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排序方式: 共有195条查询结果,搜索用时 15 毫秒
81.
SUMMARY The absorption and release of 32PO4, by Potamogeton pectinatus L during winter was investigated using a partitioned container in which the roots were separated from the stems and leaves. 32PO4 is absorbed by the roots as well as the stems and leaves under both light and dark conditions and transported to all parts of the plant. Transport rates (μg P plant?1 24 hr?1) show that more phosphorus is released by the roots than by the stems and leaves, indicating a nett movement of phosphorus from the surrounding water to the substrate. Foliar absorption of 32P exceeds root absorption under both light and dark conditions. 相似文献
82.
The induction and protective role of the UV-absorbing compounds known as mycosporine-like amino acids (MAAs) were examined in sublittoral Chondrus crispus Stackh. transplanted for 2 weeks in the spring and summer to shallow water under three irradiance conditions: PAR (photosynthetically active radiation; 400–700 nm), PAR + UVA (PAR + 320– 400 nm), PAR + UVA + UVB (PAR + UVA + 280– 320 nm). Sublittoral thalli collected around Helgoland, North Sea, Germany, from 6 m below the mean low water of spring tides contained less than 0.1 mg·g−1 dry weight (DW) total MAAs, whereas eulittoral samples contained over 1 mg·g−1 DW. Transplantation to shallow water led to the immediate synthesis of three MAAs in the following temporal order: shinorine (λmax 334 nm), asterina (λmax 330 nm), and palythine (λmax 320 nm), with the shinorine content peaking and then declining after 2 days (exposure to 100 mol photons·m−2). Maximum total MAA content (2 mg·g−1 DW) also occurred after 2 days of induction, exceeding the content normally found in eulittoral samples. Furthermore, the relative proportion of the different MAAs at this time was different than that in eulittoral samples. After 2 days the total content declined to the eulittoral value, with palythine as the principal MAA. Similar data were obtained for all treatments, indicating that MAA synthesis in C. crispus was induced by PAR and not especially stimulated by UV radiation. The ability of photosystem II (PSII) to resist damage by UVB was tested periodically during the acclimation period by exposing samples to a defined UVB dose in the lab. Changes in chlorophyll fluorescence (Fv/Fm and effective quantum yield, φII) indicated that PSII function was inhibited during the initial stage of acclimation but gradually improved with time. No difference among screening treatments was detected except in spring for the samples acclimating to PAR + UVA + UVB. In this treatment Fv/Fm and φII were significantly lower than in the other treatments. During the first week of each experiment, growth rates were also significantly reduced by UVB. The reductions occurred despite maximum MAA content, indicating an incomplete protection of photosynthetic and growth-related processes. 相似文献
83.
Morphometric analysis of root systems: application of the technique and influence of soil fertility on root system development in two herbaceous species 总被引:13,自引:1,他引:12
A. H. FITTER 《Plant, cell & environment》1982,5(4):313-322
Abstract. A method for describing root systems based on geomorphological techniques developed for river systems is described. Root systems, in common with other natural branching structures (rivers, bronchioles, trees), appear to obey Morton's Law of Branching: there is a constant ratio, the bifurcation or branching ratio, Rb , between the number of branches of a given order, Nu , and that of the next order. Nu+1 , In experiments where Poa annua , and Rumex cripus , were grown at two levels of fertility, the first-order roots (the youngest members in this system) were generally unresponsive to fertility, and differences in the root systems were largely the result of changes in the second-order roots, those formed at the junction of two first-order roots. These differences were reflected in the branching ratio, Rb Although it is possible to explain these results by a stochastic model of branch development, the Rb values for roots are higher than for other natural branching structures, and higher than the random model predicts. It is possible that a model based on optimum exploration of space may be more appropriate and provide a key to the factors governing root branching patterns. 相似文献
84.
光照、温度和氮对竹叶眼子菜生长的影响 总被引:1,自引:1,他引:0
实验选择长江中下游常见沉水植物竹叶眼子菜(Potamogeton malaianus Mig.),利用正交试验设计,通过室内静态模拟实验研究3种主要环境因子光照强度、温度、总氮浓度及其互作对竹叶眼子菜分苗生长的影响。结果表明:光照强度和温度为影响竹叶眼子菜生长的主效环境因子,且它们的交互作用对竹叶眼子菜生长有较为显著的影响;在2~8mg·L-1的总氮浓度下,竹叶眼子菜均可以正常生长。观察结果可知,竹叶眼子菜在5320~12000lx光照强度、30℃、4~8mg·L-1水体总氮浓度的条件下生长良好,竹叶眼子菜生长虽然对光照强度的要求较高,但其叶往往集中在水体表面形成冠层,能在透明度较低的水体中生长,加上对高温及高营养盐的耐受性较好,故推测竹叶眼子菜可作为夏季富营养化水体中恢复和重建沉水植被的先锋工具种。 相似文献
85.
