Timeline (Intelligent Plants?)

A timeline chronicling the evolution of plant life; from the Silurian to the end of the Quaternary periods.

Silurian 450 mya to 420 mya
The journey of the plants begins here, at the beginning of the Silurian period, and the lowering of carbon dioxide levels in the atmosphere led to global cooling.. Named the Ordovician-Silurian extinction event, the subsequent dropping of sea level and glaciation over the next 10 million years led to the extinction of approx with 100 marine families, and 49% of all fauna genera, or 60% of all life. However, following a rise in volcanic activity, most glaciers formed during the mass extinction melted, and life began to develop again.

The melting of the glaciers led to one outstanding event, life on land, as the soil of the land became moist, and aloud for the migration and flourishing of complex plant life on land, now able to support themselves. This also led to the evolution of a different type of reproduction.

During the past 200 million years, almost all plant species alive lived in the ocean, with a few exceptions to algae like lifeforms living on beaches. The reproduction method of these plants was to disperse sperm and eggs into the surrounding water, and if the two joined, it would allow for the formation of a zygote. When plants migrated and evolved onto land, this method of reproduction became obsolete. Plants then evolved motile sperm (sperm that can move freely). Male plants would deposit this into the moist ground, where it would swim through a thin film of water to a female plant, and fertilize it.

This process became the most used process of reproduction for the early land plants, and it allowed them to diversify into more distinct plant groups (Zosterophylls).

Since the end of the Ordovician period, and the melting of the glaciers, the average surface temperature had been around 17°C  . However near the end of the period, dramatic temperature rises and the the drying of the land led to the decline on plants that used the motile sperm method of reproducing, as the dry soil couldn't support the sperm. This led to the proliferation of spore releasing or asexual means of reproduction in plants.

However, some vascualr plant species that lived around the equator (Cooksonia) to develop a different method of reproduction, movement.

Devonian 420 mya to 360 mya
Vascular plants, at the beginning of the Devonian period, in an effort of gain more water and minerals from the now dry land to keep nourished, evolved larger and more far reaching  roots.

This had it's consequence though, as the plants had to develop a larger and better transport tissue (Xylem transporting water, and Phloem transporting minerals and other organic compounds). This aloud the plant, by 400 mya, to evolve a greater ability to manipulate turgor pressure, the pressure of water in plant cells that allow it to stay straight.

Using this manipulation, plants could absorb water and minerals through it's roots, and using the transport tissue, it would quickly transport water throughout the entire structure, filling individual cells with water, and increasing turgidity, then suddenly draw water away to a small bulb at the base of the plant for storage, decreasing turgidity, and allowing the plant to move in accordance to the wind. A male would use this method of "movement" to fertilize nearby females.