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UNIT 14: ASEXUAL AND SEXUALREPRODUCTION IN PLANTS
Key unit competence
Describe modes of reproduction in plants and apply various methods of
asexual and Sexual reproduction as means of increasing crop yield.
Introductory Activity
Task 1
The kingdom Plantae comprises about 260,000 known species including
flowering and non-flowering plants. All plants have a general organization
which includes vegetative and reproductive organs. Plants reproduce through
different ways: Use the books and other source of information to:
1. Write on how lower organisms such unicellular plant and another like
cassava, sugar cane and apple reproduce.
2. Describe the techniques used by people to grow Irish potatoes,
cassava and bananas.
3. Describe each of the following methods of asexual reproduction:
fragmentation, budding and spore formation.
Task 2
1. Observe the following pictures and suggest what is going on.2. How are the pictures below related to reproduction in flowering plants
14.1 Application of artificial propagation in growing
improved varieties of plants
Activity 14.1. a
Using addition resources to your textbook available in your school such
as the books from the school library and search further information from
the internet. Discuss on application of artificial propagation in growing
improved varieties of plants.
Artificial vegetative propagation is the deliberate production of new plants
from parts of old plants by humans. This can be done by following three
methods:Cutting, layering, and grafting.
Artificial vegetative propagation is usually used in agriculture for the
propagation (or reproduction) of those plants which produce either very few
seeds or do not produce viable seeds. Some examples of such plants which
are reproduced by artificial vegetative propagation methods are: Banana,
Pineapple, Orange, Grape, Rose, etc.
Vegetative propagation of particular cultivars that have desirable
characteristics is very common practice. Reasons for preferring vegetative
rather than sexual means of reproduction vary, but commonly include greater
ease and speed of propagation of certain plants, such as many perennial root
crops and vines. Another major attraction is that the resulting plant amounts
to a clone of the parent plant and accordingly is of a more predictable quality
than most seedlings. However, as can be seen in many variegated plants,
this does not always apply, because many plants actually are chimeras and
cuttings might reflect the attributes of only one or some of the parent cell
lines.
Man-made methods of vegetative reproduction are usually enhancements
of natural processes, but they range from rooting cuttings to grafting and
artificial propagation by laboratory tissue culture. In horticulture, a “cutting”
is a piece that has been cut off from a mother plant and then caused to
grow into a whole plant. A popular use of grafting is to produce fruit trees,
sometimes with more than one variety of the same fruit species growing from
the same stem. Rootstocks for fruit trees are either seedlings or propagatedby layering.
The following are methods of vegetative artificial propagation
Activity 14.1. b
Demonstration of asexual reproduction in plants by cuttings
Requirements
Growth medium or moist soil, sweet potatoes vines, elephant grass,
sugarcane or cassava stems, secateurs/sharp knife and rooting hormone.
Procedure
1. Collect clean and healthy stems from cassava, sugarcane or potato plants.
2. Using a secateurs/sharp knife, cut the stem of either cassava,
sugarcane or sweet potato stems into suitable sizes.
3. Place them in either suitable medium of growth or apply rooting
hormone if available or plant them in moist soil in the school garden.
4. Leave the set up for about 13 days, and then observe the
development of roots and leaves at nodes.
Draw and record what you will observe after 13 days on the development
of roots and leaves at nodes.
a) Cutting
This is simple procedure in which part of the plant is removed by cutting and
placed in a suitable medium for grow. The part of the plant which is removed
by cutting it from the parent plant is called a ‘cutting’. In this method oneyear-
old stem of root is cut from a distance of 20 to 30 cm. and is buried in
the moist soil in natural position. After sometime, roots develop from this
cutting and it grows into a new plant. This method is commonly used in rose
and sugar cane. Care is taken that nodes which were lower in parent plant
(morphologically) are put in the soil, while the morphologically higher nodesare kept up. Adventitious roots are given off at the lower nodes.
