PLANT BODY ORGANS Plants have organs that compose of different tissue, which in turn are composed...

UNIT 5: PLANT TISSUE

PLANT BODY ORGANS Plants have organs that compose of

different tissue, which in turn are composed of cells

of different types. A tissue is a group of cells with a

common function, structure or both. An organ consist of several types of

tissues that together carry out particular functions.

The three basis plant organs are: Roots, stems leaves.

The organs are divided into the root system (roots and

mycorhiza) shoot system (leaves and stems)

SHOOT SYSTEM

ROOT SYSTEM

ROOTS

Anchor plants Root hairs absorb water and

minerals. Stores carbohydrates. Eudicots have a taproot system

(one main vertical root that give rise to lateral roots)

Monocots have an adventitious root system (roots that originate from the stem of a plant)

Roots can be modified to perform different

functions:

Fig. 35-4

Prop roots

“Strangling”aerial roots

Storage roots

Buttress rootsPneumatophores

Many plants have modified roots

STEMS Consist of nodes (where leaves grow)

and internodes. The angle between the leave and the

stem is called the axillary bud, this can form a lateral shoot.

The shoot tip consist of an apical (end) bud.

The inhibition of axillary buds by an apical bud is called apical dominance.

Stems support the leaves and lateral branches of a plant.

Stems keep the plant upright.

Fig. 35-5

Rhizomes

Bulbs

Storage leavesStem

Stolon

Tubers

Many plants have

modified stems

Rhizome: Horizontal shoot that grows just below the surface.Vertical shoots emerge from auxillary buds on the rhizome.

Stolon: Horizontal shoots that grow along the surface. Reproduce asexually.

Tubers: Enlarged ends of rhizome or stolon, specialized to store food. The eyes are clusters of auxillary buds that mark the nodes.

LEAVES Main photosynthetic part of the plant

(in most vascular plants). Consist of a flattened blade and a

stalk, called a petiole. Monocots have no petiole. Monocots have parallel veins on the

leaves and Eudicots have net venation.

Leaf shape differs: simple leaves (single leaf) and compound leaves (where the blade consist of smaller leaflets – leaflets have no axillary buds.)

Fig. 35-6

(a) Simple leaf

Compoundleaf

(b)

Doublycompoundleaf

(c)

Petiole

Axillary bud

Leaflet

PetioleAxillary bud

LeafletPetioleAxillary bud

DIFFERENT LEAF

STRUCTURES

Fig. 35-7

Tendrils

Spines

Storageleaves

Reproductive leaves

Bracts

Some plant species have

evolved modified leaves

that serve various

functions

Tissue categories in plants Each plant organ has:

dermal, vascular and ground tissues.

Each of these three categories forms a tissue system.

The dermal tissue system is the plant’s outer protective covering.

In non-woody plants it is a single layer called the epidermis protected by a waxy layer called the cuticle found on stems and leaves.

In woody plants, the protective tissue is called periderm.

Ground tissue are neither dermal or vascular.

Internal ground tissue is called the pith.

Ground tissue that is external to the vascular tissue is called cortex.

Ground tissue includes various cells with specialized functions such as storage, photosynthesis and supports.

MERISTEMATIC TISSUE A flowering plant has the ability to grow its entire

life because it possesses meristematic (embryonic) tissue.

The apical meristem are located at or near the tips of stems and roots, where they increase the length of their structures by means of mitosis.

This increase in length is called primary growth.

Monocots also have an intercalary meristem, this allows them to regrow lost parts. (It is found between mature tissues). EXAMPLE: GRASS CUT - GROW

Organization of a plant body MERISTEMATI

C TISSUE AT TIP OF STEM

MERISTEMATIC TISSUE AT TIP OF ROOTS

APICAL MERISTEM Produces three types of meristems,

and these develop into the three types of specialized primary tissues in the body of the plant:

SPECIALIZED PRIMARY TISSUES:  Protoderm gives rise to the

epidermis Ground meristem produced ground

tissue Procambium produces vascular

tissue

FUNCTIONS OF SPECIALIZED TISSUES

Epidermal tissue: forms the outer protective covering of a plant.

