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5 Cards in this Set
- Front
- Back
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Describe the female structure of a plant |
- known as carpels & each carpel contains of a stigma, a style and an ovary - The stigma is a platform onwhich pollen grains may land - the style supports the stigma - and inside theovary there is an ovule whichcontains the female gametes |
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Describe the female structure of a plant |
- The male structures are known as stamens - each stamen contains an anther and a filament - The anthers produces pollen grains that contain the male gametes - filament supports the anther in a position that will eventually enable it toshed its pollen grain |
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Production of male gametes in plants |
- each anther has 2 or 4 lobes,within the tissues in each lobe are a number of diploid microspore mother cells - Each of these cells divides once bymeiosis to produce four haploid microspores - Each microspore then divides once by mitosis to produce two haploid nuclei; thetube nucleus, and the generative nucleus (the male gamete) - The microspore isnow called a pollen grain.This occurs in the anthers, they have alayer of diploid cells which divide by mitosis to produce microspore mother cells (2n) - These cells divide by meiosis toproduce four haploid microspores,each microspore divides by mitosis (just to telophase stage) to produce a cellwith two haploid nuclei - This is the pollen grain. 1 nucleus will form a pollen tube if the pollen grain landson the stigma of the same species, this is the tube nucleus - The other nucleusis the male gamete, which will travel down the tube to fertilise the femalegamete |
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Production of female gametes in plants |
- one or more ovules develop insidean ovary, Within its central mass of tissues, called the nucellus, is a large diploid megasporemother cell surrounded by two layers of cells, called integuments - As these integuments grow, they almost enclose thenucellus, leaving only a tiny hole called the micropyle - A megaspore mother cell divides by meiosis toproduce four haploid cells, the megaspore, three of them disintegrate - The one that survives grows until it almostfills the nucellus, the nucleus of the surviving megaspore divides three timesby mitosis. This single cell is an immature embryo sac - The cytoplasm of the embryo divides to formseven cells, the three nearest the micropyle are the ovum and the synergids. The three further from themicropyle are the antipodal cells, and the other two remain in the centre ofthe embryo sac. These are two polar nuclei - The ovule contains the tissue which divides to form the megaspore mother cell (2n) - Thisdivides by meiosis to produce 4 haploid megaspores; 3 disintegrate, 1 grows tofill the ovule - This cell divides 3 times by mitosis to produce a cell with 8nuclei, to produce an embryo sac |
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What is double fertilisation? |
- Double fertilization is a complex fertilisation mechanism of flowering plants (angiosperms). This process involves the joining of a female gametophyte (megagametophyte, also called the embryo sac) with two male gametes (sperm). |