b) Layering
This method of vegetative propagation is used in those plants whose soft
branches occur near the ground such as jasmine plant. In this method, a
branch of the plant which is near to the ground is pulled towards the ground
and a part of this branch is covered with moist soil leaving the tip of this
branch above the ground. After sometime, roots develop from that part of
the branch which was buried in the soil. This branch is then cut of along with
the roots from the parent plant and develops into a new plant. This method
of asexual reproduction is also used in the production of plants such asBougainvillea, jasmine, guava, strawberries, lemon, China rose etc.
c) Grafting
In this method of vegetative propagation the stems of two different plants are
joined together so as to produce a new plant containing the characters of
both plants. Out of the two plants one plant has a strong root system while
the other has a better flower or fruit yield. The plant of which the root system
is taken is called ‘stock’, while the other plant of which the shoot is selected
is known as ‘scion’ or ‘graft’. These two stems i.e. the stock and the scion
are fitted together by making slanting cuts in them and bound tightly with a
piece of cloth and is covered with a polythene sheet.
While joining the scion with the stock care should be taken that the diameter
of the stock and scion chosen for grafting should be equal. Scion gets the
mineral and water from the soil through the stock and develops branches
and produce fruits. This method of propagation is used in mango, apple,banana, pear, grape, pineapple and peach.
Vegetative and artificial reproduction in flowering plants
The reproductive part of the plant is a flower. The union of male and female
gametes to form a zygote is called fertilization. The transfer of pollen grains
from the anther to the stigma of the same flower or the different flower is
called pollination. In nature, plants reproduce asexually in a variety of ways.
The vegetative reproductive parts in flowering plant are stem, branches, and
leaves and they have the following characteristics:
Characteristics of Stem:
Stem develops from the plumule of embryo, Stem is generally the ascending;
part of the plant axis, It bears a terminal bud for growth in length, The
stem is differentiated into nodes and internodes, the stem nodes possess
dissimilar appendages called leaves, The young stem is green and capable
of performing photosynthesis, In the mature state it bears flowers and fruits,
Leaves and stem branches develop exogenously, Stem exposes leaves,
flowers and fruits to their most suitable position in the aerial environment
for optimum function, Hair, if present, is commonly multicellular and Stems
are usually positively phototropic, negatively geotropic and negatively
hydrotropic.
Characteristics of Leaf
– It is dissimilar lateral flattened outgrowth of the stem,
– The leaf is exogenous in origin
– It is borne on the stem in the region of a node,
– An axillary bud is often present in the axil of the leaf.
– Leaf has limited growth. An apical bud or a regular growing point is
absent,
– The leaf base may possess two lateral outgrowths called stipules,
– A leaf is differentiated into three parts: leaf base, petiole and lamina.
– The lamina possesses prominent vascular strands called veins,
– It is green and specialized to perform photosynthesis,
– Leaf bears abundant stomata for exchange of gases and it is the major
seat of transpiration.
Characteristics of branches
A branch or tree branch is a woody structural member connected to but not
part of the central trunk of a tree. Large branches are known as boughs
and small branches are known as twigs. Due to a broad range of species of
trees, branches and twigs can be found in many different shapes and sizes.
Application activity 14.1
1. Write on the methods of artificial vegetative propagation.
2. Cassava produces flowers, fruits and seeds. Why people prefer to
grow cassava by cutting rather than germination of seed?
3. Describe the characteristics of vegetative reproductive parts in a
flowering plant
4. Explain the application of artificial propagation in growing improved
varieties of plants.
14.2. Sexual reproduction in plants
Activity 14.2
Collect different forms of flowers from the school compound or around the
school, such as hibiscus, morning glory, sweet potato, or maize flower (use
any type of flower in your community not necessarily the ones mentioned
here)
1. Observe and describe the structures of collected flowers.
2. How do collected flowers differ externally?
3. Cut one of the flowers into two halves, draw and label one half offlower.
14.2.1. Types, structure and functions of flowers
a) Types of flowers
1. According to absence of some reproductive parts of the flower, we
can distinguish:
a) Unisexual flower: is a flower that consists of one type of reproductive
organ. This can be: staminate: unisexual male (with androecium
only), or carpellate: unisexual female (with gynoecium only). E.g.
flower of papaya.
b) Bisexual or hermaphrodite flower: a flower with the two
reproductive organs. It contains both male and female reproductive
organs (androecium and gynoecium). E.g. flowers of beans.
Dioecious plants are plants that have male flowers and female
flowers on separate plants (e.g. papaya/pawpaw) while monoecious
plants are plants that have both male and female flowers on the same
plant (e.g. maize).
2. According to the position of ovary in the point of insertion of calyx,
corolla and stamen, we can distinguish:
a) A flower with inferior ovary: it is when the ovary is located below
the point of insertion of calyx, corolla and stamens.
b) A flower with superior ovary: it is when the ovary is located over
the point of insertion of calyx, corolla and stamens.
c) The semi-infer or semi-super flower: when ovary is neither infer
nor super but in the middle of receptacle which is hollowed.
– When sepals are joined together, the flowers are called gamosepal,
and where are not joined together, the flower is called dialysepal.
– When petals are joined together, the flowers are called gamopetal,
and when are not joined together, the flower is called dialypetal. When
they are absent, the flower is called apetal.
3. According to the shape and symmetry of the flower, we can
distinguish:
i. Zygomorphic or irregular flower: a flower with a bilateral symmetry.
The flower cannot be divided into two similar halves. E.g. flowers of
beans, cassia.
ii. Actinomorphic or regular flower: a flower with a radial symmetry.
The flower can be divided into two or more planes to produce similarhalves. E.g. flowers of coffee, orange.
3. Dichogany: it is when male and female organs of the flower mature
at different times. We can distinguish:
– Protandry: when stamens mature before pistil.
– Protogyny: when pistil matures before stamen.
4. Inflorescence is when two or more flowers borne on a common
stalk.
a) Structure of a typical complete flowerA flower is a reproductive organ of a plant, which produces fruits and seeds.
A typical hermaphrodite or bisexual flower contains the following parts:
– Pedicel: it is the stalk which attaches the flower on the main floral axis.
– Receptacle: it is the swollen part at the end of the stalk where other
parts of the flower are attached.
– The calyx: it is the set of sepals, generally having green colour. They
protect the internal parts of the flower. In some plants, the sepals are
coloured and are called petaloids.
– The corolla: it is the set of petals, with different colours and nectar
glands that produce sugary substances which participate in attraction
of pollinating agents. In some plants, the petals are green and are called
sepaloids. Both calyx and corolla are collectively called perianth.
They are called floral envelope or accessory organs as they do not
participate directly in reproduction, or in formation of fruits and seeds,
they all insure the protection of internal parts of the flower.
– Androecium: is the male reproductive organs of the flower. It consists
of many stamens. A stamen consists of: the filament which supports
anther, and anther which contains the pollen grains or male gametes.
– Gynoecium/pistil: is the female reproductive organ. It consists of
many carpels, and each carpel is made of: stigma (plural: stigmata),
style and ovary with ovules.
a) The stigma: receive pollen grains from anther during pollination.
b) Style: supports the stigma in a good position to receive pollen
grains.
c) Ovary: a sac where ovules are produced. Ovules become seeds
after fertilisation.
A typical hermaphrodite or bisexual flower contains the following parts:
– Pedicel: it is the stalk which attaches the flower on the main floral axis.
– Receptacle: it is the swollen part at the end of the stalk where other
parts of the flower are attached
– The calyx: it is the set of sepals, generally having green colour. They
protect the internal parts of the flower. In some plants, the sepals are
coloured and are called petaloids.
– The corolla: it is the set of petals, with different colours and nectar
glands that produce sugary substances which participate in attraction
of pollinating agents. In some plants, the petals are green and are called
sepaloids. Both calyx and corolla are collectively called perianth. They
form a floral envelope or accessory organs as they do not participate
directly in reproduction, or in formation of fruits and seeds, they all
insure the protection of internal parts of the flower.
– Androecium: is the male reproductive organs of the flower. It consists
of many stamens. A stamen consists of: the filament which supports
anther, and anther which contains the pollen grains or male gametes.
Gynoecium/pistil: is the female reproductive organ.
It consists of many carpels, and each carpel is made of: stigma (plural:
stigmata), style and ovary with ovules.
