Li Dun-Hai

Effects of sand burial on biomass, chlorophyll fluorescence and extracellular polysaccharides of man-made cyanobacterial crusts under experimental conditions

Soil cyanobacterial crusts occur throughout the world, especially in the semiarid and arid regions. It always encounters sand burial, which is an important feature of mobile sand dunes. A greenhouse study was conducted to determine the effects of sand burial on biomass, chlorophyll fluorescence and extracellular polysaccharides of man-made cyanobacterial crusts in six periods of time (0, 5, 10, 15, 20 and 30 d after burying) and at five depths (0, 0.2, 0.5, 1 and 2cm). The results indicated that with the increase of the burial time and burial depth extracellular polysaccharides content and Fv/Fm decreased correspondingly and there were no significant differences between 20 and 30 burial days under different burial depths. The degradation of chlorophyll a content appeared only at 20 and 30 burial days and there was also no significant difference between them under different burial depths. It was also observed a simultaneous decrease of the values of the Fv/Fm and the content of extracellular polysaccharides happened in the crusted cyanobacterium Microcoleus vaginatus Gom. It may suggest that there exists a relationship between extracellular polysaccharides and recovery of the activity of photosystem II (PS II) after rehydration.

DEVELOPMENT CHARACTERISTICS AND DISTRIBUTION OF MICROORGANISMS WITHIN 3-YEAR-OLD ARTIFICIAL ALGAL CRUSTS IN HOPQ DESERT: DEVELOPMENT CHARACTERISTICS AND DISTRIBUTION OF MICROORGANISMS WITHIN 3-YEAR-OLD ARTIFICIAL ALGAL CRUSTS IN HOPQ DESERT

In this study, development characteristics and distribution of microorganisms within four different types of artificial algal crusts were investigated. The results showed that: (1) artificial algal crusts came into being, when desert cyanobacteria were inoculated onto surface of dunes, with their average thickness of 2.23-5.36mm, highly black and sage green, and coverage of artificial algal crusts over 70% when artificial algal crusts underwent growth and development of three years. As to the four artificial algal crusts, Salix cheilophila Schneid. -Aneurolepidium chinensis -algal crust(SAA) was found to gain the best developments and reached the most biomass, and arrived at the succession of moss crust at the same time. Plenty of desert plants occurred at the locations of artificial algal crusts, such as A. squarrosum, E. dahuricus, S. collina and A. chinensis, etc., and the coverage of vegetation accounted for 60%-90%. Algal compositions of artificial algal crusts at four different stations were entirely very single, and the quantities of algal species varied inapparently. M. vaginatus was found to be still utterly dominant, whereas, S. javanicum kept secondary. Moreover, different species of algae were discovered to inhabit distinct ecological niche. It was shown in our study that artificial algal crusts could bear high compressive strength, and compressive strength commonly achieved 35-70 N/m(2). Cyanobacteria forming artificial algal crust was found to own abundant filamentous growth forms that could band and felt soil particles by compact and high mechanical force, and simultaneously, they exude polysaccharide with their filaments to hasten soil aggregation and cement soil particles together. All those meant compressive strength of artificial crusts was able to be maintained due to the presence of filamentous cyanobacteria. The observation to ultra-microstructures of algal crusts indicated that abundant filamentous growth forms occurred between the sand soils within algal crusts during growth and development of 3 years in the fields. A great deal of filamentous growth forms were observed to band up and felt sand particles, which may be contributed to cementation process of artificial algal crusts. (2) Change trend of the total number of microorganisms was: SAA > GA > AA > SA > CK. Changes of biomass of artificial algae crusts accorded with that of the total number of microorganisms. Of all main microorganism groups, the quantities of bacteria, actinomyces and fungi within different types of artificial algae crusts were consistent with that of the total number of microorganisms. Concerning the four artificial algae crusts, the ratio of bacteria quantities to the total number of microorganisms was distinctly more than that of actinomyces and fungi. The percentage of bacteria quantities to the total number of microorganisms increased sharply in turn, while the percentage of actinomyces quantities to the total number of microorganisms decreased evidently. Need to mention that it took on very small ratio of fungi quantities to the total number of microorganisms, and differences of the ratios varied very little.

The correlation between the variation of microcystin content and environment factors in Dianchi Lake

This paper analyzed the distribution and variation of microeystin ( M C) and physicochemical factors in Macun and Haidong bay of Dianchi Lake from April to December in 2003. The correlation of some physiochemical factors, including the concentration of total nitrogen, total phosphorous, dissolve oxygen, chlorophyll-a and Seechi depth, light intensity, pH, water temperature and dominance of Microcystis population, with microcystin was evaluated. Correlation analysis showed that the distribution of MC was significantly positive correlated with TN and N: P (P < 0. 01); and affected by Seechi depth, light intensity, dominance of Microcystis ( P < 0. 05). Multiple continuously factors analysis indicated that the distribution of MC in water of the two bays was mainly affected by total nitrogen, Seechi depth, chlorophyll-a, dissolve oxygen and total phosphorous (R-2= 0. 560, P < 0. 017).

