Class 11 Biology NCERT Notes- Chapter 6: Anatomy of Flowering Plants

Detailed Study Notes – Chapter 6: Anatomy of Flowering Plants ( Class 11 Biology, Notes, PDFs, Quizzes, MCQs)

1. Introduction to Plant Anatomy

Plant anatomy is the study of the internal structure of plants. The fundamental unit of a plant is the cell. Cells are organized into tissues, which in turn are organized into organs like roots, stems, and leaves. The internal structure of these organs can vary significantly, not only between different organs but also between major plant groups like monocotyledons (monocots) and dicotyledonous (dicots). These internal structures also exhibit adaptations to diverse environmental conditions.

2. The Tissue Systems

Based on structure and location, plant tissues are categorized into three major systems:

1. Epidermal Tissue System: The outer protective covering of the plant.
2. Ground (or Fundamental) Tissue System: The bulk of the plant body.
3. Vascular (or Conducting) Tissue System: The transport system of the plant.

2.1 Epidermal Tissue System

This system forms the outermost layer of the entire plant body.

• Components: It comprises epidermal cells, stomata, and epidermal appendages (trichomes and hairs).
• Epidermis:
  • Structure: It is the outermost layer of the primary plant body, typically a single, continuous layer of elongated, compactly arranged parenchymatous cells. These cells contain a small amount of cytoplasm lining the cell wall and a large vacuole.
  • Cuticle: The outside of the epidermis is often coated with a waxy, thick layer called the cuticle, which prevents water loss. The cuticle is absent in roots.
• Stomata:
  • Function: These structures, found in the leaf epidermis, regulate transpiration and gaseous exchange.
  • Structure: Each stoma consists of a stomatal pore enclosed by two specialized cells called guard cells.
    • Guard Cells: In most plants, they are bean-shaped. In grasses, they are dumb-bell shaped. Their outer walls (away from the pore) are thin, while the inner walls (towards the pore) are highly thickened. Guard cells contain chloroplasts and control the opening and closing of the pore.
  • Subsidiary Cells: These are specialized epidermal cells found near the guard cells, differing in shape and size.
  • Stomatal Apparatus: This collective term refers to the stomatal aperture (pore), the guard cells, and the surrounding subsidiary cells.
• Epidermal Appendages:
  • Root Hairs: These are unicellular elongations of epidermal cells in the roots. Their primary function is to absorb water and minerals from the soil.
  • Trichomes: These are epidermal hairs on the stem, part of the shoot system. They are typically multicellular, can be branched or unbranched, soft or stiff, and may be secretory. Trichomes help prevent water loss from transpiration.

2.2 The Ground Tissue System

This system includes all tissues of the plant body except for the epidermis and the vascular bundles.

• Composition: It consists of simple tissues like parenchyma, collenchyma, and sclerenchyma.
• Location:
  • In primary stems and roots, parenchymatous cells form the cortex, pericycle, pith, and medullary rays.
  • In leaves, the ground tissue is called mesophyll, which consists of thin-walled, chloroplast-containing cells responsible for photosynthesis.

2.3 The Vascular Tissue System

This system is composed of the complex tissues, xylem and phloem, which are responsible for conduction.

• Vascular Bundles: Xylem and phloem are found together in structures called vascular bundles.
• Types of Vascular Bundles:
  • Open vs. Closed:
    • Open: Found in dicot stems, these bundles have a layer of cambium between the xylem and phloem. This cambium allows for the formation of secondary xylem and phloem, enabling secondary growth.
    • Closed: Found in monocots, these bundles lack cambium. Consequently, they do not form secondary tissues and cannot undergo secondary growth.
  • Arrangement:
    • Radial: Found in roots, xylem and phloem are arranged in an alternating pattern on different radii.
    • Conjoint: Common in stems and leaves, xylem and phloem are situated together along the same radius. Typically, the phloem is located on the outer side of the xylem.

