A: Primary meristems: They are present at the tips of roots and shoots.
Function: They produce primary tissues and help in vertical growth.
Intercalary meristems: They are present between mature tissues.
Function: They regenerate parts removed by grazing animals.
Secondary or lateral meristems: They are present in mature regions of roots and shoots.
Ex: Vascular cambium in the stele and cork cambium in the cortex.
Function: They produce secondary tissues and help in radial growth.
Q: A transverse section of the trunk of a tree shows concentric rings which are known as annual rings. How are these rings formed?
What is the significance of these rings?
A: During secondary growth the vascular cambium produces secondary xylem towards inside and secondary phloem towards outside. Secondary xylem formed during spring has more number of xylem vessels with wide lumens and called spring wood or early wood.
The secondary xylem formed during autumn season has less number of xylem vessels with narrow lumens and called autumn wood or late wood. The spring wood and autumn wood produced in one year appear as one concentric ring called as annual ring or growth ring.
Significance: Annual rings are useful to estimate the age of the tree approximately.
Q: Write the precise function of
a) Sieve tube b) Interfasicular cambium
c) Collenchyma d) Sclerenchyma
A: a. Sieve tube: Transport of food materials from leaves to other parts of the plant.
b. Interfasicular cambium: Formation of cambial ring and production of secondary xylem and secondary phloem.
c. Collenchyma: Mechanical support to young stems and petioles and assimilation of food.
d. Sclerenchyma: Provide mechanical support to organs.
Q: Name the three basic tissue systems in the flowering plants. Give the tissue names under each system.
A: The tissues are organized into different tissue systems at different locations in the plant body. The three types of tissue systems are:
The epidermal tissue system: It consists of epidermis, stomata, cuticle, trichomes and root hair.
The ground tissue system (fundamental tissue system): The ground tissue system composes of all tissues except epidermis and vascular bundles. It includes hypodermis or exodermis, general cortex, endodermis, pericycle, pith and medullary rays.
The vascular tissue system (conducting tissue system): The vascular tissue system consists of xylem, phloem and cambium.
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