NEM 10V Lecture Notes - Lecture 59: Circadian Rhythm, Stamen, Flowering Plant
Nematology
Angiosperms:
• Angiosperms are vascular seed plants that make flowers, and fruit.
• The production of female gametes occurs in the ovary where there are several rows of cells
called ovules.
• After fertilization, the ovule becomes the seed, and the ovary becomes the fruit.
• Diploid cells undergo meiosis, dividing twice, but duplicating their chromosomes only
once.
• This results in 4 haploid spore cells.
• Three of these haploid cells shrivel up, leaving only a single megaspore.
• The nucleus of the megaspore reproduces 3 times without ever dividing its cytoplasm.
• The new nuclei rearrange themselves inside the cell with 3 nuclei at opposite ends of the
cell, and 2 in the center.
• Out of the 8 haploid nuclei produced in this process, one becomes the female gamete egg
nucleus.
• The production of male gametes occurs in the anthers that make pollen.
• Diploid anther cells undergo meiosis and produce 4 haploid spore cells known as
microspores.
• The nucleus of each microspore divides, but its cytoplasm remains intact.
• Then, one of the two nuclei divide again to form two sperm nuclei.
• The nucleus that didn’t divide is now called the tube nucleus.
• A hard-outer coat forms around the three creating a grain of pollen.
• For fertilization to take place, and form seeds, the male pollen has to get to the female
stigma.
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