Agenda

1. Agenda • Recap : Plant tissues: Dermal, Ground and Vascular • Chapter 13 Quiz: Thursday April 26 • Wednesday April 25: microscope lab • Section 13.3 Plant Organs and their functions • Homework : Read through 650-654 and be prepared to do a lab • Page 566, questions: 1-5, 7, & 8

2. Thought of the day ! “Motivation is a fire from within. If someone else tries to light that fire under you, chances are it will burn very briefly.” - Stephen R. Covey

3. Different types of Meristematic tissue • Tips of plant’s root and stems are constantly growing longer due to the division of cells in the apical meristem (Fig 13.9) • Intercalary meristems : tissues found along the stems & at the base of the leaf blades of some vascular plants such as horsetails & grasses

4. What is the role of these Meristematic tissues? • The cells produced by these types of meristems causes roots, stems, and leaves to grow longer throughout life of plant. i.e. primary growth • If grasses had no intercalary meristems their growth would stop after first time they were mowed

5. How does the circumference or girth of roots and stems increase? • Increases because of cell division in two types of lateral meristems: vascular cambium and cork cambium which is known as secondary growth

6. Secondary growth • adds vascular tissue (needed for 2ndary growth), strengthens the stem & provides support as the plant grows taller • Vascular cambium: thin layer of Meristematic tissue that run along the length of roots & stems and produce new vascular tissue (Fig.13.9)

7. Lateral meristems: Cork Cambium • Cork cambium: produces cells that develop tough cell walls and form a protective layer on the outside of stems and roots. • Makes up of outer bark on woody plants such as maple trees

8. Dermal Tissue • Epidermis: single layer of dermal tissue that forms a protective covering over the body of non-woody (herbaceous) plants and young woody plants • Periderm: a form of dermal tissue in other woody plants produced during 2ndary growth, replaces the epidermis to form cork in woody stems and roots

9. Specialized epidermal Tissue 1) Guard cells: paired cells that together surround a stoma (stomata) • Function: Control the size of the stomata • Stomata : small openings or pores found in the leaf • When open gas exchange gas exchange can occur • Daytime: CO2 diffuses in and O2 diffuses out • Water vapour(g) also diffuses out into the atmosphere through stomata

11. Specialized epidermal Tissue cont’d.. 2) Trichomes: tiny growths on the surface of the epidermis • Often found on stems and leaves & can make the plant appear fuzzy or woolly. • May secrete sticky or toxic substance that repel herbivores • E.g. passion vines have deadly Trichomes that actually puncture the skin of herbivores Function: keep surfaces cool & reduce evaporation

12. Specialized epidermal Tissue cont’d.. 3) Root Hairs: tiny extensions of individual epidermal cells on plant roots. - They increase the surface area available for the absorption of water and nutrients

13. Ground Tissue • Forms most of the plant’s internal and external material and it contains parenchyma cells, collenchyma cells and sclerenchyma cells • Functions: wide range including photosynthesis, storage, and support • In some stems, roots & seeds, the cells of ground tissue store starch & oils

14. Vascular tissue • Internal system of tubes that run lengthwise throughout the stem connecting the roots and the leaves • Function: transport water and dissolved substances throughout the plant • 2types : xylem and phloem

15. Vascular Tissue: Xylem • is water conducting tissue.  • It starts in the roots and carries water all the way up to the leaves.  • In angiosperms, xylem is made of tracheids (dead cells) and vessel elementsthat are long tubes.  • In gymnosperms, xylem only has tracheids • Water and dissolved substances travel up through the xylem as a result of evaporation, transpiration, cohesion and adhesion. 

16. Tracheids and Vessel elements begin as living cells growing end to end in an immature system. • When they mature their living contents die leaving the non living cell walls in place. • Fluids are passed from 1 tracheid or vessel element to the next through pores known as pits

17. Vascular Tissue: Phloem • Food conducting tissue • distributes dissolved carbohydrates (which are made in the leaves) throughout the plant. • Phloem is primarily made up of sieve tube cells &companion cells.  • Carbohydrates are moved through phloem in a process called translocation.

