Investigating The Role Of Alternative Oxidase In The Effects On Photosynthesis And Photosynthesis-dependent Isoprene Release

Respiration and photosynthesis, as the most important metabolisms, have closeinteractions with other substance metabolisms. Respiration is a central metabolicprocess that contributes in many different ways to cell function. To realize therelationship among respiration, photosynthesis, and other ways of substancemetabolism could help us to know metabolism clearly. The significant characteristicdistinguishing plant and animal is cyanide-resistant respiration pathway (alternativepathway). And there has been an increasing interest in alternative pathway in recentyears because of its important role in metabolism. So in this paper, we studied therelationship among respiration (particularly alternative pathway), photosynthesis, andphotosynthesis-dependent escaping gas (isoprene) release, and disgussed theinteractions among them.In order to study the interactions between respiration and photosynthesis, First,we use chlorophyll fluorescence spectrometer PAM2500to measure the Chlorophyllfluorescence parameters in bean (Phaseolus vulgaris L.）leaves suffered from differentconcentrations of NaCl to confirm a stress condition (200mmol/L), and discuss theregulations of these parameters. Then, we use the specific inhibitor SHAM to researchthe interaction between AOX and photosynthesis under the200mmol/L NaClstress.The results suggested that inhibiting AOX can lead to a decrease ofphotosynthetic rate. Thus, we can conclute that AOX could protect photosynthesisunder salt stress.The regulations of isoprene release in poplar (Populus alba L.) leaves under acontinuousing irradiation were discussed. After exposing the fully expanded poplarleaves to continuous irradiation, the levels of photosynthetic rate and isopreneemission were increased. Continuous irradiation also enhanced the levels of totalrespiration and the capacities of the cytochrome and alternative respiratory pathways.Pretreatments with the inhibitors of the cytochrome and alternative respiratorypathways, salicylhydroxamic acid and KCN, decreased the levels of photosyntheticrate and isoprene emission. These treatments also caused the decreases in theimmediate quantum yield of PSⅡ electron transport and photochemical quenching. These results suggest that respiration plays a role in mediating the photosynthesis andisoprene emission.The ragulations of isoprene release in poplar leaves under different temperatureswere also discussed. The level of isoprene emission was increased with the increase oftemperature, while mitochondrial respiration was decreased under this condition.Under various temperatures, treatment with the chemical inhibitors of mitochondrialrespiration further enhanced the level of isoprene emission. However, this treatmenthad little effects on the photosystemⅡ chlorophyll fluorescence but decreasedphotosynthetic rate. Based on theses observations, the relationship among themitochondrial respiration, isoprene emission, and photosynthesis under changingtemperature was discussed in this paper.