Does an anther on a plant have a double set of chromosomes?

Does an anther on a plant have a double set of chromosomes?

• Hi does an anther have a double set of chromosomes or single set of chromosomes I would also like to know that for ovule, embryo

• Answer:

  The outer walls of anthers have a double (diploid) chromosome set. The pollen grains contained inside of them are haploid meaning they have a single chromosome set. Please note that in the early stages of anther development all cells are diploid but, at some point, the ones in the centre undergo meiosis and become haploid before developing into pollen grains. The haploid pollen grain constitutes what is called the microgametophyte. Things are a bit more complicated with ovules: an ovule is composed of one or two outer cell layers (integuments) surrounding a mass of cells (nucellus) which provide protection and nutrients to the few cells (megasporocytes) which will eventually produce the egg cells. As in the anthers, all these structures are initially diploid. At some point the megasporocyte will undergo meiosis, initially producing four haploid nuclei. Depending on the plant species, of these four haploid nuclei some may degenerate while some others will further divide by mitosis to create a haploid structure called megagametophyte. Some of the cells of the megagametophyte will develop into egg cells. That is pretty much it for Gymnosperms but things gets even more complicated in Angiosperms. In Angiosperms, some of the cells of the megagametophyte will create support structures (endosperm) which will store resources for the growth of the embryo. During fertilisation the pollen grain releases two (haploid) nuclei into the ovule. One of them fertilises the egg cell (which will then develop into a diploid embryo) while the other fuses with one or two of the other haploid cells of the megagametophyte to create a diploid or triploid endosperm. Once fertilisation has occurred, the ovule matures and turns into a seed where various structures will have different chromosome sets. The outer layer, originating from the integuments and nucellus, will have exactly the same diploid chromosome set as the mother plant.The intermediate layer of angiosperms (endosperm) will have a diploid or triploid chromosome set derived in part from the mother plant (1/2 if diploid, 2/3 if triploid) and in part from the pollen grain (1/2 if diploid, 1/3 if triploid). The embryo will have a diploid chromosome set (half from the mother plant and half from the pollen) and will develop into a new diploid plant. I know this is very complicated so, in hope of making it easier to understand i think you should also try to grasp the concept of "alternation of generations". In animals (which do not have alternation of generations) two haploid sex cells (created by meiosis insdide the parent organism's body) unite to create a new organism which is diploid exactly like its parents. In plants (as well as in algae and many microorganisms) the diploid parent organisms do not directly produce sex cells but rather haploid spores which develop into a distinct haploid organism (the micro- and mega-gametophyte) which in turn produces the sex cells (through mitosis). This is not apparent in plants because the diploid and haploid organisms grow on top of (or inside) each other. So the mother plant and the external structures of the ovule and anther are part of the so called "sporophytic" generation, the megagametophyte growing inside the ovule and the pollen grain developing inside the anther are distinct organisms that represent the gametophytic generation and, finally, the embryo represents the new sporophytic generation which will grow into a new plant. In algae and microorganisms the gametophyte and sporophyte generation are independent of each other so their life cycles are easier to understand.