Plant movement is an integral part of Earth’s history. Throughout the planet, plants have moved from water to land and back. This process is called translocation and has been happening for millions of years.
During this time, plant species have moved around and across open waters, moving from waterfall to waterfall or stream to stream. Once they reach a favorable location, they stabilize and grow in size and thickness, forming lush vegetation that shields itself from the elements.
This is very important when it comes to protecting against natural disasters like hurricanes or flooding as they can quickly destroy vegetation that protects against heat and cold.
uprooted trees protect themselves from precipitation and wind by having thick scales that contain water. These trees also grow large enough to Shade themselves off of other plants to protect themselves.
Loss of water through pores in the plant cell walls
Evidence of plant movement is twofold: transpiration and evaporation. Transpiration is when moisture from the plant is released through the leaves, roots, and soil. Evaporation takes place during dry periods, when water evaporates from the plant cells.
Transpiration is an important process for a plant because it controls humidity levels in its environment. A dry environment will not retain as much moisture as a wet one does. Plants that do not transpire are saying something about their drought tolerance.
If a plant does not evaporate enough during a dry period, it may be saying that it does not need to water often enough. A poor dehydrator can also make this sound like an issue of too little water.
Convergence of xylem elements towards the stem
A camouflage patterned lining that develops over time around a plant stem. Convergence of xylem elements towards the stem indicates that the plant has lived and functioned in water at some point in its history.
When a plant grows large roots, it moves its water source away from itself and concentrates on obtaining more moisture from surrounding conditions or from plants around it.
This is similar to what fish do when they reach a new area where they find freshwater, rich in oxygen and other necessary chemicals. They need more water to sustain themselves in and out of their cells, so they move to locations with more water.
If a plant had convergence of xylem elements when it grew, it indicated that it had lived in an area with little or no water.
Thinner stem walls
A plant’s stem wall may be thicker in wet periods or thinner in dry periods. This may indicate a more terrestrial lifestyle, where plants relied on moisture to grow.
Drier plants may also have thinner stems, which would be more difficult to transport and maintain in an environment where water was limited.
Thin stems may also be related to faster growing plants that needed less water during dry periods. Plants that need less water may grow very quickly, resulting in thin stem walls.
Another way to determine whether a plant is terrestrial or aquatic is by looking at the leaf shape. If the leaf is triangular with rounded corners, then it is land-based. If it is round with sharp angles, then it is underwater.
Reduction in ground tissue thickness
Another sign of plant movement is reduction in leaf thickness. When plants are immersed in water, it takes more water to maintain the same thickness of leaves.
How much water a plant has depends on how big its root system is. A small-sized root system needs less water than one that is bigger.
Size also plays a role in how quickly plants consume their water. Plants with smaller sizes tend to consume morewater than those with bigger sizes due to less self-control.
Increase in vascular tissue thickness
Another telltale sign of plant movement is increased thickness of the leaves. When a plant undergoes growth, the thickerThe thicker the leaf becomes, the more oxygen it receives and processes it. This is true of all plants, but especially for trees who must often grow in unison with their environment.
Growth also occurs in diameter at stem or trunk. A measure of development called meristics are found at this stage. When looking for evidence of movement, these can be noted.
As plants grow they need to process water and nutrients which requires room for expansion. If a plant did not develop during its initial growth cycle, then evidence of this is that they have expanded in size.
Development of roots and leaves
Another important sign of a plant’s transition from water to land is development of roots and leaves. While this phenomenon is more rare in plants, it can happen!
When a plant grows new roots or leaves, it should be examined for evidence of growth around the stem, which is typically thickened and rooted.
It is also worth examining the leaf bases as they may fold up when mature. When these features are present, paleobotanists would look for evidence that the plant moved from water to land during its life cycle.
Finally, looking for evidence of fungus deposition is a good way to confirm a plant moved from water to land. Fungus indicates an organism did not have adequate hydration, which prevents evidence from being retained in the rock record.
Fragmentation of cells in tissues surrounding the stem
A normal looking stem is one that has suffered only minor tissue damage, such as a stem being gnawed on by an aggressive plant. In contrast, overweight plants or plants that have lost their leaves are cautionary signs that the situation is poor.
Wealthy plants or ones with weak stems are indications of poor water retention. If a plant loses its leaves, it should gain in volume and thickness as it gains more water retention.
Wealthy plants may also have fragmented cells surrounding the tissue surrounding the stem. This may be due to poor water retention or excessive growth.
Loss of buoyancy due to air-filled cavities within plants
When a plant is moved from water to land, it must lose some of its initial buoyancy to settle into the soil. This is because the plant needed some space to root itself down into the ground.
This process of sinking and re-solidification occurs more than once as the plant grows, so at some point it will be completely solid. Some plants can maintain their softness longer than others, especially if they are more fragile.
If you were to shake a leafy green plant real hard, would it still be flimsy and soft? Probably not! Eventually, sufficient stress is applied enough times that it hardens up.
This process takes place at the same time that it moves away from water, which is when plants transfer their leaves to land.
