1. Chapter 9: Plant Organization
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2. Vascular Seed Plants Phyllum: Tracheophyta (Contain Xylem and Phloem)
Both gymnosperms and angiosperms disperse by seeds.
A seed has a seed coat and contains an embryonic sporophyte and stored food that supports growth when the seed germinates.
Gymnosperms have exposed or “naked” seeds.
In angiosperms (flowering plants), seeds are enclosed by a fruit.

3. Gymnosperm diversity (naked-seed plants)
a. Cycads resemble palm trees, but are gymnosperms that produce cones. Shown here is the Kaffir bread cycad, Encephalartos altensteinii.
b. Ginkgoes exist only as a single species – the maidenhair tree, Ginkgo biloba.
c. Conifers are the most common gymnosperms. Shown here is the Eastern hemlock, Tsuga canadensis.

4. Angiosperms (enclosed-seeds)
Angiosperms are flowering plants and include tropical and subtropical trees.
All hardwood trees are angiosperms.
Angiosperms are divided into monocots (such as the grass family) and dicots (such as the maple and rose families).
The many uses of angiosperms are discussed in the Ecology Focus on pages 602–603.

5. Monocot Versus Dicot Plants
Flowering plants (angiosperms) are divided into two groups depending on their number of cotyledons (seed leaves).
Monocots (monocotyledons) have one cotyledon; dicots (dicotyledons) have two.
Cotyledons provide nutrients for seedlings before true leaves begin photosynthesizing.

6. Monocot Versus Dicot Plants
Important monocots are rice, wheat and corn; oak trees and dandelions are dicots.

7. Monocot and Dicot traits
The vascular (transport) tissue is organized differently in monocots and dicots.
Monocot roots have vascular tissue in a ring; in stems, vascular bundles are scattered.
Dicot roots have vascular tissue in a star shape with phloem located between arms of xylem. Stems have vascular bundles in a ring.
The number of cotyledons, and the arrangement of vascular tissue in roots and stems distinguishes monocots from dicots.

8. Monocot and Dicot traits
Leaf veins are vascular bundles within a leaf.
Monocots usually have parallel venation.
Dicots exhibit netted venation, which may be either pinnate or palmate.
Monocots and dicots differ in the venation pattern of leaves and in number of flower parts.

9. Monocot and Dicot traits
Dicot leaves
Monocots and dicots differ in the venation pattern of leaves and in number of flower parts.

10. Plant Organization
Vascular-seed plants have characteristic organs and tissues. (Angiosperms…..)
An organ is a structure that contains different types of tissues and performs one or more specific functions.
The vegetative organs of a flowering plant – the root, stem, and leaf – allow the plant to live and grow.
The body of a plant has a root system and a shoot system.
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

11. Plant Organization
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

12. Plant Tissues
A plant grows throughout its lifespan because of meristem (embryonic tissue) in stem and root tips (apexes).
Three specialized tissues are in plants:
Epidermal tissue – forms the outer protective covering
Ground tissue – fills interior of a plant
Vascular tissue – transports water and nutrients and provides support.
Three types of meristem continually produce three types of specialized tissue in the body of the plant: protoderm, the outermost primary meristem gives rise to epidermis; ground meristem produces ground tissue; and procambium produces vascular tissue.

13. Epidermal Tissue (epi = above, dermal = skin)
Epidermal tissue forms the outer protective covering of a herbaceous plant and is modified in roots, stems, and leaves.
Exposed epidermal cells are covered with waxy cuticle to minimize water loss.
Epidermal cells in roots have root hairs.
Lower leaf epidermal cells have guard cells and stomata.
Root hairs increase the surface area of a root for absorption of water and minerals and help anchor the plant firmly in place.
Protective hairs of a different nature are produced by epidermal cells of stems and leaves. Epidermal cells may also be modified as glands that secrete protective substances of various types.
In leaves, the lower epidermis in particular contains specialized cells called guard cells. The guard cells, which unlike epidermal cells have chloroplasts, surround microscopic pores called stomata (sing., stoma). When the stomata are open, gas exchange occurs.

14. Epidermal Tissue (epi = above, dermal = skin)
In older woody plants, the epidermis of the stem is replaced by cork tissue.
Cork, a component of bark, is made up of dead cells that may be sloughed off.
New cork cells are made by a meristem called cork cambium.

