POST-FERTILISATION : STRUCTURES AND EVENTS

          Following double fertilisation, events of endosperm and embryo development, maturation of ovule(s) into seed(s) and ovary into fruit, are collectively termed post-fertilisation events.

1. Post-Fertilisation Events

Definition

The events that occur after fertilisation in a flower are called post-fertilisation events.

These include:

1. Development of endosperm
2. Development of embryo
3. Conversion of ovule into seed
4. Conversion of ovary into fruit

                Double Fertilisation

                                ↓

          Post-Fertilisation Events

                           ↓

 ┌────────┼─────────┐

 ↓                        ↓                           ↓

Endosperm        Embryo          Seed & Fruit

2. Endosperm

What is Endosperm?

Endosperm is a nutritive tissue formed inside the seed after fertilisation.

It provides food and nourishment to the developing embryo.

Formation of Endosperm

After triple fusion:

• A Primary Endosperm Nucleus (PEN) is formed.
• PEN divides repeatedly.
• It develops into a triploid (3n) endosperm tissue.

Why Does Endosperm Develop Before Embryo?

Because the embryo needs food for its growth and development.

Therefore: Endosperm develops first and supplies nutrition to the embryo.

Triple Fusion

            ↓

Primary Endosperm Nucleus (PEN)

            ↓

Repeated Cell Divisions

            ↓

Endosperm Tissue

             ↓

Food Supply to Embryo

3. Free-Nuclear Endosperm

Definition

When PEN undergoes repeated nuclear divisions without cell wall formation, the endosperm is called Free-Nuclear Endosperm.

Characteristics

✔ Many nuclei are formed.

✔ No cell walls are present initially.

✔ Nuclei remain free in the cytoplasm.

PEN

 ↓

Nuclear Divisions

 ↓

○ ○ ○ ○ ○ ○ ○

(Free Nuclei)

4. Cellular Endosperm

After the formation of free nuclei:

• Cell walls are formed around the nuclei.
• The endosperm becomes cellular.

This stage is called Cellular Endosperm.

Free-Nuclear Endosperm

          ↓

 Cell Wall Formation

          ↓

 Cellular Endosperm

Important Note

The liquid inside a tender coconut contains thousands of free nuclei and represents the free-nuclear stage of endosperm.

5. Fate of Endosperm

The endosperm may either:

A. Be Completely Consumed

The developing embryo uses all the endosperm before seed maturation.

Examples:

• Pea
• Groundnut
• Bean

Such seeds are called Non-endospermic (Exalbuminous) Seeds.

B. Persist in Mature Seed

Some endosperm remains stored in the mature seed and is used during germination.

Examples:

• Castor
• Coconut

Such seeds are called Endospermic (Albuminous) Seeds.

Non-Endospermic Seeds	Endospermic Seeds
Pea	Castor
Groundnut	Coconut
Bean	Maize

Term	Meaning
Endosperm	Nutritive tissue of seed
PEN	Primary Endosperm Nucleus
Free-Nuclear Endosperm	Endosperm with free nuclei and no cell walls
Cellular Endosperm	Endosperm with cell walls
Albuminous Seed	Seed with persistent endosperm
Exalbuminous Seed	Seed without endosperm at maturity

Check Your Progress

1. The events occurring after fertilisation are collectively known as:

A. Pollination events
B. Pre-fertilisation events
C. Post-fertilisation events
D. Germination events

2. Which tissue provides nourishment to the developing embryo?
A. Ovule
B. Endosperm
C. Cotyledon
D. Ovary

3. The Primary Endosperm Nucleus (PEN) is:
A. Haploid (n)
B. Diploid (2n)
C. Triploid (3n)
D. Tetraploid (4n)

4. Why does endosperm develop before the embryo?
A. To form fruit
B. To produce pollen
C. To provide nutrition to the embryo
D. To protect the ovule

5. The stage of endosperm development in which nuclei divide without cell wall formation is called:
A. Cellular endosperm
B. Free-nuclear endosperm
C. Albuminous endosperm
D. Embryonic endosperm

6. Coconut water represents:
A. Embryo
B. Cellular endosperm
C. Free-nuclear endosperm
D. Cotyledon

7. The white kernel of coconut is an example of:
A. Free-nuclear endosperm
B. Cellular endosperm
C. Embryo
D. Pericarp

8. Which of the following seeds is non-endospermic at maturity?
A. Coconut
B. Castor
C. Pea
D. Maize

9. Endosperm persists in mature seeds of:
A. Pea and Bean
B. Groundnut and Pea
C. Castor and Coconut
D. Bean and Groundnut

