UNIT 13: GROWTH AND DEVELOPMENT IN PLANTS AND ANIMALS
UNIT 13: GROWTH AND DEVELOPMENT IN PLANTS
AND ANIMALS.
Key Unit Competence
Account for the processes of growth and development in plants and animals
Learning Objectives
By the end of this unit, I should be able to:– Describe dormancy as a state of inactivity to absolute minimum due to theIntroductory activity
morphological and physiological state of a plant structure
– Explain how dormancy is maintained and broken
– State the conditions required for germination
– Outline the role of enzymes in the process of germination
– State types of plant growth hormones and their functions
– Identify the hypocotyl and coleoptile in a germinating seed
– Describe the stages and types of germination
– Recognize that a meristem is a growing point of the plant and the main
meristematic regions of a tree
– Describe current views about photoperiodic control of flowering
– Observe structures of endospermic and non-endospermic seeds
– Demonstrate how fruit and seed dispersal takes place
– Demonstrate hypogeal and epigeal germination
– Carry out an investigation to distinguish between primary and secondary
growth
– Appreciate the importance of fruit and seed dormancy and germination in the
life cycle of plants
– Carry out an experiment on the development of eggs at different temperatures
– Describe the process of metamorphosis in arthropods and amphibians
– Distinguish the various stages of development in frogs
– Analyse complete and incomplete metamorphosis
– Compare growth patterns in arthropods and vertebrates
– Appreciate the demands of the terrestrial environment to the adaptation of
amphibians
Suggest morphological differences by which different organisms develop and
grow to maturity.
13.1. Fruit, seed and bud dormancy
Activity 13.1– Put dry bean seeds and maize grains in boiling water for 10 minutes.A seed is a plant organ that develops from the fertilized ovule. As the seed embryo
– Use nails to make a longitudinal section of the bean and maize.
– Compare the two sections.
– From your point of view, do you think that all plants’ organs are always active?
Justify your point of view.
– Produce a picture showing how plant organ (seed and bud) behaves inrelation to oxygen, temperature and water.
develops from the zygote, the seed makes a food reserve of macronutrients including
carbohydrates, proteins and lipids. The amount of reserved food type depends on
the plant species. Legumes like peanuts and soybeans store proteins as well as
fats while beans store more starch and proteins. A seed consists of a plant embryo
surrounded by the food supply in cotyledon or endosperm and a protective coat
called seed-coat or testa. The plant embryo is composed of the radicle or embryonic
root, the hypocotyl which is the embryonic stem and the plumule, the embryonic
leaves.
Dormancy is a period of cells’ inactivity due to a very low metabolism to prevent
growth when environmental conditions are unfavorable. The dormancy can be for
fruit, bud or seed.
a. Bud dormancy
Bud dormancy is a suspension of most physiological activities and growth that can
be reactivated. It may be a response to environmental conditions such as seasonality
or extreme heat, drought, or cold. The exit from bud dormancy is marked by theresumed growth of the bud. Bud dormancy may proceed to dormancy of the whole plant.
b. Seed dormancy
Seeds exhibit dormancy to avoid growth during unfavorable conditions. During the
last stages of its maturation, the seed dehydrates until it gets dry. The embryo which
is surrounded by a food supply (cotyledons, endosperm or both), enters dormancy.
Most seeds are enough durable that can last a year or two until conditions are
favorable for germinating. However, the length of time a dormant seed remain
viable and capable of germinating varies from a few days to years depending on the
plant species and environmental conditions. This may justify the reason why after
a bushfire or other environmental disruption, vegetation reappears as their seeds
have accumulated and stayed for longer in the soil. Many plants are easily grown
from seeds. Although its embryo is alive, a dormant seed cannot germinate until
it is exposed to certain environmental conditions to break the dormancy. Thus, itgerminates and starts to grow.
Conditions needed for seed germination
Germination is the process by which a seedling develops from a seed embryo. There
are requirements for germination to be successful. Environmental conditions such as
water, oxygen, and temperature trigger seed germination. For a seed to germinate,
it must be found in place where all these conditions are available. If one condition isnot available, germination becomes impossible. These conditions include:
a. Water
For a seed to germinate, it requires water. Mature seeds are very dry and must absorb
water by imbibition to germinate. Water softens the seed coat for embryo sprouting
and provides a medium for reactions during hydrolysis. Enzymes breakdown
macronutrients such as starch, proteins and fats stored in the cotyledons and the
endosperm to simple sugars such as glucose, amino acids which provides energy
for the embryo to grow.
b. Oxygen
This is needed for needed for cellular respiration by oxidizing glucose to liberate ATP
to provide energy for embryo development.
c. Temperature
Seeds germinate only if exposed to their optimum temperature varying between
5 to 40 0c depending on the seed species. Enzymes are sensitive to temperature
because enzymes need a favorable temperature to work efficiently. Burying seeds
too deeply in the soil prevents them from germinating as they are cut off fromtemperature and air.
