Wheat ear carbon assimilation and nitrogen remobilization contribute significantly to grain yield

Abstract

The role of wheat ears as a source of nitrogen (N) and carbon (C) in the grain filling process has barely been studied. To resolve this question, five wheat genotypes were labeled with 15 N-enriched nutrient solution. N remobilization and absorption were estimated via the nitrogen isotope composition of total organic matter and Rubisco. Gas exchange analyses showed that ear photosynthesis contributed substantially to grain filling in spite of the great loss of C due to respiration. Of the total kernel N, 64.7% was derived from the N acquired between sowing and anthesis, while the remaining 35.3% was derived from the N acquired between anthesis and maturity. In addition, 1.87 times more N was remobilized to the developing kernel from the ear than from the flag leaf. The higher yielding genotypes showed an increased N remobilization to the kernel compared to the lower yielding genotypes. In addition, the higher yielding genotypes remobilized more N from the ears to the kernel than the lower yielding genotypes, while the lower yielding genotypes remobilized more N from the flag leaf to the kernel. Therefore, the ears contribute significantly toward fulfilling C and N demands during grain filling.

Stability of wheat grain yields over three field seasons in the UK

“…In addition to flag leaf photosynthesis, ear photosynthesis also contributes to grain filling (Sanchez‐Bragado, Molero, Reynolds, & Araus, ; Zhou et al., ), especially under abiotic stress (Abbad, El Jaafari, Bort, & Araus, ). Moreover, the source–sink balance can regulate photosynthesis (Paul & Foyer, ) and grain filling (Paul, Oszvald, Jesus, Rajulu, & Griffiths, ), impacting directly on wheat yields (Valluru, Reynolds, & Lafarge, ).…”

Photosynthesis in non‐foliar tissues: implications for yield

“…In cereals, although leaf photosynthesis plays a central role in biomass accumulation and yield formation over the entire growing season (Fischer et al, 1998;Gu et al, 2014), the photosynthetic activity of the ear has been shown to dramatically contribute to the pool of carbohydrates translocated to the developing grains over the post-anthesis stages (Tambussi et al, 2005;Tambussi et al, 2007;Maydup et al, 2010;Sanchez-Bragado et al, 2014). Although on an area basis, the ear CO 2 assimilation rate is lower than that of the flag leaf (Tambussi et al, 2005;Tambussi et al, 2007;Zhou et al, 2016), experimental evidence suggests that in bread and durum wheat, ear photosynthesis can contribute to the individual grain weight yield component by up to 70% in a large range of genotypes (Maydup et al, 2010) and contrasting environments (Sanchez-Bragado et al, 2014). Similarly to wheat, in Hordeum vulgare (barley), shading experiments revealed a significant contribution of the ear (up to 50%) to grain weight and therefore yield (Bort et al, 1994).…”

Natural genetic variation in photosynthesis: an untapped resource to increase crop yield potential?

“…Furthermore, the assimilates produced in the spike are directly translocated into the grains (Carr and Wardlaw, ) leading to a contribution to GW between 10 and 45% depending on environmental conditions and genotype tested (Maydup et al , ; Sanchez‐Bragado et al , ). Indeed a large variation in gross spike A (calculated as the sum of A and dark respiration (R d ) as a proxy of respiration in the light) has been shown in both durum and bread wheat (Maydup et al , ; Molero et al , ; Zhou et al , ; Sanchez‐Bragado et al , ), suggesting the existence of natural genetic diversity for exploitation. For instance, the presence of awns (lemma‐derived organs) has been considered an important source of external CO 2 assimilation of the spike (Maydup et al , ) although other factors such a spike morphology (e.g.…”