• The stigma: receive pollen grains from anther during pollination.
• Style: maintains the stigma in a good position to receive pollen grains.
• Ovary: a sac where ovules are produced. Ovules become seeds after
fertilisation.
Application activity 14.2.1
1. What are the male and female structures of a flower?
2. How might be an advantage for a plant to have many flowers
together in a single structure?
3. Where does the female gametophyte develop?
4. Describe the flower and how it is involved in reproduction.
14.2.2. Pollination and double fertilisation in flowering plants
and events in a flower after fertilisation
Activity 14.2.2
Use library resources to identify different pollinating agents and describe
the process of double fertilization in flowering plants.
1. Pollination
Pollination is transfer of pollen grains from anther to the stigma.
a) Types of pollination: there are two types of pollination such as: self pollination
and cross-pollination.
i. Self-pollination: it is the transfer of pollen grains from anther to the
stigma of the same flower, or of different flowers but of the same plants.
It involves one plant. E.g. flowers of maize and beans.
ii. Cross-pollination: it is the transfer of pollen grains from anther to
the stigma of the flower of another plants. It involves two plants. E.g.flowers of pawpaw.
b) Main Pollinating agents
Flower structure is closely related with the way they are pollinated. This
means that flowers are adapted to specific agents or mode of pollination.
The common agents of pollination are: insects (entomophily), wind
(anemophily), water (hydrophily), humans (anthropophily), and birds
(ornithophily).
Characteristics of insect-pollinated flowers: (entomophilous flowers):
– Flowers produce the nectar to attract pollinators.
– Flowers have large brightly coloured corolla to attract pollinators.
– Production of scents to attract pollinators.
– The surface of the stigma should be sticky to hold pollen grains.
– Pollen grains are stickyand rough enough to remain on the surface of
stigma.
Characteristics of wind-pollinated flowers: (enemophilous flowers)
– The flowers have large stigma to hold pollen grains.
– The surface of the stigma should be sticky to hold pollen grains.
– Pollen grains are rough enough to remain on the surface of stigma.
– The flowers are or are not brightly-colored.
– They have or do not have scent.
– They do or do not secrete nectar.
– They produce large quantities of pollen grains, as much of them never
reach the stigmas.
2. Double fertilization and events after fertilization in flowering
plants
Double fertilization is a complex fertilization mechanism of flowering plants
(angiosperms). This process involves the joining of a female gametophyte
(megagametophyte, also called the embryo sac) with two male gametes
(sperm).
a) Development of pollen grains and plant ovules.
i. Development of pollen grains
The pollen grains are produced in the anthers while the ovules are produced
in the ovary.
Pollen grains
Each anther has four pollen sacs which contain many diploid microspore
mother cells that undergo meiosis to form four microspores each. At first,
the four microspores remain together as tetrads. The nucleus of each
microspore then divides by mitosis, forming a generative nucleus and a tube
or vegetative nucleus. At this point, the content of the pollen grain may be
considered as the male gametophyte. A two-layered wall forms around each
pollen grain. The outer wall, the exine is thick and sculptured. The inner wall,
the intine is thin and smooth. There are many pores or apertures in the wallthrough which a pollen tube may emerge.
ii. Development of Plant ovule
Each ovule is attached to the ovary wall by a short stalk called funicle.
The main tissue in the ovule is the nucellus which is enclosed and protected
by the integuments.
At one end of the ovule, there is a small pore called micropyle. A single
diploid megaspore mother cell in the nucellus undergoes meiosis, producing
four megaspores. Three of the four megaspores degenerate, while the
remaining cell, called the embryo sac, grows to many times its original size.
The nucleus of the embryo sac divides mitotically three times, resulting in
eight haploid nuclei which are arranged in groups of four nuclei at the two
poles. At this point, the contents of the embryo sac may be regarded at the
female gametophyte.
One nucleus from each pole migrates to the centre of the embryo sac. These
two nuclei are called polar nuclei, and they fuse to form a single diploid
nucleus. Meanwhile, cell walls form around the remaining six nuclei and they
form the synergids, antipodals and the egg (ovum). Only the egg functionsas the female gamete.
