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. 2015 Aug 4;10(8):e0134947.
doi: 10.1371/journal.pone.0134947. eCollection 2015.

Wheat Grain Filling Is Limited by Grain Filling Capacity rather than the Duration of Flag Leaf Photosynthesis: A Case Study Using NAM RNAi Plants

Philippa Borrill  1 , Brendan Fahy  1 , Alison M Smith  1 , Cristobal Uauy  2
Affiliations

Wheat Grain Filling Is Limited by Grain Filling Capacity rather than the Duration of Flag Leaf Photosynthesis: A Case Study Using NAM RNAi Plants

Philippa Borrill et al. PLoS One. .

Abstract

It has been proposed that delayed leaf senescence can extend grain filling duration and thus increase yields in cereal crops. We found that wheat (Triticum aestivum) NAM RNAi plants with delayed senescence carried out 40% more flag leaf photosynthesis after anthesis than control plants, but had the same rate and duration of starch accumulation during grain filling and the same final grain weight. The additional photosynthate available in NAM RNAi plants was in part stored as fructans in the stems, whereas stem fructans were remobilised during grain filling in control plants. In both genotypes, activity of starch synthase was limiting for starch synthesis in the later stages of grain filling. We suggest that in order to realise the potential yield gains offered by delayed leaf senescence, this trait should be combined with increased grain filling capacity.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Flag leaf senescence characteristics of L19 NAM RNAi (open squares) and control (filled triangles) plants.
(A) Chlorophyll. For each time point, each flag leaf was measured with a hand-held chlorophyll meter at ten positions across the surface. Values are means of the average measurements for flag leaves from six plants (biological replicates), ± SEM (standard error of the mean). (B) Photosynthesis. The rate of photosynthesis was measured under ambient conditions using a portable photosynthesis system. Values are means of measurements on four to six plants (biological replicates), ± SEM. Asterisks denote significant differences between genotypes at p < 0.05 (*), p < 0.01 (**) and p < 0.001 (***).
Fig 2
Fig 2. Grain filling parameters in L19 NAM RNAi (open squares) and control (filled triangles) plants.
(A) Starch content, (B) fresh weight, (C) moisture content, (D) dry weight, (E) glucose content, (F) sucrose content, (G) fructose content, (H) AGPase activity and (I) starch synthase activity. Values are means of measurements on five or six individual plants (biological replicates), ± SEM. For each plant, measurements were on eight to ten grains from the centre of the main spike. For metabolite and enzyme assays, these grains were pooled to make a single extract per plant. Asterisks denote significant differences between genotypes at p < 0.05 (*), p < 0.01 (**) and p < 0.001 (***).
Fig 3
Fig 3. Fructan content of stem tissues in L19 NAM RNAi and control plants.
(A) Peduncle and internode tissues combined, (B) exposed peduncle, (C) enclosed peduncle, (D) internode 1 and (E) internode 2, (F) tissues harvested. Values are means of measurements on six individual plants (biological replicates), ± SEM. Asterisks denote significant differences between genotypes at p < 0.05 (*), p < 0.01 (**) and p < 0.001 (***).
See this image and copyright information in PMC

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