Ground tissue fills the interior of a plant.

Vascular tissue transports water and nutrients in a plant and provides support.

EPIDERMAL TISSUE

EPIDERMAL TISSUE Single layer of

closely packed, flat, brick shaped cells, with a large vacuole.

The aerial parts of the plant are covered with a cuticle.

Functions:- Cuticle minimizes water loss (because it has cutin) - Protects the plant against bacteria.

Longitudinal section

Cross section

Leaf contain upper and lower epidermal cells

SPECIALIZE EPIDERMAL CELLS

ROOT HAIR

TRICHOMES

STOMA OF LEAF

CORK OF OLDER STEMS

ROOT HAIRS

TRICHOMES

CORK CELLS

STOMATA

ROOT HAIRS They are specialized

epidermal cells of roots.

Unicellular outgrowth of the epidermal cell.

Functions: Increase the surface

area of the root for absorption of water and minerals.

Anchor the plant.

TRICHOMES Specialized epidermal

cell of stems and leaves.

Multicellular outgrowths of the epidermis of stems and leaves.

Functions: Protect the plant from

sun Conserve moisture. Protect plant from

herbivores, produce toxic substance.

CUTICLE

MULTICELLULAR

STOMATA Specialized epidermal

cells called guard cells, which are bean shaped, enclose an opening called the stoma or pore.

The guard cells contain a nucleus and chloroplasts.

It has a thick inner membrane and a thin outer membrane.

Woody plants have lenticels.

FUNCTIONS: Transpiration Gaseous exchange

take place through the stomata.

OPEN - DAY

CLOSED- NIGHT

GROUND TISSUE•PARENCHYMA•COLLENCHYMA•SCLERENCHYMA

GROUND TISSUES

PARENCHYMA TISSUE Occur in roots,

stems and leaves. Spherical, loosely

packed, big, thin-walled cells with large vacuoles.

Intercellular airspaces between cells.

FUNCTIONS: If they have

chloroplasts – photosynthesis.

If they have leucoplasts – they store products of photosynthesis.

They can divide to form more specialized cells

PARENCHYMA CELLS

INTERCELLULAR AIR SPACES

COLLENCHYMA TISSUE It is composed of

unevenly thickened primary walls with additional cellulose and pectin deposits especially in the corners.

Found just beneath the epidermis of young stems.

The cells are slightly elongated, tightly packed and overlap each other.

FUNCTIONS: Mechanical

strengthening and support to plant organs

SCLERENCHYMA TISSUE Cell walls have been

thickened by impregnation with lignin.

The cell wall is evenly thickened and forms a waterproof barrier impermeable to water.

In the cell walls are pit canals that serve as channels between cells and to the outside world.

The lumen is small. Two types of

Sclerenchyma: Stone cells and fibers

FUNCTIONS: Strengthening,

support and protection.

Found in shell of nuts and hard parts of fruits

Fibers give rigidity and flexibility to the plant.

VASCULAR TISSUE• XYLEM• PHLOEM

XYLEM Contains 2 types of conducting cells:

tracheids and vessel elements (VE).

Both cells are hollow and non-living but the VE is larger and has perforated plates in their end walls and are arranged to form a continuous vessel.

Tracheids have tapered ends with pits.

It also has other tissue: Xylem fibers, and Xylem parenchyma.

FUNCTIONS OF XYLEM

Transports water and minerals from the roots to the leaves.

Support and strengthening.

Xylem vessels Xylem tracheids Xylem fibers

PHLOEM Consist of sieve-tubes and

companion cells. The sieve-tubes form a continuous

tube, they have cytoplasm but no nuclei.

They have sieve plates between cells.

The companion cell has a nucleus that controls both cells because they are connected by plasmodesmata.

It also has other tissue: Phloem fibers and phloem parenchyma

FUNCTIONS OF PHLOEM Transports sucrose and

other organic substances, including hormones, from the leaves to the roots.

Support and strengthening.

Tissue organization of Leaves

KNOW CROSS SECTION THROUGH LEAF