15. Vascular Tissue
There are two types of vascular (transport) tissue that extend from roots to leaves.
Xylem transports water and minerals from roots to leaves through two types of conducting cells.
Phloem transports organic nutrients (phood) from leaves to roots and has sieve-tube elements with companion cells.
Both tracheids and vessel elements are hollow and nonliving, but vessel elements are larger, lack transverse end walls, and are arranged to form a continuous pipeline for water and minerals. The elongated tracheids, with tapered ends, form a less obvious means of transport, but water can move across the end walls and side walls through pits where the secondary wall does not form. Xylem also contains parenchyma cells that store various substances, and fibers and sclerenchyma cells that lend support.
The conducting cells of phloem are sieve-tube elements each of which has a companion cell. Sieve-tube elements contain cytoplasm but no nuclei. These elements have channels in their end walls that in cross section make them resemble a sieve. Plasmodesmata (sing., plasmodesma), which are strands of cytoplasm, extend from one cell to another through this sieve plate. The smaller companion cells have a nucleus in addition to cytoplasm; the nucleus of the companion cell controls both the companion cell and the sieve-tube element.
Vascular tissue is located in the vascular cylinder in dicot roots, in vascular bundles within stems, and in leaf veins in leaves.

16. Vascular Tissue Xylem structure Phloem structure
Both tracheids and vessel elements are hollow and nonliving, but vessel elements are larger, lack transverse end walls, and are arranged to form a continuous pipeline for water and minerals. The elongated tracheids, with tapered ends, form a less obvious means of transport, but water can move across the end walls and side walls through pits where the secondary wall does not form. Xylem also contains parenchyma cells that store various substances, and fibers and sclerenchyma cells that lend support.
The conducting cells of phloem are sieve-tube elements each of which has a companion cell. Sieve-tube elements contain cytoplasm but no nuclei. These elements have channels in their end walls that in cross section make them resemble a sieve. Plasmodesmata (sing., plasmodesma), which are strands of cytoplasm, extend from one cell to another through this sieve plate. The smaller companion cells have a nucleus in addition to cytoplasm; the nucleus of the companion cell controls both the companion cell and the sieve-tube element.
Vascular tissue is located in the vascular cylinder in dicot roots, in vascular bundles within stems, and in leaf veins in leaves.

17. Plant Organization
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

18. ROOTS! Roots have two main functions: 1. Anchorage
2. Absorption
Roots are classified according to origin or form-
Origin: The radicle is the root system of seedling, from this, the primary root develops. Secondary roots (branch roots) grow out from the primary.
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

19. ROOTS! Roots are classified according to origin or form-
Origin: The radicle is the root system of seedling, from this, the primary root develops. Secondary roots (branch roots) grow out from the primary.
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

20. ROOTS! Roots have two main functions: 1. Anchorage
2. Absorption
Roots are classified according to origin or form-
Origin: The radicle is the root system of seedling, from this, the primary root develops. Secondary roots (branch roots) grow out from the primary.
Form: There are two main forms, Dicots typically have a large, singular tap-root and Monocots have a diffuse, branched, fibrous system.
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

21. ROOTS! Roots are classified according to origin or form-
Form: There are two main forms, Dicots typically have a large, singular tap-root Monocots have a diffuse, branched, fibrous system.
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

22. Root Diversity
Roots have special adaptations and associations to better perform the functions of anchorage, absorption of water and minerals, and carbohydrate storage.
An example is the dicot plant, CARROT, where its primary root (taproot) is fleshy and stores food (also, beets).
Examples of taproots that store food are found in carrots, beets, turnips, and radishes.

23. Root Diversity
Roots may also develop from from stem, above the first root, these are called “adventitious roots.”
Because these roots tend to be thicker and pass into the soil below, they provide extra support and are also known as: PROP ROOTS.
Examples of taproots that store food are found in carrots, beets, turnips, and radishes.

24. ROOTS!
The cylindrical shape of the root allows it to penetrate the soil.
Root hairs greatly increase the absorptive capacity of the root.
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

25. ROOTS!
Generally the root system is equivalent in size and extent to the shoot system. (The iceberg principle)
Some plants store the products of photosynthesis in their roots. (Carrots or beets)
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

26. Organization of Roots
Dicot root tip:

27. Organization of Roots
Within a root are zones where cells are in various stages of differentiation.
The root apical meristem is in the zone of cell division; the root cap is a protective covering for the root tip.

28. Organization of Roots
In the zone of maturation, mature cells are differentiated and epidermal cells have root hairs.
In the zone of elongation, cells become longer as they specialize.