3. Anatomy of Dicot vs. Monocot Plants

3.1 Dicotyledonous Root (e.g., Sunflower)

• Epiblema: The outermost layer, with some cells forming unicellular root hairs.
• Cortex: Composed of multiple layers of thin-walled parenchyma cells with intercellular spaces.
• Endodermis: The innermost layer of the cortex. It is a single layer of barrel-shaped cells without intercellular spaces. Their tangential and radial walls have a waxy, water-impermeable suberin deposition called Casparian strips.
• Stele: All tissues internal to the endodermis constitute the stele.
  • Pericycle: A few layers of thick-walled parenchymatous cells just inside the endodermis. Lateral roots and vascular cambium originate here during secondary growth.
  • Vascular Bundles: Typically two to four (diarch to tetrarch) patches of xylem and phloem arranged radially.
  • Conjunctive Tissue: Parenchyma cells located between the xylem and phloem bundles.
  • Pith: The central core is small or inconspicuous.
  • Cambium Ring: Develops later between the primary xylem and phloem.

3.2 Monocotyledonous Root

• Similarities to Dicot Root: Possesses an epidermis, cortex, endodermis, pericycle, vascular bundles, and pith.
• Key Differences:
  • Vascular Bundles: Has more than six (polyarch) xylem bundles.
  • Pith: Is large and well-developed.
  • Secondary Growth: Does not occur.

3.3 Dicotyledonous Stem

• Epidermis: The outermost protective layer, covered by a thin cuticle. It may have trichomes and a few stomata.
• Cortex: Located between the epidermis and pericycle, it has three zones:
  • Hypodermis: Outer zone, a few layers of collenchymatous cells providing mechanical strength.
  • Cortical Layers: Middle zone, rounded, thin-walled parenchyma cells with conspicuous intercellular spaces.
  • Endodermis: Inner zone, also called the starch sheath because its cells are rich in starch grains.
• Pericycle: Found on the inner side of the endodermis and above the phloem, present as semi-lunar patches of sclerenchyma.
• Vascular Bundles:
  • Arrangement: Arranged in a distinct ring, a key characteristic of dicot stems.
  • Type: Conjoint, open (with cambium), and with endarch protoxylem.
• Medullary Rays: Radially placed parenchymatous cells found between the vascular bundles.
• Pith: A large central area composed of rounded, parenchymatous cells with large intercellular spaces.

3.4 Monocotyledonous Stem

• Hypodermis: Is sclerenchymatous (composed of sclerenchyma).
• Vascular Bundles:
  • Arrangement: Scattered throughout the parenchymatous ground tissue. Peripheral bundles are smaller than the central ones.
  • Type: Conjoint and closed (no cambium).
  • Bundle Sheath: Each bundle is surrounded by a sclerenchymatous bundle sheath.
• Ground Tissue: A large, conspicuous parenchymatous ground tissue fills the stem.
• Other Features: Phloem parenchyma is absent. Water-containing cavities are present within the vascular bundles.

3.5 Dorsiventral (Dicotyledonous) Leaf

• Epidermis: Covers both the upper (adaxial) and lower (abaxial) surfaces and has a conspicuous cuticle. The abaxial epidermis typically has more stomata; the adaxial may have none.
• Mesophyll: The tissue between the two epidermal layers. It contains chloroplasts for photosynthesis and is differentiated into two types of parenchyma:
  • Palisade Parenchyma: Located adaxially (towards the upper surface), consisting of elongated cells arranged vertically and parallel to each other.
  • Spongy Parenchyma: Situated below the palisade layer, extending to the lower epidermis. Cells are oval or round and loosely arranged with numerous large air cavities.
• Vascular System: Includes vascular bundles within the veins and midrib. Veins vary in thickness due to reticulate venation. Each bundle is surrounded by a layer of thick-walled bundle sheath cells.

3.6 Isobilateral (Monocotyledonous) Leaf

• Epidermis: Stomata are present on both the adaxial and abaxial surfaces.
• Mesophyll: Is not differentiated into palisade and spongy parenchyma.
• Bulliform Cells: In grasses, some adaxial epidermal cells along the veins are modified into large, empty, colorless cells. When turgid, they keep the leaf surface exposed; when flaccid due to water stress, they cause the leaf to curl inwards to minimize water loss.
• Vascular System: Parallel venation is reflected in the near-similar sizes of vascular bundles (except in main veins).