10. The ovary develops into a ______ after fertilisation.

A. Seed
B. Fruit
C. Embryo
D. Endosperm

Answer Key

1. C 

2. B

3. C

4. C

5. B

6. C

7. B

8. C

9. C

10. B

Cultivation of Chrysanthemum

Botanical Name

Dendranthema grandiflora
(Formerly known as Chrysanthemum morifolium)

Family

Asteraceae

Introduction

Chrysanthemum is one of the most beautiful and important ornamental flower crops grown throughout the world. It is popularly known as the Queen of the East or Autumn Queen because it blooms profusely during the autumn and winter seasons. In India, it is commonly called Guldaudi.

The flowers are attractive, colourful, and available in different shapes and sizes. Chrysanthemum is widely cultivated for:

• Loose flowers

• Cut flowers

• Pot decoration

• Garden decoration

• Bouquet preparation

It is also an important commercial flower crop because of its high demand in markets and festivals.

Types of Chrysanthemum

Chrysanthemum flowers are classified into different groups according to flower shape and arrangement of petals.

Important types are:

• Single

• Anemone

• Pompon

• Decorative

• Incurved

• Reflexed

• Intermediate

Important Varieties

Standard Varieties

These varieties produce large flowers.
Examples:

• Basanti

• Snowball

• Rakhi

• Purnima

• Shanti

Spray Varieties

These produce many small flowers in clusters.
Examples:

• Ajay

• Apsara

• Pusa Aditya

• Jayanti

• White Bouquets

Climate

Chrysanthemum is a short-day plant. It requires:

• Long days for vegetative growth

• Short days for flowering

Suitable Temperature

• Day temperature: 20–28°C

• Night temperature: 5–20°C

Cool and pleasant climate is best for proper flowering.

Soil

Chrysanthemum can grow in different soil types, but the best soil is:

• Sandy loam to loamy soil

• Rich in organic matter

• Well-drained

• Soil pH around 6.5

Waterlogging should be avoided because it causes root diseases.

Propagation

Chrysanthemum is propagated by:

1. Seeds

2. Suckers

3. Terminal cuttings

Terminal Cuttings

This is the most common commercial method.

• Healthy terminal cuttings of 5–8 cm length are used.

• Cuttings are treated with rooting hormones like IBA.

• Rooting occurs within 3–4 weeks.

Land Preparation

• The field should be ploughed 3 times.

• Well rotten FYM or compost is mixed during ploughing.

• Soil should be made loose and fine.

• Proper irrigation and drainage channels should be prepared.

Planting

The ideal planting time is May–June.

Planting Method

• Rooted cuttings are transplanted in beds or ridges.

• Immediate irrigation is necessary after transplanting.

Spacing

• 20 × 30 cm

• 30 × 30 cm

• 40 × 40 cm

Spacing depends on the variety and purpose of cultivation.

Irrigation

Proper irrigation is essential for healthy growth.

• Water immediately after transplanting.

• During summer, irrigation is given every 4 days.

• During winter, irrigation is given at 7–10 day intervals.

• Excess water should be avoided.

Manures and Fertilisers

Organic Manure

• Farmyard manure (FYM) is applied during land preparation.

Fertiliser Dose

• NPK: 50:160:80 kg/ha

Application

• Phosphorus and potassium are applied as basal dose.

• Nitrogen is applied in split doses.

Staking

Tall chrysanthemum plants need support.

Purpose of Staking

• Keeps plants upright

• Prevents lodging

• Improves flower quality

Bamboo sticks are commonly used as stakes.

Pinching

Pinching means removal of the growing tip of the plant.

Advantages

• Encourages branching

• Produces more flowers

• Improves flower yield

Pinching is usually done when plants reach 10–15 cm height.

Disbudding

Disbudding means removal of side buds.

Purpose

• Produces large-sized flowers

• Improves flower quality

This practice is mainly done in large-flowered varieties.

Weed Control

Weeds compete for nutrients, water, and sunlight.

Weed Control Methods

• Hand weeding

• Mulching with straw or sawdust

• Use of herbicides like trifluralin

Harvesting

Flowers are harvested when fully open.