Self-assessment 13.1
1. Define the term dormancy?
2. Explain how dormancy is maintained and broken?
3. Suggest the advantage of dormancy in plants?
4. What are conditions needed for seed germination?
5. Explain the role of enzymes during the process of seed germination.6. Draw and label endospermic and non-endospermic seeds
13.2. Types and stages of germination.
Learning activity 13.2
Conduct the experiment below to compare the two types of germination.
Requirements
Two bean seeds or soybean seeds, two sorghum or maize grains, water and two
plastic devices/containers
Procedure
– Fill each container with soil
– Put two grains of maize in the container labeled A and two seeds of bean in
the container labeled B
– Pour some water in each container simply to moisture the soil.
– Put both containers A and B in a secured place.
– Record your observations from day five to day twenty one with emphasis todevelopmental changes.
In conducive environment, a seed can germinate. Germination involves three mainstages: imbibition, radicle sprouting and plumule sprouting.
The dormant seed contains very little water, when placed in moist conditions, it
absorbs water by osmosis. The intake of water by a dry material is called imbibition.
As the seed absorbs water and oxygen, it swells, the embryo grows and the seed-coat
cracks, and the radicle also called primary root emerges downward. This is seed coat
rupture and radicle sprouting. The primary root is the first organ to appear during
embryo development. The plumule cells develop and the first leaf forms upwards inthe process known as plumule sprouting.
A germinating seed shows the primary root from which secondary roots start to
develop and the primary leaf which is surrounded by a protective sheath called
coleoptile. The Hypocotyl is the stem below the plumule while the epicotyl is thestem above the plumule.
13.2.1. Types of seed germination
There are two types of seed germination: hypogeal and epigeal seed germination.
a. Epigeal germination
Epigeal germination is typical to non-endospermic seeds like beans, soybeans and
coffee seeds.In this type of germination, the cotyledons come above the soil surface
into air and light, due to rapid growth and elongation of hypocotyl. The cotyledons
are green and make food to be used by stem during growing season. They finally dry
off and seedlings become independent . The example of the epigeal germination is likethe one found in bean seeds.
b. Hypogeal germination
In this type of germination, the cotyledons remain in soil or just above the surface.
Here the epicotyl elongates, pushing plumule upwards. Cotyledons do not turn
green and gradually dry up and fall off. An example of this type of germination isfound in pea, mango, and groundnut seeds.
Self-assessment 13.2
1. Use diagrams to demonstrate and distinguish the types of seed germination.2. Describe the three stages of seed germination.
13.3. Primary and secondary growth
Learning activity 13.3
Move around the school garden or anywhere in your surroundings, then collect
two plant species in which one is a monocotyledon and another is a dicotyledon.
1. By examining their physical characteristics, describe similarities and
differences between collected plants.
2. Predict the reason why all plants grow in length.
3. From your observation, suggest/ predict the reasons justifying whymonocotyledons do not grow in width while dicotyledons do.
Growth is a permanent increase in the size of an organism or of some parts of it.
It is brought by cell division and the assimilation of new material within the cells
which result from the division and the cell expansion which follows. Cell expansion
is particularly noticeable in plants, where rapid enlargement can occur as a result
of water taken up by osmosis. If the organism achieves its mature size, it starts
development, the formation of new structures or organs to perform specific functions.
That is the production of reproductive organs and locomotive or protective organs.It is controlled by cell differentiation. Growth is either primary or secondary.
a. Primary growth
Primary growth consists of the increase in length and formation of primary plant
organs including roots, stem, leaves, flowers, and fruits. It occurs in most herbaceous
plants. The roots elongate to penetrate the soil, and shoots elongate to reach the
sunlight. Primary growth is controlled by apical meristems. Meristematic cells
divide by mitosis. Some daughter cells absorb water and nutrients. As the cell takes
in water the cell walls stretches, the cell elongates and slightly enlarges. After this
growth by elongation, cells differentiate and specialize for specific functions. The
cells formed from apical meristems do not expand laterally and this limits their size.
