Photorespiration is a process that begins when Rubisc, RuBP, fixes molecular oxygen, as opposed to carbon dioxide, which ultimately leads to the evolution of carbon dioxide, CO2, from plants. ... Rubisco is a bifunctional enzyme that unlike the overwhelming majority of enzymes, which bind to one type of substrate, rubisco can accept both CO2 and O2, which lead to photosynthesis or photorespiration respectively. ...
Photorespiration occurs in C3 plants when the CO2 levels inside the leaf of a plant become low. ...
Several experiments have been conducted relating different variables to relative photorespiration rates such as drought, light intensities, oxidative stress, etc. ... Recently a few new findings on photorespiration were published in Plant Physiology Magazine. The mechanism of photorespiration has been in hot debate since the dawn of its discovery. ... For example, it was then found that upon initial illumination of air, the mutant plants “essentially lacked photorespiration”. ... Thus during drought cycles, it was determined that a photosynthesis-photorespiration model would explain that the O2 and CO2 recycling may be able to sustain electron transport rate, ETR, to as much as 75% of the maximum. This suggests that photorespiration plus recycling may drive “substantial” electron transport during drought. In conclusion, it was decided that an increase in photorespiration was caused under even just mild drought conditions and approximately proportionally thereafter (Abadia). ... It was reported that the leaves of the reed from fragmented parches displayed higher photorespiration rates compared to leaves from closed stands. “…Photorespiration (Rp) may act as a protection mechanism against excess light since the recycling of CO2 proceeds at the cost of excitation energy” (Bondar). ... stress could begin to provide some attributes to photorespiration that do not pose negative aspects of photorespiration. ...
The percentages of photosynthetic electrons dissipated by CO2 assimilation were calculated and found: In control leave more than 50% of the electrons were consumed in CO2 assimilation and 23% in photorespiration. Under severe stress, it was found that the percentages of electrons consumed in CO2 assimilation doubled in photorespiration. It was concluded that perhaps in photorespiration, the consumption of electrons reduces the likelihood of damage during times of water deficit (Fock 2002). ... Photosynthesis and photorespiration-related parameters were determined periodically during the growing season by measurements of gas exchange, photorespiratory enzyme activities and amino acid levels. ... On average at growth CO2 concentrations, net photosynthesis (A) increased 56% and photorespiration decreased 36% in terminal main stem leaves with CO2 enrichment. Net photosynthesis and photorespiration were suppressed 30% and 41%, respectively, by elevated O3 during late reproductive growth in the ambient CO2 treatment, but not in the elevated CO2 treatment.
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