Photosynthesis With Low CO2

overhead view of green plants growing in water

Biological Strategy

Stoneworts

AskNature Team

Image: Jeremy Halls / Flickr / CC BY - Creative Commons Attribution alone

Adapt Behaviors

The environment is constantly changing, and if living systems can’t adapt to these changes, they don’t survive. Environmental changes can be cyclic such as seasons, sudden such as floods or forest fires, or gradual but long-term, such as ecosystems shifting from early to mature stages. These changes require some flexibility in behavioral responses to match the specific conditions. For example, as a fish called the lamprey swims, it constantly faces changes in currents. Skin sensors help it detect those changes and adjust its motion accordingly.

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Regulate Cellular Processes

Cells are the basic building blocks of all living systems, so cellular processes dictate how physiological processes occur within those systems. Cells (whether entire unicellular organisms or parts of multicellular living systems) grow, metabolize nutrients (that is, chemically transform them), produce proteins and enzymes, replicate, and move. Cells as part of multicellular systems rarely act alone, instead having ways to signal to start and complete simple to quite complex interactions. How skin heals is a good example of the role of cellular processes. Blood cells called platelets release clotting factors to stop the bleeding; white blood cells rid the area of foreign materials and release molecules to coordinate healing; cells called fibroblasts start rebuilding using proteins called collagen; new blood vessels form; and skin cells called keratinocytes create the new surface.

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Capture, Absorb, or Filter Chemical Entities

Living systems often require chemical elements and chemical compounds, including complex sugars, proteins, and odor-making compounds, to perform critical activities. These compounds exist in various states–solid, liquid, and gas–and are ubiquitous in soil, water, and air. This requires that living systems not only have ways to capture, absorb, or filter them, but also ways to differentiate among them, selecting those that are valuable or harmful. For example, mangrove trees live with their roots in salty water and sediments. Various mangrove species have different strategies for removing salt from the water they take in so that their tissues can use the fresh water.

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Plants

Phylum Plantae (“plants”): Angiosperms, gymnosperms, green algae, and more

Plants have evolved by using special structures within their cells to harness energy directly from sunlight. There are currently over 350,000 known species of plants which include angiosperms (flowering trees and plants), gymnosperms (conifers, Gingkos, and others), ferns, hornworts, liverworts, mosses, and green algae. While most get energy through the process of photosynthesis, some are partially carnivores, feeding on the bodies of insects, and others are plant parasites, feeding entirely off of other plants. Plants reproduce through fruits, seeds, spores, and even asexually. They evolved around 500 million years ago and can now be found on every continent worldwide.

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Plants in calcareous peatlands photosynthesize in low CO2 levels by taking up bicarbonate and converting it to CO2.

“Some plant species live entirely submerged. The leaves are often very thin, with a large surface area, and lack stomata. Some of these plants are rooted in the bottom, but others have no roots at all (for instance Utricularia spp.). Waters around these plants can be still, slowly moving, or rapidly mixing as in case of rivers and lakes with peatland margins. Such plants take up carbon dioxide (CO₂) and nutrients directly into the leaves from the water, just in the way that bryophytes do. Carbon dioxide is rarely limiting, but in waters with very high pH (as in calcareous fens) the availability of CO₂ is much reduced, and some plants have the ability to take up bicarbonate (HCO₃ -), which is then converted to CO₂ in the cell and used in . Examples are the stoneworts (Characeae), which are characteristic species in calcareous waters, and several species of Myriophyllum and Ceratophyllum (Hutchinson 1975). Given that there are enough plants, they can produce the oxygen required for respiration themselves.” (Rydin and Jeglum 2006:46-47)