Hawassa University

College of Agriculture

School of Plant and Horticultural Science

Term Paper on:

Pollination methods of commonly cultivated cereals, legumes, and

horticultural crops (No. 15)

Submitted for the course: Seed Science and technology

By:

ID

Specialization: Agronomy

Submitted To:

August 2015 Hawassa, Ethiopia

Table of Contents

1. Introduction..............................................................................................................................3

4.2. Structure of flowers..........................................................................................................4

2.1. Types of flowers................................................................................................................4

4.2 .1. Complete flower.......................................................................................................4

3. Types of pollination..................................................................................................................4

3.1. Self pollination..................................................................................................................4

3.2. Cross pollination................................................................................................................4

3.3. Cross/self pollination........................................................................................................4

6.1. Natural Method.....................................................................................................................5

6.1.1. Biotic..................................................................................................................................5

6.1.2.Abiotic...................................................................................................................6

7. Artificial or Man made pollination techniques......................................7

8. Pollination Method in Cereals............................................................................8

9. Pollination Methods in legumes..........................................................................8

10. Pollination Method in Horticultural crops............................................8

1. Conclussion.............................................................................................................................11

2. Bibliography............................................................................................................................11

1 Introduction

Pollination is the process of mating in plants; it is the

precursor to double fertilization. In flowers, pollen is

delivered to the stigma through a wide range of mechanisms that

insure an appropriate balance in the genetic makeup of the

species. What is a flower? In human eyes it is something to

enjoy, with color and fragrance. For many plants, flowers are

vital organs of reproduction containing both male and female

gametes. For bees and other nectar-feeding animals, flowers are a

source of food. (citation absent)

Symbiosis is the close association of two or more dissimilar

organisms. Such associations can be beneficial to both organisms

(mutualistic) or detrimental to one (parasitic). Symbiotic

relationships among species occur frequently in nature. When the

two or more species in symbiosis evolve in response to each

other, they are said to coevolve. Under close examination each

symbiotic relationship stands out as an example of miraculous

complexity which has emerged.

Sugar-rich nectar is secreted by the specialized nectary tissues

strategically located in the flower to ensure that nectar-

gathering animals will receive pollen from anthers and transmit

it to stigmas. www.fastplants.org/pdf/activities/flowering_pollination.pdf

Pollinators are essential for orchard, horticultural and forage

production, as well as the production of seed for many root and

fibre crops. Pollinators such as bees, birds and bats affect 35

percent of the world’s crop production, increasing outputs of 87

of the leading food crops worldwide.

Food security, food diversity, human nutrition and food prices

all rely strongly on animal pollinators. Farmers and farming

communities have the potential to undertake measures that can

conserve and strengthen linkages between different aspects of

agro biodiversity, and contribute to long-term stability in the

face of climate change.www.fao.org/fileadmin/...pollination/Pollination-FolderFlyer_web.pd

2 What is pollination

Pollination is defined as the transfer of pollen grains from the anther (male sex structure) to the stigma (female sex structure) in flowers of angiosperms, or from the microsporangium to the megasporangium in gymnosperms directly or usually through an agent or portal. The mediating agents include wind, gravity, water and animals.

In some cases, the transfer is completed via strictures imposed by the architectural design of the flower, which allow for completion of the pollen grain transfer to the stigma before the flower opens up. https://dlc.dlib.indiana.edu/.../benefits%20of%20biotic%20pollination.pd...

3 Parts of a flower

Flowers are made of many intricate and important parts. The parts

take on different appearances from one species to another.

The male part of a flower is called the stamen. The stamen is

made of the stalk-like filament, which holds up the sack-like

anther. The anther produces pollen, the grain released by flowers

that contains the sperm. Flowers that have only male parts are

called staminate.

The female part of a flower is called the pistil. The pistil has

a sticky tissue at its end called the stigma that is receptive to

pollen. Below the stigma are a rod-shaped middle part called the

style and a swollen base containing eggs called the ovary.

Flowers that have only female parts are called pistillate.

A flower usually also has parts that are neither male nor female.

These are the petals, often colorful leaf like structures that

attract animals and insects. When all the petals are fused

together, the structure is called a corolla.

