INTERNATIONAL TURKISH HOPE SCHOOL

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1 INTERNATIONAL TURKISH HOPE SCHOOL ACADEMIC YEAR CHITTAGONG SENIOR SECTION BIOLOGY PLANT REPRODUCTION CLASS 09 and 10 Name :... Date :... EDEXCEL Students will be assessed on their ability to: 3.1 understand the differences between sexual and asexual reproduction 3.2 understand that fertilisation involves the fusion of a male and female gamete to produce a zygote that undergoes cell division and develops into an embryo Flowering plants 3.3 describe the structures of an insect-pollinated and a wind-pollinated flower and explain how each is adapted for pollination 3.4 understand that the growth of the pollen tube followed by fertilisation leads to seed and fruit formation 3.5 understand the conditions needed for seed germination 3.6 understand how germinating seeds utilise food reserves until the seedling can carry out photosynthesis 3.7 understand that plants can reproduce asexually by natural methods (illustrated by runners) and by artificial methods (illustrated by cuttings) CAMBRIDGE Candidates should be able to: (a) define mitosis as cell division giving rise to genetically identical cells in which the chromosome number is maintained and state the role of mitosis in growth, repair of damaged tissues, replacement of worn out cells and asexual reproduction; (b) define asexual reproduction as the process resulting in the production of genetically identical offspring from one parent and describe one named, commercially important application of asexual reproduction in plants; (c) define meiosis as a reduction division in which the chromosome number is halved from diploid to haploid; (d) state that gametes are the result of meiosis (reduction division); (e) define sexual reproduction as the process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically dissimilar offspring; (f) identify and draw, using a hand lens if necessary, the sepals, petals, stamens and carpels of one, locally available, named, insect-pollinated, dicotyledonous flower, and examine the pollen grains under a light microscope; (g) state the functions of the sepals, petals, anthers and carpels; (h) use a hands lens to identify and describe the anthers and stigmas of one, locally available, named, wind-pollinated flower, and examine the pollen grains under a light microscope; 1 Page

2 (i) outline the process of pollination and distinguish between self-pollination and cross-pollination; (j) compare, using fresh specimens, an insect-pollinated and a wind-pollinated flower; (k) describe the growth of the pollen tube and its entry into the ovule followed by fertilisation (production of endosperm and details of development are not required); (l) investigate and describe the structure of a non-endospermic seed in terms of the embryo (radicle, plumule and cotyledons) and testa, protected by the pericarp (fruit wall); (m) state that seed and fruit dispersal by wind and by animals provides a means of colonising new areas; (n) describe the external features of one, locally available, named example of a winddispersed fruit or seed and of one named example of an animal-dispersed fruit or seed; (o) investigate and state the environmental conditions that affect germination of seeds: suitable temperature, water and oxygen; (p) describe the uses of enzymes in the germination of seeds; Summary v Importance of Reproduction. v Basic types of reproduction and differences between them. v Mitosis vs. Meiosis. v Parts of a flower and their functions. v Pollination. v Self-Pollination vs. Cross-Pollination. v Wind pollinated flower vs. Insect pollinated flower. v Fertilization and Post-Fertilization changes in flowering plants. v Germination. v Factors affecting germination. v Reproducing plants artificially. v Dispersal. 2 Page