29. Tissues of a Dicot Root
Epidermis – single layer of thin-walled, rectangular cells; root hairs present in zone of maturation
Cortex – thin-walled, loosely-packed parenchyma; starch granules store food
Endodermis – between cortex and vascular cylinder, single layer of endodermal cells bordered by the Casparian strip; regulates entrance of minerals into the vascular cylinder
The Casparian strip is a layer of impermeable lignin and suberin that does not permit water and mineral ions to pass between adjacent cell walls. The only access to the vascular cylinder is through the endodermal cells themselves.

30. Tissues of a Dicot Root
Vascular Tissue – has star-shaped xylem in dicots with phloem in separate regions between arms of xylem; the pericycle gives rise to lateral roots
The Casparian strip is a layer of impermeable lignin and suberin that does not permit water and mineral ions to pass between adjacent cell walls. The only access to the vascular cylinder is through the endodermal cells themselves.

31. Organization of Monocot Roots
In a monocot root’s centrally located pith, ground tissue is surrounded by a vascular ring composed of alternating xylem and phloem bundles.
Monocot roots also have pericycle, endodermis, cortex, and epidermis.

32. Plant Organization
Flowering plants are extremely diverse because they are adapted to living in varied environments. Despite their great diversity in size and shape, flowering plants usually have three vegetative organs – roots, stems, and leaves.

33. Stems The shoot system of a plant includes both stems and leaves.
A stem is the main axis of the plant along with its lateral branches.
The presence of nodes and internodes is used to identify a stem even if it is underground. In some plants the nodes of horizontal stems asexually produce new plants.

34. Shoot system
The shoot system contains the stem and its branches, which support the leaves and transport water and organic nutrients.

35. Shoot system
At the tip of the stem is tissue that allows the stem to elongate and produce leaves.
A leaf attached to a stem at a node; and internode is the region beween nodes.
The shoot system contains the stem and its branches, which support the leaves and transport water and organic nutrients.

36. Shoot system
Stems also contain vascular tissue that transports water and minerals from roots to leaves, and also transports the products of photosynthesis in the opposite direction.
The shoot system contains the stem and its branches, which support the leaves and transport water and organic nutrients.

37. Organization of Stems
During primary growth, the shoot apical meristem at the shoot tip produces new cells that elongate and add length to the stem.
The shoot apical meristem is protected within a terminal bud by bud scales. Bud scales are actually modified leaves.
The growth of a stem can be compared to the growth of a root. Leaf primordia are immature leaves. In the spring, when growth resumes, bud scales fall off and leave a scar. The age of the stem can be determined by counting bud scale scars.

38. Organization of Stems
Leaves are produced at nodes; the stem between two nodes is called an internode.
Internodes increase in length as the stem grows.
Terminal buds form at the END of a branch.
Lateral buds, are located on the SIDE of a branch. Lateral buds which form at the axes of leaves are called Axillary buds.
The growth of a stem can be compared to the growth of a root. Leaf primordia are immature leaves. In the spring, when growth resumes, bud scales fall off and leave a scar. The age of the stem can be determined by counting bud scale scars.

39. Organization of Stems
Leaf scars appear if a twig is or has been dormant and the leaves have been shed.
The protective layer that forms before a leaf falls off is the Abscision layer.
Terminal bud scars appear as a flat, ring, around the stem.
Lenticles are small pores all over the stem used for gas exchange.
The growth of a stem can be compared to the growth of a root. Leaf primordia are immature leaves. In the spring, when growth resumes, bud scales fall off and leave a scar. The age of the stem can be determined by counting bud scale scars.

40. Monocot vs. Dicot Stems
- In dicot stems, vascular bundles are in a distinct ring; monocot vascular bundles are scattered throughout.
Monocot
DICOT
The waxy cuticle of herbaceous stems helps to prevent water loss.
The distinct ring of herbaceous dicot stems separates the cortex from the central pith, which stores water and the products of photosynthesis. The cortex is sometimes green and carries on photosynthesis, and the pith may function as a storage site. Monocot stems have no well-defined cortex or pith.

41. Monocot stem

42. Herbaceous dicot stem

43. Woody Stems A woody plant has both primary and secondary tissues.
Primary tissues are new tissues formed each year.
Secondary tissues develop during the second and subsequent years of growth from lateral meristems (vascular cambium and cork cambium).

44. Primary growth, which occurs in all plants, increases the length of the plant.
Secondary growth, which occurs in conifers and some dicots, increases the girth of a plant.
Trees undergo secondary growth because of a change in vascular cambium.
The secondary tissues produced by the vascular cambium, called secondary xylem and secondary phloem, add to the girth of trunks, stems, branches, and roots.

