Dwarf Water Lilies Nymphoides aquatica(J.F.Gmel)Kuntze have floating and submerged leaves.Some submerged aquatic vascular plants have a form of CAM(Crassulacean Acid Metabolism)called Submerged Aquatic Macrophyte(SAM)...Dwarf Water Lilies Nymphoides aquatica(J.F.Gmel)Kuntze have floating and submerged leaves.Some submerged aquatic vascular plants have a form of CAM(Crassulacean Acid Metabolism)called Submerged Aquatic Macrophyte(SAM)metabolism.Blue-diode based PAM technology was used to measure the Photosynthetic Oxygen Evolution Rate(POER:1O_(2)≡4e^(-)).Optimum Irradiance(E_(opt)),maximum POER(POER_(max))and quantum efficiency(α_(0))all vary on a diurnal cycle.The shape of the POER vs.E curves is different in seedling,submerged and surface leaves.Both E_(opt)and POER_(max)are very low in seedling leaves(E_(opt)≈104μmol photon m^(-2)s^(-1),PPFD;POER_(max)≈4.95µmol O_(2)g^(-1)Chl a s^(-1)),intermediate in mature submerged leaves(E_(opt)≈419µmol photon m^(-2)s^(-1)PPFD,POER_(max)≈38.1µmol O_(2)g^(-1)Chl a s^(-1))and very high in surface leaves(E_(opt)≈923µmol photon m^(-2)s^(-1)PPFD,POER_(max)≈76.1µmol O_(2)g^(-1)Chl a s^(-1)).Leaf titratable acid(C4 acid pool)is too small(≈20 to 50 mol H+m^(-3))to support substantial SAM metabolism.Gross daily photosynthesis of surface leaves is≈3.71 g C m^(-2)d^(-1)in full sun and as much as 1.4 gC m^(-2)d^(-1)in shaded submerged leaves.There is midday inhibition of photosynthesis.展开更多
Pigments are widely used as indices for estimation of phytoplankton biomass and composition,and many protocols have been developed to analyze pigments in phytoplankton.Different protocols were compared using four solv...Pigments are widely used as indices for estimation of phytoplankton biomass and composition,and many protocols have been developed to analyze pigments in phytoplankton.Different protocols were compared using four solvents(methanol,95%methanol,dimethylformamide,and 90%acetone)and two instruments(fluorometer and high-performance liquid chromatography(HPLC)coupled with diode array detector).Analysis of chlorophyll a(Chl a)with fluorometer could lead to over-or underestimation due to the interference from its derivatives in all probability.Among the four extractants,90%acetone had a high recovery for chlorophylls.In contrast,95%methanol was a poor extractant for chlorophylls due to the degradation of Chl a,especially in diatoms.The 95%methanol,however,had high extraction efficiencies for most diagnostic xanthophylls.Therefore,the selection of pigment analytical protocols should follow the specific purpose of phytoplankton study.In addition to fluorometry,an HPLC method with 90%acetone as extractant shall be a good choice for the analysis of Chl a to estimate phytoplankton biomass,especially for diatom-dominated samples,while an HPLC method with 95%methanol as extractant be more suitable to characterize different taxa in phytoplankton communities.展开更多
文摘Dwarf Water Lilies Nymphoides aquatica(J.F.Gmel)Kuntze have floating and submerged leaves.Some submerged aquatic vascular plants have a form of CAM(Crassulacean Acid Metabolism)called Submerged Aquatic Macrophyte(SAM)metabolism.Blue-diode based PAM technology was used to measure the Photosynthetic Oxygen Evolution Rate(POER:1O_(2)≡4e^(-)).Optimum Irradiance(E_(opt)),maximum POER(POER_(max))and quantum efficiency(α_(0))all vary on a diurnal cycle.The shape of the POER vs.E curves is different in seedling,submerged and surface leaves.Both E_(opt)and POER_(max)are very low in seedling leaves(E_(opt)≈104μmol photon m^(-2)s^(-1),PPFD;POER_(max)≈4.95µmol O_(2)g^(-1)Chl a s^(-1)),intermediate in mature submerged leaves(E_(opt)≈419µmol photon m^(-2)s^(-1)PPFD,POER_(max)≈38.1µmol O_(2)g^(-1)Chl a s^(-1))and very high in surface leaves(E_(opt)≈923µmol photon m^(-2)s^(-1)PPFD,POER_(max)≈76.1µmol O_(2)g^(-1)Chl a s^(-1)).Leaf titratable acid(C4 acid pool)is too small(≈20 to 50 mol H+m^(-3))to support substantial SAM metabolism.Gross daily photosynthesis of surface leaves is≈3.71 g C m^(-2)d^(-1)in full sun and as much as 1.4 gC m^(-2)d^(-1)in shaded submerged leaves.There is midday inhibition of photosynthesis.
基金Supported by the Joint Project of Guangxi Provincial and China National Natural Science Foundations(Nos.U 20 A 20104,42306152)the Taishan Scholars Program to Prof.Rencheng YU。
文摘Pigments are widely used as indices for estimation of phytoplankton biomass and composition,and many protocols have been developed to analyze pigments in phytoplankton.Different protocols were compared using four solvents(methanol,95%methanol,dimethylformamide,and 90%acetone)and two instruments(fluorometer and high-performance liquid chromatography(HPLC)coupled with diode array detector).Analysis of chlorophyll a(Chl a)with fluorometer could lead to over-or underestimation due to the interference from its derivatives in all probability.Among the four extractants,90%acetone had a high recovery for chlorophylls.In contrast,95%methanol was a poor extractant for chlorophylls due to the degradation of Chl a,especially in diatoms.The 95%methanol,however,had high extraction efficiencies for most diagnostic xanthophylls.Therefore,the selection of pigment analytical protocols should follow the specific purpose of phytoplankton study.In addition to fluorometry,an HPLC method with 90%acetone as extractant shall be a good choice for the analysis of Chl a to estimate phytoplankton biomass,especially for diatom-dominated samples,while an HPLC method with 95%methanol as extractant be more suitable to characterize different taxa in phytoplankton communities.
