Plant Structure and Function - Learner's Guide

7/30/2019 Plant Structure and Function - Learner's Guide

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LLeeaarrnneerr GGuuiiddeePPrriimmaarryy AAggrriiccuullttuurree

Plant Structureand Function

My name: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Company: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Commodity: . . . . . . . . . . . . . . . . . . . . Date: . . . . . . . . . . . . . . .

NQF Level: 2 US No: 116057

The availability of this product is due to the financial support of the NationalDepartment of Agriculture and the AgriSETA. Terms and conditions apply.


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Understand the structure and functions of a plant

Primary Agriculture NQF Level 2 Unit Standard No: 11605722

Version: 01 Version Date: July 2006

Before we startDear Learner - This Learner Guide contains all the information to acquire all theknowledge and skills leading tothe unit standard:

Title: Understand the structure and functions of a plant

US No: 116057 NQF Level: 2 Credits: 5

The full unit standard will be handed to you by your facilitator. Please read the unit

standard at your own time. Whilst reading the unit standard, make a note of your

questions and aspects that you do not understand, and discuss it with your

facilitator.

This unit standard is one of the building blocks in the qualifications listed below.

Please mark the qualification you are currently doing:

Title ID Number NQF Level Credits Mark

National Certificate in Animal Production 48976 2 120

National Certificate in Mixed Farming Systems 48977 2 120

National Certificate in Plant Production 48975 2 120

This Learner Guide contains all the information, and more, as well as the activities

that you will be expected to do during the course of your study. Please keep the

activities that you have completed and include it in your Portfolio of Evidence.

Your PoE will be required during your final assessment.

Are you enrolled in a: Y N

Learnership?

Skills Program?

Short Course?

Please mark the learning program you

are enrolled in:

Your facilitator should explain the above

concepts to you.


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What is assessment all about?You will be assessed during the course of your study. This is called formativeassessment. You will also be assessed on completion of this unit standard. This is

called summative assessment. Before your assessment, your assessor will discuss

the unit standard with you.

Assessment takes place at different intervals of the learning process and includes

various activities. Some activities will be done before the commencement of the

program whilst others will be done during programme delivery and other after

completion of the program.

The assessment experience should be user friendly, transparent and fair. Shouldyou feel that you have been treated unfairly, you have the right to appeal. Please

ask your facilitator about the appeals process and make your own notes.

How to use the activity sheetsYour activities must be handed in from time to time on request of the facilitator for

the following purposes:

The activities that follow are designed to help you gain the skills, knowledge

and attitudes that you need in order to become competent in this learning

module.

It is important that you complete all the activities and worksheets, as directed

in the learner guide and at the time indicated by the facilitator.

It is important that you ask questions and participate as much as possible in

order to play an active roll in reaching competence.

When you have completed all the activities and worksheets, hand this

workbook in to the assessor who will mark it and guide you in areas where

additional learning might be required.

You should not move on to the next step in the assessment process until this

step is completed, marked and you have received feedback from the assessor.

Sources of information to complete these activities should be identified by your

facilitator.

Please note that all completed activities, tasks and other items on which you

were assessed must be kept in good order as it becomes part of your

Portfolio of Evidence for final assessment.

Enjoy this learning experience!


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How to use this guide Throughout this guide, you will come across certain re-occurring boxes. These

boxes each represent a certain aspect of the learning process, containing

information, which would help you with the identification and understanding of these

aspects. The following is a list of these boxes and what they represent:

My Notes You can use this box to jot down questions you might have, words that you do not understand,

instructions given by the facilitator or explanations given by the facilitator or any other remarks that

will help you to understand the work better.

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What does it mean? Each learning field is characterized by unique terms anddefinitions it is important to know and use these terms and definitions correctly. Theseterms and definitions are highlighted throughout the guide in this manner.

You will be requested to complete activities, which could be group activities, or individualactivities. Please remember to complete the activities, as the facilitator will assess it andthese will become part of your portfolio of evidence. Activities, whether group or individualactivities, will be described in this box.

Examples of certainconcepts or principles tohelp you contextualisethem easier, will be shownin this box.

The following box indicates a summary ofconcepts that we have covered, and offersyou an opportunity to ask questions to yourfacilitator if you are still feeling unsure ofthe concepts listed.


