Unit 5 plant tissue
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UNIT 5: PLANT TISSUE Campbell and Reece, 2010. Chapter 35 p. 738 – 745 and 750 - 751, Edulink and learning guide notes
description
here are the notes about plan and animal tissues
Transcript of Unit 5 plant tissue
UNIT 5: PLANT TISSUE
Campbell and Reece, 2010. Chapter 35 p. 738 – 745 and 750 - 751,
Edulink and learning guide notes
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.
Some epidermal cells are modified to form hairs – roothairs on roots and trichomes on leaves and stems.
The vascular tissue system carries out transport of materials between the root and the shoot system.
The two types are xylem and phloem. 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
P. 750 – 751 (SELF STUDY) KNOW CROSS SECTION THROUGH
LEAF
