12th Botany / Bio Botany Chapter 1 Important 2, 3, 5 Mark Questions 2026
Asexual and Sexual Reproduction in Plants
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📌 TWO MARKS
1.What is Layering?(3)
- The stem of a parent plant is allowed to develop roots while still intact. When the root develops, the rooted part is cut and planted to grow as a new plant.
- Examples: Ixora and Jasminum.
- Types : Mound layering and Air layering
2.What is cryopreservation.(2)
Liquid nitrogen (-1960 C) is used to preserve pollen in viable condition for prolonged duration. This technique is called cryopreservation and is used to store pollen grains of economically important crops for breeding programmes
3.What is cantharophily?Ln1 (2)
- Cantharophily is a type of pollination carried out by beetles.
- It is the transfer of pollen from one flower to another by beetles.
4.Differentiate secretary and invasive tapetum.(2)
| Secretory Tapetum | Invasive Tapetum |
|---|---|
| Glandular/Parietal/Cellular | Periplasmodial |
| Cells retain their original shape and position | Cells lose inner tangential and radial walls |
| Cellular integrity is maintained | Cellular integrity is lost |
| Protoplasm remains within individual cells | Protoplasm of all cells merges to form a periplasmodium |
| Nourishes developing microspores by secretion | Nourishes microspores through direct contact of periplasmodium |
5.Define Pollinium.(2)
The pollen in each anther lobe of a stamen unites into a mass, forming a pollinium.
6.Define Apomixis.(2)
It is defined as the substitution of the usual sexual system (Amphimixis) by a form of reproduction which does not involve meiosis and syngamy.
THREE MARKS
1.List out the function of tapetum.(6)
- It supplies nutrition to the developing microspores.
- It contributes sporopollenin through ubisch bodies thus plays an important role in pollen wall formation.
- The pollenkitt material is contributed by tapetal cells and is later transferred to the pollen surface.
- Exine proteins responsible for ‘rejection reaction’ of the stigma are present in the cavities of the exine. These proteins are derived from tapetal cells.
2.Write a short note on Pollen kit.(2)
- Pollenkitt is contributed by the tapetum and coloured yellow or orange and is chiefly made of carotenoids or flavonoids.
- It is an oily layer forming a thick viscous coating over pollen surface.
- It attracts insects and protects damage from UV radiation.
3.What is bee pollen & Write the uses of bee pollen.(2)
- Bee pollen is a natural substance and contains high protein, carbohydrate, trace amount of minerals and vitamins.
- it is used as dietary supplement and is sold as pollen tablets and syrups.
- Further , it increases the performance of athletes, race horses and also heals the wounds caused by burns.
4.Differentiate Grafting and Layering.(2)
| Grafting | Layering |
|---|---|
| Parts of two different plants are joined to grow as one plant | A stem is made to develop roots while still attached to the parent plant |
| Involves two plants: stock (rooted plant) and scion (grafted part) | Involves only one parent plant |
| Roots are already present in the stock | Roots develop from the stem before separation |
| Scion is attached to stock and grows together | Rooted part is cut from parent after root formation |
| Ex: Citrus, Mango, Apple | Ex : Ixora, Jasminum |
5.Differentiate Endothecium and Endothelium.(2)
| Endothecium | Endothelium |
|---|---|
| Found below the epidermis | Found as the inner layer of the integument |
| Usually a single layer of radially elongated cells | Specialized layer of integument cells |
| Inner tangential walls have bands of α-cellulose (sometimes lignified); cells are hygroscopic | No such thickening; cells are adapted for nutrition |
| Helps in anther dehiscence due to hygroscopic nature | Provides nourishment to the embryo sac |
| Present in anthers of flowering plants | Found in some unitegmic tenuinucellate ovules (e.g., Asteraceae) |
6.Distinguish mound layering and air layering.(2)
| Mound layering | Air layering |
|---|---|
| A lower branch is bent to the ground and part of it is buried in soil while the tip remains exposed | The stem is girdled (cut) at a node and wrapped with moist soil using polythene |
| Used for plants with flexible, low-growing branches | Used for branches that cannot be bent to the ground |
| Roots develop from the buried portion of the stem in the soil | Roots develop on the stem above the ground where it is wrapped |
| After roots form, the branch is cut from the parent plant | After 2–4 months, the rooted branch is cut and planted separately |
FIVE MARKS
1.With suitable diagram, explain the structure of an ovule?(5)
Ovule (Megasporangium) – Exam Notes (Points)
- Ovule is also called megasporangium.