3 REPRODUCTION Asexual reproduction: Asexual reproduction is the process resulting in the production of genetically identical offspring from one parent. Sexual reproduction: Sexual reproduction is the process involving the fusion of nuclei to form a zygote and the production of genetically dissimilar offspring. Sexual reproduction involves the fusion of two gametes. During fertilization, a sperm fuses with an egg to form a zygote. Since the sperm and the egg each have a haploid number of 23, the zygote formed will have a diploid number of 46 chromosomes. The zygote then divides by mitosis resulting in all the cells in the child having a diploid number of chromosomes, except in the ovum and sperm cell. Difference between sexual and asexual reproduction: ASEXUAL REPRODUCTION SEXUAL REPRODUCTION Cell division, binary fission, vegetative reproduction, artificial propagation. One parent needed. No sex cells involved. No zygote is formed. Undergoes mitosis. Offspring genetically identical to parent. Rate rapid under favourable environment. Population increases rapidly. Plants and simple organisms do asexual reproduction. Sexual reproduction requires reproductive organs in plants and animals. Two parents needed. Male and female sex cells (haploid gametes) needed or involved. Fertilisation forms a diploid zygote. Undergoes meiosis. Offspring genetically different from both parents. Takes a long time. Population increases slowly. Plants and more complex organisms do sexual reproduction. Meiosis (n) (23) Mitosis (2n) (2x23=46) Cells divide two times Cells divide only once Four daughter cells are formed Two daughter cells are formed Variation occurs No variation Haploid cells are formed (n) Diploid cells are formed Chromosome number us halved (23) Chromosome number remains same (46) Gametes are formed. Body cells/ Somatic cells are formed Occurs only in Gonads: Occurs throughtout body except Gonads. Testes and Ovary Required for keeping the chromosome Required for preserving the characteristics. number constant. 3 Page

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8 Comparison of characteristics of flowers pollinated by insect and wind 8 Page

9 Self-Pollination vs. Cross-Pollination: Variation occurs No Variation occurs Prevent self-pollination: Different level of stigma and anther. Male and female parts mature at different times. Unisexual flower. Pollen tubes cannot germinate in the same plant. 9 Page

10 The structure and functions of different parts of a flower are described below: PEDICEL Structure: Flowers grow on a specialized reproductive shoot called the flower stalk or pedicel. Some flowers have no pedicel and are called sessile flowers. Function: Attaches the flower to the plant body. RECEPTACLE Structure: The receptacle is the enlarged end of the flower stalk to which the parts of the flower are attached. Function: 1. Floral parts are arranged on it. 2. May become fleshy after fertilization e.g apple. SEPALS Structure: Sepals are modified leaves which enclose and protect the other parts of the flower in the bud stage. All the sepals together make up the calyx. Sepals are usually green and look like small leaves. Function: 1. Protects the flower from sun and rain in bud condition. 2. Can do photosynthesis if green. 3. Serves to attract insects for pollination if colourful. PETALS Structure: Petals are modified leaves forming the conspicuous part of a flower and are usually brightly-coloured in insect pollinated flowers. In the majority of flowers, the reproductive organs are surrounded by a whorl of petals. The petals are known collectively as the corolla of the flower. The calyx and the corolla together form the perianth of the flower. Functions: 1. Attracts insects for pollination. 2. Gives protection from heat and rain. 3. Acts as support for the stamen. 4. Helps to direct insects towards the nectary. 10 Page

11 STAMEN OR ANDROECIUM Structure: Stamens are collectively known as the androecium of the flower. These are the male reproductive organs and are necessary for seed production. Each stamen consists of a filament bearing an anther. The anther is usually made up of two lobes, each containing two pollen sacs. In the pollen sacs are the pollen grains. Pollen grains contain the mail gametes. They are formed by meiosis and contain the haploid number of chromosomes. Each pollen grain gives rise to two haploid male gametes which are the reproductive nuclei of the flower. When the anther is mature, its two lobes split, setting the pollen grains free. Functions: 1. Supports the anthers. 2. Produces pollen grains. 3. Releases pollen grains. GYNOECIUM(PISTIL) OR CARPELS Structure: Carpels are situated at the centre of the receptacle, and are known collectively as the gynoecium or pistil. Carpels are the female reproductive organs. Each carpel consists of an expanded hollow base called the ovary, above which is a narrow region called the style. The stigma is a swollen structure at the end of the style which receives the pollen grains. The ovary contains one or more ovules. Functions: 1. Contains ovules which develop into seeds. 2. Collects pollen grains. 3. Stimulates germination of pollen grains. 4. Develop into fruits. 11 Page

