Sulfur dioxide assimilation

Sulfur is assimilated by plants as the sulfate ion, S04 . In addition, in areas where the atmosphere is contaminated with SOj, sulfur may be absorbed as sulfur dioxide by plant leaves. Atmospheric sulfur dioxide levels have been high enough to kill vegetation in some areas (see Chapter 11). However, some experiments designed to show SO2 toxicity to plants have resulted in increased plant growth where there was an unexpected sulfur deficiency in the soil used for the experiment. 

The discovery that certain bacteria could carry out photosynthesis opened up a new field of photosynthetic research. It was found that certain green-, red-, purple-, and brown-colored bacteria could produce organic matter from carbon dioxide upon illumination. The formation of organic matter was not accompanied by oxygen evolution. As a result of work with the green sulfur bacteria, van Niel (21) showed that their CO2 assimilation process was in close agreement with the following equation ... 

Arnon and his group have definitively established that ferredoxins (iron-sulfur proteins noted for their strongly electronegative redox potentials) are the primary electron acceptors in photosynthesis, and that they are essential electron carriers for the light-induced generation of reducing power and ATP formed in the processes of cyclic and non-c clic photophosphorylation. Reducing power—either reduced ferredoxin or reduced nicotinamide adenine dinucleotides, NAD(P)H—and ATP constitute the assimilatory power required for the further assimilation in the dark of carbon dioxide, nitrate and sulfate. ... 

The types of processes that are reviewed in this section are those that have an elevated temperature as a common denominator and, by the use of this, they target the thermally labile nature of the sulfur-sulfur bonds in the crosslinks. There are quite a few examples where chemical agents have also been used in the process to assist in the devulcanisation of the rubber. In these cases, the chemical agents that have been chosen have often been similar to those that are used in the mechanical-chemical processes (Section 4.5) and often their assimilation into the rubber matrix has been assisted by solvents that have a high affinity for both the rubber and the chemical agents. Other processes of this type have employed solvents (e.g., supercritical carbon dioxide (CO2), supercritical water, alcohols and so on) on their own, without any other chemicals, and sometimes they have reacted with the crosslinks and/or the polymer chains. 

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