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II. Quiz

Short-Answer Questions (Answer in 2-3 sentences)

1. What is plant anatomy and what is the basic organizational hierarchy in plants?
2. Name the three types of tissue systems in flowering plants.
3. Describe the structure and function of the cuticle.
4. What two processes are regulated by stomata?
5. Differentiate between the guard cells of a typical plant and those found in grasses.
6. What constitutes the stomatal apparatus?
7. Distinguish between root hairs and trichomes in terms of structure and location.
8. What is the ground tissue system composed of, and what is it called in leaves?
9. Explain the difference between open and closed vascular bundles.
10. Describe a radial arrangement of vascular bundles and state where it is found.
11. What are Casparian strips and where are they located?
12. What is the function of the pericycle in a dicot root?
13. How does the number of xylem bundles differ between monocot and dicot roots?
14. What is the stele?
15. What tissue provides mechanical strength to a young dicot stem and where is it located?
16. Why is the endodermis in a dicot stem also called the starch sheath?
17. Describe the characteristic arrangement of vascular bundles in a dicot stem.
18. What is a key feature of the hypodermis in a monocot stem?
19. Name two features of vascular bundles in monocot stems that differ from those in dicot stems.
20. Differentiate between the mesophyll of a dicot leaf and a monocot leaf.
21. Compare the distribution of stomata on a dorsiventral (dicot) and an isobilateral (monocot) leaf.
22. What are bulliform cells and what is their function?
23. What type of venation leads to variation in the size of vascular bundles in dicot leaves?
24. What are medullary rays?
25. Why do monocot roots not undergo secondary growth?

Multiple-Choice Questions (MCQ)

1. The study of the internal structure of plants is called: a) Morphology b) Physiology c) Anatomy d) Taxonomy
2. Which of the following is NOT part of the epidermal tissue system? a) Stomata b) Trichomes c) Pericycle d) Epidermal cells
3. The waxy layer on the epidermis that prevents water loss is the: a) Suberin b) Cuticle c) Periderm d) Cambium
4. In grasses, the guard cells are: a) Bean-shaped b) Dumb-bell shaped c) Round d) Elongated
5. Unicellular elongations of epidermal cells that absorb water from the soil are: a) Trichomes b) Stomata c) Lenticels d) Root hairs
6. All tissues except the epidermis and vascular bundles constitute the: a) Vascular tissue b) Ground tissue c) Meristematic tissue d) Dermal tissue
7. Open vascular bundles are characterized by the presence of: a) Phloem b) Xylem c) Cambium d) Sclerenchyma
8. In roots, the arrangement where xylem and phloem are on different radii is called: a) Conjoint b) Collateral c) Radial d) Bicollateral
9. Casparian strips, made of suberin, are found in the: a) Epidermis b) Cortex c) Endodermis d) Pericycle
10. Lateral roots originate from the: a) Cortex b) Endodermis c) Pith d) Pericycle
11. A monocot root is characterized by having: a) Two to four xylem bundles b) A small pith c) More than six (polyarch) xylem bundles d) Secondary growth
12. The “ring” arrangement of vascular bundles is a characteristic feature of a: a) Dicot stem b) Monocot stem c) Dicot root d) Monocot root
13. The hypodermis of a dicot stem is composed of: a) Parenchyma b) Sclerenchyma c) Collenchyma d) Xylem
14. In a monocot stem, the vascular bundles are: a) Arranged in a ring and open b) Scattered and open c) Arranged in a ring and closed d) Scattered and closed
15. The tissue between the upper and lower epidermis in a leaf is the: a) Cortex b) Pericycle c) Pith d) Mesophyll
16. In a dorsiventral leaf, the palisade parenchyma is located on the: a) Abaxial surface b) Adaxial surface c) Surrounding the veins d) In the midrib only
17. The mesophyll is NOT differentiated into palisade and spongy parenchyma in a: a) Sunflower leaf b) Mango leaf c) Monocot leaf d) Dicot leaf
18. Large, empty, colorless cells that help in the curling of grass leaves are called: a) Subsidiary cells b) Companion cells c) Bulliform cells d) Guard cells
19. All tissues on the inner side of the endodermis in a root are collectively called the: a) Cortex b) Stele c) Pith d) Medulla
20. Phloem parenchyma is absent in the vascular bundles of a: a) Dicot stem b) Dicot root c) Monocot stem d) Monocot root

