Nitrifying bacteria
dead and decay
•
Ntrosomonas Nitrification
Nitrates Arnonium
Compound Nitrogen in air
Nitrogen fixing bacteria Azotobacter absorb by
plants Nitrogen fixing by
Electrical discharge
Fed on by
Animals
Excretion and feaces Nitrate
co p%
O
Nutrition in Plants 135
Figure 5.2 Nitrogen Cycle
3.6 Differences Between Respiration And Photosynthesis. (Table 5.4)
Respiration Photosynthesis
1 It is a catabolic process associated with the 11 is an anabolic process associated with synthesis of break down of organic matter organic matter
2.
CT,Ii i206 + 60, —> 6CO3 + 6H 20 + energy Energy in the form of ATP is released
6CO2 + 6H20—> C,I1, 206 r 60,
Energy in form of heat is absorbed and stored as chemical energy
3. Oxygen is absorbed and used up Carbon (IV) oxide is absorbed and used up 4. Carbon (IV) oxide is liberated Oxygen is liberated
5. Water is liberated Water is used up
6. It takes place in mitochondria It takes place in the chloroplasts only 7. It takes place in all living organisms It is restricted to green plants only
8. It takes place both day and night It takes place only in the day time
3.7 Similarities Between Respiration and Photosynthesis
1. Both respiration and photosynthesis convert energy from one form to another.
2. Both require mechanism for exchange of gases (oxygen and carbon (IV) oxide) 3. Both require special organelles. Mitochondria in case of respiration and chlorop last in
case of photosynthesis
4. Both involve cycles of reaction, kreb cycle in respiration and calvin cycle in photosynthesis 5. Electron carriers ( NAD) are involved in both processes.
6. The light reactions of photosynthesis is similar to respiration in that both expend energy in the form of ATP
4.0 Conclusion
Photosynthesis plays a vital role to the survival of man and animals. Man and his animals depend on plants for food which is the basic requirement for survival on earth. Therefore, the studyof plants and the process of photosynthesis should be intensified.
Sum
mary5.0
111In this unit, we have learnt that:
I. Photosynthesis is the process whereby green plants manufacture their own food in the presence of carbondioxide, sunlight and water.
u. There are two stages in photosynthesis — light reaction and dark reaction.
iii. Light reaction occurs during the day or in the presence of sunlight, while dark reaction occur at night or in the absence of light.
iv. For photosynthesis to take place, certain material or conditions like carbondioxide, water, chlorophyll, sunlight, mineral salts, suitable temperature and enzymes must be available.
Nutrition in Plants 137
v. Photosynthesis is very important both to plants and animals for the following reasons — prodution of food, purification of the atmosphere, release of oxygen to the environment, it serves as building block for other substances.
vi. Plants require mineral nutrient or element for good growth and healthy development.
vii. Nutrient cycles refer to the circulation of certain nutrients like nitrogen, carbon, sulphur and water in nature.
viii. Nitrogen cycle involves the complex process by which nitrogen is naturally added and removed from the soil.
List the functions and deficiency symptoms of the following elements (a) Nitrogen } 4 marks
(b) Phosphorus } 4 marks (c) Potassium 4 marks (d) Calcium } 4 marks
Essential Biology
Idodo-Umeh (1996). College Biology
Page
1.0 Introduction 139
2.0 Objectives 139
3.0 Plant Hormones 139
3.1 Auxins 139
3.2 Functions or Effects of Auxin on Plants 139
3.3 Modem Application of Auxin in Agriculture 140
3.4 Gibberellins 141
3.4.1 Functions or Effects of Gibberellins 141
3.5 Cytokinins (Kinins) 141
3.5.1 Functions or Effects of Cytokinins 141
3.6 Abscisic Acid 142
3.6.1 Functions or Effects Abscisic Acid 142
3.7 Ethene (Ethylene) Gas 142
3.7.1 Functions or Effects of Ethene 142
3.8 Floregens 142
3.8.1 Functions of Floregens 142
4.0 Conclusion 142
5.0 Summary 143
6.0 Tutor MarkedAssignment 143
7.0 Further Reading and other Resources 143
138
Co-ordination and Control in Plants 139
Co-ordination in plants is simpler than in animals. It is done by a chemical known as
plant hormones.They are similar to animal hormones in that they are only needed in small amount to bring about their effects.
Therefore produced in one part of the body and transported to another part where they exert their effects (positively or negatively). Animal hormones are produced in specific glands and bring about very specific responses in specific target organs. In plants, hormones are not produced in tissues specialised only for their
• production, their effects are also more general, varying with concentration and types of target organ. Chemically too, plant hormones are not related to animal hormones, although they are organic compounds.
Plant hormones almost always stimulates or inhibit growth in the target tissues in responses to external stimuli such as light, temperature, day length, gravity and touch. As a result, they are also known as plant growth substances, though they affect other activities such as fruit formation, root development and leaf fall.
Combination of plant hormones bring about responses that are different from what each hormone would produce alone. The responses of plant hormones are usually much slower than those of animals hormones.
This is because responses in plants are mainly brought about by growth.
In this unit, we shall discuss the various type of plant hormones and their functions.
By the end of this unit, you should be able to:
i. explain what plant hormones are.
ii. explain the roles/functions of the hormones.
The growth of plants to a great extent is regulated by hormones. These chemical substances (hormones) influence the plants internally while factors such as light, temperature, water and gravity influence the plant externally. Hormones are needed in small quantities. They are manufactured in some areas (apical meristems of shoots and roots, young growing leaves, developing seeds or fruits) and diffuse to other parts to produce some special effects.
The major or well known plant hormones are auxins, gibberelins, cytokinins, floregens, abscissic acid, ethene (ethylene), traumatin, dormin, formin etc.
3.1 Auxins
The most important naturally occuring auxin is indole acetic acid (IAA). It is produced at