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151.
E. Rhiel J. Marquardt M. Eppard E. Mrschel W. E. Krumbein 《Plant biology (Stuttgart, Germany)》1997,110(2):109-117
The main chlorophyll a/c light harvesting complex of the diatom Cyclotella cryptica was isolated by sucrose density gradient centrifugation. It consisted of two polypeptides of Mrs 18000 and 22000. Both polypeptides and fragments thereof, obtained by formic acid treatment, were blocked at their N-ter-mini. An antiserum raised against the two subunits selectively immunolabeled the thylakoid within the chloroplasts. The subunits were nuclear encoded and could be immunoprecipitated from poly (A)+ RNA as precursor proteins in the Mr range of 20000 to 24000. The existence of minor chlorophyll protein complexes and their possible function in light climate adaptation processes was investigated in cells adapted to low light and high light conditions. Low light grown cells contained more fucoxanthin and less β-carotene relative to chlorophyll a than high light adapted cells. The xanthophyll cycle pigments diatoxanthin and diadinoxanthin increased five-fold relative to chlorophyll a under high light conditions. Western-immunoblotting experiments with antisera raised against several chlorophyll a/b and chlorophyll a/c antenna complexes demonstrated that, beside the dominating chlorophyll a/c light harvesting complex, minor antenna complexes might exist, which, in part, seem to react to the light climate applied. 相似文献
152.
研究了不同砍伐频率下,香港、深圳和鹤山研究样地山坡地N、P、K含量的差异.不同采样地之间,养分全量和有效量差异显著.在尚未砍伐的山坡地,土壤养分含量显著高于经常砍伐的山坡地.未伐土壤的N含量顺序为香港样地>深圳样地>鹤山样地.下层土壤P的含量高于上层土壤.深圳样地常代土壤养分含量高于鹤山.结果建议采用最适砍伐频率和在最适季节砍伐,以便减少砍伐产生的不利影响. 相似文献
153.
154.
Ecological significance and commercial harvesting of drifting and beach-cast macro-algae and seagrasses in Australia: a review 总被引:1,自引:0,他引:1
This review provides an overview of aspects of the ecology of drifting and beach-cast macroalgae and marine angiosperms in
respect to present and potential commercial use of that resource in Australia. It sets the scene with sections on industries
that utilise macro-algae and seagrasses, the ecology of littoral and nearshore sublittoral ecosystems and the processes of
deposition of beach-cast macro-algae and seagrasses on beaches. It then describes the major economic macro-algae and seagrasses
that occur as beach-cast wrack, with an emphasis on known information on habitat distribution, geographical range, and harvesting
issues. Gaps in scientific knowledge are pointed out. The priority areas of future research were found to be: • The importance
of beach accumulations of macro-algae and seagrasses on feeding and nesting shorebirds; • Whether available resource allows
for ecologically and economically sustainable harvesting; • A survey of present and potential commercial macro-algae and seagrasses:
studying biomass, density and annual production rates, interannual variability of recruitment into living stands, the effect
of harvesting on trophodynamics and community structure and the stability of the resource base for economically sustainable
harvesting; • An assessment of the importance of wrack in recycling nutrients and detritus to nearshore coastal ecosystems
at wider geographical scales than previous work. This research should assess the dependence of offshore production on nutrients
and detritus that are broken down in beachwracks.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
155.
In the coming century, forecast climate changes caused by increasing greenhouse gases may produce dramatic shifts in tree species distributions and the rates at which individual tree species sequester carbon or release carbon back to the atmosphere. The species composition and carbon storage capacity of northern Wisconsin (USA) forests are expected to change significantly as a result. Projected temperature changes are relatively large (up to a 5.8°C increase in mean annual temperature) and these forests encompass a broad ecotone that may be particularly sensitive to climate change. Our objective was to estimate the combined effects of climate change, common disturbances, and species migrations on regional forests using spatially interactive simulations. Multiple scenarios were simulated for 200 years to estimate aboveground live biomass and tree species composition. We used a spatially interactive forest landscape model (LANDIS‐II) that includes individual tree species, biomass accumulation and decomposition, windthrow, harvesting, and seed dispersal. We used data from two global circulation models, the Hadley Climate Centre (version 2) and the Canadian Climate Center (version 1) to generate transient growth and decomposition parameters for 23 species. The two climate change scenarios were compared with a control scenario of continuing current climate conditions. The results demonstrate how important spatially interactive processes will affect the aboveground live biomass and species composition of northern Wisconsin forests. Forest composition, including species richness, is strongly affected by harvesting, windthrow, and climate change, although five northern species (Abies balsamea, Betula papyrifera, Picea glauca, Pinus banksiana, P. resinosa) are lost in both climate scenarios regardless of disturbance scenario. Changes in aboveground live biomass over time are nonlinear and vary among ecoregions. Aboveground live biomass will be significantly reduced because of species dispersal and migration limitations. The expected shift towards southern oaks and hickory is delayed because of seed dispersal limitations. 相似文献
156.
