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161.
The tiny seeds of parasitic weeds of the genusOrobanche can be identified by using RAPD markers. A simple procedure for DNA extraction from single seeds, 10 μg each, followed by
RAPD-PCR and using specific DNA markers, leads to species identification. Seeds of five different species could be identified
using this method. 相似文献
162.
Polyporus admirabilis, P. dictyopus, P. guianensis, P. pseudobetulinus, P. tubaeformis andP. udus are reported for Japan for the first time.Polyporus tubaeformis had been confused withP. melanopus, but the Japanese collections were conspecific with Norwegian isolates ofP. tubaeformis. A key to allPolyporus species in Japan is provided.Polyporus hartmanni is reported for the first time outside the Australian continent. As the species has a bipolar heterothallism and produces brown rot, its taxonomic relationship withPolyporus s. str. is discussed.The Japanese Science and Technology Agency (STA) is thanked by the authors for financial support. 相似文献
163.
Selected life-history characteristics of Mesembryanthema species occurring on and off mima-like mounds (heuweltjies) were compared at Tierberg in the southern Succulent Karoo, South Africa. Seed production, the number of seeds retained in seed capsules and germination behaviour were measured in fourteen species of Mesembryanthema which were representatives of two sub-families: the Ruschioideae and the Mesembryanthemoideae. Species occurring onheuweltjies had low overall germination and high seed retention compared with those species occurring offheuweltjies. A strong negative correlation was found between the degree of seed retention and maximum germination. It was proposed that rapid germination and low seed dormancy in species occurring on the flats would be a viable strategy where competition for safe recruitment sites is strong. Species occurring on the flats are long-lived woody shrubs, thus the resulting high levels of seedling mortality probably do not have a major impact on population dynamics.Heuweltjies are sites of intense disturbance. Plant species that occur onheuweltjies can also occur offheuweltjies in disturbed vegetation. Opportunistic life-history characteristics allow these species to colonise disturbed areas.Heuweltjie species thus act as pioneers in a successional process which results ultimately in the re-colonisation of the long-lived flats species. Phylogenetic factors may also determine the species distributions. Members of the Mesembryanthemoideae did not occur offheuweltjies in undisturbed areas. Most Ruschioideae were found on the flats but the few species that occurred onheuweltjies shared similar characteristics with the Mesembryanthemoideae. The primitive life-history characteristics exhibited by the Mesembryanthemoideae enable them to exploit disturbed conditions. 相似文献
164.
Dirk Schories 《Aquatic Ecology》1995,29(3-4):341-347
For the last two decades dense mats of species of the filamentous green algaeEnteromorpha spp. have regulary occurred on tidal flats of Köningshafen Bay (island Sylt, North Sea, FRG). In calm areas overwintering of adult plants or plant fragments is a common process to guarantee the mass development during the next season. In contrast, the distribution ofEnteromorpha on exposed sandy tidal flats depends on recruitment by juvenile stages. In 1993Enteromorpha spore settlement was recorded regularly in the field. Polyethylene dishes were placed in the field and left for a period of seven days and lateron cultivated in the laboratory to checkEnteromorpha germling development. During summer 1993 — at a minimum distance of 200 m to the nearest adultEnteromorpha populations — a total of at least 82×106 spores m–2 settled. During winter the number of spores attached to the collecting dishes was close to zero and the adjacent sand flats were free of any visibleEnteromorpha plants. In further experiments it was shown that the development ofEnteromorpha juveniles in the next spring depended on the overwintering capacity of spores. More than 2×106 spores m–2 attached to large sand grains and other substrata (e.g. Hydrobia ulvae) survived the winter. In a laboratory experiment several species ofEnteromorpha were able to survive in total darkness for at least 10 months. 相似文献
165.
荔枝和龙眼种子发育过程中ABA含量及对外源ABA敏感性的变化 总被引:1,自引:0,他引:1
在荔枝和龙眼种子发育过程中,内源ABA水平先是上升,至大约78~80DPA时出现高峰,之后两者ABA含量均不断下降。果实成熟时采收的种子,ABA含量比高峰时分别下降近6倍。另外,随着种子的发育,种子及其胚轴对外源ABA的敏感性(SABA)亦持续下降。10-4mol/LABA可以完全抑制90DPA前的荔枝和龙眼种子的萌发,但对成熟种子10-2mol/LABA亦不能抑制其萌发。龙眼种子离体胚轴的SABA高于荔枝。ABA含量与敏感性的这种变化可能是两种顽拗性种子成熟时萌动,进而不耐脱水贮藏的重要原因之一。 相似文献
166.