Beneath the petals are more leaf like structures called sepals.

Regularly green, the sepals support the petals and protect the

flower before it opens. When all the sepals are fused together,

the structure is referred to as a calyx. (Citation absent)

Figure – I. Flower structure diagram

Picture source:- www.life.illinois.edu/.../pollinators/.../Pollination%20Activity

%20Book.p..

3.1 Types of flowers

Flowers come in many shapes, sizes, and colors. Some species have

flowers with all the floral parts, Where as others lack certain

parts.

A flower that has both male and female parts is called perfect

flower. Most flowers contain both male and female parts.

A flower that is missing either male or female parts is called an

imperfect flower.

If a flower has sepals, petals, pistils, and stamens, it is a

complete flower.

If a flower is missing one of those, it is an incomplete flower.

Imperfect flowers are always incomplete. Incomplete flowers may

or may not be imperfect.

(citation absent Understanding flower anatomy)

4 Modes of pollination

Pollination is of two types: viz. 1) Autogamy or self pollination

and 2) Allogamy or cross pollination.

4.1 Self pollination /Autogamy/Transfer of pollen grains from the anther to the stigma of same

flower is known as autogamy or self pollination.

Autogamy is the closest form of inbreeding. Autogamy leads to

homozygosity. Such species develop homozygous balance and do not

exhibit significant inbreeding depression.

Ex:- Rice, Wheat, Barley, Chickpea, Pea, Lentil, Linseed, Sesame

Tomato,

4.2. Mechanism promoting self-pollination

A. Bisexuality

Presence of male and female organs in the same flower is known as

bisexuality. The presence of bisexual flowers is a must for self

pollination. All the self pollinated plants have hermaphrodite

flowers.

B. Homogamy

Maturation of anthers and stigma of a flower at the same time is

called homogamy. As a

rule, homogamy is essential for self-pollination.

C. Cleistogamy

When pollination and fertilization occur in unopened flower bud,

it is known as cleistogamy. It ensures self pollination and

prevents cross pollination.

Cleistogamy has been reported in some varieties of wheat, barley,

oats and several other grass species.

D. Chasmogamy

Opening of flowers only after the completion of pollination is

known as chasmogamy. This also promotes self pollination and is

found in crops like wheat, barley, rice and oats.

E. Position of Anthers

In some species, stigmas are surrounded by anthers in such a way

that self pollination is ensured. Such situation is found in

tomato and brinjal. In some legumes, the stamens and stigma are

enclosed by the petals in such a way that self pollination is

ensured.

Ex:-, soybean, chickpea and pea.

4.2 Cross pollination /Allogamy/

Transfer of pollen grains from the anther of one plant to the

stigma of another plant is called allogamy or cross pollination.

This is the common form of out breeding. Allogamy leads to

heterozygosity. Such species develop heterozygous balance and

exhibit significant inbreeding depression on selfing.

Ex:- Corn, Rye, Alfalfa, Radish, Cabbage, Sunflower, Sugarbeet,

White clover, Safflower, Onion, Garlic, Watermelon, Cucumber,

Pumpkin, Carrot, Papaya,

4.3 Mechanism promoting cross-pollination

A. Dicliny

It refers to unisexual flowers. This is of two types: viz. i)

monoecy and ii) dioecy. When male and female flowers are separate

but present in the same plants, it is known as monoecy. In some

crops, the male and female flowers are present in the same

inflorescence such as in mango, castor and banana.

In some cases, they are on separate inflorescence as in maize.

Other examples are cucurbits, grapes, strawberry, cassava and

rubber. When staminate and pistillate flowers are present on

different plants, it is called dioecy. It includes papaya, date

palm, spinach, hemp and asparagus. B. Dichogamy

(from the Greek dikho-apart and gamous-marriage)

It refers to maturation of anthers and stigma of the same flowers

at different times. Dichogamy promotes cross pollination even in

the hermaphrodite species. Dichogamy is of two types: viz. i)

protogyny and ii) protandry.

When pistil matures before anthers, it is called protogyny such

as in pearl millet. When anthers mature before pistil, it is

known as protandry.

It is found in maize, sugarbeet and several other species.

