How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

The Most Important Fodder Crop of the Arid and Semi-Arid Tropics
Bhatt, R.K., Baig, M.J. and Tiwari, H.S. 2007. Growth, biomass production, and assimilatory characters in Cenchrus ciliaris L. under elevated CO2 condition. Photosynthetica 45: 296-298.

Cenchrus ciliaris, to quote Bhatt et al., is a "perennial multi-cut, highly palatable, and nutritious grass species that can be utilized under cut-and-carry as well as under [the] grazing system of production," which characteristics are some of the reasons they report it is "the most important fodder grass species grown in arid and semi-arid tropics."

What was done
At the experimental facilities of the Indian Grassland and Fodder Research Institute of Jhansi, India, 30-day-old seedlings of C. ciliaris were transplanted to open-top chambers - maintained at either the ambient atmospheric CO2 concentration (360 ppm) or at an elevated CO2 concentration (600 ppm) - within which the plants were grown for an additional 120 days, "using recommended agronomical practices" and with irrigation "given as and when required." During this time of outdoor field growth, numerous plant properties and physiological processes were periodically measured; and at the end of the experiment the plants were harvested and other pertinent measurements made.

What was learned
Among other things, Bhatt et al. report that the extra 240 ppm of CO2 employed in their experiment increased the following plant parameters by the following percentages: plant height (44%), number of tillers (33%), leaf length (23%), leaf width (51%), leaf area index (234%), net photosynthetic rate per unit leaf area (25%), net photosynthetic rate per unit ground area (316%), total fresh weight (134%), total dry weight (193%), and whole-crop photosynthetic water use efficiency (34%).

What it means
The three Indian researchers conclude that "C. ciliaris grown in elevated CO2 throughout the crop season may produce more fodder in terms of green biomass," which is a colossal understatement, to say the least; especially when a 240-ppm increase in the air's CO2 concentration leads to a 193% increase in dry matter production (which translates into a 242% increase in dry matter productivity for the more standard 300-ppm increase in CO2 by which we index worldwide study results in our Plant Growth Databases. Surely, such a response will be an enormous boon to the many people living in the arid and semi-arid tropics in the years and decades to come, as the air's CO2 content continues its upward climb.

Reviewed 8 August 2007