在无盐条件下,外源乙烯对苜蓿种子萌发有促进作用,但对最终发芽率无影响。盐渍严重抑制苜蓿种子萌发,加入1~50μl/L(v/v)外源乙烯或0.1~5.0mmol/L1-氨基环丙烷-1-羧酸(ACC)或5~100mg/L(w/v)乙烯利(ETH)均能极显著地减轻NaCl对苜蓿种子萌发的抑制作用。激动素(KT)也有类似作用,并能促进萌发种子的乙烯产生,它与ACC一起使用,则对种子萌发和乙烯产生均显示加成作用。在NaCl胁迫下,应用乙烯和乙烯利虽有利萌发,但幼芽鲜重和下胚轴长度明显低于无盐对照。 相似文献
167.
野生紫斑牡丹和四川牡丹种子萌发特性及与其致濒的关系 总被引:6,自引:0,他引:6
野生牡丹种子一般较小,而且不同产地之间形状、大小差异较大。其萌发特性与栽培牡丹相比也有较大差异:萌发期长达半年以上,且萌发温度在10~15℃为宜,超过20℃则明显不利于生根及上胚轴生长。四个不同分布地的四川牡丹种子萌发率较一致,均在60~77%之间。三个不同产地的紫斑牡丹种子萌发率则相差甚远,分布于甘肃文县的萌发率达76%,而分布于陕西略阳和湖北神农架的萌发率则分别只有12%和4.4%,出苗率则更低。本文认为紫斑牡丹的种子特性是其在自然界处于濒危状态的重要原因之一。 相似文献
168.
M. A. Lelu K. Klimaszewska G. Pflaum C. Bastien 《In vitro cellular & developmental biology. Plant》1995,31(1):15-20
Summary Cotyledonary somatic embryos ofLarix × leptoeuropaea that developed after various maturation times on media containing abscisic acid showed different frequencies of conversion
into plants. Drying of these somatic embryos under high relative humidity (RH) before germination improved plantlet recovery
and eliminated differences in the performance of somatic embryos matured for different times. However, dehydration of somatic
embryos under 98% RH to a water content below that of zygotic embryos excised from mature seeds (0.97 and 1.36 g H2O/g dry weight, respectively) showed a strong positive correlation between longer maturation time and desiccation tolerance.
Drying somatic embryos at 4° C under 59% RH for 1 wk resulted in desiccation to a water content of 0.30 g H2O/g dry weight, which was the closest to the hydration state of zygotic embryos in dried, stored seeds (0.20 g H2O/g dry weight). Under this condition, only somatic embryos matured for 5 wk germinated and produced plantlets at a relatively
high frequency (73 and 41%, respectively). 相似文献
169.
Naresh Pancholi A. Wetten P. D. S. Caligari 《In vitro cellular & developmental biology. Plant》1995,31(3):127-130
Summary In the genusMusa, germination is extremely variable and relatively difficult. Even more difficulties are faced when producing hybrids. The
seed yield of hybrids in breeding programs is usually low and often, to ensure the viability and survival of seeds, it is
necessary to attempt to germinate a large excess of these seeds. In this context,in vitro embryo culture might be an invaluable tool for obtaining desirable hybrid plants in a short time. Seeds ofMusa velutina were sown in seed trays in a peat-based mixture. Thein vivo seed germination reached 78% but only after 9 mo. Because of this delayed and intermittent germination, embryos were excised
from seeds and inoculated onto half-strength Murashige and Skoog (1962) medium, with or without supplementation with various
concentrations of gibberellic acid. Light and dark conditions were also used to test their effect on embryo germination. After
2 wk, 82% of embryos germinated in the dark on medium containing 0.1 μM gibberellic acid. Addition of gibberellic acid increased the shoot length and root number over the gibberellic acid-free
treatment. Similarly, dark conditions gave a significant increase over light conditions for all the parameters except root
number where light or dark conditions did not make any difference. Thus, the present study highlights the importance of various
components of thein vitro culture ofMusa embryos and the advantage over direct use of greenhouse-sown seeds both in terms of the time taken to germinate and the final
percentage. 相似文献
170.
Shili Miao 《植被学杂志》1995,6(5):697-700
Abstract. In order to explore whether seed size affects plant response to elevated CO2, plants grown from red oak (Quercus rubra L.) acorns were studied for differences in their first year response to CO2 concentrations of 350 and 700 μl/l. Overall, at final harvest, total biomass of plants grown in elevated CO2 were 47 % larger than that of plants grown in ambient CO2. There were significant interactions between CO2 treatments and initial acorn mass for total biomass, as well as for root, leaf, and stem biomass. Although total biomass increased with increasing initial acorn mass for both high and ambient CO2 plants, high CO2 plants exhibited a greater increase than ambient CO2 plants, as indicated by a steeper slope in high CO2 plants. However, CO2 levels did not affect biomass partitioning traits, such as root/shoot ratio, leaf, stem, and root weight ratios, and leaf area ratio. These results suggest that variation in seed size or initial plant size can cause intraspecific variation in response to elevated CO2. 相似文献