Improving photosynthesis of microalgae by changing the ratio of light-harvesting pigments

Changing the ratio of light-harvesting pigments was regarded as an efficient way to improve the photosynthesis rate in microalgae, but the underlying mechanism is still unclear. In the present study, a mutant of Anabeana simensis (called SP) was selected from retrieved satellite cultures. Several parameters related with photosynthesis, such as the growth, photosynthesis rate, the content of photosynthetic pigment, low temperature fluorescence spectrum (77K) and electron transport rate, were compared with those of the wild type. It was found that the change in the ratio of light-harvesting pigments in the mutant led to more efficient light energy transfer and usage in mutant than in the wild type. This may be the reason why the mutant had higher photosynthesis and growth rates.

Effects of Zinc Ion on Photosynthetic System of Anabaena azotica Ley

本实验对在不同Zn2+浓度条件下培养的固氮鱼腥藻(Anabaena azoticaLey)的生长、光合放氧速率和叶绿素荧光参数Fv/Fm进行了测定.结果表明,当Zn2+浓度为1.0mmol/L时,其比生长速率(Specific growth rate)最大,光合放氧速率和Fv/Fm值最高.当Zn2+浓度大于等于5.0mmol/L时会抑制A.azotica Ley的生长和光合作用.对在0mmol/L和5.0mmol/L Zn2+浓度下生长的藻细胞藻胆体-类囊体膜复合物吸收光谱的比较和对与5.0mmol/LIt was found that the concentration of Zn2+ at about 1. 0mol/L was essential to keep optimal growth of Anabaena azotica Ley and also important to keep a quite high value of photosynthetic oxygen evolution rate, chlorophyll fluorescence (Fv/Fm) level and carbonic anhydrase activity, whereas the relative high concentration of Zn2+(5. 0um) would inhibit the growth of A. azotica Ley, decrease its photosynthetic oxygen evolution rate, chlorophyll fluorescence and CA activity. The study of the absorption spectra of the phycobilisome-thy-lakoid membrane complex and the extraction of phycocyanin indicate that Zn2+ may affect the photosynthesis by its effect on the phycobilisome especially the phycocyanin. Since CA is a Zn2+-containing metalloenzyme and may provide a high concentration of CO2 to Rubisco in the process of CO2 fixation, it is suggested that Zn2+ may affect the photosynthesis by acting on CA.

Comparison of the photosynthetic characteristics of two developmental stages in Nostoc sphaeroides kutzing (Cyanophyta)

The photosynthetic activities between two main developmental stages, colony and hormogonium, of the edible cyanobacteriumNostoc sphaeroides Kützing, were compared. Hormogonia have a higher content of chlorophyll than that of colonies. It showed that the ratios of phycocyain (PC), allophycocyain (APC) and phycoerythrocyanin (PEC) in hormogonia and colonies were different. The room temperature chlorophyll fluorescence, 77 K chlorophyll fluorescence, measurements of PS I and PS II activities all showed that colony has higher photosynthetic competence than hormogonia. Hormogonia had a higher respiration rate were very close. The responses of hormogonia and colonies to high light illuminations also were different. Both of their oxygen evolution rates decreased quickly with the prolonged high light illumination, but hormogonia can keep relatively higher PS II activity (Fv/Fm) than that of colonies. The results suggested that colony was photosynthetically more competent than hormogonia, while the ability of hormogonia to tolerate high light illumination was higher than that of colony.

Effects of alkalinity variations on photosynthetic activity and exopotysaccharides of Chlorella pyrenoidosa

Effects of bicarbonate (HCO3-) alkalinity on the photosynthetic performance of Chlorella pyrenoidosa was investigated in present study. Photosynthetic activity, pigments, MDA and ultrastructure of Chlorella pyrenoidosa were measured for when they were cultured at two different alkalinities including 2.3mmol/L (ALK2.3) and 12.4mmol/L (ALK12.4), respectivily. At ALK2.3, photosynthetic activity was stimulated at the prophase of culture and then inhibited at the anaphase. At ALK 12.4, it represented the same phenomenon, but inhibition effects were weaker than those at ALK2.3. Ratios of Chl.b/Chl.a was increased, but Caro/TChl ratios was decreased at elevated alkalinities. The contents of MDA increased at ALK2.3 and decreased at ALK12.4. In addition, secretion of glycocalix-like layer was remarkably stimulated at elevated alkalinities. These results showed that elevated alkalinities promoted algae carbon assimilation and stimulated secretion of glycocalix-like layer. Carbohydrate could alleviate stresses at elevated alkalinities. Secretion of glycocalix-like layer could decrease the synthesis of excess products of photosynthesis and relieve feedback inhibition, which will increase the stress tolerance of C. pyenoidosa at elevated alkalinities.