The herbaceous plants exhibiting such growth tend to be short lived. They are called
annual plants because most of them do not live for more than one growing season(a year) after which they enter dormancy and survive as seeds.
b. Secondary growth
It consists of getting wider or thicker, and occurs in roots and stems of perennial
woody plants, all trees and shrubs. Woody plants grow taller than herbaceous plants
and they live longer, more than two years some plants while some others may live
for and over 30 years.
Secondary growth is controlled by lateral meristems: vascular cambium and cork
cambium. Vascular cambium is located between primary phloem and primary xylem.
Vascular cambium cells divide by mitosis. Some cells remain meristematic while
other cells expand sideways and differentiate. They form the secondary phloem
outwards and the secondary xylem inwards. As the secondary growth continues,
the outermost phloem cells die. Their death causes no matter to the whole plant as
dead cells are continually replaced by new ones.
The secondary xylem cells are strengthened by the accumulation of lignin and
cellulose. They form a wood also called secondary xylem providing the mechanical
support to very taller trees. The cork cambium situated between the epidermis and
secondary phloem produces the cork cells by mitosis. The cork cells are pushed
toward the epidermis and accumulate a waxy substance called suberin making
the cork waterproof. The cork gradually replaces the epidermis. Like the epidermis,
the cork protects the plant from dehydration and infection. The expansion of the
internal tissues results into the continual cork shedding. Because of meristematiccells that continuously divide, perennial plants have unlimited growth.
Self-assessment 13.3
1. In the table list the differences between primary growth and secondary
growth.
2. Describe briefly what the wood is and its major function.
3. What is the name given to a substance that makes the cork to resist plant
dehydration?
4. Identify the importance of apical and lateral meristems in plant growth
13.4. Determination of growth
Activity 13.4
In the learning activity 13.1 you have grown two types of seeds (bean and maize).
Based on that experiment do the following to investigate the primary growth in
a seedling.
– Use a centimeter ruler, measure the height of each plant once each five days.
– Use a thread and a centimeter ruler to measure the width.– Record your measurement in a tabular form as shown below.
1. On the basis of the period of time indicated in the above table, count the
number of leaves. What do you notice?
2. Among the two given plants, predict the one with an increased volume ofprotoplasm and dry mass.
The growth rate of an organism is measured by recording the variation in length,
in width and in mass through a period of time. The aspects that can allow the
measurement of the growth of a plant are the following:
– The increase in the dry mass
– The increase in the volume of protoplasm
– The increase in the length
– The increase in the thickness
– The ability to reproduce.
Experiments show that the growth rate is faster in young plants and starts todecrease as the plant gets older.
Self-assessment
1. A sign is hammered into a tree 2 m from the tree’s base. If the tree is 10 m tall
and elongates 1m each year, how high will the sign be after 10 years? A mark
is hammered into a tree 2 m from the tree’s base. If the tree is 10 m tall and
elongates 1m each year, how high will the mark be after 10 years
2. What features would enable you to conclude that this organism has grown?
3. Would you expect a tropical tree to have distinct growth rings? Why or why
not?
4. If a complete ring of bark is removed around a tree trunk (a process calledgirdling), the tree usually dies. Explain why?
13.5. Phytohormones
Activity 13.5
The immature avocado fruits often fall down without being mature as well as
sunflower plant which grows faster when young flourish in the opposite direction
to the sun. Have you ever think and wonder about this? From your point of
view, brainstorm the cause of the situations described above. Use internet and
textbooks, to outline roles played by cytokinines, Gibberellin and ethylene planthormones.
Plant growth is influenced by both external and internal factors. External factors
include;
– light,
– moisture
– Temperature, while internal factors include phytohormones or plant growth
factors.
Internal factors are chemical substances that are produced in the plants or
artificially synthetized for regulating plant growth. Those substances are capable
of accelerating, inhibiting or modifying growth in plants. If two hormones work
together to reinforce an effect, they are synergist but if the presence of one
hormone prevents the action of another they are antagonist.
The plant hormones include five major groups:
a. Auxins
It is produced in growing regions of plant such as shoots, tips, and young leaves,
and developing fruits. The most known auxin is Indol Acetic Acid (IAA). Artificially
produced auxins are widely used to:
– Promote the cell elongation in the region behind the apex of the stem
– Promote root formation on stem and leaf cuttings
– Increase number of fruit
– Prevent dropping of fruit– Prevent sprouting of stored potatoes and onions
b. Gibberellin or gibberellic acid (GA)
Produced in all parts of plants, especially in immature seeds. Gibberellin has different
functions:
– It promotes the parthenocarpy (formation of fruits without fertilization).
– It breaks down the bud dormancy
– It promotes the seed germination.
c. Cytokinins
They are produced in developing roots, fruits and seeds, cytokinin and have the
following roles:
– Promote cell division
– Promote the growth of lateral buds
– Promote the growth of fruits
– Are used to delay aging and death (senescence).
– Work with gibberellins to break down the bud dormancy and to promote theseed germination
d. Abscissic acid (ABA)
It is produced in leaves:
– Promotes the abscission i.e. falling of some organs of the plants
– Promotes the bud and seed dormancy
– Inhibits the stem growth during the stress
– Promotes stomatal closure
– Inhibits other hormones blocking thus the growth.
e. Ethene or ethylene (C2H4)
It is produced in fruits, flowers, leaves and roots and:
– Promotes ripening of fruit
– Promotes flowering in mangoes and pineapples– Promotes abscission (detachment of leaves).
Commercial application of synthetic phytohormones
Artificial auxins are widely used. For example, 2,4-D or 2,4-dichlorophenoxyacetic
acid and MCPA 4-chloro-2-methylphenoxyacetic acid are used as weeds killer
(selective herbicides). Synthetic auxins used in right concentration, cause excessive
growth and very rapid metabolism of broad-leaved dicotyledons herbaceous plants
that are weeds in cereals. As weeds grow faster, they soon die increasing thus thecereals crop yield.
Napthaleneacetic acid (NAA) or rooting powder is another kind of auxin sprayed
on stem cuttings for stimulating the development of adventitious root. This is
very important in vegetative propagation of plants of economic value. Synthetic
gibberellin helps to increase fruit crop yield because when sprayed on non-fertilized
flowers, they promote parthenocarpy (fruit formation without fertilization). It is
mostly used in production of seedless grapes such as seedless tomatoes or citrus.
Synthetic cytokinin is sprayed on cut flowers, fruits and vegetables to keep themfresh and extend shelf-life.
Self-assessment 13.5
1. What are the plants hormones?
2. Describe the role played by each plant hormone.3. Explain why some plants develop lateral shoots when the apex is cutoff.
13.6. Plant movements and photoperiodism
13.6.1. Plant movements
Activity 13.6.1
Take the container with the bean seedling in the classroom nearby the window
and observe the changes within one week.
Like animals, plants move as response to changes in their environment (internal or
external changes). Plant movements are grouped into two categories: tropisms and
nastic movements.
1. Tropism
A tropism is a movement of parts of a plant in response to external stimulus. The
movement is always a growth movement. External stimuli cause changes in the
direction of the plant’s growth, such as bending, turning or curving. Tropic responses
are described as positive or negative depending on whether growth is towards or
away from the source of the stimulus respectively. According to the type of stimulus,tropisms are classified as follow:
Table 13. 1: Classification of tropisms
a. Phototropism
Phototropism is a directional growth depending on the direction of the light source.
Growth towards a light source is a positive phototropism, while growth away from
light is called negative phototropism. It is believed that light destroys auxin where it
strikes the stem, causing an imbalance in which the side of the stem that receives less
light has more auxin. This causes the plant to have elongated cells on the farthest
side from the light. Because more auxin is present, the cells on the darker side are
able to elongate more than the cells on the lighted side, causing the plant to bend
toward the light.
Phototropism is caused by unequal distribution of auxins in the plant stem. There is
more auxin on the side of the stem away from the light. This results in cell elongation,but only on that side. As the cells grow, the stem bends toward light.
b. Gravitropism
When a seed germinates, the young root turns downward regardless of the way in
which the seed is planted. This bending, known as positive geotropism, enables a
plant to anchor itself in the soil. The young stem, which turns upward away from the
earth, is said to be negatively geotropic. The gravity causes auxins to concentrate
on the down side than on the upper side. High concentration of auxins on the
down side of the stem promotes elongation of its cells. Therefore, the stem grows
and bends upward. But high concentration of auxins on the down side of the stem
inhibits cell elongation; therefore, the root grows and bends downward, that is whythe root grows shorter than the stem.
