialized functions. Below is a detailed explanation along with their roles:


1. Epidermis: The outermost protective layer covered with a cuticle to reduce water loss. It may bear trichomes or stomata for gaseous exchange.


2. Cortex: Located beneath the epidermis, it has three sub-layers:

  • Hypodermis: Made of collenchyma, provides mechanical support.
  • General Cortex: Composed of parenchyma, stores food.
  • Endodermis: Innermost layer with starch grains, also called the starch sheath.


3. Pericycle: A few layers of sclerenchyma forming a hard bast, offering rigidity.


4. Vascular Bundles: Arranged in a ring, each bundle is conjoint, collateral, and open, with:

  • Xylem: Conducts water and minerals; protoxylem faces inward, metaxylem outward.
  • Phloem: Translocates organic food; includes sieve tubes, companion cells, and phloem parenchyma.
  • Cambium: A meristematic layer for secondary growth.


5. Pith: Central parenchymatous tissue for storage and sometimes aeration.


Roles in Mechanical Strength & Conduction:

  • Collenchyma and sclerenchyma provide structural support.
  • Xylem conducts water/minerals upward; phloem transports food bidirectionally.
  • Cambium adds secondary tissues, enhancing girth and strength over time.


Note: A well-labelled diagram should show all layers with clear annotations for full marks.

Question 18:
Explain the internal structure of a dicot stem with the help of a well-labelled diagram. Highlight the roles of different tissues in providing mechanical support and conduction.
Answer:

The internal structure of a dicot stem consists of several distinct tissues arranged in concentric layers, each performing specialized functions. Below is a detailed explanation along with their roles:


1. Epidermis: The outermost protective layer covered with a cuticle to reduce water loss. It may bear trichomes or stomata for gaseous exchange.


2. Cortex: Located beneath the epidermis, it has three sub-layers:

  • Hypodermis: Made of collenchyma, provides mechanical strength.
  • General Cortex: Composed of parenchyma, stores food.
  • Endodermis: Innermost layer with starch grains, also called the starch sheath.


3. Pericycle: A few layers of sclerenchyma forming a hard bast, offering rigidity.


4. Vascular Bundles: Arranged in a ring, each bundle is conjoint, collateral, and open (with cambium).

  • Xylem: Conducts water/minerals; has vessels, tracheids.
  • Phloem: Translocates food; contains sieve tubes, companion cells.
  • Cambium: Meristematic tissue for secondary growth.


5. Pith: Central parenchymatous tissue for storage and lateral conduction.


Diagram (Imaginary Representation): Draw a cross-section showing all layers with labels: Epidermis, Cortex (Hypodermis, General Cortex, Endodermis), Pericycle, Vascular Bundles (Xylem, Phloem, Cambium), and Pith.


Value-Add: In older stems, secondary growth occurs due to cambium, forming annual rings in xylem, which help in age determination and climatic studies.

Question 19:
Describe the internal structure of a dicot stem with the help of a well-labelled diagram. Explain the functions of each tissue layer.
Answer:

The internal structure of a dicot stem consists of several distinct tissue layers, each performing specific functions. Below is a detailed explanation along with a diagrammatic representation:


1. Epidermis: The outermost protective layer covered with a cuticle to reduce water loss.
2. Cortex: Comprises parenchyma, collenchyma, and sclerenchyma cells for storage and mechanical support.
3. Endodermis: The innermost cortical layer rich in starch grains, also called the starch sheath.
4. Pericycle: Composed of sclerenchyma patches, providing strength.
5. Vascular Bundles: Arranged in a ring, each bundle has:
  • Xylem: Conducts water and minerals (inner side).
  • Phloem: Transports food (outer side).
  • Cambium: Responsible for secondary growth.
6. Pith: Central parenchymatous tissue for storage and support.

Functions:
- Epidermis protects against pathogens and water loss.
- Cortex stores food and provides flexibility.
- Vascular bundles ensure efficient transport of water, minerals, and food.
- Pith aids in nutrient storage and structural support.

