1. Chapter 29 Plant Tissue

2. Overview of the Plant Body
Although no one species of the 295,000 species of plants can be considered typical, the focus here is on angiosperms

3. Shoots and Roots (Figure 29.2)
Shoots consist of stems, leaves, and flowers (reproductive structures)
Water, minerals, and organic substances are transported
Stems are frameworks for upright growth and to display flowers
Parts of the system store food.

4. Continue…
Root system absorbs water and minerals from soil and conducts them upward
Root store food
Anchor and support the plant

5. Three plant tissue system
1- Ground Tissue: makes up the bulk of the plant body (food and water storage)
2- Vascular tissue system: contains two kinds of conducting tissues that distribute water and solutes through the plant body.
3- Dermal Tissue system: covers and protects the plant’s surfaces.

6. Where Do Plant Tissues Originate?
Meristems are localized regions of self-perpetuating, embryonic cells.
Two kinds of meristems
1- Apical meristems: at tips of roots and stems is responsible for growth and elongation
Growth originating at the root and shoot tips is labeled primary growth

7. Continue…
Lateral meristem: are responsible for the increase in diameter of older roots and stems.
Vascular Cambium and cork cambium are two kinds of lateral meristems
These are responsible for secondary growth which adds to wood parts of the trees.

8. Types of Plant Tissues Simple Tissues:
1- Parenchyma makes up most of the soft, moist primary growth of plants
Thin walled pliable cells stay alive and retain the capacity to divide
Various types of participate in photosynthesis (mesophyll), storage, secretion, and other tasks.

9. 2. Collenchyma: cells are thickened and help strengthen the palnt (e.g. strings of celery)
It commonly arranged at strands or cylinders beneath the dermal tissue of stems and stalks
The primary cells walls of collenchyma become thickened with cellulose and pectin at maturity.
3. Sclerenchyma: cells provide mechanical support and protection for mature plants
Secondary walls are thick and often impregnated with lignin, which strengths and waterproofs the cell walls
Form fibers such as hemp and flax
Sclereids form strong coats around seeds as in a peach pit

10. Complex Tissues
Vascular tissues function in the distribution of substances throughout the plant
Xylem uses two kinds of cells (dead at maturity) to conduct water and minerals absorbed from the soil
Vessel members: are shorter cells joined end to end to form a vessel with perforation plates at the end of each member
Tracheids are long cells with tapered, overlapping ends

11. Continue…
Phloem: transports sugar and other solutes throughout the plant body.
Phloem contains living conducting cells called sieve tube members which bear clusters of pores in the walls through which the cytoplasm of adjacent cells is connected
Companion cells: adjacent to the sieve tubes members, help to load sugars produced in leaves and unload them in storage and growth regions

12. Continue…
Dermal Tissue System: called the epidermis covers all primary plant parts
Waxy Cuticle covers the external surfaces of the plant to restrict water loss and resist microbial attack.
Stomata openings between pairs of guard cells permit water and gaseous exchange with the air
Periderm replaces the epidermis when roots and stems increase in diameter and become woody.

13. Monocots and Dicots
Through the rest of chapter we will be talking about monocots and dicots
Moncots have one cotelydons (seed leaf) and Dicots have two cotelydons (seed leaf)
Common monocots include: grasses, lilies, irises and palms.
Common dicots include: trees and shrubs

14. Primary Structure of Shoots
Leaves develop from leaf primordia along the apical meristems of stems
A node is the point where a leaf or leaves attach to the stems
Internode is the region on the stem between the two nodes.

15. Continue…
Buds develop in the leaf axils (the upper angle where leaves attach to the stem)
A bud is underdeveloped shoot of mostly meristematic tissue covered by modified leaves (bud scales)
Buds give rise to stems, leaves, and flowers

16. Internal Structure of Stems
A vascular bundle is a multistranded cord of primary xylem and phloem running lengthwise through the ground tissue of shoots.

