As in animals, the cells of plants are grouped into tissues with characteristic functions such as photosynthesis, transport etc. There are two major categories of tissues in plants i.e. simple tissues and compound (complex) tissues.
They are all alike and there are no inter-cellular spaces among them. In plants cell division occurs solely in meristematic regions. Two main types of meristematic tissues are recognized in plants. Apical meristems are located at the apices or tips of roots and shoot.
When they divide they cause increase in the length of plant. Such a growth is called primary growth. Lateral meristems are located on the lateral sides of roots and shoot. By dividing they are responsible for horizontal expansion of the parts of plant. Such a growth is called secondary growth.
Lateral mersitems are further of two types i.e. vascular cambium and cork cambium. Vascular cambium is present between the xylem and phloem tissues. Its cells divide and form new xylem tissue toward the center and new phloem tissue towards the outside. Cork cambium is present in the outer lateral sides and its cells are responsible for making the characteristic corky layer.
Intercalary meristem occurs in the form of small patches of meristem present among the mature tissues. These are common in grasses and help in the regeneration of parts removed by herbivores etc. Permanent tissues Permanent tissues originate from the meristematic tissue.
These tissues are composed of cells, which do not have the ability to divide. They are further classified into following types: Epidermal Tissues Epidermal and sclerenchyma tissues .
Leaf hairs reflect light and are important for j plants in dry regions. Here excess light may lead to photobleaching of pigments and excess absorption may overheat the tissues. Epidermal tissues also have some specialized cells that perform specific functions. For example; Root hairs absorb water and minerals.
Leaf hairs reflect light to protect against overheating and excessive water loss. The layer of leaf hairs acts to hold in a layer of humidity 'trapped'. This layer also prevents air moving directly against the stomata which would encourage water loss. Stomata are made by guard cells and are most abundant on underside of leaves. They regulate diffusion of carbon dioxide into the leaf for photosynthesis as well as regulate loss of water from the leaf Salt glands are the waste-bins for the excess salt absorbed from the soil.
They form a crust of salt on leaves which reflects light to prevent overheating. Ground Tissues Most parenchyma cells I can develop the ability to divide and differentiate into other types of cells \ and they do so during the process of repairing an injury. Ground tissues are simple tissues made up of parenchyma cells. Parenchyma cells are the most abundant cells in plants. Overall they are spherical but flat at point of contact.
The cell walls are hardened With lignin, which is the main chemical component of wood. Mature sclerenchama cells cannot elongate and most of them are dead.
There are two types of cells in tissues,
(i) fibre cells are associated with xylem and phloem tissues, and cells are found in seed coats.
Following types of cell are found in xylem tissue;
Vessel Elements or Cells:
These are short and wide cells with thick secondary cell walls. The vessel cells are dead and hollow. They lack end walls and join together to form long tubes. b- Tracheids: These are long, slender cells with overlapping ends.
Water moves upward from tracheid to tracheid Phloem tissue is responsible for the conduction of dissolved organic matter.These are long cells. Their walls have small pores and are called sieve Plates. Many sieve tube cells join to form long Pipelines called sieve tubes. During development they lose their nuclei and ribosomes etc and Possess little protoplasm.
Simple tissues
The tissues which are made of single type of cells, are called simple tissues. They are of two types i.e. meristematic tissues and permanent tissues.Meristematic tissues
These tissues are composed 'of cells, which have the ability to divide. The cells of meristematic tissues show following properties: They have thick cytoplasm, with large nucleus in the center and with small or no vacuoles. They are thin-walled.They are all alike and there are no inter-cellular spaces among them. In plants cell division occurs solely in meristematic regions. Two main types of meristematic tissues are recognized in plants. Apical meristems are located at the apices or tips of roots and shoot.
When they divide they cause increase in the length of plant. Such a growth is called primary growth. Lateral meristems are located on the lateral sides of roots and shoot. By dividing they are responsible for horizontal expansion of the parts of plant. Such a growth is called secondary growth.