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III. Answer Keys

Answer Key: Short-Answer Questions

1. Plant anatomy is the study of the internal structure of plants. The basic organizational hierarchy is cells organized into tissues, and tissues organized into organs.
2. The three tissue systems are the epidermal tissue system, the ground tissue system, and the vascular tissue system.
3. The cuticle is a waxy, thick layer covering the outside of the epidermis. Its primary function is to prevent water loss; it is absent in roots.
4. Stomata regulate the process of transpiration (water loss) and gaseous exchange between the plant and the atmosphere.
5. In a typical plant, guard cells are bean-shaped. In grasses, they are distinctively dumb-bell shaped.
6. The stomatal apparatus consists of the stomatal aperture (pore), the two guard cells that enclose it, and the surrounding specialized subsidiary cells.
7. Root hairs are unicellular elongations of root epidermal cells for absorption. Trichomes are typically multicellular hairs found on the stem that help prevent water loss.
8. The ground tissue system is composed of simple tissues like parenchyma, collenchyma, and sclerenchyma. In leaves, this tissue is called mesophyll and contains chloroplasts for photosynthesis.
9. Open vascular bundles, found in dicots, contain cambium, which allows for secondary growth. Closed vascular bundles, found in monocots, lack cambium and thus cannot undergo secondary growth.
10. A radial arrangement is when xylem and phloem are located on different radii in an alternating pattern. This type of arrangement is found in roots.
11. Casparian strips are depositions of a water-impermeable, waxy material called suberin. They are located on the tangential and radial walls of the endodermal cells in roots.
12. The pericycle in a dicot root is the site of initiation for lateral roots and the vascular cambium during secondary growth.
13. Dicot roots usually have two to four (diarch to tetrarch) xylem bundles. Monocot roots typically have more than six (polyarch) xylem bundles.
14. The stele refers to all tissues located internal to the endodermis in a root or stem. This includes the pericycle, vascular bundles, and pith.
15. The hypodermis, which is composed of a few layers of collenchymatous cells, provides mechanical strength to the young dicot stem. It is located just below the epidermis.
16. The endodermis in a dicot stem is called the starch sheath because its cells are rich in starch grains.
17. The vascular bundles in a dicot stem are arranged in a ring. This ring-like formation is a distinguishing characteristic of dicot stems.
18. The hypodermis in a monocot stem is sclerenchymatous, meaning it is composed of sclerenchyma cells, providing rigid support.
19. Vascular bundles in monocot stems are closed (lacking cambium) and are scattered throughout the ground tissue. They are also surrounded by a sclerenchymatous bundle sheath.
20. In a dicot leaf, the mesophyll is differentiated into an upper palisade parenchyma and a lower spongy parenchyma. In a monocot leaf, the mesophyll is undifferentiated.
21. In a dorsiventral (dicot) leaf, stomata are more numerous on the lower (abaxial) surface. In an isobilateral (monocot) leaf, stomata are present on both surfaces.
22. Bulliform cells are large, empty, colorless epidermal cells found along the veins in grasses. They become flaccid during water stress, causing the leaf to curl inwards to minimize water loss.
23. The reticulate venation pattern in dicot leaves results in veins of varying thickness. Consequently, the vascular bundles within them are also of different sizes.
24. Medullary rays are radially placed parenchymatous cells located in the spaces between the vascular bundles in a dicot stem.
25. Monocot roots do not undergo secondary growth because their vascular bundles are closed, meaning they lack a vascular cambium to produce secondary tissues.

