Plant Tissues Questions in English

(A) The growth in the girth (diameter) of the stem or root is known as secondary growth.
This process is primarily responsible for the increase in the thickness of the plant body.
Lateral meristem,also known as cambium,is the specific type of meristematic tissue responsible for this secondary growth.
Apical meristem is responsible for the increase in length (primary growth) of the stem and root.
Intercalary meristem is found at the internodes and is responsible for the growth of leaves and branches.
Therefore,the correct answer is $A$.

(B) The cork cells (bark) are dead and compactly arranged without intercellular spaces.
Their cell walls are thickened by the deposition of a chemical substance called $Suberin$.
$Suberin$ is a waxy,hydrophobic substance that makes the bark cells impervious to water and gases,thereby protecting the plant from mechanical injury and preventing water loss.

(C) Sclerenchyma is a type of permanent tissue in plants that consists of dead cells at maturity.
These cells have thick,lignified secondary walls that provide structural support and rigidity to the plant body.
In contrast,Parenchyma and Collenchyma are living tissues,and Epithelial tissue is a type of animal tissue,not a plant tissue.

(D) The incorrect sentence is that $Apical$ and $intercalary$ meristems are permanent tissues.
$Apical$ and $intercalary$ meristems are types of $meristematic$ tissues, which are actively dividing tissues.
$Permanent$ tissues are those that have lost the ability to divide and have attained a definite shape, size, and function.
$Parenchyma$ cells typically have intercellular spaces.
$Collenchyma$ cells show irregular thickening at the corners due to the deposition of $pectin$ and $cellulose$.
$Meristematic$ cells are small, have dense cytoplasm, and lack vacuoles in their early stages to facilitate rapid division.

(B) The cell wall of $Tracheids$ is characterized by the presence of pits,but they are not considered 'perforated' in the same functional sense as the sieve plates of $Sieve$ $tubes$ or the open ends of $Vessels$. However,in the context of plant anatomy,$Tracheids$ are elongated cells with tapering ends and lignified walls that lack the large,open perforations found in $Vessels$ or the sieve plates of $Sieve$ $tubes$. $Companion$ $cells$ are living parenchyma cells associated with $Sieve$ $tubes$ and do not possess perforated walls. Among the options provided,$Tracheids$ are the primary conducting elements in gymnosperms and pteridophytes that lack the true perforation plates found in angiosperm $Vessels$.

(B) Phloem is a complex permanent tissue responsible for the translocation of food in plants.
It consists of four types of elements: sieve tubes,companion cells,phloem parenchyma,and phloem fibres.
Among these,sieve tubes,companion cells,and phloem parenchyma are living cells.
Phloem fibres (also known as bast fibres) are the only dead elements present in the phloem tissue at maturity.
Therefore,the correct option is $B$.

(C) In mature mammalian red blood cells $(RBCs)$,the nucleus is lost to provide more space for hemoglobin.
In the xylem tissue,mature vessel elements are dead and lack a nucleus.
In the phloem tissue,mature sieve tube elements lose their nucleus to facilitate the transport of food.
Companion cells are specialized parenchyma cells that remain living and retain their nucleus at maturity to support the metabolic activities of the adjacent sieve tube elements.

(D) In desert plants,the epidermis is often covered by a thick,waxy,water-resistant layer called the $Cuticle$.
This $Cuticle$ is composed of $Cutin$,a fatty substance.
It acts as a protective barrier that significantly reduces the rate of transpiration (water loss) from the plant surface,helping the plant conserve water in arid environments.

(B) Meristematic tissues are groups of cells that have the ability to divide continuously.
These tissues are restricted to specific regions in the plant body,such as the tips of roots and shoots,known as apical meristems.
Because they are actively involved in cell division,they are responsible for the growth of the plant.
Therefore,they are described as localised and consisting of actively dividing cells.

(C) The epidermis is the outermost layer of cells in plants. Its primary functions include:
$1$. Protection: It protects the underlying tissues from mechanical injury,pathogens,and adverse environmental conditions.
$2$. Gaseous exchange: Stomata present in the epidermis facilitate the exchange of gases ($O_2$ and $CO_2$).
$3$. Transpiration: Stomata also regulate the loss of water in the form of water vapor.
$4$. Conduction of water is the primary function of the $Xylem$ tissue,not the epidermis.
Therefore,the correct answer is $C$.