Lateral mersitems are further of two types i.e. vascular cambium and cork cambium. Vascular cambium is present between the xylem and phloem tissues. Its cells divide and form new xylem tissue toward the center and new phloem tissue towards the outside. Cork cambium is present in the outer lateral sides and its cells are responsible for making the characteristic corky layer.
Intercalary meristem occurs in the form of small patches of meristem present among the mature tissues. These are common in grasses and help in the regeneration of parts removed by herbivores etc. Permanent tissues Permanent tissues originate from the meristematic tissue.
These tissues are composed of cells, which do not have the ability to divide. They are further classified into following types: Epidermal Tissues Epidermal and sclerenchyma tissues .
Epidermal tissues
Epidermal tissues are composed of a single layer of cells and they cover the plant body. They act as a barrier between the environment and the internal plant tissues. They are also responsible for the absorption of water and minerals primarily in the root region. On stem and leaves they secrete cutin (the coating of cutin is called cuticle) which prevents evaporation.Leaf hairs reflect light and are important for j plants in dry regions. Here excess light may lead to photobleaching of pigments and excess absorption may overheat the tissues. Epidermal tissues also have some specialized cells that perform specific functions. For example; Root hairs absorb water and minerals.
Leaf hairs reflect light to protect against overheating and excessive water loss. The layer of leaf hairs acts to hold in a layer of humidity 'trapped'. This layer also prevents air moving directly against the stomata which would encourage water loss. Stomata are made by guard cells and are most abundant on underside of leaves. They regulate diffusion of carbon dioxide into the leaf for photosynthesis as well as regulate loss of water from the leaf Salt glands are the waste-bins for the excess salt absorbed from the soil.
They form a crust of salt on leaves which reflects light to prevent overheating. Ground Tissues Most parenchyma cells I can develop the ability to divide and differentiate into other types of cells \ and they do so during the process of repairing an injury. Ground tissues are simple tissues made up of parenchyma cells. Parenchyma cells are the most abundant cells in plants. Overall they are spherical but flat at point of contact.
They have thin primary cell walls and have large vacuoles for storage of food. In leaves they are called mesophyll and are the sites of photosynthesis. In other parts they are the sites of respiration and protein synthesis.
Support Tissues
These tissues provide strength and flexibility to the plants. They are further of two types,
Collenchyma Tissue
They are found just beneath the epidermis in the cortex of young herbaceous stems and the midribs of leaves and in petals of flowers. They are made of elongated cells with unevenly thickened primary cell walls. They are flexible and function to support the organs in which they are found.Sclerenchyma Tissue
They are composed of cells with rigid secondary cell walls.The cell walls are hardened With lignin, which is the main chemical component of wood. Mature sclerenchama cells cannot elongate and most of them are dead.
There are two types of cells in tissues,
(i) fibre cells are associated with xylem and phloem tissues, and cells are found in seed coats.
xylem and phloem tissue
A plant tissue composed of more than one type of cell is called a compound or complex tissue. Xylem and phloem tissues, found only in vascular plants, are examples of compound tissues.Xylem Tissue
Xylem tissue is responsible for the transport of water and dissolved substances from roots to the aerial parts. Due to the presence of lignin, the secondary walls of its cells are thick and rigid. That is why xylem tissue provides support to the plant body .Following types of cell are found in xylem tissue;
Vessel Elements or Cells:
These are short and wide cells with thick secondary cell walls. The vessel cells are dead and hollow. They lack end walls and join together to form long tubes. b- Tracheids: These are long, slender cells with overlapping ends.
Water moves upward from tracheid to tracheid Phloem tissue is responsible for the conduction of dissolved organic matter.These are long cells. Their walls have small pores and are called sieve Plates. Many sieve tube cells join to form long Pipelines called sieve tubes. During development they lose their nuclei and ribosomes etc and Possess little protoplasm.
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