Answer Key: Multiple-Choice Questions (MCQ)

1. c) Anatomy
2. c) Pericycle
3. b) Cuticle
4. b) Dumb-bell shaped
5. d) Root hairs
6. b) Ground tissue
7. c) Cambium
8. c) Radial
9. c) Endodermis
10. d) Pericycle
11. c) More than six (polyarch) xylem bundles
12. a) Dicot stem
13. c) Collenchyma
14. d) Scattered and closed
15. d) Mesophyll
16. b) Adaxial surface
17. c) Monocot leaf
18. c) Bulliform cells
19. b) Stele
20. c) Monocot stem

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IV. Essay Questions and Model Answers

1. Describe the epidermal tissue system in detail, including its components and their functions.

• Answer: The epidermal tissue system forms the outermost, protective covering of the whole plant body. It consists of three main components: epidermal cells, stomata, and epidermal appendages. The epidermis itself is usually a single, continuous layer of compactly arranged, elongated parenchymatous cells with a large vacuole. Its outer surface is often covered by a waxy cuticle that prevents water loss, though this is absent in roots. Stomata are pores in the epidermis, primarily on leaves, that regulate transpiration and gas exchange. Each stoma is enclosed by two guard cells (bean-shaped or dumb-bell shaped in grasses) that control its opening and closing. The stomatal pore, guard cells, and surrounding subsidiary cells together form the stomatal apparatus. Finally, epidermal appendages include unicellular root hairs, which absorb water and minerals, and multicellular trichomes on the stem, which help reduce water loss.

2. Compare and contrast the internal structure of a dicot root and a monocot root.

• Answer: The internal structures of dicot and monocot roots share many features, including an outer epidermis (epiblema), a cortex, an endodermis with Casparian strips, a pericycle, vascular bundles, and a central pith. However, they exhibit key differences. The primary distinction lies in the vascular cylinder. A dicot root typically has a small number of xylem bundles, usually two to four (diarch to tetrarch), while a monocot root has many, usually more than six (polyarch). Another major difference is the pith; in dicot roots, the pith is very small or inconspicuous, whereas in monocot roots, it is large and well-developed. Finally, dicot roots can undergo secondary growth due to the later development of a cambium ring, while monocot roots lack this capability and do not have secondary growth.

3. Provide a detailed anatomical description of a young dicotyledonous stem.

• Answer: A transverse section of a young dicot stem reveals several distinct zones. The outermost layer is the epidermis, covered with a cuticle and possibly bearing trichomes and stomata. Beneath this lies the cortex, which is divided into three sub-zones: an outer hypodermis of collenchymatous cells for mechanical support, middle cortical layers of parenchyma with intercellular spaces, and an inner endodermis rich in starch grains (the starch sheath). Internal to the endodermis is the pericycle, present as semi-lunar patches of sclerenchyma above the phloem. The most characteristic feature is the arrangement of vascular bundles in a ring. Each vascular bundle is conjoint (xylem and phloem together), open (containing cambium for secondary growth), and has endarch protoxylem. Between the vascular bundles are medullary rays of parenchyma. The central portion of the stem is occupied by a large pith composed of parenchymatous cells with large intercellular spaces.

4. Explain the key anatomical differences between a monocotyledonous stem and a dicotyledonous stem.

• Answer: Monocot and dicot stems differ significantly in their internal anatomy. In a dicot stem, the vascular bundles are arranged in a distinct ring, are open (contain cambium), and the cortex is well-differentiated into a collenchymatous hypodermis, parenchyma, and an endodermis. In contrast, a monocot stem has vascular bundles that are scattered throughout the ground tissue, are closed (lack cambium), and each is surrounded by a sclerenchymatous bundle sheath. The hypodermis of a monocot stem is sclerenchymatous, not collenchymatous. Furthermore, monocot stems lack a differentiated cortex and pith, having instead a large, continuous ground tissue. Lastly, phloem parenchyma is absent and water-containing cavities are often present in the vascular bundles of monocot stems.

5. Describe the structure of a dorsiventral leaf, detailing the arrangement and function of its tissues.

• Answer: A dorsiventral (dicot) leaf has three main parts: epidermis, mesophyll, and a vascular system. The epidermis covers the upper (adaxial) and lower (abaxial) surfaces, with the lower surface typically bearing more stomata for gas exchange. The entire leaf is covered by a protective cuticle. The tissue between the epidermal layers is the mesophyll, which is differentiated into two layers for photosynthesis. The adaxial palisade parenchyma consists of elongated, vertically arranged cells packed with chloroplasts, maximizing light absorption. Below this is the spongy parenchyma, with loosely arranged, irregularly shaped cells and large air spaces that facilitate gas diffusion to the palisade cells. The vascular system consists of vascular bundles located in the veins and midrib, surrounded by a thick-walled bundle sheath. This system transports water and minerals to the mesophyll and carries away sugars produced during photosynthesis.

