Photosynthetic response of Microcystis aeruginosa PCC7806 to different concentrations of phosphorus supply was studied so as to elucidate if the declining process of Microcystis bloom under freshwater ecosystem is related to soluble reactive phosphorus (SRP) decrease in water volume. Growth rate of M. aeruginosa PCC7806 was significantly reduced under P-deficient conditions, and its photosynthetic activity in terms of rETR(max) (maximum electron transport rate) decreased significantly after 48 h growth, while it kept elevating and reached to a relative stable value when supplied with rich phosphorus of 0.6 mg/L With the increasing actinic irradiance along the rapid light curves of M. aeruginosa PCC7806 cultured under low-phosphorus level, qP (photochemical quenching) and rETR (relative electron transport rate) decreased greatly, and the increase in qN (non-photochemical quenching) and Phi(ps) (actual photochemical efficiency of PSII) was obviously inhibited. The affinity of M. aeruginosa PCC7806 to inorganic carbon was reduced evidently in 0.02 mg/L P compared with in 0.6 mg/L P. When P was reduced from 0.6 to 0.02 mg/L, the decreasing rate of rETR(max) (77%) was significantly greater than that of photosynthetic carbon assimilation (22%), which indicated that down-regulation of CO2 affinity caused by P-deficiency was, but not the only reason that resulted in the decline of photosynthetic efficiency. Instantaneous low-temperature significantly limited rETR(max) under rich-P condition but had no effect on it when P was insufficient, and 1% ethanol could enhance rETR(max) at low-P level but did not influence it at rich-P level. These two results proved that the decrease in thylakoid membrane fluidity caused by P-deficiency was another important reason that results in the decline of photosynthetic efficiency of M. aruginosa PCC7806. (c) 2010 Elsevier B.V. All rights reserved.
英文摘要:
Photosynthetic response of Microcystis aeruginosa PCC7806 to different concentrations of phosphorus supply was studied so as to elucidate if the declining process of Microcystis bloom under freshwater ecosystem is related to soluble reactive phosphorus (SRP) decrease in water volume. Growth rate of M. aeruginosa PCC7806 was significantly reduced under P-deficient conditions, and its photosynthetic activity in terms of rETR(max) (maximum electron transport rate) decreased significantly after 48 h growth, while it kept elevating and reached to a relative stable value when supplied with rich phosphorus of 0.6 mg/L With the increasing actinic irradiance along the rapid light curves of M. aeruginosa PCC7806 cultured under low-phosphorus level, qP (photochemical quenching) and rETR (relative electron transport rate) decreased greatly, and the increase in qN (non-photochemical quenching) and Phi(ps) (actual photochemical efficiency of PSII) was obviously inhibited. The affinity of M. aeruginosa PCC7806 to inorganic carbon was reduced evidently in 0.02 mg/L P compared with in 0.6 mg/L P. When P was reduced from 0.6 to 0.02 mg/L, the decreasing rate of rETR(max) (77%) was significantly greater than that of photosynthetic carbon assimilation (22%), which indicated that down-regulation of CO(2) affinity caused by P-deficiency was, but not the only reason that resulted in the decline of photosynthetic efficiency. Instantaneous low-temperature significantly limited rETR(max) under rich-P condition but had no effect on it when P was insufficient, and 1% ethanol could enhance rETR(max) at low-P level but did not influence it at rich-P level. These two results proved that the decrease in thylakoid membrane fluidity caused by P-deficiency was another important reason that results in the decline of photosynthetic efficiency of M. aruginosa PCC7806. (c) 2010 Elsevier B.V. All rights reserved.
