Seed plant reproduction

So post #2 in the series about plant reproduction is here!

So in the previous post, alternation of generations was (sort of) explained.
Here we're mostly talking about the sporophyte, which is the tree you see when you walk outside, and how it manages to produce gametophytes, where these occur and how the whole thing works. Starting with seed plants, and touching on flowering plants slightly (although there will be more of those in the next post).

So imagine a pine tree. You know in spring when all the ponds and creeks get covered in yellow grime? Yep, that's pollen. Seed plants like pines are wind-pollinated, resulting in a whole lot of pollen moving around the landscape. But then, that's a price you pay with wind-pollination. It tends to me more hit-and-miss than animal pollination, so more pollen is usually produced to compensate (more on this in a later post, promise!).
The pollen is produced in the male cones, known as microsporangium, and is the entire microgametophyte phase of this plant. Remembering from the last post, where mosses and ferns may have almost a 50/50 split or at least a far more prevalent gametophyte stage, in seed and flowering plants the gametophyte is much smaller, only hangs around for a very short length of time, and is less obvious. The male cones are usually found on the outside of the tree, at the ends of the branches, and this allows for more easy pollen dispersal on the wind.

The female part of the lifecycle occurs completely within the female cone, which is the megasporangium. Under the scales of the cone, there are megagametophytes. These, along with other associated tissues, make up the ova (egg). Once pollen lands on the right part of the girl cone, fertilisation may occur. In this instance, the male pollen (microgametophyte) will fuse with the femle egg (megagametophyte) to form a new embryo (zygote, and it is the next sporophyte phase). This develops as a seed, and once it reaches maturity, can (ideally) be dispersed. So really, 3/4 of the process happens in the female cone (megasporangium) as once the pollen has been developed and dispersed, the microsporangium has little to do with it ;)

So in summary:
- Male cone (microsporangium): Produces pollen (microgametophyte), disperses via wind
- Female cone (megasporangium): Produces the egg (containing megagametophyte), is where fertilisation takes place and where the seed (new sporophyte) develops, protected, until dispersal can occur.

Edit: A picture! To hopefully make that clearer (apologies for bad quality and my terrible handwriting. Haploid stage in yellow, diploid is blue):

Flowering plants work in a very similar way, with only a couple of differences. Firstly, they still split the micro- and mega-gametophytes up, however now they have flowers too. In most flowers you can find both the male and female structures, however some plants have separate flowers for them. Also, some plants are either male or female too. In flowers with both male and female parts, sometimes the same plant can't fertilise itself, sometimes it can. Sometimes the male part sits above the female, sometimes it's the other way around. But the basic mechanics are the same: male pollen, produced in a microsporangium (in the flowers case it's called an anther) meets the female egg, produced in a megasporangium (in the flower it's the ovary), they fuse to form a zygote, which grows into an embryo and develops inside a seed.

The actual mechanics of fertilisation in flowering plants are interesting, but can be a bit complicated. I might do a post regarding basic flower anatomy, and also detail how fertilisation occurs. Then the long-anticipated post about pollination syndromes will come...