A paper just published in the Proceedings of the National Academy of Sciences USA (including Trevor Hodkinson, Botany, School of Natural Sciences, TCD; Trinity Centre for Biodiversity Research) highlights the role of leaf anatomical change in the evolution of a type of photosynthesis (classified as C4) that has allowed a large group of grass species to dominate warm regions of the world and become important crops such as maize, sorghum and sugarcane. C4 photosynthesis is a series of anatomical and biochemical modifications to the typical C3 pathway that increases the productivity of plants in warm and dry conditions. The C4 trait has evolved over 20 times in grasses, and all origins occurred within one species rich group. Leaf anatomy traits of grasses were quantified and analyzed in an evolutionary framework.
Statistical modeling indicates that C4 evolvability strongly increases when a particular type of anatomy (proportion of vascular bundle sheath) reaches 15%. A reduction in the distance between the bundle sheaths occurred before the evolution of the C4 grass group but not in other groups of grasses which lack the C4 trait. Therefore, when environmental changes promoted C4 evolution, suitable anatomy was present only in members of this group, explaining the clustering of C4 origins in this group. These results show that key alterations of leaf anatomy facilitated the repeated evolution of one of the most successful physiological innovations in flowering plant history.
Author
Trevor Hodkinson: hodkinst
Photo credit
Trevor Hodkinson