2.5 : Cells are grouped into tissue

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1 2.5 : Cells are grouped into tissue 1

2 CELL STRUCTURE AND FUNCTIONS Prokaryotic and eukaryotic cells Structures & functions: Cell membrane and organelles Animal Cells are grouped into tissue Plant Cell transport Microscopic structures of plant and animal cell Epithelial Nerve Muscle Connective Meristem Parenchyma Collenchyma Sclerenchyma Xylem Phloem

3 (B) Plant cells 3

4 Learning Outcome: AT THE END OF THIS TOPIC, STUDENTS SHOULD BE ABLE TO: Describe the structure, function and distribution following types of cells and tissues: Plant - meristem, parenchyma, collenchyma, sclerenchyma, xylem and phloem. 4

5 PLANT TISSUE MERISTEMATIC TISSUE PERMANENT TISSUE PARENCHYMA COLLENCHYMA SCLERENCHYMA XYLEM PHLOEM 5

6 PLANT GROWTH MERISTEM CELL Plant Grow continuously throughout the plant s life. Structure Meristematic tissues central large nucleus small vacuoles dense cytoplasm Small, thin-walled 6

7 CHARACTERISTIC MERISTEM CELL 1. Small, thin-walled 2. Have a central large nucleus 3. dense cytoplasm 4. small vacuoles. 5. Closely packed with no intercellular air space. 6. Actively divide by mitosis, generating additional cell. 7. Unspecialized 7

8 CHARACTERISTIC MERISTEM CELL Mitotic division Derivatives Displaced from meristem Differentiate and incorporated into tissues & organs of the growing plants. initial cells Remain as meristem Produce more cells. Mitotic division 8

9 TYPES & DISTRIBUTION MERISTEM CELL i) Apical meristem Located in root tips and shoot buds Axillary buds ii) Lateral meristems Located around the outer edge of stem & root Vascular cambium & cork cambium 9

10 FUNCTION Apical Meristem MERISTEM CELL Provide additional cells Enable plant to grow in length [Primary Growth] Root allow roots to extend throughout the soil Shoot increase shoots exposure to light. A group of cells which retain the ability to divide by mitosis Lateral Meristem Vascular cambium Add layers of vascular tissue Cork cambium replaces the epidermis with thicker, tougher periderm. 10

11 FUNCTION MERISTEM CELL 11

12 PLANT TISSUE MERISTEMATIC TISSUE PERMANENT TISSUE PARENCHYMA COLLENCHYMA SCLERENCHYMA XYLEM PHLOEM 12

13 TYPES AND SPECIALISED CELL: PLANT Each type of plant cell has structural adaptations that make specific functions possible. Cellular differentiation involve changes both in the cytoplasm and its organelles and in the cell wall. Modifications of cell walls are also important in how the specialized cells of a plant function. 13

14 Cell Wall TYPES AND SPECIALISED CELL: PLANT An adhesive layer, the middle lamella, cements together the cells wall of adjacent cells. The primary cell wall is secreted as the cell grows. Some cells have secondary walls which develop after a cell stops growing. 14

15 PLANT TISSUE TYPES AND SPECIALISED CELL: PLANT Ground Tissues are composed of three basic cell types: - parenchyma cells - collenchyma cells - sclerenchyma cells 15

TYPES OF BASIC CELL TYPES AND SPECIALISED CELL: PLANT PARENCHYMA STRUCTURE : Nucleus present Usually isodiametric or elongated Thin cell wall (primary wall) containing cellulose, hemicellulose &

16 TYPES OF BASIC CELL TYPES AND SPECIALISED CELL: PLANT PARENCHYMA STRUCTURE : Nucleus present Usually isodiametric or elongated Thin cell wall (primary wall) containing cellulose, hemicellulose & pectin Have a large central vacuole Have a thin layer of cytoplasm pushed to the periphery Cells are loosely packed together/ have large intercellular space Least specialized srtucturally. Major component of ground tissues. 16

17 TYPES OF BASIC CELL TYPES AND SPECIALISED CELL: PLANT PARENCHYMA Function : Perform most of metabolic function of plant, synthesizing and storing various organic products. Contain chloroplast for photosynthesis chlorenchyma Containain colourless plastid for starch storages. [stem & root] Contain chromoplast to attarct polinating agents. Large intercellular spaces for gas exchange 17