Question 20:
Compare and contrast the anatomical features of monocot and dicot roots. Support your answer with a labelled diagram of each.
Answer:

Monocot Root vs. Dicot Root:


1. Epidermis:
- Monocot: Single-layered with root hairs.
- Dicot: Similar but may have thicker walls.
2. Cortex:
- Monocot: Wide cortex with parenchyma cells.
- Dicot: Narrower cortex, often with intercellular spaces.
3. Endodermis:
- Both have a Casparian strip, but monocots may show passage cells.
4. Pericycle:
- Monocot: Gives rise to lateral roots only.
- Dicot: Also contributes to cork cambium during secondary growth.
5. Vascular Bundles:
- Monocot: Polyarch (many xylem strands) and radial arrangement.
- Dicot: Diarch to tetrarch (2-4 xylem strands), radial arrangement.
6. Pith:
- Monocot: Large and well-developed.
- Dicot: Reduced or absent.

Key Differences:
- Monocot roots lack secondary growth, while dicot roots show it due to cambium activity.
- Xylem strands are more numerous in monocots.
- Pith is prominent in monocots but minimal in dicots.

Case-based Questions (4 Marks) – with Solutions (CBSE Pattern)

These 4-mark case-based questions assess analytical skills through real-life scenarios. Answers must be based on the case study provided.

Question 1:
A student observed vascular bundles in a dicot stem under a microscope. Explain the arrangement and significance of these bundles in plant growth.
Answer:
Case Deconstruction

We studied that dicot stems have vascular bundles arranged in a ring. Each bundle contains xylem (inner) and phloem (outer) separated by cambium.

Theoretical Application
  • Ring arrangement provides mechanical strength.
  • Cambium helps in secondary growth, increasing stem girth.
Critical Evaluation

Our textbook shows this arrangement optimizes nutrient transport and support. Examples: Sunflower and mango stems exhibit this pattern.

Question 2:
How does the periderm replace the epidermis in older woody stems? Analyze its adaptive advantage.
Answer:
Case Deconstruction

In secondary growth, cork cambium forms periderm, replacing the epidermis which gets damaged.

Theoretical Application
  • Periderm has suberin for water loss prevention.
  • Lenticels in periderm enable gas exchange.
Critical Evaluation

Our textbook shows this adaptation protects against pathogens and desiccation. Examples: Oak and neem trees develop thick periderm.

Question 3:
Compare palisade and spongy parenchyma in dicot leaves with respect to their structure and function.
Answer:
Case Deconstruction

We studied that palisade parenchyma is tightly packed below the upper epidermis, while spongy parenchyma has air spaces near the lower surface.

Theoretical Application
  • Palisade cells maximize light absorption for photosynthesis.
  • Spongy tissue facilitates gas diffusion.
Critical Evaluation

Our textbook shows this division optimizes both light capture and CO2 exchange. Examples: Hibiscus and bean leaves show this clearly.

Question 4:
A transverse section of a monocot root shows polyarch xylem. Justify why this is an evolutionary adaptation for monocots.
Answer:
Case Deconstruction

Monocot roots have polyarch xylem with 8+ strands, unlike dicots (2-6 strands).

Theoretical Application
  • Increases water uptake efficiency in fibrous root systems.
  • Provides structural stability in varied soil conditions.
Critical Evaluation

Our textbook links this to monocots' need for rapid water absorption in grasses. Examples: Maize and wheat roots exhibit polyarch xylem.

Question 5:
A student observed secondary growth in a dicot stem under a microscope. Identify the tissues involved and explain their roles. How does this differ from monocot stems?
Answer:
Case Deconstruction

We studied that secondary growth involves vascular cambium and cork cambium. The vascular cambium produces secondary xylem (wood) and phloem, while cork cambium forms the protective periderm.

Theoretical Application
  • Vascular cambium: Adds girth via secondary vascular tissues.
  • Cork cambium: Replaces epidermis with bark.
Critical Evaluation

Monocots lack secondary growth due to absent cambium. Example: Bamboo (monocot) vs. Mango (dicot). Our textbook shows maize stems rely on primary growth only.

Question 6:
Analyze the anatomical adaptations in xerophytic leaves like Nerium. Compare these with hydrophytic leaves, citing two structural differences.
Answer:
Case Deconstruction

Xerophytes like Nerium have thick cuticles, sunken stomata, and multilayered epidermis to reduce water loss.

Theoretical Application
  • Xerophytes: Reduced stomata, succulent tissues.
  • Hydrophytes: Thin cuticles, aerenchyma for buoyancy.
Critical Evaluation

Example: Lotus (hydrophyte) has stomata on upper epidermis, while Nerium stores water. Our textbook highlights how these adaptations reflect habitat demands.

Question 7:
A cross-section of a dicot root shows distinct pericycle layers. Explain their function in lateral root formation. How does this contrast with monocot roots?
Answer:
Case Deconstruction

The pericycle in dicot roots is meristematic, initiating lateral roots and vascular cambium.

Theoretical Application
  • Dicots: Pericycle forms branch roots.
  • Monocots: Pericycle is less active; roots arise from nodes.
Critical Evaluation

Example: Bean (dicot) vs. Wheat (monocot). Our textbook shows monocots rely on fibrous root systems without secondary growth.

Question 8:
Describe the anatomy of a vascular bundle in a dicot stem. How does collateral arrangement differ from bicollateral in plants like Cucurbita?
Answer:
Case Deconstruction

Dicot stems have collateral bundles with xylem (inner) and phloem (outer). Bicollateral bundles (e.g., Cucurbita) add phloem on both sides.

Theoretical Application
  • Collateral: Single phloem strand (Sunflower).
  • Bicollateral: Dual phloem (Pumpkin).
Critical Evaluation

Our textbook explains bicollateral bundles enhance nutrient transport. Example: Bean (collateral) vs. Cucurbita (bicollateral).

Question 9:
A student observes a transverse section of a dicot stem under a microscope. Identify the vascular bundles and explain their arrangement. How does this differ from a monocot stem?
Answer:
Case Deconstruction

In a dicot stem, vascular bundles are arranged in a ring, each containing xylem (inner) and phloem (outer). Our textbook shows cambium between them for secondary growth.

Theoretical Application
  • Monocot stems have scattered vascular bundles without cambium.
  • Example: Sunflower (dicot) vs. Maize (monocot).
Critical Evaluation

This ring arrangement in dicots provides mechanical strength, while scattered bundles in monocots suit flexible stems.

Question 10:
Analyze the anatomical adaptations in xerophytic leaves like those of Nerium. How do these features reduce water loss?
Answer:
Case Deconstruction

Xerophytic leaves have thick cuticles, sunken stomata, and multilayered epidermis. We studied how Nerium’s hypodermis stores water.

Theoretical Application
  • Sunken stomata trap moist air, reducing transpiration.
  • Example: Cactus also shows similar adaptations.
Critical Evaluation

These traits are evolutionary responses to arid conditions, proven by comparing desert vs. aquatic plants.

Question 11:
Compare the secondary growth in dicot stems and roots. Highlight the role of cork cambium and vascular cambium.
Answer:
Case Deconstruction

Both stems and roots undergo secondary growth via vascular cambium (produces secondary xylem/phloem) and cork cambium (forms periderm).

Theoretical Application
  • In roots, cambium arises from conjunctive tissue; in stems, it’s between primary bundles.
  • Example: Banyan tree stem vs. carrot root.
Critical Evaluation

This dual cambial activity is crucial for woody plants, as seen in oak trees.

Question 12:
A microscope slide shows palisade and spongy parenchyma in a dicot leaf. Explain their functions and link their structure to photosynthesis efficiency.
Answer:
Case Deconstruction

Palisade cells (upper layer) are tightly packed for light absorption, while spongy parenchyma (lower) has air spaces for gas exchange.

