Carbon assimilation for biomass

Lead Research Organisation: Rothamsted Research
Department Name: Unlisted


There is an urgent need to develop perennial second generation bioenergy crops that have both a high yield and resource use efficiency. Since crop biomass is an expression of the net photosynthesis of plants over time, optimising carbon assimilation and partitioning by plants is central to improving existing crops and developing new sources of bioenergy, which will contribute towards achieving a carbon-neutral planet. This project seeks to establish the extent of variation in photosynthetic capacity, photosynthetic rate and carbon partitioning in diverse germplasm of energy grasses and trees and the extent to which this contributes to yield and composition. The research will integrate fundamental biochemistry, physiology and molecular biology within the agronomic context. The project also seeks to identify genetic markers related to increased growth rate and aboveground carbon allocation.
Description During a study of the contribution of photosynthetic traits to biomass yield among 11 diverse species of willow, the light and CO2 dependence of photosynthesis were found to differ, with absolute rates at ambient and saturating CO2, together with maximum rates of Rubsico-limited and electron-transport-limited photosynthesis (Vcmax and J, respectively) varying by factors in excess of 2 between the extremes of performance. In spite of this, the ratio, J/Vcmax - indicative of the relative investment of resource into RuBP regeneration and RuBP carboxylation - was found to fall within a narrow range (1.9-2.5) for all genotypes over two successive years. Photosynthetic rate (µmol CO2 fixed m-2 sec-1) showed a strong, inverse correlation with total leaf area per plant. Photosynthetic capacity, expressed on a leaf area basis, showed a strong, positive correlation with yield among some of the species, but when expressed on a whole plant basis all species indicated a positive correlation with yield. Thus, both leaf area per plant and photosynthetic rate per unit leaf area contribute to this relationship. The abundance and kinetic characteristics of Rubisco play a pivotal role in determining photosynthetic rate per unit leaf area and so were determined for the chosen willow species, in parallel with Rubisco large subunit (LSU) gene sequencing. Significant differences in the rate constants for carboxylation and oxygenation as well as the affinity for CO2 were identified, and rationalized in terms of LSU sequence polymorphism. Those LSU sequences with isoleucine instead of methionine at residue 309 had up to 29% higher carboxylase rate constants. Furthermore, the A/Ci curves predicted from each distinct set of Rubisco kinetic parameters under otherwise identical conditions indicated substantial differences in photosynthetic performance. Thus, genetic traits relating specifically to Rubisco and by implication to photosynthetic performance were also identified.
Exploitation Route The results have increased our understanding of the underlying biochemistry and physiology. This new knowledge can be exploited by identifying the genetic basis of natural variation that can be used in breeding approaches for crop improvement or through biotechnological approaches
Sectors Agriculture, Food and Drink

Description Food, Health and Environmental Security 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact New breeding approaches to increase the yield & quality of crops. Palma de Mallorca, February 20 - 22nd, 2018
Year(s) Of Engagement Activity 2018
Description DEFRA University Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact This workshop brought together a group of universities with Defra policy teams / evidence specialists to explore the opportunities available through academic partnerships (including fellowships, studentships and other grant processes) and the benefits of engaging with external academic experts through developing contacts and networks.
Year(s) Of Engagement Activity 2018