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What are we going to learn?What will I be able to do? .................................................................................. 6

What do I need to know? ..................................................................................... 6

Plant Structure An Introduction.. 6

Session 1: Parts and Function of Seeds............................................................ 8

Session 2: Root systems and root function.... 13

Session 3: The different stem types.. 17

Session 4: Different leaf types and their functions.......................................... 20

Session 5 Parts of a Flower and their Functions.. 27

Session 6 Types of fruit and parts of fruit.... 32

Am I ready for my test? ................................................................... 36

Checklist for Practical assessment................................................... 38

Paperwork to be done....................................................................... 39

Bibliography.. 40

Terms & Conditions.. 40

Acknowledgements.. 41

SAQA Unit Standard


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WWhhaatt wwiillll II bbee aabbllee ttoo ddoo??

When you have achieved this unit standard, you will be able to: Explain the functions of different plant parts.

Learners will gain specific knowledge and skills in order to be able to

understand the roll that each part of the plant plays in the ecological

environment as well as in plant production.

They will be capacitated to gain access to the mainstream agricultural sector,

in plant production, impacting directly on the sustainability of the sub-sector.

The improvement in production technology will also have a direct impact on

the improvement of agricultural productivity of the sector.

WWhhaatt ddoo II nneeeedd ttoo kknnooww??It is expected of the learner attempting this unit standard to demonstrate

competence against the unit standard::

NQF 1: Understand the role of plants in the ecological environment.

NQF 1: Demonstrate a basic understanding of the structure and function of a

plant in relation to its environment.

NQF 1: Demonstrate an understanding of the basic concept of sustainable

farming systems.

Plant structure An Introduction What is Plant Structure?

Plants are made up oforgans like the roots, stems and leaves, and for sexualreproduction, they form flowers and fruit containing the seed. We can see theseorgans with the naked (unaided) eye and we therefore talk about the externalstructure of the plant. All these organs are made up of cells that we cannot seewith the naked eye and need a microscope to see these cells. We therefore talk

about the internal structure or the anatomy of the plant. Cells of the same kindand/or function form tissues like the epidermis, cortex and vascular tissue. Eachtissue has a specific function in the plant organ and when we are talking about thefunction of the leaf, we must actually refer to the function of each kind of tissueinside the leaf like the stomata in the epidermis responsible for transpiration and gasexchange.

Please completeActivity 1.1 at theend of the section.

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Take a scale from an onion bulb and use a pair of tweezers to tare off a piece of the

epidermis tissue. Mount it in a drop of water and study it under a microscope. Write

down your observations and discuss it with the rest of the class.

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Explore and discuss

11..11AACC 11My Name:

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My Workplace:

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Facilitator comments: Assessment:


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SSeessssiioonn 11 PPaarrttss aanndd ffuunnccttiioonn ooffsseeeeddss

After completing this session, you should be able to:SO 1: Identify the basic parts that make up a seed andexplain the function.

1.1 IIddeennttiiffyy tthhee bbaassiicc ppaarrttss tthhaatt mmaakkee uupp aasseeeedd aanndd eexxppllaaiinn tthhee ffuunnccttiioonn

The simplest way to describe a seed is a baby in a box with food where the boxrepresents the seed coat, the baby represents the embryo and the foodrepresents the endosperm.


MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Seed coat box

Cot ledon

Plumule

Axis

Radicle

Embryo (baby)

Endosperm (Food)

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .

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Soak some bean seed and some maize seed in water for 24 hours. Remove the seed

coat and try to find the other parts shown in the diagram.

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Explore

11..22SSOO 11 AACC 11--55My Name:

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My Workplace:. . . . . . . . . . . . . . . . . .

My ID Number:

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1.2&

1.3

Functions of the seed parts and their

relation with plant organs Seed coat the seed coat derives from the integuments of the ovule and

covers and protects the seed while in a resting phase (storage).

Endosperm The endosperm derives from the fertilised central cell of the

embryo sac and contains the energy (food) for the embryo. In the immature

stage, therefore, all seeds contain endosperm. In some seeds the endosperm is

absorbed by the cotyledons of the developing embryo, so that the cotyledons

become swollen and no endosperm remains in the mature seed. Such seeds are

called ex-endospermous. In other seeds (endospermous seeds) the endosperm sstored around the embryo inside the seed coat and is. The mature seed

therefore contains endosperm that is absorbed only during germination to supply

the germinating embryo with the required energy.