12 Pollination Pollination is the transfer of pollen grains from anthers to stigmas for fusion of the male and female gametes and eventually leads to fertilization. If pollen grains are transferred to the stigma of the same flower or a different flower in the same plant, the process is called self-pollination. If pollen grains are transferred to a flower in another plant of the same kind, it is called cross-pollination. Pollination is usually affected by insects or wind. Fertilisation does not result when pollination occurs between different species. A bisexual flower produces both the stamens and the pistil. A unisexual flower has either the stamens(a male flower) or the pistil(a female flower). A plant which produces both male and female unisexual flowers is said to be monoecious e.g maize. However, if the male and female are borne on separate plants, the plant is called diocious plant e.g papaya. 12 Page

13 Fertilization When the pollen grain arrives on the stigma of the correct species of plant, the sugary solution on the stigma forms a medium in which the pollen grain will germinate. Germination of the pollen grain involves the growth of a pollen tube, which releases enzymes at its tip in order to digest the cells of the style beneath. In this way the cells of the style are removed to allow the pollen tube to grow down the style, towards the ovary. On arrival at the ovary, the end of the pollen tube enters an ovule through a small hole called the micropyle. Inside the ovule is the embryo sac which contains the female gamete within which is the female nucleus. The end of the pollen tube then burst to release the male gamete, which has traveled down the pollen tube from the pollen grain. Fertilisation occurs as the nuclei of the male and female gametes fuse. When the pollen tube is formed, the cytoplasm and the two nuclei (vegetative and generative nuclei) pass into the pollen tube. The generative nucleus divides to form two male gametes. The vegetative nucleus soon disintegrates. Within the ovule, the tip of the pollen tube absorbs sap and bursts, releasing the two male gametes. (i) One male gamete fuses with the ovum to form the zygote: this is fertilization. (ii) The other male gamete fuses with the definitive nucleus(secondary nucleus) to form the endosperm nucleus. The zygote develops into the embryo of the seed with cotyledons, plumule and radicle. The endosperm nucleus divides and gives rise to the endosperm. The ovary walls ripens to form the fruit wall(or pericarp).the ovules becomes the seeds. The funicle or seed stalk is attached to the part of the fruit called the placenta. After fertilization, the stamens, petals and eventually the sepals shrivel up and drop off. At the same time, the ovule develops into a seed, enclosed within the ovary walls which forms a fruit. 13 Page

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15 Table below shows the changes that takes place in a flower after fertilization: FLOWER PARTS Pedicel Receptacle Ovary Ovary wall Ovule Ovule stalk Style and stigma Endosperm nucleus Insteguments FLOWER-PARTS Zygote Petals Sepals Fruit-stalk. POST-FERTILISATION CHANGES Converts into flesh. Converts into fruit. Converts into fruit wall or pericarp which maybe dry or fleshy. Converts into seed. Seed stalk (funicle). Style converts into fruit wall and stigma remains at the tip of the fruit. Sometimes, they whither off but in certain cases, may persist and be modified to help in fruit dispersal. Endosperm (in some cases, this is completely absorbed by the embryo during seed formation, producing a non-endospermic seed). Testa and tegmen. POST-FERTILISATION CHANGES Embryo consisting of the developing shoot (plumule), the developing root (radicle) and cotyledons. Wither and fall off. May persist, and in some cases, may enlarge and be modified to help fruit dispersal. 15 Page

