2. The Eudicot plant, morphology, meristems, cell types and tissues Objectives of the lecture: 1. To illustrate and name some essential parts of plants, 2. show how they are produced, 3. discuss how cell and tissue structure are integrated with morphology, 4. give examples of some variation in morphology between species. Text book pages: 472-473, 792-808, 800-812

3. Figure 36-19 Plant cells have cell walls, vacuoles, and chloroplasts. Adjacent plant cells are connected by plasmodesmata. Plasma membrane Cell wall Vacuole Chloroplast Mitochondria Rough ER Golgi apparatus Smooth ER Cell 1 Cell 2 Cell wall Smooth ER Cell wall Plasma membrane Plasmodesma Plant cell walls are flexible but have considerable tensile strength Communication between cells is through plasmodesmata

4. Figure 8-9 Cell walls consist of 3 types of layers Secondary cell wall Secondary wall: formed after cell enlargement is completed provides compression strength. It is made of cellulose, hemicellulose and lignin. The secondary wall is often layered. Primary cell walls Primary wall: This is formed after the middle lamella and consists of a skeleton of cellulose microfibrils embedded in a gel-like matrix of pectic compounds, hemicellulose, and glycoproteins. Middle lamella Middle lamella is formed during cell division. It makes up the outer wall of the cell and is shared by adjacent cells. It is composed of pectic compounds and protein.

5. Figure 8-14 Plasmodesmata create gaps that connect plant cells. Tubule of endoplasmic reticulum passing through plasmodesmata Membrane of cell 1 Cell walls Smooth endoplasmic reticulum Membrane of cell 2 Cell wall of cell 1 Cell wall of cell 2 Plasmodesmata seen in Transverse Section: They are not simple openings as they have a complex internal structure.

6. A tissue is a cooperative unit of many similar cells performing a specific function within a multicellular organism Tissues usually have cells that are specialized for particular functions The vascular tissue system conducts water and nutrients from roots to leaves through specialized cells and conducts the products of photosynthesis, sugars, from leaves in different but equally specialized cells. Tissues

7. Figure 36-16 Cross sections: Meristematic tissue Leaf Stem Meristematic tissue Root Vascular tissue system (red) Dermal tissue system (brown) Dermal tissue system (brown) Ground tissue system (gray) Ground tissue system (gray) Vascular tissue system (red) Shoot system Root system Plants comprises three main tissue types each with different functions. There is continuity of these individual tissue systems through the plant Dermal tissue – protection and interface with the environment Ground tissue – frequently the site of storage, sometimes support Vascular tissue – conduction of water and materials used in synthesis

8. lateral (axillary) bud shoot tip (terminal bud) young leaf flower leaf seeds (inside fruit) withered cotyledon root hairs root tip root cap node internode VASCULAR TISSUES GROUND TISSUES SHOOT SYSTEM ROOT SYSTEM primary root lateral root The angiosperm plant body EPIDERMIS Dermal tissue A tomato plant See Fig. 36.3 in your text book

9. Figure 36-23

10. new cells elongate and start to differentiate into primary tissues Root cap activity at meristems Shoot apical meristem Actively dividing cells near the dome-shaped tip The apical meristem’s descendant cells divide, grow and differentiate to form: Protoderm Ground meristem Procambium activity at meristems Root apical meristem Function of apical meristems

11. Figure 36-15 Apical meristems and primary meristems in a root Apical meristem and primary meristems in a shoot Leaf primordia Apical meristem at tip of shoot Apical meristem in lateral bud Ground meristem Protoderm Procambium Apical meristem Root cap

12. What does a meristem look like? Coleus Apical meristem Transverse section through the apical meristem and newly forming leaves Longitudinal section through the apical meristem

13. Axilliary bud meristem The axilliary meristem may develop into a foliated branch. Coleus L4 S8

14. Tissues Meristems-> Tissues procambium primary pholem primary xylem pith procambiumcortex Meristems Immature leaf shoot apical meristem ground meristemprocambiumprotoderm Spiral thickening

16. Figure 23-7 Cotyledons Hypocotyl Root Wild-type seedling Apical mutant Central mutant Basal mutant Mutants lacking hypocotyls and roots in Arabidopsis The MONOTERPOS gene encodes a transcription factor that regulates activity of target genes and the MONOTERPOS protein is manufactured in response to signals from auxin which is produced at the apex and occurs in a concentration gradient which provides positional information.

17. The expression of genes that encode transcription factors determines cell, tissue and organ identity The fate of a cell is determined by its position and not its clonal history Developmental pathways are controlled by networks of interacting genes Development is regulated by cell-to-cell signalling Ligand-induced signalling: cell wall component chemicals that communicate local positional information Hormonal signalling: auxin and others Signalling via regulatory proteins and/or mRNAs through plasmodesmata Regulation of developmental pathways

18. Plants of the day Celery Potato Carrot Brussels sprout Cabbage

19. Simple tissues of parenchyma, collenchyma and sclerenchyma Transverse section pholem Important structural tissues of many angiosperms xylem epidermis parenchyma collenchyma sclerenchyma Pages 804- 805 of your text book

20. Table 36-1 w x b z

21. Figure 36-25 Sclereids Fibers Thick secondary cell walls Sclerenchyma

22. Figure 36-24 Cross section of celery stalk Close-up of “string,” in cross section Collenchyma cells, in cross section Collenchyma

23. Figure 36-22 In roots, parenchyma cells function in carbohydrate storage. Chloroplasts In leaves, parenchyma cells function in photosynthesis and gas exchange. Starch granules Parenchyma

24. Figure 36-18 Cortex Cross section of a eudicot stemCross section of a monocot stem Epidermis Pith Ground tissue Vascular bundles

25. Figure 36-17 Root hair Lateral root Vascular tissue Ground tissue Epidermal tissue Apical meristem Sloughed-off root cap cells Root cap Zone of Cellular Maturation Zone of Cellular Elongation Zone of Cellular Division Root meristem and structure Roots must ‘force’ their way through the soil Protection of the apical mersitem Delayed initiation of lateral meristems Different requirements for support and water collection and distribution

26. Zea mays root apex Zea mays root apex showing the junction between root apex and the root cap

27. Lateral root development in Zea mays A meristem develops from parenchyma and the lateral root grows out through the cortex

28. 1. The structure of cell walls and how communication between plant cells may take place. Things you need to know... 2. Be able to define a tissue and give examples of cell types and functions within important tissues of the plant. 3. Define the structure of angiosperm plants. 4. Define the meristems of the angiosperm plant and describe how tissues develop from them