Theoretical Application
  • Chloroplast density is higher in palisade cells.
  • Example: Hibiscus leaf vs. lotus (aquatic adaptation).
Critical Evaluation

This zonation maximizes photosynthesis, evidenced by higher oxygen output in well-lit leaves.

Question 13:
A student observed vascular bundles in a dicot stem under a microscope. Explain the arrangement and significance of these bundles in plant support and transport.
Answer:
Case Deconstruction

We studied that dicot stems have vascular bundles arranged in a ring. Each bundle contains xylem (inner) and phloem (outer) separated by cambium.

Theoretical Application
  • Xylem transports water/minerals upward.
  • Phloem transports food bidirectionally.
Critical Evaluation

This ring arrangement provides mechanical strength, preventing stem collapse. Cambium enables secondary growth, increasing girth.

[Diagram: Ring-shaped vascular bundles]
Question 14:
Compare the anatomical differences between monocot and dicot roots. How do these adaptations affect their functions?
Answer:
Case Deconstruction

Our textbook shows monocot roots have polyarch xylem (12+ strands) versus dicots with 2-6 xylem poles. Monocots lack secondary growth.

Theoretical Application
  • Polyarch xylem enhances water absorption in monocots.
  • Dicot roots develop lateral roots from pericycle.
Critical Evaluation

Monocot adaptations suit fibrous root systems for soil anchorage, while dicot taproots store food.

[Diagram: Cross-sections of both root types]
Question 15:
Analyze how the structure of stomata in leaves relates to transpiration and gas exchange. Provide experimental evidence.
Answer:
Case Deconstruction

Stomata consist of guard cells with unevenly thickened walls. We observed their opening/closing via potassium ion flux in lab experiments.

Theoretical Application
  • Daytime opening enables CO2 intake for photosynthesis.
  • Night closure reduces water loss.
Critical Evaluation

NCERT experiments show light-dependent stomatal activity, proving their role in balancing transpiration and gaseous exchange.

Question 16:
A plant shows abnormal secondary growth with uneven cork formation. Diagnose possible tissue malfunctions and their impact.
Answer:
Case Deconstruction

Secondary growth involves cork cambium and vascular cambium. Uneven cork suggests irregular phellogen activity.

Theoretical Application
  • Faulty cork exposes inner tissues to pathogens.
  • Asymmetric growth may disrupt nutrient flow.
Critical Evaluation

Our textbook cites Rhizophora as an example of adaptive cork, highlighting how deviations compromise protection and transport.

[Diagram: Abnormal vs normal cork layers]
Question 17:
Analyze the anatomical adaptations in xerophytic leaves like Nerium. How do these differ from hydrophytic leaves?
Answer:
Case Deconstruction

Nerium leaves have thick cuticles, sunken stomata, and multilayered epidermis to reduce water loss, as we learned in class.

Theoretical Application
  • Hydrophytic leaves (e.g., Hydrilla) lack cuticles and have air cavities for buoyancy.
  • Example: Nerium stores water in palisade tissue, while Hydrilla has thin leaves for gas exchange.
Critical Evaluation

These adaptations reflect evolutionary responses to arid vs. aquatic environments, as per NCERT diagrams.

Question 18:
Compare the vascular bundles in dicot roots and stems. Why are they arranged differently?
Answer:
Case Deconstruction

In dicot roots, vascular bundles are radial, whereas in stems, they are conjoint and collateral, as per our practical observations.

Theoretical Application
  • Radial arrangement in roots aids in water absorption from all sides.
  • Example: Sunflower stem bundles are ring-shaped for mechanical strength, unlike its roots.
Critical Evaluation

The textbook explains this divergence as a functional adaptation for support (stems) and absorption (roots).

Question 19:
A botanist noted annual rings in a tree trunk. Explain their formation and significance. How can they indicate climate changes?
Answer:
Case Deconstruction

Annual rings form due to seasonal activity of vascular cambium, producing light (spring) and dark (autumn) wood layers.

