BOTANY LABORATORY PRACTICAL (PLANT ANATOMY AND MORPHOLOGY) - O.A. SHEVCHUK - 2014

FLOWER

TOPIC 11. PLANT REPRODUCTION. PLANT REPRODUCTION CYCLES

General Remarks. Reproduction is defined as the ability of organisms to produce offspring similar to themselves.

Multiplication is the process whereby The production of offspring leads to an increase in the number of individuals of a given species. Multiplication ensures the long-term survival of a species in space and time. The loss of the capacity for both reproduction and multiplication leads to the extinction of the species.

New individuals can arise from parental forms asexually (without the participation of Gametes and a sexual process) and sexually (As a result of a sexual process).

Sexual reproduction is defined as reproduction in which new individuals are formed as a result of a sexual process, i.e., the fusion of two gametes — sex Cells. Typically, two gametes of opposite sexes fuse: a male gamete — a motile spermatozoid or a non-motile sperm, and a female gamete — an egg Cell. The fusion of such gametes is called Fertilization or syngamy.

As a result, a zygote is formed, which has a diploid set of Chromosomes; due to recombination, the offspring become more diverse than the parental forms.

Spore reproduction is characteristic of lower plants (Algae), Fungi, and Water/56.html">LOWER SPORE PLANTS (bryophytes, clubmosses, horsetails, psilophytes, ferns), in contrast to gymnosperms and angiosperms, which reproduce by seeds and are therefore called seed plants. The formation of spores on a plant is called sporulation.

Spores are specialized cells that ensure both reproduction and dispersal of plants. They are haploid and arise through mitosis in certain fungi and algae (these are mitospores) or through Meiosis in higher plants (these are meiospores). In many plants, all spores are of the same size and have identical physiological properties. Such spores are called isospores, and the plants are homosporous. Heterosporous plants produce spores of different sizes: smaller microspores (which germinate into male individuals) and larger megaspores (which germinate into female individuals).

Spores are formed in special Organs of asexual reproduction called sporangia.

Morphology/12.html">ALTERNATION OF GENERATIONS refers to the regular succession in The life cycle of generations (generations, or bionts) that differ in their mode of reproduction.

Diplobiont is the asexual (sporous) generation, the sporophyte, which develops from a zygote resulting from the fusion of two gametes and produces spores.

Haplobiont is the sexual generation, the gametophyte, which develops from a megaspore and produces gametes.

Organs of asexual reproduction (sporangia, zoosporangia) develop on the sporophyte; as a result of meiosis, they form haploid spores that germinate into new sexual generations.

Sex organs are formed on the gametophyte, which can be unisexual (Polytrichum, Marchantia, Salvinia) or bisexual (Lycopodium, bracken, male fern). The gametophyte and sporophyte can be morphologically and developmentally similar (isomorphic alternation of generations) or drastically different (heteromorphic alternation of generations).

The sporophyte (also known as the diplobiont) is a leafy-stemmed plant on which sporangia develop. The gametophyte generation (prothallium) is less developed, short-lived (except in clubmosses), and represented by an independent bisexual or unisexual thallus (ferns, clubmosses, horsetails).

A reproduction cycle is a segment of a species' life bounded by two identical stages: from haplobiont to haplobiont, from sporophyte to sporophyte, from zygote to zygote, from meiospore to meiospore. During the reproduction cycle, A change in nuclear phases necessarily takes place.

Objective: to understand The Essence of METABOLISM/2.html">THE CONCEPT OF "reproduction cycle", to study the reproduction cycles of mosses (using common haircap moss, *Polytrichum commune*, as an example), clubmosses: homosporous (using stag's-horn clubmoss, *Lycopodium clavatum*); heterosporous - (using spikemoss, *Selaginella*); homosporous ferns (using male fern, *Dryopteris filix-mas*); horsetails (using field horsetail, *Equisetum arvense*); gymnosperms (using Scots pine, *Pinus sylvestris*) and their specific features.

Materials and equipment: herbarium specimens, dynamic charts, tables of reproduction cycles of the studied representatives.

Tasks

1. Examine the provided herbarium specimens, permanent slides, dynamic charts, and development cycle tables.

2. Review and study the life cycle diagrams.

Label the figures.

Conclusion

Review Questions

1. Define the concept of "life cycle".

2. Why is the sporophyte called the asexual generation, given that it develops from a zygote?

3. Explain the evolutionary advantages of the transition from isogamy to oogamy. What type of sexual process is characteristic of angiosperms?

4. In the animal kingdom, a process analogous to plant grafting is called transplantation. Unlike plant grafting, animal transplantation rarely results in the successful fusion of Tissues from different organisms. Why?

5. Are gametes always formed as a result of meiosis and spores through mitosis? Provide Examples.

6. What is The ratio of the diplophase to the haplophase in the plant life cycles discussed?

7. What is the core Significance of the plant life cycles studied?

8. What are the Structural Features of the gametophyte and sporophyte in the studied plants?

9. Which Features of the fern developmental cycle indicate its descent from ancestral aquatic forms?

10. What constitutes an individual Organism in plants that reproduce vegetatively under natural conditions? WHAT IS A clone?

11. The Significance of heterospory in the evolution of higher plants.

12. How can you explain the great diversity of life cycles in lower plants versus the uniformity of sporophyte dominance in higher plants?

13. Explain the meaning of the following terms and concepts: antheridium, apomixis, archegonium, Vegetative Reproduction, gametangium, diplobiont, life cycle, clone, megaspore, meiospore, microspore, mitospore, asexual reproduction, oogamy, parthenogenesis, homospory, reproduction, syngamy, spore, sporangium, sporophyte, sexual reproduction, alternation of generations.