presentation organization of plants 56tt

Chapter 7: stemPlant Body

1- Vegetative organs: Roots, Stems and Leaves

2- Reproductive organs:Flowers and Fruits

1. Morphology of stem2. Stem modifications3. Structure of stem

- Primary structure of dicotyledon plants- Primary structure of monocot plants- Secondary structure of dicot plants

Chapter 7: stem

Chapter 7: stemMorphology

Stem is vegetative organs of plants. Has node and internodes, with one or more leaves attached at each nodeAxillary bud: A bud formed on the upper angle of each node. Axillary bud consist of an Apical meristem and leaf primordia. When it grows, it becomes a new shoot.

2. Stem modifications

rhizome In botany, a rhizome (from Ancient Greek: rhízōma "mass of roots", is a modified subterranean stem of a plant that is usually found underground, often sending out roots and shoots from its nodes. Rhizomes develop from axillary buds and are diageotropic (hướng ngang đất) or grow perpendicular to the force of gravity. The rhizome also retains the ability to allow new shoots to grow upwards

Turmeric

Ginger

Arrowroot

Stolons(runners)

Stolons: above ground horizontal stems. It help the plant to spread, such as strawberries

Tubers: Underground stem primarily composed of starch filled parenchyma cells. Eyes of potato are axillarybuds arranged in a helical fashion along the surface of the potato

Thorn growing from the axil

• garlic, tulips, narcissus (thủy tiên), arrowroot, Turmeric, ginger, pennywort (rau má), strawberries, onions, grapefruit (pomelo), turnips, potatoes, cactus, pumpkin, Aloe, sweet potatoes,

• rhizome:8/11; 5/7; 1/3• Stolons:4/6; 3/5; 0/2• Tubers:5/6; 2/4; 2/3• Bulbs:2/3; 3/.6; 1/3• Thorn:4/6; 3/6;

The stems have 2 type of growth state- Primary growth (primary growth of dicots plants and monocot plants)- Secondary growth (secondary growth of dicots)

3. Structure of stem

a. Primary structure of monocot plants

Structure of stem and vascular bundle

Stem:- Epidermis- Sclerenchyma- Parenchyma- Vascular bundle (primary phloem and primary xylem)

1. Primary growth

Structure of monocot stem

Epidermis

Sclerenchyma

Vascular bundle

Primary phloem

Primary xylem

Parenchyma Cross section of stem of monocot plant

Cross section of stem of monocot plant

Describe structure of  stem of monocot plant

Sclerenchyma

Protoxylem

lacuna

Helical xylem

Annular xylem

Reticulate xylem

Satellite cell (companion cell)

Sieve cell

Detail of a vascular bundle of monocot stems

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Detail of a vascular bundle of monocot stems

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b. Primary structure of dicot plants

Diagram of Primary structure of dicot plants

- Cortex: Collenchyma (layers below epidermis) and parenchyma- The vascular system in dicots is forming a ring

Medullary rays

Difference between primary structure of dicot stem and monocot stem

Dicot stem Monocot stem1. Epidermis: Trichomic and

cuticle are present 2. Hypodermis is made up of

collenchymatous cells.3. Pericycle is present4. Pith is present5. Medullary rays are present6. Vascular bundles are open

1. Epidermis: Trichomic is absent, cuticle is present

2. Hypodermis is made up of sclerenchymatous cells.

3. Pericycle is absent4. Pith is absent5. Medullary rays are absent6. Vascular bundles are closed.

Difference between primary structure of dicot stem and monocot stem

Dicot stem Monocot stem7. Vascular bundles are arranged

in a ring.

8. Bundle cap is present9. Bundle sheath is absent10. Protoxylem lacuna is absent11. Phloem parenchyma is

present

7. Vascular bundles are scattered in the ground tissue.

8. Bundle cap is absent9. Bundle sheath is present10. Protoxylem lacuna is present11. Phloem parenchyma is absent

2. Secondary growth a. Secondary structure of dicot plants

- Secondary growth is produced by a cambium. It occurs in rows or ranks of cork, secondary xylem or secondary phloem cells. - Cork cells (produced by a cork cambium) are part of the epidermis, and contribute to the bark of woody stems. - Dicot secondary growth occurs by growth of vascular cambium, to complete a full vascular cylinder around the plant. Secondary xylem is produced to the inside of the vascular cambium, secondary phloem to the outside. The living parts of the woody plant are next to the vascular cambium.