Theoretical Application
  • Wider rings indicate favorable growth conditions (e.g., high rainfall).
  • Example: Bristlecone pine rings help reconstruct past climates.
Critical Evaluation

Our textbook correlates ring patterns with historical droughts, proving their utility in dendrochronology.

Question 20:

Rahul observed a transverse section of a dicot stem under a microscope and noticed the following features:

  • Presence of epidermis with cuticle
  • Well-developed cortex with hypodermis
  • Distinct vascular bundles arranged in a ring

Based on these observations, answer the following:

(a) Why is the cuticle important for the stem?

(b) How does the arrangement of vascular bundles differ in a monocot stem?

Answer:

(a) The cuticle is a waxy layer present on the epidermis of the stem. It plays a crucial role in:

  • Preventing water loss by reducing transpiration.
  • Protecting the stem from mechanical injury and pathogens.

(b) In a monocot stem, the vascular bundles are scattered throughout the ground tissue and are not arranged in a ring like in dicot stems. Additionally, monocot vascular bundles are closed (lack cambium), whereas dicot bundles are open (have cambium for secondary growth).

Question 21:

A student was studying the anatomy of a dicot root and made the following observations:

  • Outermost layer is epiblema with root hairs
  • Central stele surrounded by pericycle
  • Xylem is exarch and tetrarch

Answer the following:

(a) What is the function of root hairs in the epiblema?

(b) Explain the significance of exarch condition of xylem in roots.

Answer:

(a) The root hairs in the epiblema serve the following functions:

  • Absorption of water and minerals from the soil due to increased surface area.
  • Anchoring the plant firmly in the soil.

(b) The exarch condition means the protoxylem (first-formed xylem) is located towards the periphery, and the metaxylem (later-formed xylem) is towards the center. This arrangement is significant because:

  • It helps in efficient water conduction from the root hairs to the central xylem.
  • Provides mechanical strength to the growing root tip.
Question 22:

Rahul observed a transverse section of a dicot stem under a microscope and noticed the following features:
1. Presence of vascular bundles arranged in a ring.
2. Cambium present between xylem and phloem.
3. Large pith in the center.
Based on these observations, answer the following:
a) Why are the vascular bundles arranged in a ring in dicot stems?
b) What is the role of cambium in secondary growth?

Answer:

a) Arrangement of vascular bundles in a ring:
The vascular bundles in dicot stems are arranged in a ring to provide mechanical strength and support to the growing plant.
Vascular bundles contain xylem (for water transport) and phloem (for food transport).
The ring-like arrangement ensures efficient distribution of nutrients and structural stability for secondary growth.

b) Role of cambium in secondary growth:
Cambium is a lateral meristem responsible for secondary growth in dicot stems.
It produces secondary xylem (wood) towards the inner side and secondary phloem towards the outer side.
This leads to an increase in stem girth, allowing the plant to grow taller and support more branches and leaves.

Question 23:

Priya was studying the anatomy of a monocot root and made the following observations:
1. Epidermis with root hairs for absorption.
2. Large cortex with parenchyma cells.
3. Endodermis with Casparian strips.
4. Pith is large and well-developed.
Answer the following:
a) How do root hairs enhance water absorption?
b) What is the significance of Casparian strips in the endodermis?

Answer:

a) Role of root hairs in water absorption:
Root hairs are extensions of the epidermis that increase the surface area for absorption.
They absorb water and minerals from the soil through osmosis and active transport.
The thin walls of root hairs allow efficient movement of water into the root.

b) Significance of Casparian strips:
Casparian strips are thickenings of suberin in the endodermal cell walls.
They block the apoplastic pathway, forcing water and minerals to pass through the cytoplasm of endodermal cells.
This ensures selective absorption and prevents harmful substances from entering the vascular tissue.

Question 24:
A student observed a transverse section of a dicot stem under a microscope and noted the presence of vascular bundles arranged in a ring. Explain the significance of this arrangement and how it differs from a monocot stem.
Answer:

The ring-like arrangement of vascular bundles in a dicot stem is significant because it provides mechanical strength and efficient transport of water, minerals, and food.