C. Heterostyly

When styles and filaments in a flower are of different lengths,

it is called heterostyly. It

Promotes cross pollination, such as linseed.

D. Herkogamy

Hinderance to self-pollination due to some physical barriers such

as presence of hyline membrane around the anther is known as

herkogamy. Such membrane does not allow the dehiscence of pollen

and prevents self-pollination such as in alfalfa.

E. Self incompatibility

The inability of fertile pollens to fertilize the same flower is

referred to as self incompatibility. It prevents self-pollination

and promotes cross pollination. Self incompatibility is found in

several crop species like Brassica, Radish, Nicotiana, and many grass

species.

F. Male sterility

In some species, the pollen grains are non functional. Such

condition is known as male sterility. It prevents self-

pollination and promotes cross pollination.

It is of three types: viz. genetic, cytoplasmic and cytoplasmic

genetic. It is a useful tool in hybrid seed production.

Study of floral biology and aforesaid mechanisms is essential for

determining the mode of pollination of various crop species.

Moreover, if selfing has adverse effects on seed setting and

general vigour, it indicates that the species is cross

pollinated. If selfing does not have any adverse effect on these

characters, it suggests that the species is self-pollinated.

The percentage of cross pollination can be determined by growing

a seed mixture of two different varieties together. The two

varieties should have marker characters say green and pigmented

plants. The seeds are harvested from the recessive (green)

variety and grown next year in separate field. The proportion of

pigmented plants in green variety will indicate the

Percentage of out crossing or cross pollination.

4.4 Cross/self pollination

Often Allogamous Species Ex. Sorghum, Cotton, Triticale,

Pigeon pea, Tobacco

(citation absent)

5 Methods of pollinations

5.1 Natural Method

Almost 90% of all flowering plants rely on animal pollinators for

fertilization, and about 200,000 species of animals act as

pollinators. Of those, 1,000 are humming birds, bats, and small

mammals such as mice. The rest are insects like beetles, bees,

ants, wasps, butterflies and moths. (citation absent)

Pollination occurs in several ways. People can transfer pollen

from one flower to another, but most plants are pollinated

without any help from people. Usually plants rely on animals or

the wind to pollinate them. (citation absent)

5.1.1. Biotic

Insect-mediated syndromes: are generically termed entomophily but

may further be classified according to the specific insect groups

as:

Bee pollination syndrome called melitophily

Butterfly pollination syndrome referred to as psychophily

Moth pollination syndromes called phalaenophily

Fly pollination syndrome or myophily,

Beetle pollination syndrome or cantharophily

Bird pollination syndrome or ornithophily.

Bat pollination syndrome or chiropterophily.

Snail-slug pollination syndromes otherwise termed

This effectively occludes activities of “visitors” to the flower

and thus it (the flower) self-pollinates. Suites of

circumstances, known as pollination syndromes, make for success

in each pollination event as a result of natural selection and

co-evolution of plants and their pollinators. These syndromes are

either mutualistic or antagonistic traits shared by plants and

their pollinating agents for successful pollination for the plant

on one hand, and for nectar or pollen grain thievery for the

pollinator on the other.https://dlc.dlib.indiana.edu/.../benefits%20of%20biotic%20pollination.pd...

Bees are essential components of almost all of the world’s

terrestrial ecosystems. They provide both pollination services,

and are excellent indicators of the state of terrestrial

environments including responses to global warming.

A major challenge to knowing how to

manage wild bees for pollination

services or to using their occurrence as

an indicator of ecosystem health is the

taxonomic impediment to identifying the

exact name of a pollinator

Knowing the taxonomy of a bee assists in

knowing many aspects of its ecology and

natural history where it nests,

www.fao.org/fileadmin/...pollination/Pollination-FolderFlyer_web.pd??????????????

When animals such as bees, butterflies,

moths, flies, and humming birds

pollinate plants, it's accidental. They

are not trying to pollinate the plant.

Usually they are at the plant to get

food, the sticky pollen or sweet nectar

made at the base of the petals.