Use of clinostat in tropism
A clinostat is a piece of laboratory equipment with a turntable that allows a plant
placed on it to be exposed to a stimulus such as light or gravity equally on all sides.
As the clinostat is turning, all parts of the plant receive the stimulus equally and
therefore the plant will not bend but will grow straight away. In otherwise theclinostat is used to minimize the effect of the direction of a stimulus.
c. Chemotropism
Chemotropism is a growth of a plant or plants parts, navigated by chemical stimulus
from outside of the organism. An example of chemotropic movement can be seen
during the growth of the pollen tube, where growth is always towards the ovules.
Fertilization of flowers by pollen is achieved because the ovary releases chemicals
that produce a positive chemotropic response from the developing pollen tube. It is
different from chemotaxis. The major difference being that chemotropism is related
to growth, while chemotaxis is related to locomotion. For example, the movement ofantherozoids (sperm) in ferns, swim toward the chemicals produced by archegonia.
d. Thigmotropism
Thigmotropism is a movement in which an organism grows in response to touch or
contact stimuli. Usually thigmotropism occurs when plants grow around a surface,
such as a wall, pot, or trellis. Climbing plants, such as vines, develop tendrils that
coil around supporting objects. Touched cells produce auxin and transport it to
untouched cells. Some untouched cells will then elongate faster so cell growth
bends around the object. Some seedlings also inhibit triple response, caused by
pulses of ethylene which cause the stem to thicken (grow slower and stronger) andcurve to start growing horizontally.
2. Nastic movement
Nastic movements are non-directional responses to stimuli such as temperature,
humidity, light and irradiance. An example of such a response is the opening and
closing of flowers known as photonastic response and the opening and closing of
carnivorous plants known as thigmonastic response. The folding and unfolding of
some sensitive plants like Mimosa pudica when touched, is a nastic response which
protects them from insect damage or water loss during winds. They are named with
the suffix “-nasty” and have prefixes that depend on the stimuli:
– Photonasty (response to light),
– nyctinasty (movements at night or in the dark),
– chemonasty (response to chemicals or nutrients),
– hydronasty(response to water),
– thermonasty (response to temperature).
Self-assessment 13. 6
1. A bean seedling has been placed on horizontal position as shown by the diagrambelow.
a. Illustrate the expected shape of the shoot and that of the root after a week.
b. Suggest names (of what) for the expectations in the above experiment.
c. Based on the above experiment, draw a diagram illustrating the shape and
size of cells of both upward and downward side of the root.
d. Suggest a technique that can be used to minimize the effect of the stimulus
in this experiment.
2. a. What is the difference between ‘antagonistic’ and ‘synergistic’ when referring
to plant growth substances?
b. What are the two plant growth substances that act antagonistically and
which act synergistically?
3. Copy and complete the following table
Activity 13.6.2
Most of plants grow toward the sunlight direction. The few which have been
observed respond to external stimuli like touching and temperature.
1. From your experience, brainstorm what will happen to the plant when:
– it is exposed to the direction of the sunlight
– its growing part is exposed to a physical material like a stone
– a living organism touches on it (Mimosa pudica)2. Use internet and textbooks to describe why some plants flourish during long
daylight while others do not?
3. What names can be given to the above processes.
13.6.2. Photoperiodism
The light provides energy that plants need to make its own food. The duration of
daylight affects the plant growth and plant development.
Photoperiodism is a plant physiological response to relative lengths of daylight and
darkness. Photoperiodism affects many plant processes, including the formation of
storage organs, flowering and bud dormancy.
Plants monitor changes in day length with a bluish, light-sensitive pigment called
phytochrome. The alternation of darkness and light triggers the phytochrome to
change from one chemical form to another. By detecting the type and the amount
of phytochrome present, plants determine the length of darkness and light eachday.
One of the effects of photoperiodism is that plants produce fruits at different times
and are classified into three categories:
– Short-day plants (SDP),
– Long-day plant (LDP)– Day–neutral plants (DNP).
– Short-day plants (SDP): they only flower when the days are short and the night
are longer than a certain length. Examples strawberry, blueberry, goldenrods,
cocklebur and soybeans, tobacco are short day plants for flowering.
– Long-day plant (LDP): they produce flower when the period of daylight
exceeds a critical minimum length. Radishes, asters, apple trees, squash trees,
and beets.