Harvesting Time

• Early morning is the best time.

Yield

• Average yield is about 10–15 tonnes per hectare.

Important Insect-Pests

Major insect-pests of chrysanthemum are:

• Aphids

• Thrips

• Leaf miners

• Whiteflies

• Mealybugs

• Hairy caterpillars

• Red spider mites

• Root-knot nematodes

Control Measures

• Maintain field sanitation

• Remove infected plant parts

• Spray recommended insecticides

• Use sticky traps where necessary

Important Diseases

Common diseases are:

• Root rot

• Damping off

• Wilt

• Leaf spot

• White rust

• Bacterial leaf spot

• Viral diseases

Control Measures

• Proper drainage

• Use healthy planting materials

• Remove diseased plants

• Spray fungicides such as mancozeb or carbendazim

Conclusion

Chrysanthemum is an important ornamental and commercial flower crop. Proper management practices such as:

• Good land preparation

• Proper irrigation

• Balanced fertiliser application

• Pinching and disbudding

• Pest and disease control

help in obtaining better flower quality and higher yield. Chrysanthemum cultivation can provide good income to farmers and flower growers.

Check your progress

Practical Exercise

Activity 1

Propagation of chrysanthemum by cutting.

Material required

Healthy chrysanthemum plant, secateur, IBA, water can, etc.

Procedure

• Select the terminal branches of a healthy plant for cutting.

• Terminal tip cuttings of 5–8 cm long are cut with the help of secateur.

• Remove basal leaves and half of the other open leaves.

• Base of the cutting is dipped in IBA 500 ppm or Seradix.

• Plant the cutting by inserting them 3–5 cm apart in sand beds.

• Immediately after planting, light watering with fine rose can should be given.

• Irrigate it regularly daily until 3–4 weeks.

The Future Crisis and the Need to Prepare Our Young Generation

Today, the world is facing many serious problems. Wars between countries are increasing day by day. The present conflict between Israel and Iran has already created fear across the world. If powerful countries like America directly enter the war, the situation may become more dangerous. One major concern is the supply of oil and natural gas through the Strait of Hormuz, which is one of the world’s most important routes for energy transportation.

If Iran restricts oil and gas supply through this route, many countries including India may face serious problems. Transportation, industries, electricity production, and daily life depend heavily on fuel. In such situations, governments may impose temporary lockdowns or restrictions to control the crisis. However, these lockdowns will only be short-term solutions.

The bigger question is about the future of humanity.

After 40 or 50 years, the world may naturally face a much bigger “lockdown.” This lockdown will not be announced by any government. It may happen because natural resources are rapidly decreasing. Oil, coal, natural gas, clean water, fertile land, and forests are being used faster than nature can replace them.

If resources continue to decrease at the present rate, future generations may face:

• Shortage of fuel and transportation
• Lack of food and essential commodities
• Water scarcity
• Environmental disasters
• Increased conflicts and wars over resources
• Economic collapse in many regions

Wars and overconsumption can make this crisis come even earlier.

Today, most people are busy with modern lifestyles and technology, but very few are thinking about long-term survival. We must now start teaching our young generation how to live sustainably and survive in difficult times.

Children and students should learn:

• Importance of nature and biodiversity
• Water conservation
• Organic farming and food production
• Renewable energy sources
• Recycling and reducing waste
• Simple and sustainable living
• Community cooperation and self-reliance

Nature itself is the best teacher. Forests, villages, and traditional lifestyles can teach us many survival skills that modern society has forgotten.

This article is not written to create fear. It is written to create awareness. If we act wisely today, we can reduce future problems. The future of humanity depends on how responsibly we use our natural resources today.

Let us educate, prepare, and inspire the younger generation to protect nature and build a sustainable future.

“The Earth does not belong to us; we borrow it from our children.”

Plant water relationaships

       Water is one of the most essential components of plant life. It constitutes about 80–95% of the fresh weight of actively growing plant tissues. Water acts as -a  solvent, a transport medium, a reactant in photosynthesis, a temperature regulator and a source of turgidity

The study of absorption, transport, utilization, and loss of water in plants is known as Plant–Water Relations.

Water Potential (Ψw)

Water potential is the potential energy of water that determines the direction of movement of water in a system.

