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Q.1 Why is there a need for coordination?
Ans. COORDINATION
All organisms respond to environmental stimuli.
The stimuli may be internal or external, at molecular, sub-cellular, cellular or organism level to which the organisms respondThe activities of different body parts in response to these stimuli must be coordinated. The coordination makes possible the integration of functions essential to organismic behaviour Coordination is must for any organismi to survive
COORDINATION IN UNICELLULAR ORGANISMS:
In the unicellular organisms a coordination exists between Various cellular processes, and they respond to changes in their environments such as temperature, light intensity, concentration of various chemicals and even to electric current
COORDINATION IN MULTI-CELLULAR ORGANISMS:
In multi-cellular organisms, although there is a division of labour among cells yet every cell can respond to changes in its immediate vicinity
LIMITED HUMAN RESPONSE
It must be noted that even the most highly developed organisms cg, humans are unable to detect and respond to many changes or stimuli in our environment.
We are unaware and not able to respond to presence of bactena on the surface of our body because our sensory cells do not detect their presence - but some of our internal body cells do respond and produce chemicals or phagocytose them to destroy them
We are unable to see different radiations except for visible spectrum. of light, but our body cells do respond to some of them
Q.2 Describe coordination in plants. How does it differ from animals? Explain the role of hormones in plant coordination
And COORDINATION IN PLANTS:
Plants are complex organisms that grow, change, react to external/internal stimuli, and show response.
BEHAVIOUR:
We can say that plants have - but their behaviour is fundamentally different from that of animals. The difference is because the plants are sessile, while animals are motile. So plants are passive than animals.
Much of the behaviour of plants depends on variations: In growth rates or changes in the turgidity of cells, when they show movement.
Plants show slow speed of response than animals.
CONTROL SYSTEMS:
Plants and animals use different ways to respond and have evolved control systems accordingly In plants the control is solely by the plant hormones while animals much more variety of hormones and the nervous control. That is why animals respond with greater speed to specific stimuli.
HORMONAL CONTROL IN PLANTS:
Hormonal control in plants is relatively a slow process. Even after hormone is transported, there is a delay between the release, its Rival at the target cells, and its action in the body. So, response to stimulus that induced the secretion of hormone is usually not immediate
All the activities of plants from growth to fruit production and ripening are under the control of plant hormones.
Plants therefore, respond to the stimuli by
Regulating their growth and development in appropriate ways.
Controlling their body functions through plant hormones or growth hormones.
Q.3 What is meant by plant movements?
Ans. PLANT MOVEMENTS
Many plants do not show locomotion (movement of the whole organism). However, movements of plant organs are possible and are modified according to the nature and intensity of external stimuli.
There are two kinds of plant movements:
1 Turgor movements and
2 Growth movements.
Q.4 What are the responses to environmental stresses in plants?
Ans. RESPONSES TO ENVIRONMENTAL STRESSES IN PLANTS
All plants need water, light, carbon dioxide and a variety of nutrients from their environment for optimal development and growth. The absence or short supply of any of these factors in environment may exert environmental stresses on plants comprising their health and survival
ETIOLATED PLANTS:
If plants are grown without light, they become extremely long and fail to form chlorophyll. They are sard to be etiolated
CHLOROSIS:
Many plans take on a yellowish hue when they fail to form sufficient chlorophyll. This condition known as chlorosis usually arises from short supplies of mineral nutrients in the soil.
(1) CIRCADIAN OR DIURNAL RHYTHMS:
Biorhythms may occur showing periodicity of about 24-hours. These are called circadian (Latin circa =about, dies day) which means about one day, so they are also called diurnal rhythms.
(ii) CIRCANNUAL:
If the biorhythms are less than or about 365 days, these rhythms in activity are called circannual
BIOLOGICAL CLOCK:
The organisms come across environmental changes that are cyclical in nature such as days, tides, and seasons etc. Many organisms maintain internal rhythm or clock; to predict the onset of the periodic changes and to koep them prepared for these changes. This internal rhythm or clock is called biological clock.
