Q: Describe the T.S of dicot stem.
A: The transverse section of a dicot stem shows: Epidermis, Cortex and Stele.
Epidermis: The epidermis is outer most protective layer covered by a cuticle. It may bear multicellular trichomes and stomata. It helps in protection, transpiration and
gaseous exchange.
Cortex: The cortex is the region between epidermis and stele. It is differentiated into: 1) Hypodermis 2) General cortex 3) Endodermis
The hypodermis is present below the epidermis and made up of collenchyma. It gives mechanical strength to young stems.
General cortex is parenchymatous with intercellular spaces. It helps in assimilation and
storage. The inner most layer of cortex is endodermis also called starch sheath. It
stores starch.
Stele: The stele is the central conducting cylinder and occupies large area in the stem.
It is differentiated into: 1) Pericycle 2) Vascular bundles 3) Medulla 4) Medullary rays
Pericycle is in the form of a semi lunar patch of Sclerenchyma above the vascular bundle.
The vascular bundles are arranged in a ring (eustele). Each vascular bundle is collateral, conjoint, open (cambium present between xylem and phloem) with endarch xylem.
Xylem is present towards centre and phloem towards periphery separated by cambium. Pith is large and parenchymatous at the centre and radiates as medullary rays in between the vascular bundles.
Junior Intermediate Imp Questions for 4 Marks - Botany Chapters 12-13
Q: Define plant succession. Differentiate primary and secondary successions.
A: The gradual change in the composition of species in a given area is called ecological succession.
Plant succession may occur through xerosere or hydrosere. When plant succession starts on a bare rock it is called xerosere. When it starts on an aquatic habitat it is called hydrosere.
The sequence of communities that successively change in a given area are called seres.
If the succession starts where no living organisms ever existed like bare rock it is
called primary succession.
Ex: Cooled lava, bare rock, newly created reservoir or pond. It takes long period to
reach a climax community in primary succession.
If the succession starts in an area where organisms were existing but somehow lost is
called secondary succession. Ex: Abandoned farm lands, burned forests, flooded lands. Climax community is reached in less time when compared to primary succession.
Q: Define ecosystem / ecological services. Explain in brief with regard to pollination.
A: Ecosystem services or ecological services are the services provided by nature that are life supporting and life enhancing.
Ecosystem service - pollination: Pollination is an essential part of healthy ecosystem.
It is the transfer of pollen grains from the anthers to the stigma of a flower to facilitate fertilization process.
In many plants pollination is carried out by different species of animals especially
insects. The pollination carried out through insects is called entamophily. The animals (insects) which carry out pollination are called pollinators.
They are very important to ensure fertilization and seed and fruit production in majority of our crop plants. Decline in pollinator activity results in loss of
crop yield. Nearly one lakh species of invertebrates and 1035 species of vertebrates act as pollinators. According to US Fish and Wildlife Service lists 50 pollinator species are threatened or endangered. Causes of decline in pollinators are deforestation and chemical pesticides.
A: The gradual change in the composition of species in a given area is called ecological succession.
Plant succession may occur through xerosere or hydrosere. When plant succession starts on a bare rock it is called xerosere. When it starts on an aquatic habitat it is called hydrosere.
The sequence of communities that successively change in a given area are called seres.
If the succession starts where no living organisms ever existed like bare rock it is
called primary succession.
Ex: Cooled lava, bare rock, newly created reservoir or pond. It takes long period to
reach a climax community in primary succession.
If the succession starts in an area where organisms were existing but somehow lost is
called secondary succession. Ex: Abandoned farm lands, burned forests, flooded lands. Climax community is reached in less time when compared to primary succession.
Q: Define ecosystem / ecological services. Explain in brief with regard to pollination.
A: Ecosystem services or ecological services are the services provided by nature that are life supporting and life enhancing.
Ecosystem service - pollination: Pollination is an essential part of healthy ecosystem.
It is the transfer of pollen grains from the anthers to the stigma of a flower to facilitate fertilization process.
In many plants pollination is carried out by different species of animals especially
insects. The pollination carried out through insects is called entamophily. The animals (insects) which carry out pollination are called pollinators.
They are very important to ensure fertilization and seed and fruit production in majority of our crop plants. Decline in pollinator activity results in loss of
crop yield. Nearly one lakh species of invertebrates and 1035 species of vertebrates act as pollinators. According to US Fish and Wildlife Service lists 50 pollinator species are threatened or endangered. Causes of decline in pollinators are deforestation and chemical pesticides.
Junior Inter Botany Important Questions for 4 Marks - Chapters 12-13
Q: State the location and function of different types of meristems.
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.
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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