扁穗牛鞭草草地高效饲草生产系统研究

秋季在'广益'扁穗牛鞭草(Hemarthia compressa'Guangyi')草地上分别补播'中饲828'小黑麦、'冬牧70'黑麦、'长江2号'多花黑麦草等冷季型牧草,对补播系统牧草产量、质量进行比较研究.结果表明:补播'中饲828'小黑麦、'长江2号'多花黑麦草均能显著增加'广益'扁穗牛鞭草草地牧草产量和质量,其中补播'长江2号'多花黑麦草的处理干物质和粗蛋白(CP)产量比不补播分别提高12.3%、15.6%;补播'中饲828'小黑麦的处理分别提高11.3%、10.4%;但补播'冬牧70'黑麦的处理增效作用不明显.'长江2号'多花黑麦草的补播效果最好,是较优的冬季补播草种.     

GROWTH-INHIBITORS AND GROWTH-PROMOTERS IN ENTEROMORPHA COMPRESS A (CHLOROPHYTA)1

Methanol extracts from the alga Enteromorpha compressa (L.) Grev. contain substances which inhibit the elongation of Lepidium roots. Chromatographic separation of the inhibiting substances revealed that one of the inhibitory zones of the chromatograms had properties of the so-called inhibitor β. Neither abscisic acid (ABA) nor lunularic acid proved to be responsible for the growth-inhibiting property of this zone. Moreover, the extracts contain substances which promote the elongation of Avena coleoptile segments. One of these substances could be tentatively identified as indole-3-acetic acid by thin-layer and gas-liquid chromatography. (In addition to indole-3-acetic acid a second growth-promoting factor with the properties of the so-called accelerator α could be detected.)     

草坪型扁穗牛鞭草种质资源的坪用价值初步评价

采用景观-性能-应用适合度的综合评价体系,以暖季型狗牙根和冷季型高羊茅为对照,分春季、夏季、秋冬季对西南地区扁穗牛鞭草坪用性状和使用性能进行评价,结果表明：春季草坪景观质量H050、H049的坪用性状好于对照;夏季H036、H049、H011坪用性状好于对照;秋冬季H036、H049表现好于对照;综合一年的表现进行指标权重分析,H036、H049得分分别为17．60和18．08,可作为过渡性气候区建植观赏草坪、游憩草坪、运动草坪、保土草坪的优质材料进行开发利用。     

ASYMMETRY OF EYESPOT AND MATING STRUCTURE POSITIONS IN ULVA COMPRESSA (ULVALES,CHLOROPHYTA) REVEALED BY A NEW FIELD EMISSION SCANNING ELECTRON MICROSCOPY METHOD1

Gametes of the marine green alga Ulva compressa L. are biflagellate and pear shaped, with one eyespot at the posterior end of the cell. The species is at an early evolutionary stage between isogamy and anisogamy. In the past, zygote formation of green algae was categorized solely by the relative sizes of gametes produced by two mating types (+ and ?). Recently, however, locations of cell fusion sites and/or mating structures of gametes have been observed to differ between mating types in several green algae (asymmetry of cell fusion site and/or mating structure positions). To use this asymmetry for determining gamete mating type, we explored a new method, field emission scanning electron microscopy (FE‐SEM), for visualizing the mating structure of U. compressa. When gametes were subjected to drying stress in the process of a conventional critical‐point‐drying method, a round structure was observed on the cell surfaces. In the mating type MGEC‐1 (mt⁺), this structure was located on the same side of the cell as the eyespot, whereas it was on the side opposite the eyespot in the mating type MGEC‐2 (mt^?). The gametes fuse at the round structures. TEM showed an alignment of vesicles inside the cytoplasm directly below the round structures, which are indeed the mating structures. Serial sectioning and three‐dimensional construction of TEM micrographs confirmed the association of the mating structure with flagellar roots. The mating structure was associated with 1d root in the MGEC‐1 gamete but with 2d root in the MGEC‐2 gamete.     

野生扁穗牛鞭草无性系构件组成及生物量结构变异性

对60份野生扁穗牛鞭草的无性系种群构件数量、质量性状及生物量结构进行比较分析,结果说明：不同种群构件性状与数量呈现出变异性,叶长、叶宽、单蘖叶片数、无性系叶片数的变异系数分别为24．95％、20．00％、14．12％、43．56％;茎直径、节直径、节间长、单蘖节数、直立茎长度、匍匐茎长度、直立茎数、匍匐茎数的变异系数分别为21．11％、22．42％、20．10％、12．14％、46．73％、20．14％、72．76％、37．97％;根系深度、根系分布范围、分蘖面积的变异系数分别为19．81％、37．65％、33．68％;花序长、花序宽、花序厚、单蘖花序数、直立茎生殖蘖比例、匍匐茎生殖蘖比例的变异系数分别为13．33％、13．42％、14．80％、36.10％、118．96％、81．44％。不同种群构件生物量结构变异性丰富,叶生物量、茎生物量、根生物量、花序生物量变异系数分别为78．51％、91．66％、45．64％、192．24％;构件的数量差异高于性状差异,无性系种群差异主要体现在分蘖能力与空间拓展能力上。野生资源生态型变异性和对环境的适应性,为优异性状选择、品种选育、资源开发利用提供了丰富的物质基础。     