CAUSES OF BIORHYTHMS:
Biorhythms may be the result of the following
There may be direct response to various changes in the external (exogenous) stimuli There may be an internal (endogenous) rhythm that progresses the organism's behavior in synchronicity With the exogenous temporal (life) period, particularly a 24-hour or a 365-day period The synchronization mechanism may be a combination of
RHYTHMS IN GENES:
The rhythms are in one's genes but the environment influences the rhythms to some extent.
TIMING OF BEHAVIOUR:
Timing of behavior results from a combination of effects of rhythmical internal processes and timed events of the environment.
WORK OF ERVIN BUNNING:
Basic period of the clock is innate. Ervin Bunning of the University of Tubingen, Germany, has shown that exposure of Drosophila to constant condition for 15 consecutive generations fail to eliminate the essentially 24 hour rhythm of this insect
Q.7 What are plant hormones? Explain the functions of different types of hormones and their commercial importance.
Ans
PLANT HORMONES (PHYTOHORMONES)
"Some of the special substances produced by the plants which influence the growth and plant responses to various stimuli are called plant hormones."
These include
(a) Auxins (b) Gibberellins (c) Cytokinins (d) Abscisic acid (e) Ethene
Q.9 Describe the functions and commercial applications of Gibberellins.
Ans
FUNCTIONS GIBBERELLINS:
These are produced commercially from fungal cultures Cell enlargement: Promote cell enlargement in presence of auxins.
Cell division: Also promote cell division in apical meristem and cambium.
Bolting: Promote 'bolting of some rosette plants
Bud initiation: Promote bud initiation in shoots of chrysanthemum callus.
Leaf and fruit growth: Promotes leaf growth and fruit growth. .
Parthenocarpy: May induce parthenocarpy
Apical dominance: In apical dominance, enhance action of auxins.
Dormancy:" Break bud and sced dormancy
Substitute for red light: Sometimes may substitute for red light. Therefore, promote flowering in long Available online on day plants, while inhibit in short-day plants
Leaf senescence: Causes delay in leaf senescence in a few species
COMMERCIAL APPLICATIONS
1. Fruit setting: GA promote fruit setting e.g. in tangerines und pears and are used for growing seedless grapes (parthenocarpy) and also increase the berry size.
2 Used in the brewing industry: GA3 is used in the brewing industry to stimulate c-amylase production in barley and this promotes malting
3. Delay fruit ripening: Il is used to delay ripening of fruits.
4. To improve storage life: It is used to improve storage life of bananas and grape fruits.
Q.11. Describe the functions and commercial applications of Abscisic acid.
Ans
FUNCTIONS OF ABSCISIC ACID:
Stem root growth: Inhibits stem and root growth notably during physiological stress, e.g drought, water logging
Dormancy: Promotes bud and seed Dormancy
Flowering: Promotes flowering in short day plants. and inhibits in long day plants (antagonistic to gibberellins).
Leaf senescence: Sometimes promotes leaf senescence
Abscission: Promotes abscission
Closing of stomata: Promotes closing of stomata under conditions of water stress (wilting).
7. COMMERCIAL APPLICATIONS:
Abscisic acid can be sprayed on tree crops to regulate fruit drop at the end of the season. This removes the need for picking over a large time-span
Q.12. Describe the functions and commercial applications of Ethene.
Ans. FUNCTIONS OF ETHENE:
Stem growth: It Inhibits stem growth, notably during physiological stress Root growth: Inhibits root growth
Dormancy: Breaks dormancy of bud
Flowering: Promotes flowering in pineapple
Fruit ripening: Promotes fruit ripening
COMMERCIAL APPLICATIONS:
Ethene induces flowering in pineapple.
Stimulates ripening Of tomatoes and citrus fruit
The commercial compound ethephon breaks down to release ethylene in plants and is applied to rubber plant to stimulate the flow of latex.
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