Senin, 28 Februari 2011

PLANT TISSUE STRUCTURE

by.
Alit Adi Sanjaya

Standard Competency:    
 Understanding the relationship between structure and function of plant and animal tissues, and also its application in the science, environment, technology and community context.

Basic Competency:
2.1 Identify the structure of plant tissues and related it with its function, explain the totipotency as the basic of tissue culture.

Indicator :
1.     Draw many kinds of the plant tissues structure
2.     Identify many kinds of the plant tissues based on its form and location
3.     Identify the mayor characteristic of plant tissues
4.     Explain the function many kind of plant tissues

The Plant Tissues

Plant tissue is formed from plant cells that undergo fission, magnification, and differentiation. Base on its ability to split, plant tissue is grouped into, those are meristematic tissue and permanent tissue.
1.      Meristematic tissue
Meristematic tissue is often called embryonic tissue or basic tissue. It is called embryonic tissue because its cells always make fission to multiply their self. Meanwhile it is called basic tissue because after adult, this tissue will form another tissues.
Meristematic tissue has several characteristic those are:
·         Its cells have thin wall
·         Its shape and size of cell are equal
·         Its relatively rich of protoplasm
·         The content of its cell does not contain crystal and food reservation
·         Commonly it has very small cell cavity.

Base on its origin, meristematic tissue is separated into two those are:
a.  Primary meristem
Primary meristem is a meristem that its cells are direct development of embryonic cells so the advance of embryonic vessels. Its example is in stem tip bud and the trip of root. Meristem found in the trip of stem and the trip of root is called also apical meristem. The activity of this meristem cause stem and root grow enlengthen. Growth caused by the activity of primary meristem is called primary growth.
b.   Secondary meristem
Secondary meristem is a meristem that comes from adult tissue that has make differentiation, such as cambium and crock cambium that happens from parenchyma and collenchyma. Cambium in root and stem od dicotyledon plant is found in the bundle of transport vascular (between xylem and pholem) called vascular cambium. Besides there is also cambium found between two bundles of transport vascular called intervascular cambium. The activity of secondary meristem cause plant ‘s body becomes big. Growth caused by the activity of secondary meristem is called secondary growth.

2. Permanen Tissue
Permanent tissue is a tissue that has undergone differentiation. Base on its shape or function, permanent tissue is separated into epidermis tissue, parenchyma tissue, supporter or strengthener tissue, transport tissue, and crock tissue.

a.   Epidermis tissue
This tissue is tissue that is located most outer so cover all of plant body surface. Epidermis tissue can be found in the surface of root, stem, leaf, fruit, and flower. Epidermis tissue has main function to protect tissue inside of it. Another function is to protect of mechanical destruction, keep tissue temperature for not to high, to prevent the excessive vaporization. Epidermis tissue is found in root has function suck water and mineral salts. In several place, epidermis cells of leaf make modification to be leaf cover cells (stomata). Meanwhile stem epidermis of dicotyledon make modification to be lenticel. The characteristic of epidermis tissue are as follows:

·      The shape of its cells is like cuboid, consist of one layer of cell, and commonly it has no chlorophyll
·      Commonly its covered by wax layer of cuticle. The presence of these wax layer and cuticle have relationship with is function to protect tissue inside of it.
·      In several kind of plant epidermis make modification to be scale of hair
·      The outer part of cell wall of root epidermis that still young will grow to form hair that has function to absorb mineral substance.
b. Parenchyma tissue
Parenchyma tissue is frequently called as ground tissues. The parenchyma tissue is form from living cells with varied morphological as well as physiological structures that still can perform all of their living processes. The characteristic of parenchyma tissues are:
·      The cell membranes composing the tissues are thin
·      Parenchyma cells are alive cells, there is a big vacuole which contains alternative food substance
·      Parenchyma cells is generally polygonal
·      The space between cells in it enables the exchange or circulation of any substance or gases
Parenchyma has functions as follows.
a.      As a place for photosynthesis. This is caused by parenchyma which contains chlorophyll (called chlorenchyma), in young leaf and stem.
b.     As a place of storing food alternative, the characteristic is not colorful, is located inside root, tubers, fruits, and stem.
c.    As a place of storing water, foe example in Agave, Aloe.
d.    As a place of storing air. Air parenchyma is called aerenchyma. Aerenchyma has a rather big intracellular space that has air inside
e.    As a means of transportation. The carrier parenchyma is usually gets longer in the same direction as the way of transporting. This tissue enables to get connected to the tissue inside and outside.