When feeding, the animals accidentally rub against the stamens

and get pollen stuck all over themselves. When they move to

another flower to feed, some of the pollen can rub off onto this

new plant's stigma. Plants that are pollinated by animals often

are brightly colored and have a strong smell to attract the

animal pollinators. (citation absent)

Hummingbirds – have long beaks and

brush-like tongues, and they are good

pollinators of many plants in the

Western hemisphere. They generally look

out for long, tube-shaped, flowers

colored red or orange.

Bats – like moths, nectar-eating bats

are attracted to pale or white flowers

that blossom after dark. Bats search for

flowers with a large amount of nectar

and that emit strong, musky or fruity

odors. These flowers include the agave

and many other tall, cactus species.

5.1.1.1 Attractive cuesAnimals are attracted to flowers by the colour or odour given off by the flowers at certain periods of their life cycles.

Firstly, the attraction is for food or mate (in case of floral mimicry of the opposite sex of the animal) or some sort of reward or thievery (for nectar or pollen) for the pollinator.

Secondly,the plant or flower precisely advertises itself with some attractant including odour, colour, shape and texture to which its preferred pollinator responds to more than others do. Another variant of this is the presence of structures that make for effective transfer of pollen material to next flower by the pollinator.

Thirdly,The pollinator must establish a pattern of repeated visits to the flower on a regular basis to try to perform the vitaltransfer apparently dictated by the structure and function

of the flower. (www.researchgate.net/.../242574392_ Pollination _A_threatened_vital_biodi ..)

5.1,2. Abiotic

Wind:- Another way plants are pollinated is by the wind. The windpicks up pollen from one plant and blows it onto another. Plants that are pollinated by wind often have long stamens and pistils. Since they do not need to attract animal pollinators, they can bedully colored, unscented, and with small or no petals since no insect needs to land on them. (citation absent)

Wind pollination syndromes: termed anemophily whereby pollen grains are carried by wind to the receptive stigma of the same plant, related species or another unrelated plant.Water pollination syndromes: called hydrophily involving the transfer of pollen grains from anthers to stigmata through the agency of water.??????????????????

6. Artificial or Man made Pollination

Pollination and Emasculation

6.1. Pollination and Emasculation technique

Clean pollinating tools thoroughly with ethanol before

starting.

Apply pollen to the exposed stigma with a dissecting

needle (see below), or by dipping the flower into the

pollen.

If using a gelatin capsule, first shorten the capsule

with scissors so the stigma can reach the pollen.

Transfer an excess of pollen onto the stigma to ensure

good seed set.

If fertilization was successful, you should notice the ovaries

enlarging after a few days. If fertilization did not occur, the

flowers will abort and abscise.

This can happen for various reasons –

damage to the pistil during emasculation,

low pollen viability or fertility,

excessive temperatures, etc. –

So it’s often worthwhile to make extra crosses to be sure that at

least a few will take. For best results, re pollinate the same

flowers one or two days later.

B. Marking flowers.

A simple way to mark flowers that have been cross pollinated

is with colored twist ties

Cut them into short lengths (4 cm) and wrap around pedicel

of pollinated flower by folding into three sections.

Tags of different colors can be used to indicate the date of

pollination or the pollen source. Striping tags with a

colored pen provides additional color combinations.

The crossing dates, pollen parents, or other treatments

associated with each tag color can be recorded on a large

manila shipping tag tied to the plant stake.

tgrc.ucdavis.edu/guidelines_emasculating_and_pollinating_tomatoes.pdf

6.2. Pollination and Emasculation technique of commonly

Cultivated crops.

6.3. In Cereals

6.4. In legumes

6.5. In Horticultural crops ……………..Ex. Tomato.

A. List of Materials Needed.

Tomato plants with flowers to serve as the female and

male parents

Colored twist-ties or other types of labels

A dissecting needle, scalpel, or other sharp and pointed

instrument to collect pollen

A bottle of 70% ethanol or rubbing alcohol to clean the

pollinating needle between crosses

A. Basic Steps. (refer to the corresponding images next)

1. Choose flowers of the right stage. On each

inflorescence (flower cluster), choose a

well developed flower that has not yet

opened. Immature buds at the -1 or -2 days

stage are usually suitable (Rick 1980). By

the time flowers have opened, they may

have released some pollen, and therefore

should not be used. Flowers showing a

little yellow wing of the petals are

ideal, as these should be receptive to

pollen and will set fruit if pollinated

the same day they are emasculated. Younger

flower buds should be pollinated 1-2 days

after emasculation to ensure fruit set.