In summary, the pollen grain: contains two haploid nuclei: one called
generative nucleus, and the other the tube nucleus.
On the other hand, the ovule or embryonic sac contains eight nuclei:
– Three antipodal nuclei/cells at one end
– Two polar nuclei/cells in the middle of ovule
– Two synergids (non-functional nuclei)– One big egg cell.
The process of double fertilization: It begins when a pollen grain adheres
to the stigma of the carpel, the female reproductive structure of a flower. The
pollen grain then takes in moisture and begins to germinate, forming a pollen
tube that extends down toward the ovary through the style.
The growth of the pollen tube is controlled by the pollen tube nucleus.In
the pollen tube, the generative nucleus divides mitotically into two haploid
nuclei which are the male gamete nuclei. These follow behind the tube
nucleus as the pollen tube grows down the style towards the ovule. The tip of
the pollen tube then enters the ovary and penetrates through the micropyle
opening, releasing the two sperms in the megagametophyte or ovule.
The tube nucleus degenerates, leaving a clear passage for the entry of male
nuclei. One nucleus fertilizes the egg cell to form a diploid zygote (2N),
which will grow into a new plant embryo; the other fuses with polar nuclei
to form a triploid nucleus (3N), which will grow into a food-rich tissue knownas endosperm, which nourishes the seedling as it grows.
This process is described as double fertilisation and is typical of
angiosperms. If there is more than one ovule in the ovary, each must be
fertilised by separate pollen grain and hence the fruit will have many seeds
genetically different from each other.
3. Events in a flower after fertilization
After fertilisation, the calyx, corolla, stamens and style may wither gradually
and fall off, but in some flowers the calyx may persist. The ovule forms the
seed, the two integuments of the ovule will form the seed coat, and the ovary
will develop into fruit, with the ovary wall forming the pericarp (fruit wall).
The diploid zygote undergoes cell division to form the embryo, the triploid
primary endosperm nucleus develops into endosperm, a store used by the
developing embryo. This persists in endospermic seeds of monocotyledons.
The micropyle persists as a small hole in the seed coat through which water
is absorbed during germination.Table 14.2: Floral parts and their fate after fertilization
Application activity 14. 2.2
1. Are angiosperms typically wind or animal pollinated? How does
this process occur?
2. What is meant by the term endosperm?
3. How are brightly coloured petals advantageous to the plant?
4. What do you understand by the term double fertilization?
5. What happens to the antipodal cells and synergids cells after
fertilization?
14.2.3 Structures and types of fruits and seeds
Activity 14. 2.3
Observe slides containing micrographs of different fruits and seeds.
According to their characteristics:
a) Differentiate fruits.
b) Draw and show a structure of seed as seen on microscopeBelow are some examples of fruits:
A fruit is a structure formed from the ovary of a flower, usually after the
ovules have been fertilized. In nature, a fruit is normally produced only after
fertilization of ovules has taken place, but in many plants, largely cultivated
varieties such as seedless citrus fruits, grapes, bananas, and cucumbers,
fruit matures without fertilization, a process known as parthenocarpy.
Ovules within fertilized ovaries develop to produce seeds. In unfertilized
varieties, seeds fail to develop, and the ovules remain with their original size.
A fruit consists of two main parts; pericarp (fruit wall) and the seed. The
pericarp has three layers: epicarp or exocarp (outermost), mesocarpe(middle) and endocarp (inner).
The fruit can have a dry pericarp or fleshy pericarp. The fruits with fleshy
pericarp include: berry and drupe. Drupe is a fleshy fruit with only one seed,E. g. avocado.
Berry is a fleshy fruit having many seeds inside of it. E.g. tomatoes, orange,
and pawpaw.
The fruits with dry pericarp include indehiscent fruit or dehiscent fruit.
Indehiscent fruits do not open. Seeds remain inside of the fruits. E.g. fruits of
coconuts. Dehiscent fruits open and release seeds. These include: dehiscent
fruits with one carpel, and those with many carpels. Dehiscent fruits with one
carpel include; those which open along one side, e.g. follicle; and those
which open along both sides, e.g. legume (beans). Fruits of eucalyptus areexam of dehiscent fruits with many carpels.