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17 Dispersal The possible vectors of dispersal are: Wind Insect Water Self 1. Dispersal by wind: Fruits and seeds that depend on dispersal by the wind may have the following features: (i) Small and light so that they can float in the air and be readily blown about by the wind e.g orchid seeds. (ii) Large, flattened, wing-like structures or a parachute of fine hairs. This way the surface area is enlarged ad this increases air resistance or buoyancy in air. 2. Dispersal by animals: The fruits and seeds which can form a source of food for animals are likely to be dispersed by them. Succulent fruits are scented and their skins are often brightly-coloured to attract animals. The process of dispersal by animals is described below: The whole fruit maybe eaten by animals such as birds, bats, cats, dogs etc. The seeds maybe small and hard. They are indigestible and are removed in the faeces, thus dispersed away from the parent plant. Sometimes the seeds are spat out by the animals. Very often, the seeds are still capable of germination. Sometimes, the fruits are carried away by the animals which eat only part of them, leaving the seeds behind to germinate. Dry, indehiscent fruits can also be dispersed by animals. Fruits adapted to this method of dispersal process hook-like structures by which they can adhere onto the fur or skin of animals passing by. These fruits may later be brushed off the animals bodies or they may fall off when the hooks shrivel. The fruits may also adhere to the clothing of man and be dispersed in a similar manner. 17 Page

18 3. Dispersal by water: Water currents in the ocean, rivers and streams are important agents of dispersal. Fruits and seeds dispersed by water are adapted for floating and they can drift for considerable distances. Aquatic plants and many plants living on river banks or the seashore depend on water dispersal. For example, the coconut fruit has a waterproof skin and a fibrous husk containing numerous air spaces which lighten the fruit. The seed within it contains a store of food (the meat in the coconut) and there is sufficient water in the seed to enable its germination even on sandy shores. 4. Self dispersal: Some fruits, on drying up, burst open with great force to throw out the seeds. For example, when ripe balsam fruits dry up, they burst open and eject the seeds away from the parent plant. Importance of dispersal: Dispersal is necessary in order to: 1. Avoid overcrowding and competition for food and light with the parent plants. 2. Enable plants to colonise new and favourable habitats. 3. Reduce the spread of diseases. 18 Page

19 The proper conditions needed for germination of a seed: Air Water Warmth 19 Page

20 Chemical changes in a seed during germination A seed contains hardly any water. When it was formed on the plant, the water in it was drawn out, so that it became dehydrated. Without water, almost no metabolic reaction can go on inside it. The seed is inactive or dormant. This is very useful because it means that the seed can survive harsh conditions, such as cold or drought, which would kill a growing plant. When a seed germinates, it first takes up water through the micropyle. As the water goes into the cotyledons, they swell. Eventually they burst the testa. Once there is sufficient water, the enzymes in the cotyledons become active. Amylase begins to break down the stored starch molecules to maltose. Proteases break down the protein molecules to amino acids. Maltose and amino acids are soluble, so they dissolve in the water. They diffuse to the embryo plant, which uses these foods for growth. When a seed first begins to germinate, it increases in weight. This is because it absorbs water from the soil. As soon as it begins to grow, it starts to use its food stores. The stored protein is broken down to amino acids, which are used to make new protein molecules for cell membranes and cytoplasm. The stored starch is broken down to maltose and then to glucose. Some of the glucose will be made into cellulose, to make cell walls for the new cells. All this requires energy. The seed, like all living organisms, gets its energy by breaking down glucose, in respiration. Quite a lot of the glucose from the stored starch will be used up in respiration, so the seed loses weight. After a few days, the plumule of the seed grows above the surface of the ground. The first leaves open up and begin to photosynthesise. The plant can now make its own food faster than it is using it up. It begins to increase in weight. Growth curve of an annual plant Explanation on next page! 20 Page

21 a: The seed has a dry mass (mass without water) and is dormant. (inactive) b: The seed after sowing, absorbs water and increases in size (wet mass- mass with water) c: the enzymes become active and the mass decreases, as digestion occurs in the cotyledon. d: The leaves grow and starts photosynthesis, increasing the size of the plant. It grows into a tree and produces fruit. e: after the production of food, the plant dies. v 21 Page

22 Germination: Germination is the growth of a plant from a dormant seed, under favourable conditions like temperature, oxygen and availability of water. Steps involved in germination: 1. Seeds absorb water and swell in size. 2. The seed coat tears. 3. The enzymes get activated and start digesting the stored food in the cotyledon. 4. Starch is broken down into glucose, by carbohydrase enzymes which is used for respiration to release energy. 5. Protein is broken down by protease enzymes into amino acids, which is used for making new cells.. 6. Fats are broken down by lipase enzymes into fatty acids and glycerol, which are used for making cuticles. 7. The digested foods are transported to the radicle through the phloem vessel. 8. The radicle grows into the soil and develops into roots, anchoring and the seed and absorbing the water. 9. The radicle pushes the cotyledon out of the soil. 10. The cotyledon gets broken, until the Plumule grows and develops leaves. 11. The leaves photosynthesize and start making food, which is used for plant growth. 12. Water is transported to the leaves from the root by the xylem vessel. 22 Page

23 GERMINATION OF SEEDS A. Structure of a seed 1. A seed consists of three parts, i.e. testa, cotyledon and embryo. 2. The testa is the seed skin that protects the seed. 3. The hilum (seed scar) and the micropyle can be found on the testa. Structure of a seed 4. The cotyledon is the part of the seed that stores food. Cotyledon contains starch. 5. The cotyledon supplies food to the embryo during germination. 6. Some seeds contain only one cotyledon and are called monocotyledons, for example maize seed. 7. Some seeds contain two cotyledons and are called dicotyledons, for example green pea seed. 8. The embryo is situated between two cotyledons in a pea seed. 9. The embryo consists of the plumule and the radicle. 10. The plumule and the radicle are parts of an embryo that will grow to become the shoot and the root respectively. 23 Page

24 Functions of the parts of a seed B. Germination of seed 1. Germination is the process in which the embryo in a seed grows to become a seedling. 2. During germination, water and oxygen (air) are absorbed into the seed through the micropyle. 3. Water is used to soften the testa and the seed will expand. 4. Oxygen is used to oxidise food turning it into energy during cell respiration. This energy is used for seed germination. 5. The testa will crack and the radicle grows out of the seed. 6. The radicle grows downwards and forms roots that absorb water. 7. The plumule gros upwards and becomes the shoot. 8. The cotyledon supplies food to the seed during germination. 9. When food is used up, the cotyledon will shrivel and fall off. 10. Green leaves on the seedling are able to carry out photosynthesis to produce food. 11. There are two types of seed germination, i.e. epigeal germination and hypogeal germination. Epigeal germination 12. During epigeal germination, the cotyledons are carried above the ground as the shoot grows. 13. Plants which experience epigeal germination include groundnut and sunflower. Hypogeal germination 24 Page

25 14. During hypogeal germiantion, the cotyledon remains in the ground. 15. Plants that experience hypogeal germination include maize, coconut, rubber and rambutan. C. Condition for germination 1. A seed will germinate if condition are suitable. 2. Conditions required for germination are the presence of: (a) water (b) air (c) suitable temperature (heat) (a) that are kept constant: Size of test tube, type of seed, quantity of cotton (b) that are manipulated: Conditions for germination (c ) that respond: Germination of seed Arrangement of apparatus to determine the conditions for seed germination 1. Four test tubes labelled A, B, C and D with respective contents as shown in figure above are prepared. 25 Page

26 2. Test tube A, B and C are kept in the laboratory while test tube D is placed in a refrigerator. 3. The apparatus with the respective contents are left for two days. 4. The observations obtained are recorded in a table. 1. Test tube A acts as a control to compare the results of the experiment. 2. Boiled water that has been cooled is used because it does not contain air. 3. The layer of oil in the test tube C prevents air from dissolving in the cooled boiled water. 4. Germination of seeds requires water, air and heat. 1. The hypothesis made can be accepted. 2. Germination of seeds requires water, air and heat. 26 Page

27 VEGETATIVE REPRODUCTION IN FLOWERING PLANTS 1. Some plants carry out vegetative reproduction. 2. Flowering plants can be classified according to the apart of the plant involved in vegetative reproduction. 3. Vegetative reproduction contributes significantly to agriculture. A. Vegetative Reproduction 1. Vegetative reproduction is a type of asexual reproduction 2. Vegetative reproduction involves only one parent. 3. Vegetative reproduction produces many new plants that have the same characteristics as the parent plant. 4. The part of the plant that carries out vegetative reproduction is known as the vegetative part. 5. Vegetative parts include the leaves, stems, roots and special structures such as rhizomes, tubers, runners and bulbs. 6. Young tissues in a plant, such as the shoots and roots, are used as vegetative parts in tissue culture techniques. B. Part of Plants Involved in Vegetative Reproduction 1. Leaves A Bryophyllum leaf (a) Plants that reproduce through leaves are Bryophyllum and begonia. (b) Buds form at the edges of the leaf. (c) Young plants have adventitious roots. (d) The young plant separates from the parent plant and becomes a new plant. 27 Page

28 2. Stems The stems of plants that carry out vegetative reproduction include underground stems, horizontal stems (runners) and modified stems (bulbs). (a) Underground stems (i) Underground stem are stems that swell because it has a lot of food. (ii) Buds and roots grow on these stored parts, forming new plants when separated from the parent plant. (iii) Potatoes and ginger reproduce through underground stems. 28 Page

29 (b) Horizontal stems (i) Plants that reproduce through runners are strawberries and grass. (ii) Long runners spread on the surface of the soil. Roots grow at the nodules. (iii) The nodules form buds and produce new plants with roots. The new plants with roots. The new plants separate from the parent plant when the runner decays. (c) Modified stems (bulbs) Strawberry runners An Onion bulb (i) Examples of plants that reproduce through bulbs are tulips, lilies, morning glory and red onions. (ii) A bulb is an underground storage organ. It is short, upright and surrounded by succulent leaves. (iii) The apex of the bud grows between the slimy leaves. It develops into a new plant. 29 Page

30 3. Roots (a) Plants that reproduce through roots include sweet potatoes and carrots. A sweet potato plant A carrot plant C. Application of Research on Vegetative Reproduction in Agriculture 1. There has been tremendous progress in asexual reproductive techniques. 2. In agriculture, many types of new plants are produced through tissue culture techniques and stem cutting. 3. Tissue culture involves the in vitro culturing of individual cells or small bits of tissue. 4. Figure below shows the tissue culture technique carried out in carrots. A carrot tissue culture 30 Page

31 5. New plants formed through tissue culture are known as clones. 6. (a) Tissue culture techniques carried out in nutrient media enables large-scale vegetative reproduction to be carried out. (b) This produces large number of clones that are genetically the same as the parent plant. (c) These clones have good characteristics which include resistance to diseases, large yields and producing fruits whith a shorter time. (d) This technique and can be carried out all year round. 7. Commercial plants that have been successfully cloned include bananas, paddy, tomatoes, coffee, maize, rubber and others. 8. Stem cuttings involve cutting off a piece of twig or branch from the parent plant. The twig or branch is then placed in soil. If the conditions are favourable, roots will develop after a few days. 9. Plants like tapioca, bamboo and bougainvilla are examples of plants that reproduce succesfully through stem cuttings. A bougainvillea steam cutting 31 Page

32 Different methods of vegetative propagation Vegetative reproduction or propagation is the separation of some part of the parent plant which can develop into a new complete plant. Methods such as (i) cutting (ii) layering (iii) marcotting and (iv) budding and grafting, are used to produce plants with desired qualities. These are known as artificial methods of vegetative propagation. Cuttings A cutting is any proportion of a root or shoot which, after being severed from a parent, can be induced to grow into a new individual. The process of using a cutting to grow a new plant is described below: 1. The stems of certain plants are cut just below the node. 2. The cutting is planted in suitable soil so the node can develop adventitious roots to form a new plant. 3. It is useful to remove most of the leaves from the cuttings before planting them to reduce excessive water loss by transpiration. Sugar-cane and tapioca are plants that can be propagated in this way. Layering 1. In layering, a low branch with a node is bent down and a ring of bark about 5cm wide is removed from the node. 2. The ringed section is completely covered with moist soil while the end of the branch is allowed to remain free. 3. A weight or stone is placed on the branch to prevent it from being lifted off the ground. 4. When roots have developed, the branch is cut off from the parent plant and allowed to grow on its own. Layering can be done on plants such as lime. Marcotting Marcotting makes use of the same principle as layering. 1. A layer of moist soil is wrapped round the cut portion of the stem. 2. The soil is kept in place with coconut husk and polythene and tied with string. 3. It is kept moist by watering everyday. 4. Roots will soon appear and the branch can be cut and planted. Marcotting can be done in trees like rambutan and durian. 32 Page

33 Budding and grafting In budding and grafting, a healthy plant with an established root system is selected. This is called the stock. A portion of the plant to be propagated is carefully cut off and is called the scion which is attached to the stock, and the two grow together. The stock absorbs water and dissolved mineral salts through its roots and transports them to the growing scion(for such purposes, the scion and stock are usually of related species. 1. In budding, a bud together with some cambium is taken from a selected plant. This is the scion. 2. A T-shaped cut is made in the bark down to the cambium in the stock. 3. The scion is carefully inserted with the bud still exposed beneath the bark of the stock. The thin cambium in the scion is now in contact with the cambium of the stock. 4. The scion and stock are tied together and the junction is protected with wax. 5. The tissues of the two plants soon unite and the bud grows into a shoot. Lemon and hibiscus are plants which are grafted in this way. In grafting, a twig bearing several buds is cut off. Its lower V-shaped end is inserted into a corresponding shaped end of the stock. The two are tied as in budding and the buds will develop into shoots. Name of Parenting Origin of Region of Food Storage Examples Organ Organ Bulb Short, Vertical Fleshly scale leaves surrounding the Onion, daffodil. stem vertical stem. Corm Short, vertical stems Swollen stem base Gladiolus, crocus Rhizome Horizontal stem The entire length of horizontal stem Ginger, lotus, iris Tuber Side branch of stem At the tip of the side branch of stem Potato, arrowhead 33 Page

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35 Micro propagation/tissue Culture: Very small pieces are cut or removed. They are called explants. They are cut to a size of about 0.5 to 1mm. they are then placed in agar medium containing nutrients / glucose / water / vitamins and growth regulators / auxin / cytokinin which helps the pieces to grow into small plants. When the small plants have grown roots they are transferred to a glasshouse. They are grown into pots containing compost / soil and conditions such as temperature, oxygen, sunlight and humidity are controlled. The small plants produced are called clones, which means they are genetically identical. Hydroponics: Plants are grown in culture solution which contains elements which are essential for healthy plant growth. Plants such as balsam are grown with their roots immersed in solutions of mineral salts. Culture solutions consist of, distilled water, potassium nitrate, magnesium sulphate, potassium acid phosphate, calcium nitrate and iron (II) chloride. Similarities between micro propagation and hydroponics: 1. Both produce large numbers of economically important plants. 2. Both consume a small space. 3. Both can be controlled. Differences: Hydroponics Tissue Culture 1. Plants are grown without soil. 1. Plants are grown from small sections. 2. Small plants are grown, until they 2. Plants are already matured before mature before planting. transportation. 3. Uses culture solution- i.e. water with necessary minerals. 3. Uses growth hormones like auxin and cytokinin. 35 Page

36 Layering Marcotting Grafting Budding Tuber Rhizome Bulb Corm 36 Page