| 其他摘要 | Duckweed is anideal starch feedstock to produce bioethonal for its rapid growth, high starch content and the ability to grow using wastewater directly. The biomass and starch production of duckweed are two key factors for producing bioenergy in large scale. For photoautotrophic plants, the light intensity and photoperiod are critical components in determining the biomass production and starch content. To investigate the effects of light conditions on duckweed growth and starch production, we measured biomass and starch production of Lemna aequinoctialis 6000 cultivated at different photoperiods (12:12, 16:8 and 24:0 h) and light intensities(20, 50, 80, 110, 200 and 400 μmol m-2 s-1).Also, the ability of growth and stimulating starch are different within different species and geographic isolates. A good duckweed strain, which has high starch content and rapid growth rate, is theprecondition for producing bioenergy effectivelyin industrial scale. Earlier, We have established a large scale duckweed cropping system based on wastewater. In order to get anideal duckweed strain with desirable straits used in large scale cropping system, we have screened 90 promising geographic isolates using wastewater and compared the differences of biomass production, starch content and total starch production between different species and geographic isolates.The main results as follow: (1) The results of the effects of light condition showed that the duckweed biomass and starch production wereincreased with increasing light intensity and photoperiod except at 200 and 400 μmol m-2 s-1. Considering the light cost, 110 μmolm-2 s-1was optimum light condition for starch accumulation with the highest maximum growth rate, biomass and starch production of 8.90 g m-2 day-1, 233.25 g m-2 and 98.70 g m-2, respectively. Moreover, the duckweed starch accumulated rapidly under the light intensity of 400μmolm-2 s-1,which suggested that high light induction is a promising method for duckweed starch accumulation. This study provided optimized light conditions for future industrial large-scale duckweed cultivation. (2) We got Landoltia punctata6050with the highest starch production(53.38 g m-2) through screen of 90 duckweed geographic isolates. The results of screen showed that Lemna aequinoctialiswasthe species with the fast growth rate, but its starch content and dry weight were low. The starch production ofLandoltia punctatawas the highest, so did its starch content and itsdry weight.The starch content, dry weight production and total starch production of Spirodela polyrhizawere between those of L. punctataand L. aequinoctialis.Futher analysis, we stipulated that the duckeed with high growth rate is always related with low starch content and starch production, and the duckweed with high ratio of dry-and-wet weight alwayshas high starch content and starch production. Moreover, the differencesof biomass production, starch content and starch production between different duckweed species and geographic isolates were great. We also found that the duckweed derived from distant geographies may have different characteristics and the far the distance of geographic isolates are, the more the differences they may have. This study providedsome useful information for future screen of ideal duckweed strains. |
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