18. Sieve tube elements have no nuclei and have plates at both ends that are punctured with holes, make them very much like a sieve • Each sieve tube element has an associated companion cell that does have a nucleus • Companion cells carry out life functions to maintain both types of cells

20. 13.3 Plant Organs and Their Functions Page 552

21. Topics to be covered • Roots structure and function • Stems structure and function • Leaves structure and function

22. Roots • First structure to emerge from a seed when it sprouts • Serves 3 functions: • Takes in water and dissolved minerals • Anchor the plant in soil or to some other plant or object, supporting the plant against forces such as wind and water • Store the carbohydrates that are produced by photosynthesis in the leaves or green stems, as well as water and other nutrients

23. Root Structure and Function Root cap: a protective covering on the tip of the root • Consists of parenchyma cells that help protect the growing tissues as the root extends through soil or more resistant material i.e. rock • Root’s apical meristem produces new cells that develop into different types of root tissues that perform different functions • E.g. new cells replaces cells that have been removed by friction as the root grows • While others increase in length of the root

25. Outer root layer • Covered in a layer of dermal tissue • Epidermal cells produce root hairs that the surface area of the root • inside epidermis is the cortex, it lies between the epidermis & the vascular tissues of the root (Fig. 13.15) • Cortex is composed of ground tissue made of parenchyma cells that transport & store water, minerals and food in the plant.

26. Outer root layer cont’d.. Casparian strip: creates barrier that forces water & dissolved minerals to cross the plasma membrane & pass through the cytoplasm of endodermal cells • Inside the edge of cortex, between the cortex & vascular tissue is the layer called the endodermis • Endodermis acts as a control point that allows only water & certain dissolved nutrients & ions to enter the vascular system • Each cell in the endodermis is surrounded by a waterproof band called Casparian strip

27. Inner Root Vascular Tissue • Inside the endodermis vascular tissues, xylem and phloem  make up center of the root • Arrangement of xylem and phloem is different in monocots & dicot flowering plants • Monocots  produce seeds in which the embryo has 1 seed leaf • Dicots  produce seeds in which the embryo has 2 seed leaves

28. Monocots vs. Dicots (Pg 553 & 558)

29. Monocots vs. Dicots

31. Types of Root systems

32. Types of Root systems

33. Stems • Many different kinds: soft & flexible (herbaceous) to hard & rigid (woody) • E.g. Asparagus stems: soft , flexible & green . Contain chloroplasts & can perform photosynthesis • Annuals (herbaceous) & Perennials (some herbaceous & most woody) • Some perennials that are herbaceous have stems that are not only woody but covered with bark

34. Stem Structure & Function • Function: provide support for the plant’s leaves & reproductive structures • Structure: stems increase in length due to the shoot apical meristem • As woody plants grow taller, the diameter of the stem also increases • New vascular tissue is produced each year  pattern of annual growth rings visible in xylem tissue

35. Types of stems • Tuber: is an enlarged part of an underground stem found. E.g. white potato • Bulbs: shortened, compressed stems surrounded by fleshy leaves. E.g. onion, tulips • Corms: composed almost entirely of stem tissue with some scaly leaves at its top. E.g. Crocuses & gladiolas • Stolons: horizontal stems that grow above ground along the surface of the soil. E.g. strawberry plant • Rhizome: horizontal stems that grow underground . E.g. Irises

36. Leaves Structure & Function Function: convert light energy from the sun into chemical energy photosynthesis Structure: External: flat portion – Blade (has relatively large surface area) Blades : in some species attached to the stem & in other plants attached to stem via petiole

37. Leaf structure

38. The epidermal cells of leaves secrete a waxy substances that forms the cuticle • Cuticle: reduces water loss from leaves by reducing evaporation • Veins: conduct water and dissolved minerals into the leaf and they conduct dissolved carbohydrates made from photosynthesis from the leaf to the rest of the plant

39. The cuticle & epidermis of a leaf are transparent, allowing light to penetrate to the next layer • The guard cells of epidermal cells are the only ones that have chloroplasts • Guard cells: exchange gases and control water loss

40. Upper and middle layer of leaf • Between the upper & middle layer of leaf is the mesophyll (made up of parenchyma cells that contain many chloroplasts) • below the upper epidermis is a row of tightly packed parenchyma cells called palisade mesophyll cells (contain chloroplasts) • Most photosynthesis takes places in palisade mesophyll

41. Identifying leaves • Look at the size, shape & texture of leaves • Simple leaf Blades are not divided into smaller parts • Compound leaf has blades that are divided into smaller leaflets • Leaf’s venation is the pattern of the veins in the leaf

42. Homework • Read through 650-654 and be prepared to do a lab • Page 566, questions: 1-5, 7, & 8