Embryo the embryo consists of four parts:

Radicle It is the root apical meristem of the embryo that gives rise to

the primary root.

Plumule It is the apical meristem (growing point) of the young embryo

that gives rise to the stem and leaves of the new plant.

Cotyledon(s) One in monocotyledonous seeds and two in

dicotyledonous seeds, is (are) the first leaf (leaves) of the embryo

produced by the plumule and do (es) contain axillary buds like any other

leaf. They act as haustoria (absorbing) nutrients from the endosperm. In

endospermous seeds (seeds containing endosperm), the cotyledons

become active during germination and absorb the nutrients from the

endosperm as they are required by the embryo. In ex-endospermous

seeds, (seeds without endosperm), the endosperm is absorbed by the

cotyledons before the seed matures and the nutrients are, therefore stored

inside the swollen cotyledons.

Axis the part of the embryo connecting the plumule and the radicle. In

seeds with epigeal germination (cotyledons appear above the ground),

the axis elongates to push the cotyledons above ground and that part of

the axis below the cotyledons is then called the hypocotyls. In seeds with

hypogeal germination, the axis does not elongate during germination and

the cotyledons therefore remain underground.


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1.4 TThhee ddiiffffeerreennccee bbeettwweeeenn mmoonnoo-- aanndd

ddiiccoottyylleeddoonnoouuss sseeeeddssMonocotyledonous seeds contain only one cotyledon and the plumule is situated on

the side of the embryo axis. In dicotyledonous seeds there are two cotyledons and

the plumule is situated between the two cotyledons.

In monocotyledonous plants the leaf base is a sheath covering a part of the stemabove the node. In the seedling the first leaf above the cotyledon is usually reduced.

In dicotyledonous seeds there are two cotyledons and the plumule is situated

between the two cotyledons.

Different dicotyledonous seedlingsshowing the cotyledons (c) andthe first leave produced by theplumule between the cotyledons.1- Lupin, 2 - Vetch, 3 - Plantago,4 Escholzia, 5 Geranium, 6 Eranthis.

Different monocotyledonous seedlings showingthe cotyledon (c) imbedded in the endosperm,

some elongated to push the plumule into thesoil, and (sp) the first leaf covered by a sheath.1 Palm (Phoenix), 2 longitudinal section of 1to show the sheath and plumule at the base, 3 Maize, 4 section of 3, 5 wheat.


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Concept(SO 1)

I understandthis concept

Questions that I stillwould like to ask

Different parts, which make up aseed, are identified and correctterminology is used.

The role of the embryo in thegermination of the seed is described.

The fact that the radicals form theroots, hypocotyls, the stem,cotyledons and the leaves areexplained as well as the function ofthe cotyledons and hypocotyls.

The difference betweenmonocotyledons and dicotyledons isexplained.

The functions of roots, stems andleaves are described and discussed.

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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SSeessssiioonn 22Root systems and root function

After completing this session, you should be able to:SO 2: Understand different root systems and root function.

2.1 TThhee ddiiffffeerreenntt rroooott ssyysstteemmss

The tap root system the tap root derives from the radicle and produceslateral roots of different orders (First order, second order etc. Indicotyledonous plants the tap root can usually has the same life span as theplant A tap root system can therefore develop only from seedlings.

Adventitious root system - in monocotyledonous plants the tap rootfunctions during the seedling stage, but may thereafter stop growing andadventitious roots develop from the base of the stem, forming an adventitiousroot system. In grasses and some other plants the adventitious roots arefibrous They are thin and hair-like and usually contain more fibres than other

roots The whole root system is then called a fibrous root system Thefeeding roots of many other plants, however, can also be hair-like and fibrouseven if they form part of a taproot system. And are often called hair roots.

2.2 TThhee ffuunnccttiioonn ooffrroooottss For anchoring the plant to the substrate (soil) and

For the absorption of water and nutrients dissolved in the soil water. Theabsorption function is carries out by the young epidermis cells, of which somemay grow out to form root hairs.

Root hairs are single, elongated epidermis cells found close to the roottip.

Hairy roots, on the other hand are complete roots, containing all the

parts like growing tip, epidermis with root hairs, cortex and vascular

tissue, but they are thin and hair-like.


MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Collect 10 weed plants from the garden and describe the root system of each.

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Go outside and explore


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2.3 How do roots take up water andnutrients

Almost all the water the plant takes up from the soil enters through the youngest

part of the root where the root hairs develop a few millimetres behind the root tip.

Absorption takes place directly through the epidermis and root hairs that provide an

enormous area of absorption. The walls of the root cells is made up of cellulose

fibrils (threads). The open spaces between the fibrils are filled with water which

means that water can move through the cell walls from one cell to the other and this

movement is called apoplastic movement of water. Water can therefore move fromthe soil water into the cell walls of the root hairs, through the cell walls of the cortex

up to the endodermis where the water is blocked by the casparian strips in the

endodermis. The water is then forced through the cytoplasm of the endodermis

cells, the pericycle and then into the xylem vessels that takes the water through the

root and stem into the leaves. Water can also be absorbed by the root hairs through

the process ofosmosis (water molecules moving from an area of high

concentration in the soil water - to an area of low concentration inside the root

hair). The water then moves from the root hairs symplastically through the

cytoplasm of the root tissues to the endodermis.

2.4 WWhhaatt iiss ggrraavviittrrooppiissmm?? ((TThhee oolldd tteerrmm iissggeeoottrrooppiissmm))

Gravity is a force that pulls everything towards the earth and tropism is a turning

into the direction from where a stimulus comes. The growth of most roots is

positively gravitropic which means that they grow towards the direction of the

pull of the earth. This phenomenon can be illustrated by planting maize seeds withthe sharp end (radicle) of the seed pointing upwards. During germination the root

will turn around and grow downwards. Stems on the other hand tend to grow

negatively gravitropic, meaning that they grow away from the stimulus coming

from the pull of the earth.

Gravity A force that pulls everything towards the earth and

Tropism A turning into the direction from where a stimuluscomes.


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Concept (SO 2)I understandthis concept


The different root systems found ondifferent plants are explained.

The way roots function to supportthe plant is discussed.

The function of roots in the uptakeof water and plant nutrients isdescribed.

Gravitropism is explained withreference to roots and stems.

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .

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SSeessssiioonn 33The different stem types

After completing this session, you should be able to:SO 3:Demonstrate an understanding of different stemtypes.

3.1 Different stem types

Herbaceous stems stems of most monocotyledonous plants with no

secondary growth. Or stems of most annual dicotyledonous plants with very

limited secondary thickening growth.

Woody stems stems of dicotyledonous plants and gymnosperms with theextensive secondary thickening growth. A source for commercial wood.

Stems of vines long, slender stems that con not support themselves and useother plants or structures to support them like that of runner beans.

Tuber a fleshy, terminal end of an underground stem that can be used forpropagation like that of the potato. Some can also be used as food.

Rhizome a swollen underground with distinct nodes and internodes, oftenwith sympodial growth like in Iris and kikuju grass. Can be used for propagation.

Corm a swollen stem base like that of Gladiolus. Can be used for propagation. Bulb a reduced stem with succulent leaf bases covering the growing point like

that of onion. Can be used as food and for propagation.

3.2 The stem as a support systemStems form the framework of the plant, exposing the leaves to the maximum

available sunlight. A good example is vines that are often found in forests. They do

not spend extra energy to develop strong stems, but rather use other supports to

grow out of the forest canopy as quickly as possible to expose their leaves to the

sun.

Please completeActivity 3.1 herebelow.

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Cut a shoot with leaves from a weed plant, put the cut end in a natural stain solution

and leave it for 24 hours. Make a longitudinal section of the stem and try to explain

what you see.

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My Workplace:

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My ID Number:

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3.3 The stem as a transport system

Stems contain vascular tissue like the vessels and tracheids of the xylem thattransport water and inorganic solutes (dissolved minerals) from the roots to other

plant organs like leaves, flower and fruit. The sieve tubes and sieve cells of the

phloem are transporting organic products from the leaves to other plant organs like

stem growing points, flowers, fruit, seed and roots where it is utilised for energy or

stored as reserve food.



Different stem types and theirfunctions are described.

The fact that the stem supports thebranches and leaves and connects tothe roots is explained.

The fact that water and plantnutrients pass through to the leaves,and carbohydrates passes along thestem down to the roots, is explained

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .

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SSeessssiioonn 44Different leaf types and theirfunctions

After completing this session, you should be able to:SO 4: Understand different leaf types and their functions

4.1 Types of leafs and their functionAll leaves originate from a stem apical meristem or apical dome as small

protuberances called leaf primordia, but during their further development and

maturation leaves can take on different forms, shapes and sizes depending on the

specific function they have to perform.

Ordinary or typicalphotosynthetic leaves have green, flattened laminas (leafblade) and their main function is photosynthesise. These leaves can be simple withan undivided lamina or compound with a subdivided lamina.

Lamina

Petiole

Pinnae

Simple leaf Compound leaf


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Bracts Bracts or scales are leaves that matured in their primordial (baby)

form and are mostly colourless or brown. Their main function is to protect buds

like flower buds in the young inflorescence, apical buds and axillary buds.

Tendrils Parts of the leaf in some vines are transformed into thin tendrils that

curl around support structures to help the plant in its climbing habit like in sweet

pea (Lathyrus odoratus)and Bignonia.

Succulent leaves the leaves of some plants are adapted to store water like

the leaves of aloes or they can store food like bulb scales and cotyledons of the

bean seed. Cotyledons have an additional function by acting as haustoria,

extracting nutrients from the endosperm.

Please completeActivity 4.1 at theend of the session

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Bud scales

Scars offallen

scales

Leaf tendrils of a Bignoniasp.


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4.2 TThhee rroollee oofflleeaavvee aass tthhee ffoooodd ffaaccttoorryy

For the manufacturing of food (carbohydrates), the leaf needs:

Chlorophyll found in the chloroplasts of the palisade (Pal) and spongyparenchyma cells (SP) of the leaf.

Sunlight - leaves to be exposed to light the light passes through thecolourless upper epidermis (UE) and is absorbed by the chlorophyll.

Water supplied by the xylem elements in the vascular bundle (VB).

Carbon dioxide (CO2) passing through the stomata (St) from the atmosphereinto the open spaces between the cells inside.

The process :

Step 1- dependent on light

Energy from the sunlight is converted to chemical energy by chlorophyll. The energy is used to split water into hydrogen (H2) and oxygen (O2).

The released oxygen leaves the leaf through stomata into the atmosphere.

Step 2- not dependant on light, but influenced by temperature.

In another process, which is temperature sensitive, the hydrogen is boundto the Carbon dioxide to form carbohydrate.

CO2

O2

Sunlight

H2O

UE

Pal

SP

LE

St


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The formula:

6CO2 + 12H2O light C6H12O6 + 6O2 + 6H2O

The carbohydrates (sugar) is then loaded into the phloem in the vascular bundleand transported to the different parts of the plant.

4.3 TThhee rreeaassoonn ssuunnlliigghhtt iiss iimmppoorrttaanntt ffoorrcchhlloorroopphhyyllll pprroodduuccttiioonn

Chloroplasts can only develop from proplastids (young plastids) present in dividingcells. Each chloroplast is surrounded by a double membrane. The internal structureof the chloroplast is rather complex and can only become fully developed if the cellis exposed to sufficient light. In flowering plants the chloroplasts are usually disk-shaped and measure 4 to 6 micrometers in diameter (1micrometer (m) = 0.001mm). The ground substance of the chloroplast inside the double membrane is calledthe stroma and the stroma is traversed by an elaborate system of membranes inthe form of flattened sacs called thylakoids, packed in stacks like coins, calledgrana (singular granum). The grana are interconnected by a similar doublemembrane system as the thylakoids. The chlorophyll is contained in the thylakoids ofthe grana and in the absence of light the grana becomes disorganised and the

chlorophyll breaks up.

4.4 TThhee wwaayy lleeaavveess rreeaacctt ttoo eennvviirroonnmmeennttaallffaaccttoorrss

Etiolation in the absence of light or greatly reduced light, leaves become yellowdue to the breaking down if the chlorophyll and the thylakoids in the chloroplastsand we say the leaves are etiolated. The green colour will however return if theplants are returned to light conditions.

Leaves sensitive to touch The pinnae ofMimosa pudicaleaves will close whenthey are touched. Leaves of the insectivorous Venus Fly Trap contain sensitivehairs and when these hairs are touched by an insect, the two halves of the leafclose quickly to catch the insect Leaf tendrils of plants like the sweet pea willturn around a support as they make contact.


