Invasive plants are versatile users of carbon

Posted on March 28, 2013

The growth, survival and competitive success of plants is crucially dependent on the efficiency with which they can exploit the key resources of light, nutrients and inorganic carbon through the process of photosynthesis.  Although their supply of carbon is mainly in the form of carbon dioxide (CO2), some plants can harness  bicarbonate (HCO3) when CO2 levels are low, and this ability to use multiple sources of carbon may help to give them a competitive edge.  In this connection, it’s of interest to know whether highly invasive aquatic plants can use bicarbonate.  Three such species, (Dense Waterweed (Egeria densa, from South America), Hornwort (Ceratophyllum demersum, from Europe) and Curly Waterweed (Lagarosiphon major, from South Africa), have invaded waterways around the world and their capacity to exclude native plants makes them three of the most aggressive and problematic waterweeds.  For each of these species, rates of photosynthesis at low, medium and high levels of alkalinity were measured in an experimental chamber, and the efficiency of bicarbonate use was assessed by plotting oxygen production as a function of bicarbonate concentration.   In all three cases, the rate of photosynthesis was fastest, and the efficiency of bicarbonate use greatest, when alkalinity was low (i.e., when bicarbonate was high), and it seems that all three of these global invaders adapt to low inorganic carbon availability by increasing their efficiency of bicarbonate use.  Under low-alkalinity conditions Lagarosiphon was the most efficient user of bicarbonate and had a higher rate of photosynthesis than the other two species.

Reference:  Cavalli, G., Riis, T. & Baattrup-Pedersen, A.  2012.  Bicarbonate use in three aquatic plants.   Aquatic Botany 98, 57– 60.