6. What are the three types of vascular bundle arrangements based on the presence of cambium and the position of xylem and phloem? Provide examples of where each is found.

• Answer: Vascular bundles can be classified based on cambium presence and tissue arrangement. First, they can be open or closed. Open vascular bundles have a strip of cambium between the xylem and phloem, allowing for secondary growth; these are characteristic of dicot stems. Closed vascular bundles lack cambium and cannot undergo secondary growth; these are found in monocots. Second, the arrangement can be radial or conjoint. In a radial arrangement, xylem and phloem lie on different radii in an alternating pattern; this is the typical arrangement in both monocot and dicot roots. In a conjoint arrangement, xylem and phloem are situated on the same radius; this is common in stems and leaves of both monocots and dicots.

7. How do the anatomical features of an isobilateral (monocot) leaf adapt it to its environment, particularly in grasses?

• Answer: The anatomy of an isobilateral leaf shows several adaptations. Unlike dicot leaves, the mesophyll is not differentiated, and stomata are present on both surfaces, which is suitable for leaves that are oriented vertically and receive sunlight on both sides. In grasses, a key adaptation is the presence of bulliform cells. These are large, empty, modified adaxial epidermal cells. When water is plentiful, these cells are turgid and keep the leaf blade flat and exposed to the sun. However, during water stress, the bulliform cells lose turgor and become flaccid, causing the leaf to curl inwards. This curling reduces the exposed surface area, minimizing water loss through transpiration, which is a crucial survival mechanism in dry conditions.

8. Explain the concept of the stele in a dicot root. What tissues does it comprise and what are their functions?

• Answer: In a dicot root, the stele refers to all the tissues located internal to the endodermis. It is the central cylinder of the root. The stele comprises the pericycle, the vascular bundles (xylem and phloem), the conjunctive tissue, and the pith. The outermost layer of the stele is the pericycle, which is composed of parenchymatous cells and is functionally significant as it is the site of origin for lateral roots and the vascular cambium. The vascular bundles contain the xylem for water and mineral conduction and the phloem for transporting sugars. The parenchymatous conjunctive tissue lies between the xylem and phloem bundles. At the very center is the pith, which is often small or absent in dicot roots.

9. Discuss the role of ground tissue in different parts of a plant, such as the stem, root, and leaf.

• Answer: The ground tissue system constitutes the bulk of the plant body and performs various functions depending on its location. In the primary stem and root, parenchymatous ground tissue forms the cortex, pith, and medullary rays, which are primarily involved in food storage and short-distance transport. In a dicot stem, the outer ground tissue (hypodermis) is made of collenchyma for flexible support. In a leaf, the ground tissue is called mesophyll, which is rich in chloroplasts and is the primary site of photosynthesis. The mesophyll is specialized into palisade and spongy parenchyma in dicots to optimize light capture and gas exchange. In monocot stems, the ground tissue is not differentiated and functions mainly for storage while also embedding the scattered vascular bundles.

10. Why is the study of plant anatomy important?

• Answer: The study of plant anatomy is fundamentally important for understanding the relationship between structure and function in plants. It reveals how different tissues are organized to perform essential life processes like photosynthesis, transport, support, and storage. Anatomical studies help in differentiating between plant groups, such as monocots and dicots, which have distinct internal structures. This knowledge is crucial for plant classification and evolutionary studies. Furthermore, understanding plant anatomy shows how plants have adapted to diverse environments, for example, through the development of cuticles to prevent water loss or specialized cells like bulliform cells. This information can be practically applied in fields like agriculture, horticulture, and forestry to improve crop yields and manage plant health.