17. Similarities and Differences Among Leaves
Leaves are metabolic factories equipped with photosynthetic cells.
Deciduous trees drop their leaves as winter approaches
Evergreen retain their leaves

18. Leaves vary enormously in shape, size, texture, and surface features.
Monocots leaves tend to have a flat surface – like a knife blade, the base of which encircles and sheaths the stems
Dicots leaves have broad blade attached by a petiole to the stem; the blade may be lobed or composed of leaflets
Simple leaves: undivided leaves
Oak
Compound leaves: divided leaflets
Locust
Leaves represent a large surface area that is exposed to sunlight and carbon dioxide

19. Leaf Fine Structure
Epidermis covers every leaf surface exposed to air (waxy layer)
A cuticle layer minimizes water loss.
Stomata are located mostly on the lower epidermis

20. Continue…
Mesophyll consisting of photosynthetic parenchyma cells extends throughout the interior of the leaf
Air spaces, which connect to the stomata, participate in gaseous exchange
Palisade mesophyll cells lies closer to the epidermis and are columnar in shape compared to the spongy mesophyll below them
Leaf veins are vascular bundles of xylem and phloem that form a network for movement of water , solutes, and photosynthetic products

21. Primary Structure of Roots
Taproots and Fibrous Root Systems
In most dicots, the primary root emerges from the seedling, increases in diameter, and grows downward.
Lateral roots emerge sideways along its length
Primary root plus lateral roots form from the taproot system

22. Continue
Monocots: the taproot is replaced by adventitious roots that arise from the stem
The roots and their branching form a fibrous root system
Fibrous roots do not penetrate as deeply.

23. Internal Structure of Roots
Cells in the apical meristem divide and then differentiate into root epidermis, ground tissues, and vascular tissues behind the meristematic region
The root cap protects the apical meristem and pushes through the soil
Cells are torn loose as the root grows

24. Continue…
Protoderm gives rise to the root epidermis with its extensions called root hairs for the outer absorptive interface with the environment
Vascular tissues form a vascular cylinder arranged as a central column
The column is surrounded by root cortex (ground tissue), which has abundant air spaces
The endodermis- the innermost layer of the cortex –surrounds the vascular cylinder and helps control water movement into it

25. Woody and Nonwoody Plants
Seasonal growth cycles proceed from germination, to seed formation to death.
Annuals complete life cycle in one season, they are nonwoody , or herbaceous plants such as corn.
Biennials such as carrots, live two seasons: vegetative growth first , flower and seed formation second season

26. Perennials live many years and have secondary growth (roses, grape vines, and apple trees)
Woody plants such as dicots and gymnosperms show secondary growth by producing large amounts of secondary xylem

27. Vascular Cambium Vascular Cambium is a cylinderlike lateral meristem.
It produces a secondary xylem on its inner face and secondary pholem on its outer.
The secondary growth displace the cells of the vascular cambium toward the stem surface
Secondary xylem and phloem form at the vascular cambium of the roots

28. Formation of Bark
In response to rupture of the outer cortex (by girth expansion), cork cambium produces the periderm – a corky replacement of the epidermis
Periderm and secondary pholoem constitute of bark
Periderm consist of cork, secondary cortex, and cork cambium
Lenticels are small channels through the corky surface of bark that allow for exchange of gases

29. Heartwood and Sapwood
Heartwood lies at the center of older stems and roots.
It depository for resins, oils, gums and tannins
It makes tree strong and able to defy gravity/
Sapwood is secondary growth located between heartwood and the vascular cambium
Wet, pale in color and is not strong
Rich in the sugar-rich fluid of the phloem

30. Early Wood, Late Wood, and Tree Rings
In regions with cool winters or dry spells, the vascular cambium is inactive during part of the year
Early wood (start of the growing season) contains xylem with large diameters and thin walls
Late wood contains xylem with small diameter and thick walls
Growth rings appear as alternating light bands or early wood and dark bands of late wood

32. Continue…
Hardwood: (OAK) has vessels, tracheids, and fibers in its xylem
Softwood (CONIFERS) have no vessels or fibers

33. Limits to Secondary Growth
Some trees live in habitats too harsh and remote for most invaders
Most trees use a strategy of compartmentalization to wall off invaders, building a fortress of thickened cells walls around wounds or deploying toxic compounds

34. The End