Water always moves from:

• Higher water potential → Lower water potential

Pure water has the highest water potential:
[Psi_w = 0]

Water potential helps explain how water moves from soil into roots and from one plant cell to another. The presence of dissolved substances and pressure affects the water potential of cells.

It determines the direction of water movement.

Water always moves:

• From higher water potential
• To lower water potential

Pure water has the highest water potential:

$$\Psi_w = 0$$

Water potential is measured in:

• Pascal (Pa)
• Megapascal (MPa)

Components of Water Potential

Water potential is mainly composed of:

$$\Psi_w = \Psi_s + \Psi_p$$

Where:

• $\Psi_w$ = Water potential
• $\Psi_s$ = Solute potential (osmotic potential)
• $\Psi_p$ = Pressure potential

Example

• Water moves from pure water into a concentrated sugar solution because the sugar solution has lower water potential.

Solute Potential (Ψs)

Solute potential is the decrease in water potential due to dissolved solutes.

It is always negative.

When solutes like salts or sugars dissolve in water, they reduce the free energy of water molecules. Therefore, water tends to move toward the region containing more solutes.

• Also called osmotic potential.
• Addition of solute decreases water potential.
• Always negative.

Example:

• Pure water = 0
• Sugar solution = negative value

Example

• Salt water has lower solute potential than pure water.

Pressure Potential (Ψp)

Pressure potential is the pressure exerted by the cell wall on the cell contents.

Pressure exerted by cell wall on cell contents.

Usually positive in living cells.

Responsible for turgidity.

Explanation

When water enters a plant cell, the vacuole expands and presses the cytoplasm against the cell wall. This creates turgor pressure which keeps plants upright.

Example

• Fresh green leaves remain firm because of positive pressure potential.

Osmosis

Osmosis is the movement of water molecules through a semipermeable membrane from higher water concentration to lower water concentration.

Explanation

Osmosis is the major method by which roots absorb water from soil. Cell membranes allow water molecules to pass while restricting many dissolved substances.

Example

• Raisins swell when kept in water due to osmosis.

Diffusion

Diffusion is the movement of molecules from higher concentration to lower concentration.

Explanation

Diffusion occurs without energy expenditure and continues until equilibrium is reached.

Example

• Perfume smell spreading throughout a room.

Imbibition

Imbibition is the absorption of water by hydrophilic substances resulting in swelling.

Explanation

Certain substances such as cellulose and proteins attract water molecules and absorb them rapidly.

Example

• Dry seeds swell after soaking in water.

Root Pressure

Definition

Root pressure is the positive pressure generated in roots due to active absorption of mineral ions and water.

Explanation

Mineral accumulation in xylem lowers water potential, causing water to enter xylem vessels. This creates pressure that pushes water upward.

Example

• Water droplets ooze out from cut stems of herbaceous plants.

Guttation

Definition

Guttation is the loss of liquid water droplets from leaf margins through hydathodes.

Explanation

When transpiration is low and soil moisture is high, root pressure forces excess water out through hydathodes.

Example

• Water droplets seen at the tips of grass leaves early in the morning.

Transpiration

Definition

Transpiration is the loss of water in the form of water vapor from aerial parts of plants.

Explanation

Most transpiration occurs through stomata. It creates transpiration pull and helps cool the plant body.

Example

• Water vapor loss from leaves of sunflower plants during daytime.

Transpiration Pull

Definition

Transpiration pull is the suction force generated due to evaporation of water from leaves.

Explanation

As water evaporates from mesophyll cells, tension develops in xylem vessels, pulling water upward from roots.

Example

• Water transport to the top of tall trees such as eucalyptus.Cohesion

Definition

Cohesion is the attraction between water molecules.

Explanation

Hydrogen bonding between water molecules keeps the water column continuous inside xylem vessels.

Example

• Continuous water column during ascent of sap.

Adhesion

Definition

Adhesion is the attraction between water molecules and other surfaces.

Explanation

Water molecules adhere to xylem walls, helping maintain the water column against gravity.

Example

• Water sticking to inner walls of xylem vessels.

Aquaporins

Definition

Aquaporins are specialized membrane proteins that facilitate rapid movement of water across membranes.

Explanation

They form channels in the plasma membrane allowing quick transport of water molecules.

Example

• Rapid water absorption by root cells.

Apoplast Pathway

Definition

Movement of water through cell walls and intercellular spaces.

