The Eudicot plant, morphology, meristems, cell types and tissues

1. 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

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

3. Figure 8-9 Secondary cell wall Primary cell walls Middle lamella Cell walls consist of 3 types of layers • 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. • 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. • 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.

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

5. Tissues A tissueis 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.

6. Plants comprises three main tissue types each with different functions. 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 There is continuity of these individual tissue systems through the plant Cross sections: Meristematic tissue Leaf Shoot system Dermal tissue system (brown) Ground tissue system (gray) Stem Vascular tissue system (red) Dermal tissue system (brown) Root system Root Ground tissue system (gray) Meristematic tissue Vascular tissue system (red) Figure 36-16

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

8. Figure 36-23

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

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

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

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

13. Meristems-> Tissues Immature leaf shoot apical meristem procambium protoderm procambium ground meristem Meristems Tissues Spiral thickening primary xylem cortex procambium primary pholem pith

15. Figure 23-7 Cotyledons Hypocotyl Root Wild-type seedling Central mutant Basal mutant Apical 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.

16. Regulation of developmental pathways 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

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

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

19. Table 36-1 b z x w

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

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

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

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

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

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

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

27. Things you need to know ... 1. The structure of cell walls and how communication between plant cells may take place. 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