Abstract
During grain filling in C3 cereals, the shoot (particularly the flag leaf) and the ear are believed to play major roles as sources of assimilates. However, both the cost and the intrusive nature of most of the methodologies available to investigate this have prevented conclusive results being obtained. This study compared the carbon isotope composition (δ(13)C) in its natural abundance in mature kernels with the δ(13)C of the water-soluble fraction of the peduncle, glumes, and awns to assess the relative contribution of the shoot (understood as the whole set of photosynthetic organs below the peduncle) and ear to grain filling in a set of highly productive wheat lines from the International Maize and Wheat Improvement Center, Mexico, under good agronomic conditions. In overall terms, the contribution of the ear was greater in comparison with that of the shoot. The specific contribution of the flag leaf blade to grain filling was also assessed by comparing the δ(13)C of grains with the δ(13)C of the water-soluble fraction of the flag leaf and the awns. The contribution of the flag leaf was minor, ranging between 3 and 18%. Complementary analyses performed such as gas-exchange rates and the accumulated water-soluble carbohydrates in both organs and light intercepted by the canopy at different strata suggested that the ear has a photosynthetic capacity at least comparable to that of the flag leaf. In this sense, selection for a higher contribution of ear photosynthesis to grain yield in breeding programmes could be addressed with the use of stable isotopes.
Highlights
The United Nations prediction for 2050 is that the world’s human population will reach 9.3 billion (Food and Agriculture Organization of the United Nations, 2013)
This study compared the carbon isotope composition (δ13C) in its natural abundance in mature kernels with the δ13C of the water-soluble fraction of the peduncle, glumes, and awns to assess the relative contribution of the shoot and ear to grain filling in a set of highly productive wheat lines from the International Maize and Wheat Improvement Center, Mexico, under good agronomic conditions
The ear in wheat and other small-grain cereals is believed to play a significant role as a source of photoassimilates during grain filling, under drought or other abiotic stresses and under good agronomical conditions
Summary
The United Nations prediction for 2050 is that the world’s human population will reach 9.3 billion (Food and Agriculture Organization of the United Nations, 2013). One of the avenues proposed to increase yield potential and improve adaptation to abiotic stresses, such as drought, is to select for higher ear photosynthesis (Tambussi et al, 2005, 2007; Parry et al, 2011). The ear in wheat and other small-grain cereals is believed to play a significant role as a source of photoassimilates during grain filling, under drought or other abiotic stresses and under good agronomical conditions
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