18 TYPES OF BASIC CELL TYPES AND SPECIALISED CELL: PLANT PARENCHYMA Function : Perform most of metabolic function of plant, synthesizing and storing various organic products. Retain the ability to divide and differentiate into other types of plant cells. epidermis, mesophyll, endodermis, pericycle, aerenchyma and secretory cells. Can form secondary meristematic tissue Vascular cambium and cork cambium. 18

TYPES OF BASIC CELL TYPES AND SPECIALISED CELL: PLANT COLLENCHYMA STRUCTURE : Nucleus present Polygonal-shaped and elongated Cells are closely packed /

19 TYPES OF BASIC CELL TYPES AND SPECIALISED CELL: PLANT COLLENCHYMA STRUCTURE : Nucleus present Polygonal-shaped and elongated Cells are closely packed / no or little intercellular space Cell wall (primary wall) unevenly thickened with cellulose, pectin and hemicellulose Pits are present between cell wall 19

20 TYPES OF BASIC CELL TYPES AND SPECIALISED CELL: PLANT COLLENCHYMA Function : Supporting tissue for young parts of plant (shoot,stem,leaf)/ herbaceous plant Provide flexible support without restraining growth. lack secondary cell wall, absent of hardening agents lignin in primary wall. Giving strength Giving flexibility 20

21 TYPES OF BASIC CELL TYPES AND SPECIALISED CELL: PLANT SCLERENCHYMA STRUCTURE : Has thick secondary cell wall containing lignin No nucleus when mature Elongated with tapering end (almost spherical) Has small lumen (pits) No intracellular space / cells closely packed 21

22 TYPES OF BASIC CELL TYPES AND SPECIALISED CELL: PLANT SCLERENCHYMA Function : As supporting elements of the plant Strengtening by lignin, specialized for support 22

23 TYPES SCLERENCHYMA 1) FIBER - Fibers are long, slender and tapered, and usually occur in groups. -Those from hemp fibers are used for making rope and those from flax for weaving into linen. 2) SCLEREIDS - Sclereids, shorter than fibers and irregular in shape, impart the hardness to nutshells and seed coats and the gritty texture to pear fruits. 23

24 24

25 PLANT TISSUE MERISTEMATIC TISSUE PERMANENT TISSUE PARENCHYMA COLLENCHYMA SCLERENCHYMA XYLEM PHLOEM 25

26 INTRODUCTION VASCULAR TISSUE Vascular tissue, continuous throughout the plant, is involved in the transport of materials between roots and shoots. Two types of vascular tissue are: Xylem - conveys water and dissolved minerals upward from roots into the shoots. Phloem - transports food made in mature leaves to the roots and to nonphotosynthetic parts of the shoot system. 26

27 XYLEM The water conducting elements of xylem, the tracheids and vessel elements, are elongated cells that are dead at functional maturity, when these cells are fully specialized for their function. Both tracheids and vessels have secondary walls interrupted by pits, thinner regions where only primary walls are present 27

Tracheids Long, thin cells with tapered ends.

secondary walls are hardened with lignin Function in support as well as

Vessel elements XYLEM Generally wider, shorter, thinner walled, and

28 Tracheids Long, thin cells with tapered ends. Water moves from cell to cell mainly through pits because their secondary walls are hardened with lignin Function in support as well as transport. Vessel elements XYLEM Generally wider, shorter, thinner walled, and less tapered than tracheids. Vessel elements are aligned end to end, forming long micropipes, xylem vessels. The ends are perforated, enabling water to flow freely. 28

29 XYLEM 29

30 PHLOEM In the phloem, sucrose, other organic compounds, and some mineral ions move through tubes formed by chains of cells, sieve-tube members. These are alive at functional maturity, although they lack the nucleus, ribosomes, and a distinct vacuole. The end walls, the sieve plates, have pores that presumably facilitate the flow of fluid between cells. A nonconducting nucleated companion cell, connected to the sieve-tube member, may assist the sieve-tube cell. 30

31 PHLOEM 31

32 End of session Thank you for your attention 32

Topic 2: Plant Structure & Growth Ch. 35 Angiosperms are the most complex plants. They are composed of cells, tissues, organs and organ systems.

Topic 2: Plant Structure & Growth Ch. 35 Angiosperms are the most complex plants. They are composed of cells, tissues, organs and organ systems. Fig. 35.8 Plant Cells pp.798-802 Types of plant cells Include: