Biological Sciences
Asexual Reproduction in Plants
Asexual reproduction in plants is a process where new individuals are produced from a single parent without the involvement of gametes. This can occur through various methods such as fragmentation, budding, or the production of specialized structures like runners or bulbs. Asexual reproduction allows plants to rapidly propagate and colonize new areas, but it limits genetic diversity.
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9 Key excerpts on "Asexual Reproduction in Plants"
eBook - ePub- Peter Scott(Author)
- 2013(Publication Date)
- Wiley-Interscience(Publisher)
Longevity . Plants may, in many instances, be long-suffering and long-lasting, but if the great extinctions of the past teach us anything, it is that nothing lasts forever. No matter how old an individual plant is, one day conditions will change to make survival impossible. Plants need some means of surviving such adverse conditions, which may be local or temporary, and reproduction can offer a solution to this. Clonal plants may move away from the point of origin of the mother plant and therefore widen the spread of the plant, thereby escaping a particular stress. In addition, seeds offer even greater opportunities to disperse genetic material well away from the parent plant and also provide a structure that can remain dormant over prolonged periods. This permits a plant to survive temporary changes in conditions. Clones or seeds also produce new individuals which are free from fungal infections or damage present in the parent plant.3. Genetic variation . Finally, reproduction offers opportunities for genetic variation, which is essential in a changing habitat. Asexual reproduction offers little opportunity for genetic variation but the potential from sexual reproduction is immense.In this chapter we will look in greater detail at how plants reproduce and the merits and limitations of the different methods.Asexual reproduction
Many plant species use asexual reproduction as a means of propagation. Asexual reproduction has several advantages and disadvantages (Figure 9.1 ). This form of reproduction produces individuals that are genetically identical and does not support much scope for phenotypic variation. This can lead to plants being vulnerable to changes in the habitat. In addition, offspring are generated close to the parent plant, so parent and offspring often have to compete for nutrients and light. However, asexually produced plants usually attain adulthood in advance of seedlings of the same parent and hence rapidly out-compete neighbouring plants reliant on seeds. Under many conditions, asexual reproduction is more successful than sexual reproduction for plants and a large number of species use this as their sole means of reproduction.Figure 9.1 Asexual Reproduction in Plants. Plants possess a range of different means of asexual reproduction. (A) Apomixis: using this method, the flowers spontaneously produce seeds without the need for any fertilization. The actual source of the embryo can come from the egg cell or the cells surrounding it. (B) A hyacinth bulb (Hyacinthus hybrid); bulbs frequently produce bulbils (small offset bulbs) at the base of the bulb. (C) A gladiolus corm (Gladiolus hybrid); corms frequently produce small offset corms at the base of the stem. (D) Strawberry plant (Fraxinus hybrid), forming runners, modified stems that form new plants. (E) Black poplar (Populus nigra
eBook - PDF- Emea, N(Authors)
- 2018(Publication Date)
- Agri Horti Press(Publisher)
This suggests that cross-fertilization, the union of sperm and egg from different prothalli, necessary for increasing genetic variability within species, is promoted in at least some ferns. ASEXUAL REPRODUCTION Asexual propagation can occur in various ways. Many This ebook is exclusively for this university only. Cannot be resold/distributed. Plant Reproduction 215 plants produce genetically identical copies of themselves, through a mechanism referred to as asexual reproduction. However, botanists more properly refer to this mechanism as “sexual propagation” or “vegetative propagation” because many hold that only sexual reproduction should be referred to as true reproduction, since this is the only kind of propagation that results in the production of new, genetically unique individuals. Another type of asexual propagation occurs when plants develop underground stems (or rhizomes) which grow outward, or new shoots which grow upward to form new shoots that are genetically identical to the parent. One such example is the trembling aspen ( Populus tremuloides), which sometimes develops entire stands of trees growing out of the ground as seemingly individual stems, but are actually genetically identical and interconnected below-ground. Another example is the strawberry ( Fragaria virginiana ), although this species has its vegetative runners above-ground. Other plants develop bulbils on their stems, which can detach, fall to the ground, and sprout to develop new plants that are genetically identical to the original one. One familiar species that does this is the tiger lily ( Lilium tigrinum. Other plants can propagate from twigs or stem pieces that fall from the parent, then lodge into a suitable site and develop into a new plant. The crack willow ( Salix fragilis) can spread itself along watercourses in this manner (as well as by disseminating seeds).
eBook - PDFAdvanced Plant Production NQF4 SB
TVET FIRST
- W Burger(Author)
- 2013(Publication Date)
- Macmillan(Publisher)
Natural plant propagation Overview In this module you will: • explain asexual plant propagation methods with examples • explain sexual plant propagation methods including pollination and fruit setting. Introduction Production of food – vegetables, fruit, cereals and fibre (such as cotton) – can only happen if the plant is able to reproduce. You must have noticed that under natural conditions, plants reproduce themselves. There are two main methods of reproduction or propagation in nature. These methods are sexual reproduction and asexual reproduction. In nature, flowers develop on plants as a result of pollination and fertilisation. Pollen is carried by wind, water or animals (mainly insects). The pollen grain is transferred from the male flower to the female flower. This is sexual reproduction as it involves a male and a female. But in nature you will also find that some plants reproduce through root development from various parts of the plant, i.e. the vegetative parts. We call this kind of plant reproduction asexual or vegetative reproduction. During domestic plant production practices, the farmer uses the same basic principles of plant propagation that are found in nature – the farmer will use seeds for sexual reproduction of plants or will use vegetative parts of the plant for asexual production. 2 Module 1 Module 1 Propagation: reproducing or making more of the same Sexual reproduction: in a plant, sexual reproduction happens when pollen is transferred from the anthers onto the stigma of a flower in a process called ‘pollination’ Asexual reproduction: in a plant, asexual reproduction takes place through the non-reproductive or vegetative parts of a plant, e.g. the roots, stems and leaves Pollination: to transfer pollen from the anthers to the stigma of a flower Vegetative: the non-reproductive parts of a plant, e.g. the roots, stems and leaves Words & Terms
eBook - PDF- Singh, Pradeep Kumar(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
There are finer differences in these types. For example, there may be differences between the time of pollen shed and stigma receptivity. This ebook is exclusively for this university only. Cannot be resold/distributed. 3. Self-fertilization versus cross-fertilization: Just because a flower is successfully pollinated does not necessarily mean fertilization will occur. The mechanism of self-incompatibility causes some species to reject pollen from their own flowers, thereby promoting out crossing. 4. Sexuality versus asexuality: Sexually reproducing species are capable of providing seed through sexual means. Asexuality manifests in one of two ways – Vegetative reproduction (in which no seed is produced) Or Agamospermy (in which seed is produced). TYPES OF REPRODUCTION Plants are generally classified into two groups based on mode of reproduction as either sexually reproducing or asexually reproducing. Sexually reproducing plants produce seed as the primary propagules. Seed is produced after sexual union (fertilization) involving the fusion of sex cells or gametes. Gametes are products of meiosis and, consequently, seeds are genetically variable. Asexual or vegetative reproduction mode entails the use of any vegetative part of the plant for propagation. Some plants produce modified parts such as creeping stems (stolons or rhizomes), bulbs, or corms, which are used for their propagation. Asexual reproduction is also applied to the condition whereby seed is produced without fusion of gametes (called apomixis). It should be pointed out that some plants can reproduce by either the sexual or asexual mode. However, for ease of either propagation or product quality, one mode of reproduction, often the vegetative mode, is preferred. Such is the case in flowering species such as potato (propagated by tubers or stem cuttings) and sugarcane (propagated by stem cuttings).