45. Dicot stems
The drawing in the upper left shows a dicot stem with no secondary growth. The other diagram shows a dicot stem with some secondary growth. Cork has replaced the epidermis, and vascular tissue produces secondary xylem and secondary phloem.

46. The bark of a tree contains cork, cork cambium, and phloem.
As a result of secondary growth, a woody dicot stem has an entirely different type of organization.
A woody stem now has three distinct areas: the pith, the wood, and the bark.
Pith rays are composed of living parenchyma cells that allow materials to move laterally.
The bark of a tree contains cork, cork cambium, and phloem.
Cork cambium replaces epidermis with cork cells impregnated with suberin.
Although secondary phloem is produced each year by vascular cambium, phloem does not build up for many seasons. The phloem tissue is soft, making it possible to remove the bark of a tree; however, this is harmful to the tree because without phloem organic nutrients cannot be transported.
Cork cambium is meristem located beneathe the epidermis. Cork cells are impregnated with suberin, a waxy layer that makes them waterproof but also causes them to die. This is protective because now the stem is less edible. Gas exchange is now impeded, however, except at lenticels, which are pockets of loosely arranged cork cells not impregnated with suberin.

47. Secondary growth in a dicot stem
This shows a three-year-old stem in which cork cambium produces new cork. The primary phloem and cortex will eventually disappear, and only the secondary phloem (within thet bark), produced by vascular cambium, will be active that year. The secondary xylem, also produced by vascular cambium, builds up to become annual growth rings.

48. Annual Rings
In trees that have a growing season, vascular cambium is dormant during winter.
In spring, with plentiful moisture, xylem contains wide vessels with thin walls in spring wood; summer wood has a lower proportion of vessels.
Spring wood followed by summer wood makes up one year’s growth or annual ring.
It is possible to tell the age of a tree by counting annual rings.

49. Section of woody stem
This section of a woody stem shows tissues at a higher magnification.

50. Tree trunk
The relationship of bark (cork and phloem), vascular cambium, and wood is retained in a mature stem. The pith has disappeared.
In older trees, the inner annual rings, called heartwood, no longer function in water transport. The cells become plugged with deposits, such as resins, gums, and other substances that inhibit the growth of bacteria and fungi. Heartwood may help support a tree, although some trees live for many years after the heartwood has rotted away.

51. Stem Diversity Stem Diversity - Some stems have functions other than
transport; some are specialized for storage.
Stems nay also function in reproduction, climbing (tendrils on a pea plant).
Modified stems aid adaptation to different environments.
Examples of stem modifications include:
-Stolons -Rhizomes -Tubers -Corms
The growth of a stem can be compared to the growth of a root. Leaf primordia are immature leaves. In the spring, when growth resumes, bud scales fall off and leave a scar. The age of the stem can be determined by counting bud scale scars.

52. Stem Diversity Stolons and Bulbs Onion or Garlic Bulb Bulb
The growth of a stem can be compared to the growth of a root. Leaf primordia are immature leaves. In the spring, when growth resumes, bud scales fall off and leave a scar. The age of the stem can be determined by counting bud scale scars.
Bulb

53. Stem Diversity Tubers and corms Potato! Gladiola
The growth of a stem can be compared to the growth of a root. Leaf primordia are immature leaves. In the spring, when growth resumes, bud scales fall off and leave a scar. The age of the stem can be determined by counting bud scale scars.

54. Leaves A leaf is a broad, thin organ that carries on photosynthesis.
This shape maximizes the surface area for collection of solar energy and absorption of carbon dioxide.
The wide portion of a leaf is the blade, a petiole is the stalk of the leaf, and axillary buds are found at the leaf axil.
Some leaves have other functions.
The upper and acute angle between the petiole and the stem is designated the leaf axil, and this is where an axillary (lateral) bud, which may become a branch or a flower, originates.
Not all leaves make up foliage. Some leaves are specialized to protect buds, attach to objects (tendrils), store food (bulbs), or even capture insects.

55. Leaves
Leaves, such as these from a tomato plant, are often broad and thin. They carry on photosynthesis. A tomato plant has a compound blade with several leaflets.

56. Stoma of leaf
Epidermal modifications include stomata in leaf epidermis that functions in gas exchange. The stoma (pore) is opened or closed by guard cells.

57. Section 1107 Biology 10 4-Units
Dr. L Humphries
Spring 2005: Fundamentals of Biology
Section Biology Units
EXERCISE 12:
Angiosperm Stem

58. Section 1107 Biology 10 4-Units
Dr. L Humphries
Spring 2005: Fundamentals of Biology
Section Biology Units
EXERCISE 13:
Angiosperm Root