– Day–neutral plants (DNP) are not dependent on day length for flowering. They
produce flower regardless of the length of the daylight. Day neutral plants for
flowering include tomatoes, roses, corn, cucumber, carrot, cotton and beans.They can produce fruit throughout the entire growing season.
Self –assessment 13.6.2
1. What role does phytochrome play in photoperiodism?
2. What is the difference between a short-day plant and a long-day plant?3. What could happen if a short-day plant is grown in the long days of summer?
13.7. Metamorphosis and growth patterns in insects and
amphibians
Activity 13.7
From a pond or swamp, collect frog eggs together with water. Keep some eggs in
warm conditions at room temperature between 2 to 30 days.
1. Visit them regularly and note the observation.
2. Use the diagram below and relate your observation from question (1) tothe one given in the diagram.
1. Metamorphosis and growth patterns in animals
Metamorphosis is a process consisting of changes in body form of a young organism
before it reaches its adult size and becomes sexually mature, for example, the change
from tadpole to frog or from caterpillar to butterfly.
a. Metamorphosis and growth patterns in insects
All insects develop and grow by metamorphosis. Some insects show incomplete
metamorphosis. In incomplete metamorphosis, an immature nymph is hatched
from the egg that looks like the adult, but it is smaller, and its wings and reproductive
organs are undeveloped. It molts several times with each molt, the wings become
larger and more fully formed. The final molt transforms the nymph into an adult
that can reproduce and fly. Insects with incomplete metamorphosis are known
as heterometaboles e.g. weevil, cockroach (Periplaneta americana), Grasshopper;mayflies; dragonflies and termites.
In complete metamorphosis eggs hatch into larvae which are morphologically,
physiologically and behaviorally different from adult (wormlike larva) or caterpillar.
The caterpillar molts several times, when it reaches its full size, it prepares the pupa,
or chrysalis, a hard, sometimes thorny and oval structure. Inside the pupa, the larval
tissues break down and group of cells called imaginal disks develop into wings
and other tissues of the adult: imago stage, the pupa becomes sexually mature.Examples: Butterflies, moths, mosquitoes, beetles, bees, housefly.
Importance of metamorphosis
In life cycle based on complete metamorphosis, the larval and adult stages often
fulfill different functions, live in different habitat and eat different foods. Example:
mosquitoes.
Metamorphosis also enhances insect survival by helping insects survive harsh
period. Example: butterflies (caterpillars feed on leaves, but adult butterflies feed onnectar from flowers).
b. Metamorphosis and growth patterns in amphibians
Many amphibian species like the frog breed in water and their eggs are fertilized
externally. The fertilized eggs hatch into swimming, tailed larvae called tadpoles.
Tadpoles, which usually live in water, look somewhat like small fish. A tadpole has an
oval body, gills for breathing, and a long, muscular tail with fins along the upper and
lower edges for swimming.
Then the tadpole grows legs—the hind legs appear first—and resorbs its tail. It
loses its gills and grows lungs, and the structure of the heart, digestive system, and
skeleton changes. The horny beak and other mouthparts adapted for eating algae
disappear and are replaced by the long, sticky, projectile tongue that helps adult
frogs catch insects. Frogs reach reproductive age anywhere from several months toseveral years after metamorphosing.
Self-assessment 13.7
1. What is metamorphosis?
2. Describe the changes that occur during metamorphosis in frog.
3. Discus reasons why complete metamorphosis may have greater adaptive
value for an insect than incomplete metamorphosis.4. Compare metamorphosis of a butterfly and that of a grasshopper.
End of unit assessment 13
1. What do you understand by:a. Dormancy2. a. What factors can allow to measure the growth of a plant?
b. Gravitropism
c. Chemonasty
d. Phytochrome
e. Short-day plants
b. State any four external factors that can affect the growth of a plant.3. a. State any three characteristics of the phytohormones.c. What is meant by parthenocarpy? Give one example of a plant that shows
b. What is phytohormone (s) responsible for:
i. The falling of some plant organs during the stress
ii. The fruit ripening.
iii. Development of the lateral buds
iv. Stem growth and parthenocarpy
this phenomenon
4. A seedling has been grown in an opaque box receiving the light from a single
direction as shown by the diagram below.
a. What will happen on the coleoptile (seedling) as it grows?b. Suggest a name to the phenomenon investigated in this experiment.