Explanation

Water does not cross membranes in this pathway and therefore moves rapidly.

Example

• Water movement through cortex before reaching endodermis.

Symplast Pathway

Definition

Movement of water through the cytoplasm connected by plasmodesmata.

Explanation

Water enters the cytoplasm once and then moves cell-to-cell through plasmodesmata.

Example

• Water movement among cortical cells of roots.

Transmembrane Pathway

Definition

Movement of water across plasma membranes repeatedly from one cell to another.

Explanation

Water alternates between cytoplasm and cell wall while moving through tissues.

Example

• Water transport across root cortical cells.

Hydathodes

Definition

Hydathodes are specialized openings present at leaf margins through which guttation occurs.

Explanation

They remain permanently open and are connected to xylem endings.

Example

• Hydathodes present at the leaf margins of grasses.

Turgor Pressure

Definition

Turgor pressure is the pressure exerted by cell sap against the cell wall.

Explanation

It maintains rigidity and prevents wilting in plants.

Example

• Young shoots remain erect due to turgor pressure.

Flaccid Cell

Definition

A flaccid cell is a cell that has lost water and become limp.

Explanation

Loss of water decreases turgor pressure causing wilting.

Example

• Wilted leaves during drought conditions.

Antitranspirants

Definition

Antitranspirants are chemicals that reduce transpiration in plants.

Explanation

They help conserve water by reducing stomatal opening or forming protective films on leaves.

Example

• Phenyl mercuric acetate (PMA) used as stomatal closing antitranspirant.

Eukaryotic Cell

A eukaryotic cell is a complex type of cell that contains a true nucleus enclosed by a nuclear membrane and several membrane-bound organelles such as mitochondria, endoplasmic reticulum, Golgi bodies, chloroplasts (in plants), etc.

The word “Eukaryotic” comes from the Greek words:

• Eu = true

• Karyon = nucleus

Thus, eukaryotic cells possess a well-defined nucleus.

Eukaryotic cells are found in:

• Animals

• Plants

• Fungi

• Protists

Characteristics of Eukaryotic Cells

1. Presence of a true nucleus.

2. DNA arranged in chromosomes.

3. Presence of membrane-bound organelles.

4. Larger and more complex than prokaryotic cells.

5. Cell division occurs through mitosis and meiosis.

6. Cytoplasm is well organized.

Diagram of a Typical Eukaryotic Cell

Fig: A typical eukaryotic cell

Major Organelles of a Eukaryotic Cell and Their Functions

Organelle	Function
Cell Membrane	Controls movement of substances into and out of the cell
Cytoplasm	Jelly-like matrix where organelles remain suspended
Nucleus	Controls all cellular activities and contains DNA
Nucleolus	Formation of ribosomes
Mitochondria	Site of cellular respiration and ATP production
Ribosomes	Protein synthesis
Endoplasmic Reticulum (ER)	Transport of materials inside the cell
Rough ER	Protein synthesis due to attached ribosomes
Smooth ER	Lipid synthesis and detoxification
Golgi Apparatus	Packaging and secretion of proteins
Lysosomes	Intracellular digestion
Vacuoles	Storage of food, water, and wastes
Centrosome/Centrioles	Help in cell division (mainly animal cells)
Chloroplast (plant cells)	Photosynthesis
Cell Wall (plant cells)	Provides rigidity and protection

Types of Eukaryotic Cells

1. Animal Cell

• No cell wall

• Small vacuoles

• Centrosome present

2. Plant Cell

• Cell wall present

• Large central vacuole

• Chloroplast present

Difference Between Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cell	Eukaryotic Cell
Nucleus	Absent	Present
Size	Small	Large
Organelles	Absent	Present
DNA	Naked circular DNA	Linear chromosomes
Examples	Bacteria	Plants, animals, fungi

        Eukaryotic cells are highly organized cells possessing a true nucleus and membrane-bound organelles. Their complex internal structure enables advanced cellular functions in plants, animals, fungi, and protists.

Diagrammatic presentation of a eukaryotic cell & functions

Do you want to know more?

Important Scientists Related to the Discovery of Eukaryotic Cells

1. Robert Hooke (1665)

• Observed cork cells using a microscope.
• Coined the term “cell” in his book Micrographia.
• These were dead plant cells.

2. Antonie van Leeuwenhoek (1674)

• First observed living cells and microorganisms.
• Called them “animalcules”.

