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

Borrill P, Fahy B, Smith AM, Uauy C - PLoS ONE (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: John Innes Centre, Norwich Research Park, Norwich, United Kingdom.

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.

No MeSH data available.


Related in: MedlinePlus

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 (***).
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pone.0134947.g001: 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 (***).

Mentions: Under our growing conditions the NAM RNAi plants developed similarly to control plants before anthesis, reaching anthesis one day later than control plants at 53 days after sowing (p = 0.008, 47 control and 50 RNAi plants, transgenic line L19). After anthesis the NAM RNAi plants showed a strong delay in monocarpic senescence. Their flag leaves retained high chlorophyll levels and high rates of photosynthesis for approximately ten days longer than those of control plants (Fig 1). In control plants both chlorophyll content and the rate of photosynthesis fell from a maximum to nearly zero between 20 and 30 days after anthesis (DAA). In the NAM RNAi plants this fall occurred ten days later, between 30 and 40 DAA. Similar development and senescence patterns were observed in a second transgenic line (L23). L23 NAM RNAi plants reached anthesis 3 days later than control plants at 59 days after sowing (p < 0.001, 50 control and 49 RNAi plants). Flag leaf chlorophyll content and rate of photosynthesis were maintained at high levels for longer in L23 NAM RNAi than control plants (S1 Fig), similar to L19.


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

Borrill P, Fahy B, Smith AM, Uauy C - PLoS ONE (2015)

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 (***).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4524614&req=5

pone.0134947.g001: 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 (***).
Mentions: Under our growing conditions the NAM RNAi plants developed similarly to control plants before anthesis, reaching anthesis one day later than control plants at 53 days after sowing (p = 0.008, 47 control and 50 RNAi plants, transgenic line L19). After anthesis the NAM RNAi plants showed a strong delay in monocarpic senescence. Their flag leaves retained high chlorophyll levels and high rates of photosynthesis for approximately ten days longer than those of control plants (Fig 1). In control plants both chlorophyll content and the rate of photosynthesis fell from a maximum to nearly zero between 20 and 30 days after anthesis (DAA). In the NAM RNAi plants this fall occurred ten days later, between 30 and 40 DAA. Similar development and senescence patterns were observed in a second transgenic line (L23). L23 NAM RNAi plants reached anthesis 3 days later than control plants at 59 days after sowing (p < 0.001, 50 control and 49 RNAi plants). Flag leaf chlorophyll content and rate of photosynthesis were maintained at high levels for longer in L23 NAM RNAi than control plants (S1 Fig), similar to L19.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: John Innes Centre, Norwich Research Park, Norwich, United Kingdom.

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.

No MeSH data available.


Related in: MedlinePlus