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fotosyntese øget ved gensplejsning Genetic manipulated crop use more sunlight to grow

  • 17 November 2016

Scientists have improved "the most important biological process on the planet" – photosynthesis. This is a breakthrough, published in the journal Science, Scientists used genetic modification to increase the amount of sunlight energy crop plants can channel into food production.
That increased yield in an experimental crop by 15%. Researchers say this is a critical step towards increasing crop production to feed a growing global population. Lead researcher Prof Stephen Long, based at the the University of Illinois and the University of Lancaster, said decades of research into the 140-step process by which plants convert sunlight energy into food had revealed specific inefficiencies in crops – or bottlenecks The new research has tackled one of those bottlenecks. Researchers targeted a plant's inbuilt Sun-protection mechanism Plants have evolved to produce food using sunlight energy, but they have also evolved to protect themselves from Sun damage, which slows the process down. To protect itself, the leaf induces a process that gets rid of excess energy as heat. When a cloud moves across the Sun, there's less sunlight energy – the plant could use it all, but it carries on dispensing that energy as heat. So what we've done is speed up the process by which that heat loss switches off. The team inserted extra copies of the genes responsible for this heat-loss switch.
And when they then grew their genetically modified crop, it grew 15% larger than normal. "They are now making this change in rice, in soy bean and wheat Globally – rice, wheat, maize and soybean are the biggest crops. By 2050 the world will need to grow 70% more food, as the global population rises to more than nine billion people. We don't yet know if these plants will require more of other resources like water.

Crop plants protect themselves from excess sunlight by dissipating some light energy as heat, readjusting their systems when shadier conditions prevail.

But the photosynthetic systems do not adapt to fluctuating light conditions as rapidly as a cloud passes overhead, resulting in suboptimal photosynthetic efficiency.
Kromdijk et al. sped up the adaptation process by accelerating interconversion of violaxanthin and zeaxanthin in the xanthophyll cycle

and by increasing amounts of a photosystem II subunit.

Tobacco plants tested with this system showed about 15% greater plant biomass production in natural field conditions.

Science, p. 857

Crop leaves in full sunlight dissipate damaging excess absorbed light energy as heat.

When sunlit leaves are shaded by clouds or other leaves, this protective dissipation continues for many minutes and reduces photosynthesis.

Calculations have shown that this could cost field crops up to 20% of their potential yield.

The scientists describe the bioengineering of an accelerated response to natural shading events in Nicotiana (tobacco), resulting in increased leaf carbon dioxide uptake and plant dry matter productivity by about 15% in fluctuating light.

Because the photoprotective mechanism that has been altered is common to all flowering plants and crops, the findings provide proof of concept for a route to obtaining a sustainable increase in productivity for food crops and a much-needed yield jump.

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