3. Édouard Chatton (1925)

• Introduced the terms:
  • Prokaryote
  • Eukaryote
• Distinguished cells based on the presence of a true nucleus.

Therefore, Édouard Chatton is credited with distinguishing and defining eukaryotic cells, while Robert Hooke first discovered cells in general.

Check your progress

Cultivation of Commercial F lower Crops — I China Aster

China Aster

Botanical Name: Callistephus chinensis

Family: Asteraceae

Introduction

China aster is one of the most important annual ornamental flower crops cultivated throughout the world. It is native to China and belongs to the family Asteraceae. In India, it is mainly grown as a traditional flower crop for loose flowers, while internationally it is also popular as a cut flower crop.

In Northeast India and Assam, China aster has good commercial potential because of:

• Favourable climatic conditions

• Availability of fertile soils

• Increasing demand for flowers in local markets

• Scope for protected cultivation and floriculture entrepreneurship

It is commonly used for:

• Garlands

• Religious and social functions

• Floral decoration

• Bedding and border planting

• Bouquet preparation

Scope of China Aster Cultivation in Northeast India and Assam

The agro-climatic conditions of Assam and Northeast India are highly suitable for flower cultivation due to:

• Moderate temperature

• High humidity

• Adequate rainfall

• Fertile alluvial soils

Districts around:

• Dibrugarh

• Tinsukia

• Jorhat

• Sivasagar

• Kamrup

• Cachar

have good potential for commercial cultivation of China aster.

The crop is especially suitable for:

• Small and marginal farmers

• Kitchen gardens

• Nursery business

• Commercial floriculture units

Flowers are sold in:

• Local markets

• Temple markets

• Marriage ceremonies

• Festival decorations

Demand increases during:

• Durga Puja

• Bihu

• Weddings

• Religious functions

Important Varieties

Important varieties suitable for Indian conditions include:

• Kamini

• Poornima

• Phule Ganesh Pink

• Phule Ganesh Purple

• Phule Ganesh Violet

• Phule Ganesh White

• Shashank

• Violet Cushion

These varieties perform well under Assam conditions with proper drainage management.

Climate Requirement

China aster prefers cool and mild climate.

Optimum Conditions

• Day temperature: 20–30°C

• Night temperature: 10–18°C

• Relative humidity: 50–60%

• Bright sunlight is essential

In Assam and Northeast India

• Winter season is ideal for cultivation.

• Excessive monsoon rainfall may cause fungal diseases and root rot.

• Therefore, proper drainage is essential.

Soil Requirement

Best suited soils are:

• Well-drained sandy loam or loamy soils

• Rich in organic matter

• Soil pH: 6.8–7.5

In Assam

Alluvial soils of Brahmaputra valley are suitable for cultivation if:

• Drainage is maintained

• Organic manure is adequately applied

Waterlogging should be strictly avoided due to heavy rainfall conditions.

Propagation

China aster is propagated through seeds.

Seed Requirement

• 2.5–3.0 kg seed per hectare

Nursery Raising

• Seeds are sown in raised nursery beds during September–October.

• Seedlings become ready in about one month.

• Seedlings of about 10 cm height are transplanted to the main field.

In Northeast India

Raised nursery beds are very important to avoid:

• Water stagnation

• Damping-off disease

Land Preparation

• Land should be ploughed 3–4 times for fine tilth.

• Proper drainage channels should be prepared.

• Farmyard manure (FYM) @ 10–15 tonnes/ha should be mixed during land preparation.

• Vermicompost can also be used.

Special Recommendation for Assam

Because of heavy rainfall:

• Raised beds are highly recommended.

• Drainage channels should be maintained throughout the field.

Planting Time

Assam and Northeast India

• Nursery sowing: September–October

• Transplanting: October–November

Flowering generally occurs during winter when climatic conditions remain favourable.

Spacing

Recommended spacing:

• 30 × 30 cm

• 45 × 45 cm

According to soil type:

• Light soils: 45 × 20 cm

• Medium soils: 60 × 20 cm

Manures and Fertilisers

Organic Manure

• FYM @ 10–15 tonnes/ha

Fertiliser Dose

• NPK @ 120:80:120 kg/ha

Application

• Full phosphorus and potassium as basal dose

• Nitrogen in 2–3 split doses

In Assam

Use of organic manures and vermicompost improves:

• Soil structure

• Water-holding capacity

• Flower quality

Irrigation

China aster requires moderate irrigation.