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Flowering response Some plants are sensitive to the number of dark hours inthe daily 24-hour cycle. Some plant, called short day plants likechrysanthemum, will flower as soon as the nights become longer than the critical

16 hours. When planted outside, they usually flower in autumn. Long dayplants on the other hand, will flower if the nights become shorter than16 hours.Day neural plants are not sensitive to day length.

Heat Stomata on leaves usually close when the maximum temperature risesabove a certain value, meaning that photosynthesis will also stop.

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Write an illustrated essay on the different leaf types and their function as well as

some responses of leaves to the environment.

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Literature search anddiscussion


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My Workplace:. . . . . . . . . . . . . . . . . .

My ID Number:

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Morphology of different types ofleaves is identified and described.

The role of the leaves as the foodfactory of the plant(photosynthesis) is discussed.

The reason sunlight is important forchlorophyll production is explained.

The way leaves react to differentenvironmental factors (drought,flooding darkness etc) is explained.

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .

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SSeessssiioonn 55Parts of a flower and theirfunctions

After completing this session, you should be able to:SO 5:Understand the different parts of a flower and theirfunctions.

5.1 5.3

BBaassiicc ssttrruuccttuurree aanndd ffuunnccttiioonn oofftthhee fflloowweerr

A flower is actually a modified shoot, deriving from an axillary bud, with whorls ofmodified leaves with very specific functions.

Pedicel an elongated internode attaching the flower to the stem.

Recepticle- a set of very closely spaced nodes bearing the whorls of modified

leaves (flower parts).

Calyx the first whorl of flower leaves (sepals) protecting the other leaf whorlsduring the development of the flower up to the bud stage.Corolla the second whorl of modified leaves, (petals) usually brightly coloured to

attract pollinators to visit the flower.

Pedicel

Receptacle

Stigma

Style


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Stamens - one or two whorls of highly modified leaves forming the stamensconsisting of the filament (petiole) and the anther (lamina) producing the pollen.

Pistil composed of one or more separate or fused carpels (leaves). The terminalparts of the leaves form the stigma that receives the pollen during pollination. Theextended central parts of the leaves form the style while the basal parts of theleaves form the ovary carrying the ovules. In most flowers the carpel leaves aresessile (with no petiole), but in some flowers like those f the Capparidaceae, thepetioles form the gynophores

The one or more whorls of anthers of the same flower is referred to as theandroecium, which forms the male part of the flower producing the pollen (theterm gynophore above therefore means the carrier (-phore) of the gynoecium.One or more carples of the same flower is referred to as the gynoecium, formingthe female part of the flower and contain the ovules. After pollination andfertilisation, the stigma and style withers and die while the ovary gives rise to thefruit. The fertilised ovules inside the fruit give rise to the seeds.

5.4 TThhee rroollee oofftthhee ffeemmaallee ppaarrttss oofftthheefflloowweerr iinn ffrruuiitt aanndd sseeeedd pprroodduucctionAs mentioned above, the pistil, consisting of the stigma. style and ovary, is the

female par of the flower. The function of the stigma is to receive the pollen during

pollination. If recognised by the stigma, the pollen grain will germinate and produce

a pollen tube that grows down the style in the direction of the ovary. The pollen

tube carries the two sperm cells derived from the generative cell in the pollen grain.

On reaching the ovary, the pollen tube grows to an ovule, enters the ovule through

the micropyle, penetrates the embryo sac and sheds the two sperm cells into one ofthe synergid cells inside the embryo sac from where one will fertilise the egg cell

Section of ovule

ChalazaAntipodal cells

Polar nuclei of centralcell

Egg cellSynergid

IntegumentsMicropyle

Seed Stalk (funicle)


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(the nuclei of the two cells fuse) and the other one fuses with the two nuclei of the

central cell of the embryo sac. (Double fertilisation)

The fertilised egg cell then develops into the embryo (the baby) of the seed, the

fertilised central cell produces the endosperm (the food) and the integuments of the

ovule forms the seed coat. (the box) The whole ovule, therefore gives rise to the

seed. The developing seed produces hormones that stimulate the ovary wall to

develop into the wall of the fruit (pericarp)

The whole ovary, therefore develops into the fruit, provided the ovules develop intoseeds. There are, however exceptions where the fruit will develop withoutfertilisation and seed formation as in the case of the banana and pineapple. Thisprocess is called parthenocarpy and the fruits are called parthenocarpic fruit.

