Letter: Letters: Protein problem

From DAVID MURRAY

In his article ‘Running down to Rio’ (2 May), Jeremy Leggett rightly
focuses on the major climatic effects anticipated from an increasing atmospheric
content of CO₂. Another serious consequence is a declining protein
content of leaves, fruits and seeds.

This will come about because the extra CO₂ available to the
leaves will go into sugars and their polysaccharide derivatives rather than
into amino acids, the building blocks of polypeptides or proteins.

There is clear evidence of this effect on leaf nitrogen content. The
leaves of most plants (C₃ types) growing under higher CO₂
regimes will be less nutritious for leaf-eating insects, or domestic animals
like cattle. A lower leaf nitrogen content also means that less serine and
glutamine can be transported to the seeds. This will lower the ceiling for
protein content for important food sources such as the legumes and wheat.

David Murray University of Sydney, Australia