General Recommendation

• Irrigation at 10–12 day intervals during winter

In Northeast India

• Irrigation requirement is less during winter due to residual soil moisture.

• Excess irrigation should be avoided.

Pinching

Pinching is done one month after transplanting.

Advantages

• Promotes branching

• Increases flower production

• Improves flower yield

Disadvantage

• Slight delay in flowering

Harvesting

Loose Flowers

Harvested when flowers are fully open.

Cut Flowers

Harvested when flower colour fully develops.

Post-Harvest Handling

• Stems should be immediately placed in clean water.

• Flowers should be graded and packed carefully.

Yield

Average loose flower yield:

• 15–20 tonnes/ha

Yield depends on:

• Variety

• Soil fertility

• Drainage

• Weather

• Crop management

Important Insect-Pests

Major Pests

• Black blister beetle (Epicauta pennsylvanica)

• Asiatic beetle (Autoserica castanea)

• Tarnished plant bug (Lygus lineolaris)

• Leafhopper (Macrosteles fascifrons)

• Leaf miners

• Semilooper caterpillars

Control Measures

• Field sanitation

• Light traps

• Need-based insecticide application

• Removal of infected plant parts

Nematode Problems

Root-knot Nematode

(Meloidogyne incognita)

Foliage Nematode

(Aphelenchoides ritzemabosi)

Control

• Application of Furadan @ 1 g/m²

• Proper field sanitation

• Crop rotation

Diseases

Major Diseases

• Wilt

• Collar rot

• Stem rot

• Gray mould

• Leaf spot

• Rust

• Canker

Common Disease Problems in Assam

High humidity and rainfall favour:

• Fungal diseases

• Root rot

• Leaf spot diseases

Control Measures

Spraying with:

• Mancozeb

• Carbendazim

• Captan

• Zineb

• Wettable sulphur

Proper drainage and wider spacing reduce disease incidence.

Viral Diseases

Important Viruses

• Chrysanthemum mosaic virus

• Aster yellows

• Spotted wilt

• Curly top virus

Control

• Removal and destruction of infected plants

• Control of insect vectors such as leafhoppers

Conclusion

China aster is a profitable ornamental flower crop with excellent scope in Assam and Northeast India. The favourable climate, fertile soils, and increasing market demand make it suitable for commercial cultivation.

For successful production in Northeast India:

• Raised beds and drainage are essential

• Proper nutrient management should be followed

• Fungal diseases must be carefully managed during humid conditions

With scientific cultivation practices, China aster cultivation can become an important source of income for farmers and floriculture entrepreneurs in Assam and the Northeast region.

Check Your Progress

Practical exercise 

Activity 1 

Demonstrate the harvesting of China aster as a cut flower. 

Material required

Scissor or secateur, a bucket with water. China aster flowers are harvested as loose (without stalk, for making garlands, and worshipping purposes), and with stalks as cut flower use.

Procedure

1. Select long stalked fully colour developed flowers. 

2. With the help of scissor or secateur, cut the stalk of the flower as long as possible.

3. After cutting, immediately place their cut ends in distilled or palatable water.

4. Then bring the flowers inside the shed for grading and packaging.

5. The life of the cut flowers can be extended by the use of holding solution.

HS II Agriculture

 

Male Papaya bears fruit, how?

In papaya, sex expression can sometimes change due to physical injury, environmental stress, or hormonal imbalance. Normally, a male papaya plant produces only staminate (male) flowers and does not bear fruits. However, when the plant body or growing tip is injured, the balance of plant hormones may be disturbed. This can induce the development of bisexual (hermaphrodite) or female flowers on a male plant.

These newly formed flowers contain functional ovaries, so after pollination they can develop into fruits. This phenomenon is called sex reversal or sex modification in papaya.

Why this happens

• Injury affects the apical meristem and hormone regulation.
• Papaya is highly sensitive to environmental and physiological changes.
• Stress conditions (injury, temperature fluctuation, nutrition imbalance, pruning, etc.) may alter flower sex expression.

Important point

The fruits produced on such injured male plants are usually:

• fewer in number,
• irregular in shape,
• and sometimes temporary in occurrence.

This is a well-known characteristic of papaya (), which shows considerable plasticity in sex expression.