围隔中鲢和菹草控藻效果及其生态学意义 总被引:11,自引:0,他引:11
在滇池沿岸的池塘中 ,构建了面积为 10 0m2 ,水深为 85cm ,底质均为淤泥的四个围隔 ,其中在三个围隔内分别放养密度为 10 0g/m3 、75g/m3 、5 0g/m3 的鲢。它们均在一定程度上控制浮游植物的生物量并改善水体透明度 ,其中初始放养鲢 75g/m3 的围隔控制效果最明显。放养三种密度的鲢在有效控制微囊藻水华的同时 ,原先水体的优势种类发生质的变化 ,水体中浮游植物的多样性也明显增加。放鱼 2个月后 ,在生物操纵的围隔中同时种入菹草 ,在75g/m3 的鲢控藻的围隔中 ,菹草长势良好 ,浮游动物大量出现 ,透明度进一步增加 相似文献
86.
Shallow lakes can occur in two alternative stable states, a clear-water state and a turbid state. This is associated with
separate assemblages of fish, zooplankton and plants. Little is known about whether macroinvertebrate assemblages differ across
both stable states. This study investigated this in a connected set of three turbid and three clear-water shallow lakes. To
overcome confounding effects of differences in spatial structure of macrophytes in turbid and clear-water lakes, we sampled
three microhabitats that occurred in both alternative stable states: open water, sago pondweed (Potamogeton pectinatus) and reed (Phragmites australis). Univariate analyses indicated no differences in the number of organisms, taxon richness or diversity between turbid and
clear-water lakes. Multivariate analysis, however, showed significant differences in the macroinvertebrate community structure
of both stable states. Nine taxa explained a significant amount of the variation between both lake types, of which seven preferred
the clear-water lakes. The number of organisms and the taxon richness were higher in reed than in the other microhabitats,
but diversity and evenness did not differ among the microhabitats. Multivariate analyses could separate all three microhabitats.
Eight taxa, mainly detritus feeders and collector–gatherers, explained most of the variation in the data and preferred the
reed microhabitat. The effects of stable state (6.8% explained variance) and microhabitat (13.1% explained variance) on the
macroinvertebrate assemblages were largely independent from each other (1.5% shared variance). Although macroinvertebrates
are not implemented in the initial theory of stable states, our results show clearly different assemblages across both stable
states. 相似文献
87.
对菹草 (Potamogeton crispus) 叶在高CO2 (1 000±50 μmol·mol-1)和对照浓度(约380 μmol·mol-1)下的表型及一些生理生化指标进行了比较研究。结果表明:CO2浓度升高明显地改变了菹草叶的表型特征,外形更为粗短,叶宽、单叶面积、单株总叶面积、叶面积率、叶重比明显增加,但特殊叶面积和叶长增加不明显。线性回归分析表明单株总叶面积和植株大小密切相关。异速生长分析表明叶面积的变化不是可塑性反应,而是受植株大小所制约。此外,CO2浓度升高后植物的色素含量和一些化学物质含量明显改变。叶绿素a、叶绿素b、总叶绿素及类胡萝卜素含量减少,且叶绿素a/b也降低;可溶性糖含量增加,而蛋白质、N和P浓度降低。 相似文献
88.
沉水植物菹草的人工种子技术 总被引:2,自引:0,他引:2
为满足水生态系统重建及水体景观对沉水植物种苗的需求,本文建立了菹草(Potamogeton crispus L.)人工种子的制作方法,并分析了菹草人工种子的萌发条件。结果表明,以海藻酸钠为包埋剂,在包埋剂中添加IBA 1.0 mg/L + 6-BA 0.5 mg/L,制备的菹草人工种子在灭菌自来水中萌发率可达80%,且转株率达20%。在15-25℃之间,温度对菹草人工种子萌发和转株的影响不显著;氮磷水平对菹草人工种子萌发和转株的影响不显著;光强对菹草人工种子的萌发和转株有显著影响,较高的光强有较高的萌发率和转株率,光强为40μmol/ m2. s时,菹草人工种子萌发率、转株率可达67.8%、35.6%;底质对菹草人工种子的萌发和转株有显著影响,菹草人工种子在黄沙壤上的萌发率、转株率分别为60%和42.2%,黄沙壤比淤泥和砂石更适合菹草人工种子萌发和转株;菹草人工种子在野外湖水的试验中萌发率、转株率分别达到28%、15%。 相似文献
89.
Fennel (= Sago) pondweed (Potamogeton pectinatus L.) is a submersed macrophyte of nearly cosmopolitan distribution. The plant is of worldwide ecological importance as structuring component of shallow lakes, and as food for waterfowl. We developed nine polymorphic microsatellite primers for the population genetic analysis of P. pectinatus. The loci were identified using a GA/CT‐enriched genomic library using subtractive hybridization with magnetic particles. All nine loci were highly polymorphic with 6–9 alleles and heterozygosities ranging from 0.23 to 0.80 in a subset of N = 40 genotypes from five locations. 相似文献
90.