Key differences from monocot stems:

  • In dicots, vascular bundles are arranged in a ring, whereas in monocots, they are scattered throughout the ground tissue.
  • Dicot stems have cambium (for secondary growth), while monocots lack it.
  • Dicot vascular bundles are open (capable of secondary growth), while monocot bundles are closed.

This arrangement in dicots supports greater structural stability and allows for secondary growth, making the stem thicker over time.

Question 25:
While studying the anatomy of a leaf, a student noticed that the mesophyll tissue is differentiated into palisade and spongy parenchyma. Describe the functions of these tissues and how their structure aids in photosynthesis.
Answer:

The palisade parenchyma and spongy parenchyma are specialized tissues in the mesophyll layer of leaves, each playing a crucial role in photosynthesis.

Palisade parenchyma:

  • Located just below the upper epidermis, it consists of tightly packed, columnar cells.
  • Contains a high number of chloroplasts to maximize light absorption.
  • Primary site for light-dependent reactions of photosynthesis.
Spongy parenchyma:
  • Found below the palisade layer, it has loosely arranged cells with air spaces.
  • Facilitates gas exchange (CO2 in, O2 out) due to large intercellular spaces.
  • Supports light-independent reactions (Calvin cycle) by allowing efficient diffusion of gases.

Together, these tissues optimize photosynthesis by ensuring maximum light absorption and efficient gas exchange.

Question 26:
A student observed a transverse section of a dicot stem under a microscope and identified the following tissues: epidermis, cortex, pericycle, vascular bundles, and pith. Explain the role of each of these tissues in the stem's structure and function.
Answer:

The epidermis is the outermost protective layer covered with a cuticle to prevent water loss.
The cortex consists of parenchyma cells that store food and provide mechanical support.
The pericycle is involved in secondary growth and forms part of the vascular cambium.
Vascular bundles are arranged in a ring and contain xylem (water transport) and phloem (food transport).
The pith, located at the center, stores nutrients and aids in structural support.

Question 27:
In an experiment, a student compared the anatomy of a monocot root and a dicot root. Highlight the key differences observed in their vascular bundles, pith, and pericycle.
Answer:

Vascular bundles: In monocot roots, they are numerous and arranged in a ring, whereas in dicot roots, they are fewer (2-6) and radial.
Pith: Monocot roots have a large, well-developed pith, while dicot roots usually lack a prominent pith.
Pericycle: In dicot roots, the pericycle gives rise to lateral roots and cork cambium, but in monocots, it mainly forms lateral roots only.

These differences reflect their adaptation to different growth patterns and functions.

Question 28:
A student observed a transverse section of a dicot stem under a microscope and noted the presence of vascular bundles arranged in a ring. Explain the significance of this arrangement and how it differs from a monocot stem.
Answer:

The ring-like arrangement of vascular bundles in a dicot stem is significant because it provides mechanical strength and efficient transport of water, minerals, and food.

Key differences from monocot stems:

  • In dicots, vascular bundles are arranged in a ring, whereas in monocots, they are scattered.
  • Dicot stems have cambium between xylem and phloem, allowing secondary growth, while monocots lack cambium.
  • Dicot stems show clear differentiation into cortex, pith, and vascular bundles, unlike monocots.

This arrangement in dicots supports secondary growth, leading to thicker stems over time, which is absent in monocots.

Question 29:
While studying the anatomy of a leaf, a student noticed that the stomata were more abundant on the lower epidermis. Explain the adaptive advantage of this feature and describe the role of guard cells in stomatal function.
Answer:

The higher abundance of stomata on the lower epidermis reduces water loss through transpiration as the lower surface is shaded and cooler.

Role of guard cells:

  • Guard cells are kidney-shaped and regulate stomatal opening and closing.
  • They swell due to osmosis when turgid, opening the stomata for gas exchange (CO2 intake and O2 release).
  • They shrink when flaccid, closing the stomata to prevent water loss.

This adaptation balances photosynthesis and water conservation, crucial for plant survival in varying environments.

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