Epidermis (periderm + lenticel)

Cortex (parenchyma)

Fibers (sclerenchyma)

Parenchyma (phloem)

Cambium (secondary meristems)

Meta-xylem

Parenchyma (xylem)

Pith ray

lenticel

Figure 13.3 Lenticels.(a) Transverse section showing alenticel in sectional view from astem of Prunus serotina.(b) Drawing of an early stage in the development of a lenticel.(c) Sectional view of a lenticel ofPrunus avium.

Large Conductive Elements (SEM x220).

Meta-xylem

Parenchyma (xylem)

Pith ray

Three cross-sections of older basswood twigs. Note the annual growth rings and the complete vascular cylinder producing secondary xylem to the inside and secondary phloem to the outside.

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Chapter 8: Leaf

8.1 Parts of a leaves8.2 Functions of leaves8.3 Leaf form8.4 Leaf Arrangement8.5 Leaf modifications 8.6 Structure of leaves

8.6.1 Structure of dicots leaf8.6.2 Structure of monocot leaf

Parts of a leaves

- Leaf is vegetative organs of plants, its attach to stems at nodesThe leaf consists of the (generally) flat blade, one or more leaf veins, a petiole, and usually an axillary bud.

- The petiole can be long (as in celery and bokchoy) or short (as in cabbage and lettuce).

- Leaves may be simple or compound: simple leaves have a single subdivision or leaflet, compound leaves have more than one leaflet.

Parts of a leaves

Leaf typesConifer. The leaves of conifers are needle-like ason pines or scale-like as on junipers (Juniperus). They are usually evergreen, some conifers have deciduous. Each conifer leaf has a single vein.

Ginkgo. As fan-shaped leaf blades with dichotomous venation in which the veins branch into two equal or unequal lengths.

Dicot. Most dicot blades have pinnate (feather-like) venation in which major veins diverge from one large mid-vein. Some dicot blades have palmate (hand-like) venation where several large veins diverge from the petiole to the margins.

Monocot. Most Temperate Zone monocots have narrow strap-shaped blades (f) with sheathing bases (g) surrounding the stem (h). With parallel venation, major veins arise at the base, and converge at the tip with small vein interconnections.

vein

Monocot with parallel venation

Dicot blades have pinnate venation

Dicot blades have palmate venation

Functions of leaves• Photosynthesis:

- Collect light energy (chlorophyll in palisade, spongy)

- Regulate gas exchange: absorbing carbon dioxide (CO2) and releasing oxygen (stoma)

• Transport H2O: Evaporation of water from leaf surface

• Specialized functions- Water storage (aloe vera)- Protection

Leaf Form* Simple. A simple leaf has one blade and one petiole* Compound. A compound leaf is one petiole has two or more blade-like (leaflets) such as (pinnately compound, palmately compound.

Detail of a simple leaf

Base

Leaf Arrangement

- Alternate - Opposit- Whorled

- Alternate. In an alternate arrangement, single leaves are attached spirally along the stem. it is a widespread phenomenon in nature

-Opposite. Two leaves emerge opposite each other on a stem. The example shown is guava tree- Other examples: rose apple, coffee tree...

- Whorled. In a whorled arrangement, several leaves emerge together around a stem node. (Oleander)

Leaf modifications

Bract. Associated with a flower, bracts are reduced or modified leaves. Very small bracts are found in sedge and grass flowers.

Carnivorous Leaves. Carnivorous plants are plants that derive some or most of their nutrients (but not energy) from trapping and consuming animals or protozoans (mainly insects). Carnivorous plants have adapted to grow in places where the soil is thin or poor in nutrients, especially nitrogen, such as acidic bogs and rock outcroppings

Types of Spines– Cells with hard cell wall– Pointed and dangerous to potential predator, Reduce evaporation of water from leaf surface - When a "spine" originates from a stem modification and arise from the axillary or apical bud it is defined thorn. If it arises from the epidermis outside the branch it is called prickle, when it originates in leaves' margin or tip it is defined a marginal tooth. Nearly all cacti have spines

Types of Tendrils. Most vines have tendrils which are formed from a leaf part of the plant. The pea family have tendrils that are formed from the leaflet of the compound leaves. Not all tendrils are modified leaves, tendrils of cucumber are modified stem

Scale Leaves: In most of the desert plants, leaves are reduced and they appear as scales. The scale are thin, dry, membranous, stalk-less. This modification is evolved in order to minimize the rate of transpiration. The function of photosynthesis is performed by the stemExample: Cedar, casuarina.

