Sample Paper_Submission.pdf

More documents

Recommendations

Info

262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 pyrenoidosa and Microcystis aeruginosa. By analyzing the types and relative content of phospholipid fatty acids in algal cell membrane, Li et al. found that unsaturated fatty acid contents of C18:3 and C18:2 in Chlorella pyrenoidosa were increased from 23.31%, 11.46% to 37.68%, 25.91%, respectively. And the unsaturated fatty acid contents of C18:1 and C18:2 of Microcystis aeruginosa were increased from 30.26%, 18.85% to 42.88%, and 28.46%, respectively. The proportion increase of unsaturated fatty acids in the algal cell membrane directly caused the increase of fluidity of cell membrane, the decrease of substance selectivity of cell membrane, the decrease of cell stability and the leakage of intracellular contents (such as K + ,Mg 2+ ,Ca 2+ ). In addition to the damage of cell membrane, the cellular thylakoid lamellar structure disappeared; the nucleolus area became irregular, starch grains increased, and the volume of vacuole increased. The allelochemicals of Phragmites communis did not inhibit Chlorella vulgaris, accordingly, in which the relative content of fatty acids of the cell membrane did not change and the cell structure was intact, aside from a slight abruption between cell wall and membrane and the volume increase of starch grains[91]. Men et al. found the algae-algae conjointed structure reduced significantly, nucleus disappeared and cell organs like mitochondria disintegrated after inspecting the influence of allelochemicals from Phragmites communis on Scenedesmus obliquus[92]. A lot of irregular fragments of broken cells formed when the root exudates of Pistia stratiotes inhibited Chlamydomonas reinhardtii [35]. Microscopic observations on the effects of the exudates of Hydrilla verticillata on Microcystis aeruginosa showed that the cell membrane apparently separated from the cell wall and thylakoid lamellae became loose and cluttered and the damage effects aggravated with the extension of time [93]. (2) To affect the photosynthesis of algal cells Damage on the photosynthesis of algal cells can be divided into damage on light reaction (thylakoid reaction) and damage on dark reaction (carbon fixation reaction). The root exudates of Eichhornia crassipes were able to disintegrate chloroplast of Scenedesmus. The content of chlorophyll a decreased significantly and the content of its degradation products (chlorophyll a esters without magnesium) increased. The photosynthetic rate dropped sharply, resulting in serous damage on thylakoid reaction[34]. When Hydrilla verticillata and Microcystis aeruginosa were co-cultured, the chlorophyll a content of Microcystis aeruginosa cells was significantly lower than that of the control (after 9d of cultivation, only 12.5% of the control)[93]. The exudates of Ceratophyllum demersum and Myriophyllum spicatum could - 14 -
291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 suppress the growth of several species of algae by inhibiting their photosystem II[88]. Leu et al. indicated that eugeniin inhibited the electron-transfer process between the acceptor and donor in the photosystem II when investigating the mode of action of polyphenol-like allelochemicals from Myriophyllum spicatum [44]. Wium-Andersen et al. reported that the unstable sulfide or sulfur exudates of Chara globularis could inhibit the dark reaction process(carbon fixation process) in the photosynthesis of diatoms and other phytoplankton[58,87]. At present many kinds of aquatic plants has been discovered to be able to suppress the algal photosynthetic process. For example, Stratiotes aloides affected the photosynthesis of Scenedesmus obliquus[49,56], Berula erecta and Nitella sp. inhibited the photosynthesis of Nitzschia palea[49], Chara could inhibited the photosynthesis of several algal species[51, 89]. (3) To affect the respiration of algal cells The allelochemical α-asarone of Acorus tatarinowii reduced the growth rate of Selenastrum capricornutum. Through observation of cell ultrastructure, the increase in the number of algal mitochondria was found, base on which the cellular respiration was speculated to be affected; the results of assay pointed out that after 48h of cultivation, the algal respiration rate with α-asarone treatment was only 60% of the control, but the algae increased the respiratory rate to 120% of control later. Pollio et al. considered the cell respiration was destroyed, the decrease in phosphorus/oxygen ratio(adenosine diphosphate/oxygen, ADP/O) might cause the decoupling of oxidative phosphorylation, so even if the respiration rate and the number of mitochondria was increased, but the efficiency of cell respiration has not improved [86]. During the inhibition process of the allelochemicals of Phragmites communis on algae, the damage of cell respiration was also observed. That the respiration rate was increased early at low concentration but decreased at high concentration was observed, but with the extension of time the respiration rate gradually decreased[91]. (4) To affect the enzymatic activity of algal cells Different allelochemicals could affect the activities of different enzymes in algal cells. Because of the functional differences of enzymes, allelochemicals could increase some enzymatic activities but inhibited other enzymatic activities. Eugeniin from Myriophyllum spicatum, as well as several other phenolic acid-like allelochemicals could effectively inhibited the alkaline phosphatase activity in algal cells, and mixed phenolic acid-like allelochemcials showed stronger inhibition than anyone of them[41,82]. The - 15 -
Page 1 and 2: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Page 3 and 4: 58 59 60 61 62 63 64 65 66 67 68 69
Page 5 and 6: 80 81 82 83 84 85 86 87 88 89 90 91
Page 7 and 8: 96 97 98 99 100 101 102 103 104 105
Page 9 and 10: 134 135 136 137 138 139 140 141 142
Page 11 and 12: 186 187 188 189 190 191 192 193 194
Page 13: 234 235 236 237 238 239 240 241 242
Page 17 and 18: 349 350 351 352 353 354 355 356 357
Page 19 and 20: 410 411 412 413 414 415 416 417 418
Page 21 and 22: 478 479 480 481 482 483 484 485 486
Page 23: 546 547 548 549 550 551 552 553 554

Sample Paper_Submission.pdf

Create successful ePaper yourself

Delete template?

Save as template?