eBook - PDF- Dhar, T praveen(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
Chapter 2 PROPAGATION METHODS Plant propagation is the process of creating new plants. There are two types of propagation, they are sexual and asexual. Sexual reproduction is the union of the pollen and egg, drawing from the genes of two parents to create a new, third individual. Sexual propagation involves the floral parts of a plant. Asexual propagation involves taking a part of one parent plant and causing it to regenerate itself into a new plant. The resulting new plant is genetically identical its parent. Asexual propagation involves the vegetative parts of a plant: stems, roots or leaves. Propagation of plant is defined as production of new individuals from a selected plant having all the characters of the original one. Importance of Plant Propagation 1. Multiply the different species in large number. 2. Protect the plant species which are endangered. 3. Improve the characteristics and quality of the plants. 4. Produce quality and healthy plants on commercial base. 2.1. Plant Propagation Types a. Sexual Propagation As the name suggests, sexual propagation involves contribution of both female and male sexes for creation of new plants. It is a natural process in which a parent species create offspring that are genetically different from them. This ebook is exclusively for this university only. Cannot be resold/distributed. An Introduction to Horticulture | 20 | Advantages of Sexual Propagation P Simplest, easiest and the most economical process among various types of plant propagation . P Some plants, trees, vegetables or fruits species can propagate only through sexual propagation. E.g. – marigold, papaya, tomato. P Sexual propagation leads to better crop species that are stronger, disease-resistant and have longer life-span. P Viral transmission can be prevented in this type of propagation. P Sexual propagation is responsible for production of large number of crops and that too with different varieties.
- Caula A. Beyl, Robert N. Trigiano, Caula A. Beyl, Robert N. Trigiano(Authors)
- 2016(Publication Date)
- CRC Press(Publisher)
65 5 Sexual Reproduction and Breeding Timothy A. Rinehart, Robert N. Trigiano, Phillip A. Wadl, and Haley S. Smith In this second edition of Plant Propagation Concepts and Laboratory Exercises , we have combined the first edition Chapters 36, “Sexual Reproduction in Angiosperms,” and 37, “Breeding Horticultural Plants,” into this single chapter, “Sexual Reproduction and Breeding.” These top-ics are so closely related that we believe that concepts are best presented as one unit. In addition to combining the aforementioned chapters, we have added some high-resolution microscopic photographs of mitotic events that are comparable to the line drawings depicting the vari-ous phases of mitosis. We have maintained some black-and-white figures for clarity of presentation. Lastly, we have included in this edition a simple laboratory exer-cise involving the observation and frequency of mitotic phases in the cells of onion as seen in longitudinal sec-tions of root tips on prepared slides. Many horticultural crops are produced exclusively by vegetative or asexual means. Asexual reproduction using grafting, rooted cuttings, and various other meth-ods ensures clonal fidelity of a cultivar. Phenotypic and genetic variation in these crops is undesirable, especially if the consumer is expecting to purchase a plant that they have seen growing somewhere else or pictured in a catalog. For example, all Cornus florida L. (flowering dogwood) ‘Cherokee Sunset’ plants have yellow variegated leaves and pink bracts subtending the floral disk, and are produced exclusively by a grafting technique (Chapter 25). There is little variation using this technique, and it produces Concept Box 5.1 • Most plants exhibit alternation of generations. In this case, the plant generations are the sporophytic or diploid (2n) phase that produces spores and the gametophytic or haploid (n) phase that produces gametes. • The four parts of flowers are sepals, petals, anthers, and pistils.