Structure of leaves• Structure of dicots leaf• Structure of monocot leaf

Anatomy of dicots leafs- Structure of Mid-vein leaf- Structure of blade leaf

Mid-vein

Blade of leaf

Upper epidermis (wax cuticle)

Collenchyma (angular)Parenchyma (cortex)Sclerenchyma (fibers)

Xylem (tracheids)

Phloem (sieve tube)

Parenchyma (pith)

Lower epidermis (wax cuticle)

Mid-vein• Upper epidermis (wax cuticle)• Collenchyma (angular)• Parenchyma (cortex)• Sclerenchyma (fibers)• Xylem (tracheids)• Phloem (sieve tube)• Parenchyma (pith)• Phloem (sieve tube)• Xylem (tracheids)• Sclerenchyma (fibers)• Parenchyma (cortex)• Collenchyma (angular)• Lower epidermis (wax cuticle) and (within stomata cells)

Blade leaf

• Upper epidermis (wax cuticle)• Palisade mesophyll• Spongy mesophyll• Lower epidermis (wax culticle) within stomata

Structure of monocot leaf

• Upper epidermis (within bulliform cell, stomata)

• Mesophyll cells• Primary varcular bundle (phloem and xylem)• Bundle sheath• Sclerenchyma cells• Lower epidermis (within stomata)

Bundle sheath cellPhloem

XylemSclerenchyma

Upper epidermis Bulliform cell

Mesophyll cells

Chapter 9. Periderm • The periderm is a protective tissue of

secondary origin replacing the epidermis in stem and roots.

• Increase in thickness by secondary growth.• Occurs in herbaceous dicots, specially in the

oldest parts of stems and roots.• Formation from protective layers.

Characteristics of cork

• Several layers of thin walled and flattened cells that die at maturity• Walls have suberin (Walls may also contain lignin.)• Provides mechanical protection to stem• There may be a region of parenchyma cells produced interior to the cork cambium.

Chapter 10. RootsThe root is the underground organ of the plant. Its primary functions include uptake of water and minerals and anchorage of the above-ground (aerial) portions of the plant.

Root Types+ In conifers and dicots, a primary root, called a radicle in the seed embryo, develops lateral branching roots.

+ In many monocots, the first-formed roots of the seedling, called seminal roots, eventually die. They are replaced by adventitious roots, which emerge from the stem.

Radicle roots Seminal roots

Root Modifications

Storage Roots. Roots are an adaptation for food storage and are seen in many biennials and perennials. Plants may develop thickened roots: carrot, beet, sweet potato.

Prop Roots. (re chong) shoot system in the soil, preventing them from capsizing in strong winds, heavy rains, and impact from predators and human activities. corn, mangrove (Rhizophora).

Contractile Roots. Contraction, or shortening of some roots, helps pull down and anchor the plant more firmly in the soil.

Root TissuesBasic Differentiation Regions of the Root

Apical Meristem. The root apical meristem (a) is located at root tips. It produces new root cap (b) cells below, and above, it produces cells that contribute to protoderm (c), ground meristems of the cortex (d), and pro-cambium (e), the three primary meristems that initiate tissues.

Root Cap. The function of the root cap (b) is to protect the apical meristerm and to aid the developing root as it penetrates the soil as the root elongates. It is composedof parenchyma cells whose walls, along the surfaces of the root cap, are mucilaginous to provide easier passage through soil particles. As cells (f) are sloughed off, more cells are produced by the apical meristem.

Elongation Region. Back of the apical meristem the region (g) where most elongation of the root takes place.

Mature Root. In primary growth, the epidermal cell walls of the mature root (j) become cutinized or suberized with wax-like substances. With secondary growth, the cork cambium replaces epidermis (k) and cortex with root bark tissues, cork and phelloderm.

Primary structure of roots

• Epidermis • Cortex • Vascular cylinder (phloem + xylem vasculars)

Secondary structure of roots

• Periderm• Pericyle (parenchyma)• Phloem (fiber and collenchyma cells)• Cambium• Xylem (meta xylem and collenchyma xylem)