title: POTASSIUM ALLEVIATES THE INHIBITORY ACTION OF AMMONIUM UPON THE PHOTOSYNTHETIC RECOVERY OF NOSTOC FLAGELLIFORME (CYANOPHYCEAE) DURING REHYDRATION1.
abstract: Effects of ammonium on the photosynthetic recovery of Nostoc flagelliforme Berk. et M. A. Curtis were assayed when being rehydrated in low-K+or high-K+medium. Its photosynthetic recovery was K+limited after 3 years of dry storage. The potassium absorption of N. flagelliforme reached the maximum after 3 h rehydration in low-K+medium but at 5 min in high-K+medium. The K+content of N. flagelliforme rehydrated in high-K+medium was much higher than that in low-K+medium. The maximal PSII quantum yield (Fv/Fm) value of N. flagelliforme decreased significantly when samples were rehydrated in low-K+medium treated with 5 mM NH4Cl. However, the treatment of 20 mM NH4Cl had little effect on its Fv/Fmvalue in high-K+medium. The relative Fv/Fm24 h EC50(concentration at which 50% inhibition occurred) value of NH4+in high-K+medium (64.35 mM) was much higher than that in low-K+medium (22.17 mM). This finding indicated that high K+could alleviate the inhibitory action of NH4+upon the photosynthetic recovery of N. flagelliforme during rehydration. In the presence of 10 mM tetraethylammonium chloride (TEACl), the relative Fv/Fm24 h EC50value of NH4+was increased to 46.34 and 70.78 mM, respectively, in low-K+and high-K+media. This observation suggested that NH4+entered into N. flagelliforme cells via the K+channel. Furthermore, NH4+could decrease K+absorption in high-K+medium.
authors.affiliation: College of Life Sciences, Central China Normal University, Wuhan 430079, Hubei, China Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, China.
authors.forename: Ying-Hui
authors.initials: YH
authors.lastname: Liu
authors.affiliation: College of Life Sciences, Central China Normal University, Wuhan 430079, Hubei, China Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, China.
authors.forename: Guo-Zheng
authors.initials: GZ
authors.lastname: Dai
authors.affiliation: College of Life Sciences, Central China Normal University, Wuhan 430079, Hubei, China Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, Hubei, China.
authors.forename: Bao-Sheng
authors.initials: BS
authors.lastname: Qiu
keywords: Nostoc flagelliforme; ammonium; cyanobacterium; photosynthesis; potassium