Pollen–Pistil Interaction

Introduction

After pollination, pollen grains land on the stigma of a flower. But every pollen grain may not be suitable for fertilization.

The pistil has the ability to identify whether the pollen grain is:

• Compatible (right type)   or

• Incompatible (wrong type)

This process is called Pollen–Pistil Interaction.

What is Pollen–Pistil Interaction?

Pollen–pistil interaction is the series of events from:

• deposition of pollen on stigma to entry of pollen tube into the ovule.

It includes:

• Recognition of pollen

• Acceptance or rejection of pollen

• Growth of pollen tube

• Entry into ovule

Compatible and Incompatible Pollen

Compatible Pollen

Compatible pollen is pollen from the same species that can successfully fertilize the ovule.

Result

• Pollen germinates

• Pollen tube grows

• Fertilization occurs

Example

Pollen of Pea on another pea flower.

Incompatible Pollen

Incompatible pollen may come:

• From another species   OR

• From the same plant in self-incompatible plants

Result

• Pollen germination is prevented   OR

• Pollen tube growth stops

Example

Pollen of Mustard rejected by its own stigma in self-incompatible varieties.

Recognition of Pollen by Pistil

The pistil recognizes pollen through chemical interaction between:

• pollen grains and

• pistil tissues

This chemical communication helps the pistil decide whether to:

• accept pollen OR

• reject pollen

Steps of Pollen–Pistil Interaction

1. Pollination

Pollen grains are deposited on the stigma.

Diagram

Anther →→→ Stigma (Pollen transfer)

2. Pollen Germination

If pollen is compatible, it germinates on the stigma through a germ pore and forms a pollen tube.

Diagram

     Pollen grain
          ●
         / \
        /   \
     Pollen tube

Example

Pollen germination can be observed in:

• Pea

• Chickpea

• Balsam

• Vinca

3. Growth of Pollen Tube

The pollen tube grows through:

• stigma

• style

• ovary

to reach the ovule.

Diagram

 Stigma
    |
    |
  Style
    |
    |
  Ovary
    |
  Ovule

(Pollen tube grows downward)

4. Formation of Male Gametes

In Two-Celled Pollen

Pollen grain contains:

• One vegetative cell

• One generative cell

During pollen tube growth, the generative cell divides to form:

• Two male gametes

In Three-Celled Pollen

Pollen already contains:

• One vegetative cell

• Two male gametes

So pollen tube carries the male gametes from the beginning.

5. Entry into Ovule

The pollen tube enters:

• Ovule through micropyle

• One synergid through filiform apparatus

Role of Filiform Apparatus

It guides the pollen tube into the embryo sac.

Diagram

        Ovule
      __________
     |          |
Micropyle →  Pollen tube
     |          |
     | Synergid |
     |__________|

Importance of Pollen–Pistil Interaction

• Ensures correct fertilization

• Prevents wrong pollination

• Helps in hybrid formation

• Important in plant breeding

Artificial Hybridisation

Artificial hybridisation is a technique used by plant breeders to produce plants with desirable characters.

Example

Developing disease-resistant or high-yielding crops.

Techniques Used in Artificial Hybridisation

1. Emasculation

Removal of anthers from bisexual flower buds before anther dehiscence.

Purpose

Prevents self-pollination.

Diagram

Flower bud
   ↓
Removal of anthers
(using forceps)

Example

Used in hybridization of:

• Pea

• Hibiscus

2. Bagging

After emasculation, flowers are covered with butter paper bags.

Purpose

Prevents unwanted pollen contamination.

Diagram

   Flower
     ↓
 [Covered with bag]

When stigma becomes receptive:

• Desired pollen is dusted

• Flower is rebagged

Artificial Hybridisation in Unisexual Flowers

In unisexual flowers:

• Emasculation is not required

• Female flowers are directly bagged before opening

Example

• Maize

• Papaya

Simple Summary Table

Process	Function
Pollen recognition	Identifies compatible pollen
Pollen germination	Produces pollen tube
Pollen tube growth	Carries male gametes
Emasculation	Prevents self-pollination
Bagging	Prevents unwanted pollination

    

           Pollen–pistil interaction is a very important process in flowering plants. It helps the pistil recognize the correct pollen and ensures successful fertilization. Knowledge of this process is very useful in plant breeding and artificial hybridisation for developing improved crop varieties.