The major function of a fruit is the protection of developing seeds. In many
plants, the fruit also aids in seed distribution (dispersal).
Food value
Fruits are eaten raw or cooked, dried, canned, or preserved. Carbohydrates,
including starches and sugars, constitute the principal nutritional material.
Citrus fruits, tomatoes, and strawberries are primary sources of vitamin C,
and most fruits contain considerable quantities of vitamin A and vitamin B.
In general, fruits contain little protein or fat. Exceptions are avocados, nuts,
and olives, which contain large quantities of fat, and grains and legumes,
which contain considerable protein.
A seed is an embryonicplant enclosed in a protective outer covering. The
formation of the seed is part of the process of reproduction in seed plants,
the spermatophytes, including the gymnosperm and angiosperm plants.
Seeds are the product of the ripened ovule, after fertilization by pollen and
some growth within the mother plant. The embryo is developed from thezygote and the seed coat from the integuments of the ovule.
The main components of the seed:
A seed is made up of a seed coat (testa), one or two cotyledons and an
embryonic axis. The embryonic axis is made up of a plumule, an epicotyl,
a hypocotyl and a radical. A seed which has one seed-leaf is described as
monocotyledonous, and one which has two, as dicotyledonous. Maize is
monocotyledonous seed while bean is a dicotyledonous seed.
– The cotyledons, the seed leaves, attached to the embryonic axis. There
may be one (Monocotyledons), or two (Dicotyledons). The cotyledons
are also the source of nutrients in the non-endospermic Dicotyledons,
in this case they replace the endosperm, and are thick and leathery. In
endospermic seeds the cotyledons are thin and papery.
– The epicotyl, the embryonic axis above the point of attachment of the
cotyledon(s).
– The plumule, the tip of the epicotyl, and has a feathery appearance due
to the presence of young leaf primordia at the apex, and will become
the shoot upon germination.
– The hypocotyl, the embryonic axis below the point of attachment of
the cotyledon(s), connecting the epicotyl and the radicle, being the
stem-root transition zone.
– The radicle, the basal tip of the hypocotyl, grows into the primary root.
Monocotyledonous plants have two additional structures in the form of
sheaths. The plumule is covered with a coleoptile that forms the first leaf
while the radicle is covered with a coleorhiza that connects to the primary
root and adventitiousroots form from the sides. Here the hypocotyl is arudimentary axis between radicle and plumule.
Application activity 14.2.3
1. Describe the structure of a drupe
2. Differentiate between a drupe and a berry
3. What would happen to the fruit if ovules in the flower did not
develop?
4. Compare the typical structure of seeds that are dispersed by
animals to those dispersed by wind and water.
14.2.4. Fruits and seeds dispersal with their adaptations
Activity 14.2.4
Use library resources like books, internet and search to find answers for
the following questions:
1. Suggest ways of fruits and seeds dispersal.
2. Explain adaptation of fruits dispersed by animals.
Dispersal of fruits and seeds is the scattering of fruits and seeds from their
mother plants. They are four methods of seeds and fruits dispersal such as:
1. Dispersal by Wind
2. Dispersal by Water
3. Dispersal by Animals and
4. Mechanical Dispersal.
Seeds disperses by wind or water are typically lightweight, allowing them
to be carried in air or to float on the surface of water. The wind carries also
small seeds that have wing-like structure. Seeds dispersed by animals
are typically contained in sweet, nutritious flesh fruits. They can be carried
externally on their feet, fur, feathers, or beaks. Those seeds with hooks or
sticky substances rely on the chance that they will attach themselves to a
passing animal. Other seeds are eaten by animals and passed out in the
faeces.
With mechanical Dispersal: all dehiscent fruits scatter the seeds when they
burst. This dehiscence is accompanied by the expression of great force in
many fruits so that seeds are jerked a considerable distance away from the
mother plant. Such fruits are called explosive fruits.
These seeds will germinate where the faeces will be deposited. The dispersal
of seeds is important for the survival of the plant species because:
– It minimises overcrowding of plants growing around the parent plant
that could then result in too much competition for nutrients and light;
– It allows the plant species to colonise new habitats which can offer
suitable conditions.