- It is protected by one or two integuments.
Structure of Ovule
- A mature ovule has two parts:
- Stalk (Funiculus/Funicle) → attaches ovule to placenta
- Body of ovule
- Hilum → point where funicle attaches to ovule body
- Raphe → ridge formed when funicle is fused with ovule (in inverted ovule)
Internal Parts
- Nucellus:
- Central parenchymatous tissue
- Contains reserve food
- Integuments:
- Protective layers around nucellus
- Leave a small opening called micropyle
- Micropyle → pore at the top for entry (important in fertilization)
- Types based on integuments:
- Unitegmic → one integument
- Bitegmic → two integuments
- Chalaza:
- Basal region where nucellus, integuments, and funicle meet
Embryo Sac
- Located in nucellus near micropylar end
- Also called female gametophyte
- Develops from functional megaspore
Special Structure
- Endothelium (Integumentary tapetum):
- Inner integument layer becomes nutritive
- Seen in some plants (e.g., Asteraceae)
Types of Ovules (based on sporogenous cell)
- Tenuinucellate:
- Sporogenous cell is hypodermal
- Nucellus is small
- Crassinucellate:
- Sporogenous cell is subhypodermal
- Nucellus is large
Additional Structures
- Hypostase:
- Group of cells between chalaza and embryo sac
- Epistase:
- Thick-walled cells above micropylar end of embryo sac
2.Give detailed account on parthenocarpy. Add a note on its significance?Pg27 (3)
Parthenocarpy
- Sometimes fruits develop without fertilization
- Such fruits are called parthenocarpic fruits
After fertilization:
- Ovary → Fruit
- Ovule → Seed
Key Features
- No fertilization involved
- Seeds are absent (seedless fruits)
- Fruit develops directly from ovary
Importance
- Produces seedless commercial fruits
- Preferred for consumption and market value
Examples
- Banana , Grapes , Papaya
Significance
- The seedless fruits have great significance in horticulture.
- The seedless fruits have great commercial importance.
- Seedless fruits are useful for the preparation of jams, jellies, sauces, fruit drinks etc.
- High proportion of edible part is available in parthenocarpic fruits due to the absence of seeds.
3.Enumerate the characteristics features of Entomophilous flowers?Pg18 (3)
- Flowers are generally large or if small they are aggregated in dense inflorescence. Example: Asteraceae flowers.
- Flowers are brightly coloured. The adjacent parts of the flowers may also be brightly coloured to attract insect. For example in Poinsettia and Bougainvillea the bracts become coloured.
- Flowers are scented and produce nectar.
- Flowers in which there is no secretion of nectar, the pollen is either consumed as food or used in building up of its hive by the
honeybees. Pollen and nectar are the floral rewards for the visitors. - Flowers pollinated by flies and beetles produce foul odour to attract pollinators.
- In some flowers juicy cells are present which are pierced and the contents are sucked by the insects
4.What is endosperm? Explain its types? (3)
Endosperm
- Endosperm is a nutritive tissue formed inside the seed.
- It develops from the Primary Endosperm Nucleus (PEN) after fertilization.
- PEN is triploid (3n), formed by triple fusion (one sperm nucleus + two polar nuclei).
- Function: Nourishes and supports the developing embryo.
