In order for plants on Twylo to get onto the land, over a long period of time they needed to develop root systems. Roots are important because they anchor the plant to the ground and they provide water to the plant which is required for plant maintenance and photosynthesis. Water is obtained through toe roots and then is transported up the stem to the leaves and finally out of the stomata, which are small openings in the leaves which regulate water loss and gas exchange. Dehydration is dealt with by having most of the stomata on the bottom of the leaves, this way they are in the shade and there is less evaporation. Also, plants have developed a cuticle that is a type of wax that helps retard evaporation. Figure 1 is a picture of one of the first land plants on Twylo. It is called a zibit.
Figure 1 Zibit Plant
The way plants support themselves is through their stem structure. The tips of the stem are called meristems. The meristems are areas of growth for the stem, and plants continue to grow throughout their life times. Meristems are located at the tips of the shoots and the roots. Roots continue to grow so that they can find new sources of water and minerals. Shoots continue to grow towards light. There are two types of growth, primary growth and secondary growth. Primary growth is involved on the elongation of the plant, while secondary growth is involved in the thickening of stems and trunks. If a plant has too much primary growth without a sufficient amount of secondary growth it can fall due to its own weight. Figure 2 is a cross section of a plant called Zestron. Zestron is a small bushy plant that grows in the Northern latitudes and has a trunk about the size of your wrist.
Figure 2 Zestron growth rings
Plants on Twylo reproduce sexually. This means that plants undergo a process of meiosis and fertilization. Meiosis is a process of nuclear division in which cells divide and break up into four cells called daughter cells. Each daughter cell has one half the chromosomes of the parent cells. Fertilization is a process where two daughter cells join together to form a parent cell. On Twylo, the main form of fertilization is by a mechanism whereby a plant will shoot its pollen to another plant near it. The pollen will mate with the ovaries of the other plant, therefore you usually find plants of similar types growing in clusters on Twylo. These clusters can be quite large, some extending for hundreds of kilometers. The larger land plants can be dangerous to animals as the pollen pods can shoot off with explosive force which has been known to kill animals if they are struck in the head. Once fertilization takes place, The plants undergo a period of dormancy and after about three months the baby plant drops down to the soil and the parent plant dies. When the parent plant dies, its decaying matter is a source of nutrients for the baby plant. Figure 3 shows a zibit plant which is shooting off its pollen.
Figure 3 Reproduction of plants on Twylo
The distribution of plants on Twylo are somewhat limited compared to Earth. This is because Twylo is on average 15 C colder than Earth, therefore there are not a lot of tropical rain forest areas. Also, because of the increased gravity, there are not a lot of tall trees that have been able to overcome the gravitational pull. Near the equator, there are mostly small trees with large leaves and a lot of small bushy shrubs. Going North and South from the equator there are mostly small shrubs and lots of grasslands. Near the poles, there is very little vegetation, usually just small clumpy grasses. The main flora at about 30 degrees above and below the equator is the zibit; near the equator, where it is warmer, it's the zestron and far north and south, you can find the zinfy, which is a clumpy type of grass found in between rock crags.
Figure 4 Distribution of plants in different climate zones
Figure 5 Evolutionary stages of plants on Twylo
The least evolved plant is the zynoff. Its main stem grows horizontally along the ground with small root structures called rhizomes. This was the first land plant, and it has not evolved much further than its current stage. The next plant that evolved was the zinfy: this is a type of grass that has a much better root structure than the zynoff, which has allowed it to hold onto to rocky crags. The ainfy has found its niche in the colder climates of Twylo. The next plant evolutionarily is the zibit. This plant has well developed leaves, and it has an interesting system of delivering its pollen to its neighbor. It shoots its pollen forcefully. The plant is very pretty with red pollen and it leaves turn a brilliant red during fall. The most highly evolved plant is the zycamore tree which is a small tree that grows near the equator. The tree has developed a type of wood that has helped it to overcome gravity and can grow up to 10 meters tall. The tree reproduces sexually as do all the plants on Twylo (it's more fun!). The tree has a well developed leaf system which is similar to pine trees on Earth.
Figure 6-7 Three examples of plant life on Twylo: Zycamore, Zinfy and Zynoff