Application activity 14.2.4
1. Why is it adaptive for some seeds to remain dormant before they
germinate?
2. The seeds of a bishop pine germinate only after they have
undergone a forest fire. Evaluate the significance of this structural
adaptation.3. Evaluate the importance of seed dispersal.
SKILLS LAB
After studies, and completion of this unit 14, student-teachers will use the
acquired knowledge to increase the crop productivity using different modes
of vegetative and artificial propagation. They will also improve the quality
of fruit plants by using for example grafting method.
End unit assessment 14
PART A
A) Multiple choice questions: choose the best answers.
1. In cutting method of vegetative propagation, cuttings are mainly
taken from
a) Leaves of parent plant
b) Roots or stems of parent plant
c) Shoots of parent plant
d) Buds of parent plant
2. Artificial methods of vegetative propagation includes
a) Cloning
b) Grafting
c) Cuttings
d) Both b and c
3. Example of plant in which vegetative propagation is occurred by
leaves is called
a) Cannabis
b) Chrysanthemum
c) Bryophyllumd) Brassica
4. Which of the following is NOT an advantage of asexual reproduction?
a) Rapid reproduction.
b) High genetic diversity.
c) No need for a mate.
d) Low resource investment in offspring.
B) Questions with short and long answers
1. Name the plants which are grown by grafting method.
2. What do you understand by grafting?
3. How will you show that vegetative propagation takes place in
potatoes?
4. Explain the method by which the sugarcane and rose are grown.
5. Give the names the different methods of artificial vegetative
reproduction.
6. Explain the term vegetative reproduction and give one example of
plant which reproduces by using this type of asexual reproduction.
PART B
1. Answer by true or false
a) Seeds that are dispersed by animals are not contained in a flesh sweet
tissue.
b) During pollination, pollen grains move from stigma to anther.
2. Chose the letter that best answers the question or complete
the statement.
a) Which of the following is not part of a flower?
i. Stamens
ii. Petals
iii. Carpels
iv. Stem
v. Sepals.
b) Which flower structure that includes all the others listed below?
i. Stigma
ii. Carpel
iii. Ovary
iv. Style
v. Ovule
c) The thickened ovary wall of a plant may join with other parts of the
flower stem to become the
i. Cotyledon
ii. Fruit
iii. Endosperm
iv. Seed
d) In angiosperms the structures that produce the male gametophyte
are called the
i. Pollen tubes
ii. Stigma
iii. Anthers
iv. Sepals
e) In angiosperms, the mature seed is surrounded by a
i. Flower
ii. Fruit
iii. Cotyledon
iv. Cone
3. Which are more likely to be dispersed by animals- the seeds of
angiosperms or the spores of a fern? Explain your reasoning.
4. Pollination is a process that occurs only in seed plants. What
process in seedless plants is analogous to pollination?
5. Propose a hypothesis to explain why angiosperms have become
the dominant type of plant on the earth.6. Study the structure of the seed bellow
a) Name the parts labelled by: A, B and C
b) What is the importance of the part C for a growing seedling?
7. Many flowers have bright patterns of coloration that directly
surround the reproductive structures. Evaluate the importance of
those bright-coloured patterns to plants.
8. What is the function of endosperm?
9. Some plants form flowers that produce stamens but no carpels.
Could fruit form on one of these flowers? Explain your answer.
10. Distinguish between pollination and fertilization.
11. Give names of letters from A to J, and explain the function of theparts represented by: B, G, and E.
12. Explain why the relationship between bees and flowers is described
as mutually beneficial.
13. What is the main advantage of cross-pollination?
14. Why are the stamens of wind-pollinated plants and insect-pollinated
plants different?
15. Differentiate wind-pollinated flowers from insect-pollinated flowers.
16. Give one example of a plant that uses each of the following
dispersal mechanism:
a) An explosive device which works by being inflated with water.
b) A winged seed lifted by air currents
c) A buoyant seed carried by sea currents
d) A gluey substance which sticks the seed to an animal.
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