Prediction of Prosopis species invasion in Kenya using geographical information system techniques

Tree species from Prosopis genus were widely planted for rehabilitation of degraded drylands of Kenya. However, they have invaded riverine ecosystems where they cause negative socio‐economic and ecological impacts. GIS was used to estimate the reverine area threatened by Prosopis invasion in Kenya. Landsat satellite images, field surveys and past studies were also used to assess the resulting potential ecological impacts in the Turkwel ecosystem in Kenya. The study revealed that 3.0 to 27.7 million hectares are threatened by invasion, based on documented riverine forests width of 0.5–3 km. Image analysis showed that 34% of the sites under positive change were invaded, with most invasions occurring in natural forests and abandoned farms. Prosopis had overall occurrence of 39% in all the sampled sites in 2007, in contrast to 0% in 1990 that was reported in an earlier study. In these areas, Acacia tortilis occurrence dropped from 81% in 1990 to 43% in 2007, suggesting that Prosopis could be displacing it. Utilization of Prosopis for fodder, fuel wood and pods for animal feeds is recommended as a management tool to reverse the trend. The methods used in this study are also recommended for invasion prediction and management in other similar ecosystems.     

ION FLUXES AND MODIFICATION OF THE EXTRACELLULAR MATRIX DURING GAMETE RELEASE IN FUCOID ALGAE

A rapid phase transition in the extracellular matrix (ECM) of the reproductive tissues (= receptacles) has been proposed to cause gamete release in fucoid algae. We tested this model with cryoanalytical energy dispersive x-ray microanalysis (EDX) scanning electron microscopy (SEM) of rapidly frozen hydrated receptacles of Silvetia compressa Serrão, Cho, Boo et Brawley that were planed to smooth faces using a cryoultramicrotome. Every receptacle typically contained a region(s) of intracellular accumulation of K and Cl and a region(s) of efflux of K and Cl to the ECMs, regardless of treatment (e.g. calm vs. shaken conditions in the light, anthracene-9-carboxylic acid). Although longitudinal variations in [K] and [Cl] between ECM and cells were common, a tissue within any transverse plane of the receptacle was in the same state of efflux or accumulation of K and Cl. The strongest and most extensive effluxes occurred during the time of irreversible commitment to gamete release (i.e. 2–4 min darkness after light potentiation). A receptacle may oscillate rapidly between global states of accumulation and efflux at this time. The polysaccharide collar between the oogonium and stalk cell expanded during Cl and K efflux into the ECM of the conceptacle and condensed when [K] and [Cl] were low in the conceptacle ECM. During periods of strong efflux associated with gamete release, the collar and other components of the exochiton ruptured. Detached gametangia were guided to the pore by the paraphyses. The ECM of the conceptacle is sulfur rich (226 mM) compared with the ECM of the medulla (8 mM). This analysis supports the importance of osmotic modification of the ECM during gamete release and demonstrates that the receptacle is a dynamic signaling organ.     

Cryptic diversity of Ulva (Ulvales,Chlorophyta) in the Great Bay Estuarine System (Atlantic USA): introduced and indigenous distromatic species

Distromatic foliose blades of the algal genus Ulva are notoriously difficult to identify due to their simple morphologies and few diagnostic characteristics that often exhibit intraspecific variation and interspecific overlap. Hence, species differentiation is difficult and diversity estimates are often inaccurate. Two major goals of this study were to assess the diversity of distromatic Ulva spp. in the Great Bay Estuarine System (GBES) of New Hampshire and Maine, USA, and to compare historical and present day records of these species. Molecular analysis (using ITS sequences) of field-collected specimens revealed four distinct taxa: Ulva lactuca, U. rigida, U. compressa, and U. pertusa. Prior to molecular screening, Ulva lactuca was the only distromatic Ulva species reported for the GBES. Ulva pertusa and the foliose form of U. compressa are newly recorded for the Northwest Atlantic, and the range of U. rigida has been extended. Molecular analysis of historical herbarium voucher specimens indicates that U. rigida, U. pertusa, and the foliose form of U. compressa have been present in the GBES since at least 1966, 1967, and 1972, respectively. The distromatic morphotype of U. compressa is found only in low salinity areas, which suggests that salinity may influence its morphological development. Molecular and morphological evaluations are critical if we are to distinguish between cryptic taxa, accurately assess biodiversity, and effectively monitor the spread of non-indigenous macroalgae.