Physiologically, living things regulate the intake and removal of various metabolic precursors within their systems. In this context, it is true that plants will not increase their CO2 uptake in response to increased levels of the gas (CO2) in the atmosphere.
Additionally, plants will not increase their relative significance in the removal and sequestration of CO2 (a greenhouse gas) despite the characterizing expectations. It is important to agree that most terrestrial and aquatic plants only absorb considerable amount of CO2 during photosynthesis (Taub, 2010). This uptake stops at the optimal levels despite the concentration of the gas in the atmosphere.
The phenomenon is termed as ‘downregulation’ as indicated earlier. For example, experiments (using soya beans leaves) indicate that plants will only synthesis enough Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) to operate in the Calvin Cycle depending on the energy demands of the concerned plants.
This is not dictated by the levels of CO2 in the atmosphere. Plants usually make and store ATP only to their respective optimal levels. Thus, they can minimally reduce the atmospheric CO2 concentration.
Obviously, the levels of CO2 intake might increase tremendously at the initial stages of the photosynthetic processes; nonetheless, this trend is bound to reduce upon saturation of plant cells with the gas (CO2). In the Calvin cycle, CO2 sequesters/combines with Rubisco to form 1, 3-Bisphosphoglycerate. The process requires a constant supply of Rubisco (Raghavendra, 2000).
Despite the abundance of CO2, the cycle cannot proceed minus Rubisco whose synthesis is not pegged to the CO2 abundance but to the physiological demands of the concerned plants. This is an important provision that indicates why plants should not be considered as the ultimate liberator from greenhouse gases.
When plants have synthesized and stored enough energy they require, they will obviously disable the Calvin Cycle during dark stage of photosynthesis. For example, plants will hardly synthesis metabolites more than they require for immediate use and storage. The metabolic cycles within terrestrial plants are under stringent regulations.
This is evident during photosynthesis where various processes are regulated accordingly. It is important to agree that various processes within the plant regulatory systems are responsive to environmental factors. Nonetheless, the alleged response can only occur to some levels despite the CO2 increment. This provision is relevant in this case.
Plants should not be expected to respond extraordinarily to the environmental factors (Shwartz, 2002). It is agreeable that plants need CO2 for photosynthetic processes and they can also increase their responses depending on the levels of such precursors; however, this is only relevant to some extent.
Although atmospheric scientists prospect to enhance the growth of plants in order to remove excess CO2 from the atmosphere, this will not materialize as expected. There are numerous challenges that characterize this move. These consider physiological provisions of various plants with regard to photosynthesis.
The aspect of ‘downregulation’ mentioned earlier is relevant in this context. There are various physiological limitations that regulate plants’ metabolic, photosynthetic, and other physiological systems. Shwartz (2002) argues that higher CO2 concentrations might retard the growth of some plants contrary to the expected higher CO2 sequestration rates. This is an important provision when considered critically in this context.
For example, the tissues of most terrestrial plants might change their chemical compositions in response to higher CO2 levels thus causing their premature death. Consequently, plants must undergo ‘downregulation’ in order to restore the situation. This provision defies the claims that plants will help in reducing CO2 levels in the atmosphere.
References
Raghavendra, A. (2000). Photosynthesis: A comprehensive treatise. Cambridge, UK: Cambridge University Press.
Shwartz, M. (2002). Climate change surprise: High carbon dioxide levels can retard plant growth, study reveals. Web.
Taub, D. (2010). Effects of Rising Atmospheric Concentrations of Carbon Dioxide on Plants. Nature Education Knowledge. Web.