Photosynthesis and Partitioning Flashcards
What is a source?
Provides assimilates. e.g. green photosynthesising leaves.
What is a sink?
Uses assimilates. e.g. flowers, seeds, developing leaves.
How much solar energy is outside of the spectrum so cannot be used by plants?
51.3%
How is energy lost?
Energy lost by reflection
NPQ- energy dissipated as heat
Carbohydrate synthesis loss
What is photorespiration?
Carbon or O2 is fixed into sugars.
Wasted energy
What is the reaction of photorespiration, and what do the products do?
RuBisCO + O2 ~> 2 phosphoglyolate + 3 phosphoglycerate
2 phosphoglycolate: Useless, costs energy to turn it into something useful
3 phosphoglycerate: Stores energy
What is non photochemical quenching (NPQ)?
Photosynthetic proteins absorb excess energy and dissipate it as heat.
Done by the Xanthophyll cycle.
What is the Xanthophyll cycle?
Violaxanthin ~> Antheraxanthin ~> Zeaxanthin
Done by light stress
What does Zeaxanthin do?
Protects lipid membranes
Stimulates NPQ
What is partitioning?
Fewer assimilates go to roots, stems and tillers and more go into growth and grain filling
What did the sugar beet ten year breeding programme do to the ratio of AGM : BGM and Marc : Sugar
AGM : BGM
1:2 ~> 1:2.8
Marc : Sugar
1:3 ~> 1:3.8
What is sink strength determined by?
Determined by genetics
Also by biotic and abiotic stresses.
What is SWEET11?
A group of sugar transporters.
Expressed heavily in developing grains