1. Meristems and plant structure

2. The plant body Apical Meristems: how the plant grows
Cell walls and plasmodesmata
Some basic cell types not mentioned yet

3. Apical meristems Indeterminate growth e.g., many tomato varieties
e.g., wheat

4. Biennial and determinate plants
Digitalis purpurea
Triticum aestivum
Foxglove is a biennial
Like many grass species wheat is determinate. It produces a fixed number of leaves and a terminal inflorescence
A rosette of leaves is produced close to the ground in the first year of growth

5. Ricinus: Shoot apical meristem
Castor bean

6. Meristems: how tissues are produced
Coleus
Apical meristem
Transverse section through the apical meristem and newly forming leaves
Longitudinal section through the apical meristem

7. Myriophyllum SEM picture
Scanning electron microscope picture
of Myriophyllum apical meristem
The apical dome is usually convex or flat, as in this example, and its surface is smooth.
Myriophyllum SEM picture
Developing leaves cover the apex
Most recently budded leaves
Water-milfoil

8. Diagram of shoot apical growth
Cell division
Elongation zone
Differentiation of vascular tissue

9. Coleus Auxiliary bud meristem
The auxiliary meristem may develop into a foliated branch.

10. Equisetum shoot apex with a single apical cell
Equisetum meristem
The organization of the meristem is different from Coleus

11. Root apical meristem

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

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

14. … structural carbohydrates?

15. Cellulose

16. Cell walls and plasmodesmata

17. Microfibers
Electron microscope picture of cellulose-microfibrils in the wall of the green alga Oozystis solitaria
Growing plant cells expand through water uptake. In a growing cell enzymes weaken cross-links between the cellulose microfibres of the cell wall allowing it to expand as water flows in by osmosis.

18. Plasmodesmata
Plasmodesmata

19. Plasmodesmata seen in Section through the cell wall: They are not simple openings but have a complex internal structure.

20. Some basic cell types 1. Parenchyma 2. Collenchyma 3. Sclerids
4. Bulliform cells

21. 1. Parenchyma Note the nucleus and chloroplasts
Young parenchyma tissue cut parallel with the epidermis of Euphorbia pulcherrima (poinsettia). Note the cell contents.  

22. 2. Collenchyma
Collenchyma is the typical supporting tissue of the primary plant body.
It develops from parenchyma.
The cell walls are unevenly thickened.
It is common in organs like stems, petioles, laminae or roots.
Apium petiole, collenchyma  
Apium is celery – and it is the petiole that you eat!

23. Fig 31.5 B and C

24. 3. Sclerids
Thickening of the cell wall
Sclerenchyma cells are the principal supporting cells in plant parts that have ceased elongation. Sclerenchyma fibres are the source material for many fabrics, e.g., flax, hemp and jute.
Parenchyma
Developing sclerid

25. A sclerid with the cell completely occupied by wall
Contrary to collenchyma mature sclerenchyma is composed of dead cells with extremely thick cell walls (secondary walls) that make up to 90% of the whole.
Leaf of Podocarpus
Note the wall laminations and the Pits around 3 & 5 o'clock. Viewed with polarized light

26. Fig 31. D

27. turgor pressure?

28. Bulliform cells Transverse section of grass leaf Poa praetense.
During drought water is lost from the thin walled bulliform cells and the two sides of the leaf blade fold up toward each other so the leaf is less exposed to sunlight and is heated less.
Once adequate water is available, turgor increases, and the leaves open again.

29. Sections you need to have read
4.19, through 31.8
Courses that deal with this topic
Botany 441 Morphology and anatomy of land plants