Wildlife can cause serious crop damages, and factorial analyses focusing ecological aspects have been conducted to resolve this problem. However, ethological perspectives should also be considered. Individuals often show consistent biases in behaviour—so-called personality; e.g., boldness may cause to intrude into a farmland. Here, we hypothesized that boldness–shyness traits in wildlife could be managed through selective harvesting on the base of personality traits. We considered several scenarios involving the selective harvesting and fencing as means to prevent crop damage, and assessed their effects on the average boldness and population size using simulation models, assuming that bold individuals tend to enter farmlands, while shy ones prefer to stay in forests. The results showed that fencing and selective harvesting in farmlands reduced both the average boldness and crop damages, while harvesting in forests caused the increase of the both. Those results came from the selective harvesting and fencing on the base of personality traits, and indicate that not only population ecology but also an ethological approach is needed for wildlife management. 相似文献
157.
Every year, several hundred tonnes of dry Gymnogongrus furcellatus are exported from Chile for carrageenan production. The present study provides ecological information for rational harvesting
practices, including an understanding of the effects of environmental factors on growth. Field results indicate that the species
is abundant in areas where disturbing factors do not destroy the crustose base of the plants, which can survive sand burial,
but is grazing sensitive. In central Chile the erect axes have a clear seasonal pattern of growth which, as extrapolated from
laboratory experiments, is most affected by seasonal changes in quantum dosage and photoperiod. Laboratory experiments show
that vitamins and CO2 additions also influence growth rates significantly. Field data indicate that harvesting in central Chile should be done
bi-monthly, within the six most productive months of the year and be stopped before March, when the female gametophytes become
fertile. Hand picking is the least destructive harvesting method. Even though the daily growth rate of the species could be
raised to 7% in laboratory experiments, tank cultivation appears uneconomical. The cost of some of the factors required for
the growth of this species, such as daily vitamin additions, aeration and CO2 supplements, are unlikely to be recovered by the 25% average carrageenan content of this species. In addition, the high light
requirements of the species would restrict culture to only 6 months a year at these latitudes. Therefore adequate management
of the beds is required for sustained production. 相似文献
158.
159.
对玉米(Zea mays)营养生长期中的下位叶(第5叶)和生殖生长时期的中位叶(果穗叶)和上位叶(顶生叶)的成熟叶片的冰冻撕裂电镜观察,发现叶绿体类囊体膜所有撕裂面上各种功能蛋白颗粒的密度均以果穗叶中的最大,依次是顶生叶和第5叶的。以果穗叶与顶生叶相比,其类囊体膜中包含有绝大多数 LHCP 的 EFs 颗粒增加28%;包含有 PSI 反应中心与LHCP 相结合的 PFu 颗粒增加20%;包含有 PSII 反应中心与 LHCP 相结合的 EFs 颗粒增加19%。这一超分子结构的电镜观察结果与其 SDS-聚丙烯酰胺梯度凝胶板电泳解析的结果相一致。即 SDS-聚丙烯酰胺梯度凝胶板电泳解析的色素带上,同样是果穗叶类囊体膜上呈现的21kD(LHCP Ⅰ)和25 kD(LHCPⅡ)多肽的色素带相应地也比顶生叶的加宽,表明果穗叶叶绿体类囊体膜上镶嵌的叶绿素 a/b 蛋白复合体等比顶生叶的显著地增多,这有利于果穗叶光合作用中光能的吸收、传递、分配和转化。 相似文献
160.