Parthenocarpic fruit (seedless fruit) can also be artificially produced by spraying

flowers with hormones like auxin (seedless tomatoes) of gibberellic acid (seedless

grapes).

Please completeActivity 5.1 at theend of the session

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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Pick any crop, make the following observations and describe and explain your

observations:

Bud stage of the flowers Description of flowers Pollination, stage of flowers when pollinated and pollination agent Fruit set and stages of fruit development

Seed development

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Explore and discuss


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My Workplace:. . . . . . . . . . . . . . . . . .

My ID Number:

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Concept (SO)I understandthis concept


The basic structure of a flower isillustrated.

The different structures that makeup a flower are identified anddescribed

The function of the male and femalestructures of a flower is explained

The role of female parts of flowersin relation to fruit and seed

production is described

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .

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Session 66 TTyyppeess ooffffrruuiitt aanndd ppaarrttss ooffffrruuiittAfter completing this session, you should be able to:SO 6: Understand the different types of fruit and parts offruit.

From the information presented in chapter 5, it is clear that fruit can only developfrom the female parts of a flower and normally after pollination and fertilisation.

Mature fruit are classified n different categories based on the structure of the fruitwall. Different parts of the flower can, however, also take part in determining fruitstructure.

6.1 Simple fruit

Fruit developing from a single ovary from a single flower

Single, fleshy fruit the pericarp is soft and fleshy.

Drupe or stone fruit. like peach and mango. Thepericarpcan be dividedinto exocarp, (the peel of the peach and mango) mesocarp(the soft ediblepart) and the endocarp, (hard, stone-like or leather-like layer surroundingthe seed.

Berry also a fleshy fruit, but the mesocarp and endocarp are both fleshyand not distinguishable from each other as in the grape berry, tomatoes,papayas, avocado, coffee, blueberries, gooseberries and many others.

Pepo the fruit of the cucurbit family like pumpkins, cucumber and

watermelon are actually also berries, but the carpels are imbedded in theconcave receptacle (hypogynous or inferior ovary) that takes part in theformation of the fruit wall.

Pome like the pepo the fruit also derives from an inferior ovary with thereceptacle taking part in the formation of the fleshy fruit wall, but it alsohas a firm partly woody endocarp surrounding the seeds.

Single, dry fruit in dry fruits the pericarp (combination of eso- meso-and

endocarp) in the mature fruit is a dry, leathery or papery structure and the

three layers are not distinguishable.

Nut an indehiscent (not opening) fruit consisting of a single carpel as inthe nuts falling from oak trees.


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Achene an indehiscent fruit consisting of two carpals as in the sunflowerfruit (mostly called a seed).

Capsule It is a single, dry dehiscent fruit, usually consisting of more the

one carpel and as the classification indicates, the mature fruit dehisces(opens by itself) and the seeds are distributed as in the case of theSterilities fruit depicted in the figure above. Capsules are also found inMaturaand fruit of orchids.

Pod or legume It is also a dehiscent fruit, but consists on one carpelonly as in the case of a pea pod, a bean, soybean most of the acacias.

6.2 AAggggrreeggaattee fruit

Fruit that derive from a single flower but is made up of a number of separate ovaries

on the same receptacle like the fruit of the strawberry consisting of an aggregation

of small drupelets.

6.3 MMuullttiippllee fruit

A collection of fruit on a common inflorescence axis as in the syconium of the fig

where a great number of achenes deriving from minute flowers are collected in a

concave, fleshy inflorescence axis. In the malberry (Morus) and the pineapple,

(Ananas) a collection of fleshy fruit and flower parts are collected on a common axis.

Please completeActivity 6.1 at theend of the session.

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .

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Collect a variety of fruits dissect the fruits, describe their structure and try to relate

the structure of the parts to specific functions.

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Explore and discuss


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My Workplace:. . . . . . . . . . . . . . . . . .

My ID Number:

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Different types of fruit are identifiedand examples of each are given.

The differences between single andmulti-seeded fruits are explained

The different parts of a fruit areillustrated and described.

The function of the different parts ofthe fruit is described.

MMyy NNootteess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .

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Documents

Plant Structure and Function - Learner's Guide