Ear photosynthesis in C3cereals and its contribution to grain yield: Methodologies, controversies, and perspectives

TAMBUSSI E.A.; MAYDUP M.L.; CARRIÓN C.A.; GUIAMET J.J.; J.L. ARAUS

Journal of Experimental Botany

Oxford University Press

Año: 2021 vol. 72 p. 3956 - 3970

In C3 cereals such as wheat and barley, grain filling was traditionally explained as being sustained by assimilates fromconcurrent leaf photosynthesis and remobilization from the stem. In recent decades, a role for ear photosynthesisas a contributor to grain filling has emerged. This review analyzes several aspects of this topic: (i) methodologicalapproaches for estimation of ear photosynthetic contribution to grain filling; (ii) the existence of genetic variability inthe contribution of the ear, and evidence of genetic gains in the past; (iii) the controversy of the existence of C4 metabolism in the ear; (iv) the response of ear photosynthesis to water deficit; and (v) morphological and physiologicaltraits possibly related to ear temperature and thermal balance of the ear. The main conclusions are: (i) there are anumber of methodologies to quantify ear photosynthetic activity (e.g. gas exchange and chlorophyll fluorescence)and the contribution of the ear to grain filling (individual ear shading, ear emergence in shaded canopies, and isotopecomposition); (ii) the contribution of ear photosynthesis seems to have increased in modern wheat germplasm; (iii) thecontribution of the ear to grain filling increases under resource-limitation (water deficit, defoliation, or pathogen infection); (iv) there is genetic variability in the contribution of the ear in wheat, opening up the possibility to use this traitto ameliorate grain yield; (v) current evidence supports the existence of C3 metabolism rather than C4 metabolism; (vi)the ear is a ‘dehydration avoider organ’ under drought; and (vii) thermal balance in the ear is a relevant issue to explore, and more research is needed to clarify the underlying morphological and physiological traits.