Types of Endosperm
- Nuclear Endosperm
- PEN divides without wall formation
- Results in free nuclei in cytoplasm
- Walls may form later
- Examples: Coccinia, Capsella, Arachis
- Cellular Endosperm
- Each nuclear division is followed by wall formation
- Endosperm becomes completely cellular
- Examples: Adoxa, Helianthus, Scoparia
- Helobial Endosperm
- PEN divides into two and forms a wall immediately
- Forms:
- Large micropylar chamber
- Small chalazal chamber
- Micropylar nucleus divides actively; chalazal may or may not
- Examples: Hydrilla, Vallisneria
Additional Points
- Endospermous (albuminous) seeds → Endosperm present (e.g., Paddy, Coconut)
- Non-endospermous (ex-albuminous) seeds → Endosperm absent (e.g., Pea, Groundnut)
5.Explain the types of ovule with diagram? (2)
Classification
- Ovules are classified based on orientation, form, and position of micropyle with respect to funicle and chalaza.
Main Types of Ovules
- Orthotropous
- Ovule is straight
- Micropyle, funicle, and chalaza lie in one straight line
- Example: Piperaceae, Polygonaceae
- Anatropous (Most common)
- Ovule is completely inverted
- Micropyle lies close to funicle
- Found in most dicots and monocots
- Hemianatropous
- Ovule is placed transversely
- Lies at right angles to funicle
- Example: Primulaceae
- Campylotropous
- Ovule is curved (bean-shaped)
- Embryo sac is slightly curved
- Micropyle, hilum, and chalaza are close together
- Example: Leguminosae
Other Types
- Amphitropous
- Ovule is curved
- Nucellus becomes horse-shoe shaped
- Distance between hilum and chalaza is less
- Example: Alismataceae
- Circinotropous
- Funicle is long and coils around the ovule
- Example: Cactaceae
5.Discuss the steps involved in microsporogenesis? (2)
Definition
- Microsporogenesis is the process of formation of haploid microspores (pollen grains) from diploid microspore mother cells (MMC) through meiosis.
Steps Involved
- Formation of Sporogenous Tissue
- Primary sporogenous cells are formed in the anther
- They may undergo mitotic divisions to produce sporogenous tissue
- Formation of Microspore Mother Cells (MMC)
- The last generation of sporogenous tissue functions as MMC (2n)
- Meiotic Division
- Each MMC undergoes meiosis
- Produces four haploid microspores
- Formation of Microspore Tetrad
- The four microspores remain together as a tetrad
- Arrangements:
- Tetrahedral
- Decussate
- Linear
- T-shaped
- Isobilateral
- Separation and Development
- Microspores separate from tetrad
- Become free in anther locule
- Develop into pollen grains
Special Cases
- Pollinium: Microspores remain united (Example: Calotropis)
- Compound pollen grains: Found in Drosera, Drymis
6.Explain the pollination mechanism in salvia?Pg17 Pg18 (2)
Pollination in Salvia (Lever Mechanism)
Key Features
- Flower is protandrous (anthers mature before stigma)
- Corolla is bilabiate (two-lipped)
- Only 2 stamens present
Structure of Stamen
- Each anther has:
- Upper fertile lobe
- Lower sterile lobe
- These are connected by a long connective
- The connective acts like a lever
Mechanism of Pollination
- Visit of Insect (Bee)
- Bee sits on lower lip (platform) of flower
- Enters flower to suck nectar
- Activation of Lever
- Bee’s body pushes against sterile lobe
- This causes the fertile lobe to swing down
- Pollen Transfer
- Fertile lobe touches the back of the bee
- Pollen grains get deposited on the bee
- Pollination Completion
- When bee visits another flower
- Pollen gets transferred to stigma
- Pollination occurs
Other Pollination Mechanisms (Examples)
- Trap mechanism – Aristolochia
- Pitfall mechanism – Arum
- Clip/Translator mechanism – Asclepiadaceae
- Piston mechanism – Papilionaceae