c.  Supporting Tissues
   Supporting tissue is also called stereo that functions to strengthen the body parts of                                 plants.  This supporting tissue is divided into collenchyma and sclerenchyma tissue.
a.     Collenchyma tissue
Collenchyma is a homogenous tissue, consisting of one kind of cell, the primary cell wall is thickened by pectin, cellulose, and hemicellulose. Collenchyma has no lignin. One the cell wall, collenchyma experience local thickening, not at the whole cell wall. Generally collenchyma tissue comes from procambium, but there is also which from the basic meristem. Collenchyma tissue has function as a plant lasing, particularly in growing active organs of plants. Collenchyma is usually located in stems, and leaves, located right under epidermis, rarely in root.

b.     Sclerenchyma tissue
Sclerenchyma is located in the organs of plants that no longer grow and develop. This enables the organs to defend in dealing with any stresses and forces without affecting tissue cells, which are weaker, sclerenchyma cells are dead. The cell wall gets thicker and consist of lignin substances.
Sclerenchyma is divided into two: fibre and sclereid.
·           Fibre
The form of fibre is long and pointed, located in xylem, phloem tissue, or other parts. Both in monocotyledon and dicotyledon. Scelernchyma is generally 2 mm in leght.
·            Sclereid
The form of sclereid cell is round and short. The cell wall contains lignin substance (wood substance) so it rigid and solid. The sclereid cell that that is not branched does not have any extreme form, named brick cells. Sclereid is located in the coconut shell, seeds, or solid part of fruit (pear).

   d.  Endodermis tissue
Endodermis consists of cells that partly experience crock substance thickening on the walls, and partly do not, called repeating cells. These repeating cells have function to side water from cortex to stele (central cylinder). The repeating cells are well known as the caparian strip or band.

e.  Transport Tissue
Vascular tissue pays the role in carrying substances to cover the needs of plants. Vascular tissues is divided  into, they are phloem and xylem.
 Xylem (Wood Vessel)
The cells composing xylem tissue are dead cells and have lignin substance on the cell wall. Xylem has functions to transport of water and mineral salts from roots to leaves for photosynthesis. Xylem consist of xylem elements, including trachea, tracheid, xylem fibres, and xylem parenchyma.
Trachea and tracheid belong to cells that are formed due to secondary cell wall development and continue with cytoplasm removal during maturity. When cells function as carrier tissue, they are dead. Tracheid has characteristic; the cells are cylinder and interrelated on each edge. The interrelated edges will change into perforation hole.
Trachea is also related vessel elements. The fibre in trachea is not clear. Trachea has porous intercelluler fibres. The cell is pointed and long. The trachea wall is perforated called pits. Xylem fibres have long and pointed-edge cells. The wall is thick and narrow pits. Xylem or wood parenchyma contains various substance, for example food stock, tannin substance and crystal.

 Phloem (Sieve Vessel)
The main function of phloem is to transport the photosynthesis result from leaves to the all plants body. Similar to xylem, phloem also has phloem elements. The first elements of pholem is sieve tubes, which has cylindrical cells with perforated edges. Contrary to cells composing xylem tissue, the cells composing sieve tube in phloem tissueare still alive during its functioning as the vascular tissue. However, the cells have no nucleus, ribosome, and vaculoe. The companion cells are cylinder and smaler than sieve tube cells. The companoin cells are located side by side the sieve tube cells and interrelated though plasmodemata.
The third phloem element is phloem fibre, which has long and edge-packed cells. Phloem fibre have a thick cell wall and have function as phloem lasing. The fourth phloem element is phloem parenchyma, which primary  cell walls and belongs to alive cell. Phloem parenchyma has little holes called pits.  Phloem parenchyma contains flour substance, resin, and crystal.

         f.  Cork Tissue
Cork is an elastic, homogeneous mass of flattened dead cells with a fatty substance that makes it almost impermeable to water and gases. Cork oak grows in forests and may exceed 30 m (100 ft) in height, although the average is about 9 m (about 30 ft). The young trees are first stripped of their bark when 15 to 20 years old. This cork is coarse, but successive strippings at intervals of about ten years yield a closer-grained product as the trees mature. The useful life of a tree may be more than 150 years.


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