One of the most dramatic changes in the world over the past couple of generations that has affected all of us has been the explosion of high technology. From ultra-reliable cheap watches to computers to the Web to cell phones to iPods to televisions to fuel-injection to coffee-makers, technology touches all of us. Now it’s fairly unreasonable to expect an average joe to understand how all of these things actually work, but there’s one fundamental building block, one common root, one thread, upon which all of these technologies and so many others are based: the transistor. If you understand how a transistor works, you understand the basic functional mechanism of all of these technologies.
Prior to actual pollination, each ovule contains a megaspore, which is a fancy word for a “starter” cell that divides a bunch of times. The megaspore undergoes a complex development of its own via meiosis. Each megaspore divides via meiosis into 2 cells, each of which in turn divides again- via mitosis*- resulting in 4 cells, 3 of which are spontaneously aborted. The 4th cell becomes the Embryo Sac Nucleus, and undertakes a mitotic process of its own, dividing twice, resulting in 8 haploid cells.
Side Note: My earlier posts on Dandelion genetics and polyploidy in Sagebrush explained the terms: haploid, diploid and triploid. In the case of Oak, the diploid number is 24, the haploid number is 12.
A pollen grain contains two (diploid) cells, each of which performs a specific function. The first cell starts growing a tube downward through, and along the length of, the pistil, toward the ovule chamber, and the three haploid cells (1 egg and 2 polar nuclei) within.
The second cell divides meiotically into 2 sperm cells, which travel down the tube- or more accurately, are carried downward by the burrowing tip of the pollen tube, since the sperm can’t move/swim on their own- toward the ovule chamber.