Hill reaction

[1][2][3] Hill's finding was that the origin of oxygen in photosynthesis is water (H2O) not carbon dioxide (CO2) as previously believed.

Hill's observation of chloroplasts in dark conditions and in the absence of CO2, showed that the artificial electron acceptor was oxidized but not reduced, terminating the process, but without production of oxygen and sugar.

[6] Isolated chloroplasts placed under light conditions but in the absence of CO2, reduce and then oxidize artificial electron acceptors, allowing the process to proceed.

Chloroplasts placed under dark conditions and in the absence of CO2, oxidize the artificial acceptor but do not reduce it, terminating the process, without production of oxygen or sugar.

[4] The association of phosphorylation and the reduction of an electron acceptor such as ferricyanide increase similarly with the addition of phosphate, magnesium (Mg), and ADP.

Dilution does not cause a further increase in the rate in which ferricyanide is reduced with the accumulation of ADP, phosphate, and Mg to a treated chloroplast suspension.

Studies of light intensities revealed that the effect was largely on the light-independent steps of the Hill reaction.

[7] It is possible to introduce an artificial electron acceptor into the light reaction, such as a dye that changes color when it is reduced.

Plant cells with visible chloroplasts (from a moss, Plagiomnium affine )
Noncyclic photophosphorylation through light-dependent reactions of photosynthesis at the thylakoid membrane
A diagram of the Hill reaction which shows with the usage of an artificial electron acceptor such as DCPIP , and the chloroplast is subjected to light there is a release of oxygen, Also with the absence of CO 2 there is no sugar production
A diagram of the Hill reaction taking place under dark conditions there is no oxygen emitted and the no reduction of the electron acceptors occur
A diagram of the hill reaction under light conditions and the use of a natural electron acceptor
A diagram of the light-independent reaction as found by Arnon(1954) which shows the formation of sugar without the presence of light
The addition of DCPIP experimentally to a chlorophyll molecule containing solution which shows a change in color due to the reduction of DCPIP
Isolated chloroplasts from spinach leaves, viewed under light microscope