2. Remove sepals. Pull off two or more

sepals to expose the petals on one side of

the flower. The missing sepals also

provide a marker to indicate that the

fruit resulted from a cross pollination

3-4. Remove petals and anthers. Pinch

the side of the petals between thumb and

forefinger, gently rock side to side,

then pull straight off (away from

flower). If the petal tears off but not

the anthers, then remove more sepals and

grab the petals from the other side.

Avoid pinching the anthers so as not to

damage the female parts of the flower

inside (or transfer pollen). If this

does not work well, try using a pair of

sharp jeweler’s tweezers to remove the

anthers by skewering them on both sides

and pulling straight off. If all else

fails, use a dissecting needling to cut

off the anthers individually.

5. Remove older flower buds. All older

flowers should be pulled off to prevent

shedding of pollen onto the freshly

emasculated flower.

6. Collect pollen from the male parent.

Pick a mature flower(s) off the male

parent (pollen donor).Using a dissecting

needle or scalpel, slice open the anther

cone lengthwise. Collect pollen on the

tip of the needle by dragging upwards

through the side of one of the anthers.

You should have enough pollen to see the

whitish clump of it on the tip of the

needle.

If you’re making large numbers of crosses with the same pollen

source, it’s more efficient to collect pollen using a pollen

collector

Apply pollen to emasculated flower.

Holding the emasculated flower in one

hand, apply the pollen to the stigma

surface using the dissecting needle.

Apply enough

pollen to cover the entire stigma. Wash

hands and sterilize the pollinating

needle in alcohol between crosses.

8. Tag flower. Fold a piece of colored

twist tie around the flower to indicate

it has been pollinated. Different colors

of twist ties can be used to indicate

different pollen parents or pollination

dates.

.tgrc.ucdavis.edu/

guidelines_emasculating_and_pollinating_tomatoes.pdf

The global benefit of pollinationhis folder highlight different

aspects of

Pollination is one major biodiversity service that cannot be

adequately quantified economically yet the variety of approaches

nature has engaged to accomplish it is hardly appreciated. In

this review, the types and agents of pollination, faunal and

floral architectural and behavioral adaptations and special rare

cases of pollination syndromes are highlighted. Anthropogenic

roles that have resulted of threats to pollination and

pollinators were identified as habitat fragmentation and loss,

deforestation, desertification, industrial and infrastructural

development. These eventually impinge on the unique ecological

and economic services that pollination renders to sustain life on

planet earth.

www.researchgate.net/.../

242574392_Pollination_A_threatened_vital_biodi..

Crop pollination – key to food production and security – has been

little understood, in part because it has been provided by

biodiversity at essentially no cost. As farm fields have become

larger, production systems have intensified, and the use of

agricultural chemicals that impact beneficial insects such as

pollinators has increased. A result of this is that pollination

services are showing declining trends in a number of instances. A

major barrier to enhanced pollinator conservation and management

is that the existing knowledge base is scattered and often

inaccessible to people who need such information to introduce

appropriate pollinator-friendly practices into agricultural

management.

The Food and Agriculture Organization of the United Nations (FAO)

has coordinated a response to these needs by developing a

pollination information management system.tb

The selection of environmentally-friendly pesticides is an

important agricultural management practice, with critical

implications for pollinators. The current status of information

on pesticide toxicities for pollinators is available through the

Pollination Information Management System, along with profiles of

best practices in managing wild pollinators for crop production.

a Consolidating the current knowledge base on the management of

pollination services, and making this accessible to field

practitioners is the first and most fundamental step in building

human capacity to secure the benefits of biodiversity for

improved management of pollination services..

((www.fao.org/fileadmin/...pollination/Pollination-FolderFlyer_web.pdf

1. Conclussion

2. Bibliography

www.mbgnet/bio plant/pollination.html. Biology of plants (Vol. ii). usa: rensissance publishers.