- Shoichi Kawano(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Beginning in the 1960's, this explanation began to be challenged, because it depended on natural selection working at the level of groups rather than on individ-uals (Williams, 1966, 1975; Steams, 1987). This challenge was provoked by the recognition that, because asexual individuals produce no sons and expend little or no energy on male function (an expense often termed the cost of sex), they ought to be able to produce up to twice as many daughters as sexual individuals can, and BIOLOGICAL APPROACHES AND Copyright © 1990 Academic Press Limited. EVOLUTIONARY TRENDS IN PLANTS ISBN 0-1 2-402960-4 All rights of reproduction in any form reserved 294 P. Bierzychudek thus increase rapidly at the expense of sexual individuals (Williams, 1975; Maynard Smith, 1978; Lloyd, 1980; Uyenoyama, 1984). In the face of this twofold advan-tage for asexual individuals, the group selection explanation was judged insufficient (Steams, 1987). Attention turned from why are so many species sexual? to why doesn't a mutation permitting asexual reproduction rapidly spread through a popu-lation of sexual individuals? Theoreticians met this challenge by offering a variety of possible advantages that might be gained by individuals producing genetically variable offspring, relative to individuals producing genetically uniform offspring. These explanations can be summarized as follows (see Bierzychudek, 1987b and references therein for de-tails): 1. One possible advantage of sexual reproduction is that it generates rare geno-types (the minority advantage hypothesis). Levin (1975) first pointed out that predators, pathogens, and parasites would be expected to decrease the fitness of common genotypes to a greater extent than that of rare ones.
eBook - PDF- Richard N. Arteca(Author)
- 2014(Publication Date)
- Cengage Learning EMEA(Publisher)
Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. CHAPTER 6 PLANT PROPAGATION 117 handle than seeds. One of the advantages of asexual propagation that can also be a dis-advantage is that an entire population of genetically identical plants can be completely wiped out with a single disease infection. Lastly, in some cases, mechanized methods for asexual propagation may not be technically possible with the technology currently available. Methods of Asexual Propagation There are a variety of types of asexual propagation. In this section, eight types of asexual propagation will be discussed: apomixis, cuttings, grafting, budding, layering, separation, division, and tissue culture. Apomixis Apomixis is a form of asexual propagation in which seeds are produced without fertil-ization; for example, there is no fusion of the male and female gametes, so these seeds are solely maternal in origin. An excellent example of this type of asexual propagation is the common dandelion, found in most lawns; it is capable of reproducing by seeds, vegetatively, or by apomixis. Cuttings Cuttings are detached vegetative portions of the plant that are used to produce a new plant. Propagation by cuttings is the most common method of asexual propagation. Cuttings can be derived from three sources, which include the three primary plant organs: stem, leaf, and root. The time of year, stage of growth, and type of wood will determine if cut-tings produce roots. The following sections describe the most common types of cuttings. Stem cuttings Stem cuttings use portions of the stem containing terminal or lateral buds (Figure 6-6).
eBook - PDF- Mary Ann Clark, Jung Choi, Matthew Douglas(Authors)
- 2018(Publication Date)
- Openstax(Publisher)
32 | PLANT REPRODUCTION Figure 32.1 Plants that reproduce sexually often achieve fertilization with the help of pollinators such as (a) bees, (b) birds, and (c) butterflies. (credit a: modification of work by John Severns; credit b: modification of work by Charles J. Sharp; credit c: modification of work by "Galawebdesign"/Flickr) Chapter Outline 32.1: Reproductive Development and Structure 32.2: Pollination and Fertilization 32.3: Asexual Reproduction Introduction Plants have evolved different reproductive strategies for the continuation of their species. Some plants reproduce sexually, and others asexually, in contrast to animal species, which rely almost exclusively on sexual reproduction. Plant sexual reproduction usually depends on pollinating agents, while asexual reproduction is independent of these agents. Flowers are often the showiest or most strongly scented part of plants. With their bright colors, fragrances, and interesting shapes and sizes, flowers attract insects, birds, and animals to serve their pollination needs. Other plants pollinate via wind or water; still others self-pollinate. 32.1 | Reproductive Development and Structure By the end of this section, you will be able to do the following: • Describe the two stages of a plant’s lifecycle • Compare and contrast male and female gametophytes and explain how they form in angiosperms • Describe the reproductive structures of a plant • Describe the components of a complete flower • Describe the development of microsporangium and megasporangium in gymnosperms Sexual reproduction takes place with slight variations in different groups of plants. Plants have two distinct stages in their lifecycle: the gametophyte stage and the sporophyte stage. The haploid gametophyte produces the male and female gametes by mitosis in distinct multicellular structures. Fusion of the male and females gametes forms the diploid zygote, which develops into the sporophyte.
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