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V. Glossary of Key Terms

Term	Definition
Abaxial Epidermis	The lower surface of a leaf.
Adaxial Epidermis	The upper surface of a leaf.
Anatomy	The study of the internal structure of organisms.
Bulliform Cells	Large, empty, colorless epidermal cells in grasses that control leaf curling in response to water stress.
Bundle Sheath	A layer of cells (parenchymatous or sclerenchymatous) that surrounds a vascular bundle.
Cambium	A layer of meristematic tissue between xylem and phloem in open vascular bundles, responsible for secondary growth.
Casparian Strips	A band of waxy, water-impermeable material (suberin) in the radial and tangential walls of endodermal cells.
Closed Vascular Bundle	A vascular bundle that lacks cambium and therefore cannot undergo secondary growth. Common in monocots.
Collenchyma	A simple tissue composed of cells with unevenly thickened walls, providing flexible mechanical support.
Conjoint Vascular Bundle	A vascular bundle where xylem and phloem are located on the same radius. Common in stems and leaves.
Conjunctive Tissue	Parenchymatous cells that lie between the xylem and phloem bundles in roots.
Cortex	The region of ground tissue between the epidermis and the stele in stems and roots.
Cuticle	A waxy, water-resistant layer covering the epidermis of a plant.
Endarch	A pattern of xylem development where the protoxylem is towards the center (pith) and metaxylem is towards the periphery.
Endodermis	The innermost layer of the cortex, often characterized by the presence of Casparian strips.
Epidermal Tissue System	The outermost covering of the plant body.
Epiblema	The outermost layer of cells in a young root.
Ground Tissue System	All tissues of a plant other than the epidermal and vascular tissues.
Guard Cells	A pair of specialized cells that surround a stomatal pore and regulate its opening and closing.
Hypodermis	The layer or layers of cells just beneath the epidermis.
Isobilateral Leaf	A leaf (typical of monocots) in which the mesophyll is not differentiated into palisade and spongy layers and stomata are on both surfaces.
Medullary Rays	Strips of parenchyma cells that extend radially between vascular bundles in a dicot stem.
Mesophyll	The ground tissue of a leaf, located between the epidermal layers, which is the primary site of photosynthesis.
Open Vascular Bundle	A vascular bundle that contains cambium between the xylem and phloem. Common in dicots.
Palisade Parenchyma	A layer of elongated, columnar cells rich in chloroplasts, located under the adaxial epidermis of a dicot leaf.
Parenchyma	A simple tissue composed of thin-walled, living cells that functions in photosynthesis, storage, and secretion.
Pericycle	A layer of cells just inside the endodermis of a root, from which lateral roots and vascular cambium arise.
Phloem	The complex vascular tissue that transports sugars from the leaves to other parts of the plant.
Pith	The central core of parenchyma cells in the stems of dicots and roots of monocots.
Polyarch	A condition in roots where there are many (more than six) strands of xylem.
Radial Vascular Bundle	An arrangement in which xylem and phloem are on different radii, alternating with each other. Found in roots.
Root Hairs	Unicellular extensions of root epidermal cells that increase the surface area for water and mineral absorption.
Sclerenchyma	A simple tissue composed of cells with thick, lignified walls that provides rigid support.
Spongy Parenchyma	A layer of loosely arranged, irregularly shaped cells with large air spaces, located below the palisade layer in a dicot leaf.
Starch Sheath	Another name for the endodermis in a dicot stem, due to its cells being rich in starch grains.
Stele	The central cylinder of a root or stem, containing the vascular tissues, pericycle, and pith (if present).
Stomata	Pores in the epidermis of a plant, each surrounded by two guard cells, that regulate gas exchange and transpiration.
Stomatal Apparatus	The complex consisting of the stomatal pore, guard cells, and surrounding subsidiary cells.
Suberin	A waxy, waterproof substance found in Casparian strips and cork cells.
Subsidiary Cells	Specialized epidermal cells adjacent to guard cells.
Trichomes	Hair-like outgrowths of the epidermis, typically on stems and leaves.
Vascular Tissue System	The tissue system responsible for transport, consisting of xylem and phloem.
Xylem	The complex vascular tissue that transports water and dissolved minerals from the roots to the rest of the plant.