蕨类植物孢子萌发及原叶体发育的观察

以腐叶土为培养基质,对21种蕨类植物进行了孢子萌发和原叶体发育的研究,结果表明：①不同时期播种的同种蕨类的孢子,发育出原叶体和幼孢子体所历经的时间长短不同;②孢子萌发和配子体生长发育的适宜温度约为15～24℃;⑨稀有蕨类的孢子萌发率低,而在野外能形成较大种群的蕨类的孢子萌发率高;④用GA3处理孢子可以促进萌发;⑤当原叶体上长出幼孢子体时,原叶体由大变小,由绿变黄,21种蕨类的原叶体都在幼孢子体上长出第3片叶时消失;⑥幼孢子体上长出的第1、2片叶在形态上与以后长出的叶不同;⑦孢子萌发需要光;⑧1片原叶体尽管有多个颈卵器,但仅发育出1株幼孢子体;⑨利用腐叶土进行蕨类孢子繁殖是一种经济实用的繁殖方法。     

Endogenous Gibberellins from Sporophytes of Two Tree Ferns, Cibotium glaucum and Dicksonia antarctica

Gibberellin A₁ (GA₁), 3-epi-GA₁, GA₄, GA₉, 11α-hydroxyGA₁₂, 12α-hydroxyGA₁₂, GA₁₅, GA₁₇, GA₁₉, GA₂₀, GA₂₅, GA₃₇, GA₄₀, GA₅₈, GA₆₉, GA₇₀, and GA₇₁ have been identified from Kovats retention indices and full scan mass spectra by capillary GC-MS analyses of purified extracts from sporophytes of the tree fern, Cibotium glaucum. Abscisic acid, dihydrophaseic acid, an epimer of 4′-dihydrophaseic acid, and the epimeric ent-6α, 7α, 16α, 17-(OH)₄ and ent-6α, 7α, 16β, 17-(OH)₄ derivatives of ent16, 17-dihydrokaurenoic acid, in addition to the epimeric 16α, 17- and 16β, 17-dihydroxy-16, 17-dihydro derivatives of GA₁₂, were also identified in extracts of C. glaucum. An oxodihydrophaseic acid and a hydroxydihydrophaseic acid were also detected. In extracts of sporophytes of Dicksonia antarctica, GA₄, GA₉, 12α- and 12β-hydroxyGA₁₂, GA₁₅, GA₂₅, and GA₃₇ were identified by the same criteria, as well as abscisic acid, phaseic acid, 8′-hydroxymethylabscisic acid and dihydrophaseic acid. This is the first time that GA₄₀ has been identified in a higher plant; it is also the first report of the natural occurrence of the two gibberellins, 11α- and 12β-hydroxyGA₁₂. The total gibberellin (GA) content in C. glaucum (tall) was at least one order of magnitude greater than that of D. antarctica (dwarf) based on total ion current response in GC-MS and bioassay data. Abscisic acid was a major component of D. antarctica and the oxodihydrophaseic acid was a major component of C. glaucum.     

Shade does not ameliorate drought effects on the tree fern species Dicksonia antarctica and Cyathea australis

We examined the responses of two tree fern species (Dicksonia antarctica and Cyathea australis) growing under moderate and high light regimes to short-term water deficit followed by rewatering. Under adequate water supply, morphological and photosynthetic characteristics differed between species. D. antarctica, although putatively the more shade and less drought adapted species, had greater chlorophyll a/b ratio, and greater water use efficiency and less negative δ¹³C. Both species were susceptible to water deficit regardless of the light regime showing significant decreases in photosynthetic parameters (A _max, V _cmax, J _max) and stomatal conductance (g _s ) in conjunction with decreased relative frond water content (RWC) and predawn frond water potential (Ψ_predawn). During the water deficit period, decreases in g _s in both species started one day later, and were at lower soil water content, under moderate light compared with high light. D. antarctica under moderate light was more vulnerable to drought than all other plants as was indicated by greater decreases in Ψ_predawn, lowest stomatal conductance, and photosynthetic rates. Both tree fern species were able to recover after a short but severe water stress.     

Spore morphology and ultrastructure of Cyathea (Cyatheaceae,Pteridophyta) species from southern South America

Spore sculpture and wall structure of eight Cyathea (Cyatheaceae) species from southern South America were studied using light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Two layers, i.e. an inner and an outer layer, were observed in the perispore. The inner layer has two strata: the inner stratum is attached to the exospore and composed of rodlets tangentially oriented to the spore surface and randomly intermixed; the outer stratum consists of a three-dimensional network of rodlets with either free or fused distal edges forming spinules. The outer layer is thin, darkly contrasted and covers the rodlets. In most cases, the exospore has two layers and a pitted surface. In Cyathea atrovirens, the exospore surface is smooth, while in C. delgadii and C. myriotricha it is verrucate. The homogeneity of perispore features within the genus Cyathea is evident, while exospore features are heterogeneous. The exospore has different kinds of surface-structures that are of potential interest for assessing evolutionary trends within the group.     

Tree Ferns in the Interior and at the Edge of a Mexican Cloud Forest Remnant: Spore Germination and Sporophyte Survival and Establishment1

The three most common tree fern species in a Mexican montane cloud forest fragment (Alsophila firma, Lophosoria quadripinnata and Sphaeropteris horrida) were selected for laboratory and transplant experiments. The objectives were: (1) to determine the percentage of spore germination and gametophytes producing sporophytes, and (2) to compare early establishment of sporophytes at the edge and in the interior of the forest. Percent spore germination varied between 16 and 86 percent, and the number of gametophytes that produced sporophytes was high (>50%). Survival and growth of sporophytes differed between species and habitats. Survival was greater at the edge than in the forest interior for Lophosoria, but it was similar for Alsophila and Sphaeropteris. Number and length of fronds were higher at the forest edge for individuals of Alsophila and Lophosoria, but not for Sphaeropteris. RGR was higher at the forest edge than in the forest interior for sporophytes of the three species. This study suggests that the forest edge is an appropriate habitat for establishment of Alsophila and Lophosoria, but Sphaeropteris is apparently a forest interior species.     

Analysis of the Dynamics of a Bacillus subtilis Spore Germination Protein Complex during Spore Germination and Outgrowth

Germination of Bacillus subtilis spores is normally initiated when nutrients from the environment interact with germinant receptors (GRs) in the spores'' inner membrane (IM), in which most of the lipids are immobile. GRs and another germination protein, GerD, colocalize in the IM of dormant spores in a small focus termed the “germinosome,” and this colocalization or focus formation is dependent upon GerD, which is also essential for rapid GR-dependent spore germination. To determine the fate of the germinosome and germination proteins during spore germination and outgrowth, we employed differential interference microscopy and epifluorescence microscopy to track germinating spores with fluorescent fusions to germination proteins and used Western blot analyses to measure germination protein levels. We found that after initiation of spore germination, the germinosome foci ultimately changed into larger disperse patterns, with ≥75% of spore populations displaying this pattern in spores germinated for 1 h, although >80% of spores germinated for 30 min retained the germinosome foci. Western blot analysis revealed that levels of GR proteins and the SpoVA proteins essential for dipicolinic acid release changed minimally during this period, although GerD levels decreased ∼50% within 15 min in germinated spores. Since the dispersion of the germinosome during germination was slower than the decrease in GerD levels, either germinosome stability is not compromised by ∼2-fold decreases in GerD levels or other factors, such as restoration of rapid IM lipid mobility, are also significant in germinosome dispersion as spore germination proceeds.     

New Materials of the Early Cretaceous Monolete Spore Ferns and Their Taxonomic Study

Based upon the characters of the fertile segments and the reproductive structures, four early Cretaceous monolete spore ferns: Athyrium asymmetricum (Meng) comb. nov. of Athyriaceae, Asplenium popovii Samylina of Aspleniaceae, Dryopterites gracilis sp. nov. and D. liaoningensis sp. nov. of Dryopteriaceae have been described from Xiaoming′anbei Formation, Tiefa Basin, Liaoning Province, China.     

Fine Structure and Spore Germination in Fusarium culmorum

The fine structure of the macroconidium of Fusarium culmorum(W. G. Smith) Sacc. is described. The presence of a mucilaginouscoat around the conidium and its expansion during germinationare confirmed. Studies of germinating conidia have shown changesin the numbers of organelles. The germ tube is shown to be formedfrom an entirely new wall laid down in the conidium, and theemergence of the germ tube is brought about by lysis of theoriginal condial wall.     

Ribosomal Competence and Spore Germination in Fusarium solani

Extracts prepared from macroconidia of Fusarium solani f. sp. phaseoli are capable, under defined conditions, of incorporating phenylalanine into polypeptide with exogenous polyuridylic acid as messenger. Extracts from ungerminated and germinated spores have approximately the same activity. With endogenous template, leucine incorporation occurs, but in this reaction extracts from germinated spores have about 10 times more activity than do those from ungerminated spores. It is suggested that the low rate in ungerminated spores is attributable to a relative deficiency in the number of ribosomes which are organized into polysomes.     

Cytology of Spore Germination in Clostridium pectinovorum

The process of spore germination in Clostridium pectinovorum has been followed by phase-contrast and electron microscopy. Unlike most other Bacillaceae, germination of this species takes place within the sporangium. Under phase-contrast, the spore darkens and swells slightly, and then the vegetative rod slips out through the end opposite the collar-like extension of the sporangium. In thin sections, a spore from an early stage in germination consists of a central protoplast, core membrane, germ cell wall, cortex, and two coats. Within a short period, the cortex disintegrates and the young cell develops. It possesses a large fibrillar nucleoplasm and several mesosomes. Subsequently, the young cell elongates, becomes somewhat deformed, and then emerges through a narrow aperture in the inflexible coats of the spore, finally rupturing the sporangium. Free vegetative cells of C. pectinovorum resemble in their structure other gram-positive rods.     

Photoinduction of Spore Germination in a Fern, Mohria caffrorum

Irradiation of spores of the fern Mohria caffrorum Sw. witheither red light (67.4 µW cm^–2) or far-red light(63.2 µW cm^–2) for a period of 24 h induced maximumlevels of germination. Brief irradiations with blue light (127.6µW cm^–2) administered before or after photoinductioncompletely nullified the effects of red or far-red light; however,with prolonged exposure to blue light, germination levels roseto near maximum. The similar effects of red and far-red lightin promoting spore germination makes the involvement of phytochromein this process questionable. Based on energy requirements,the promotive and inhibitory phases of blue light appear toinvolve independent modes of action. Mohria caffrorum, ferns, spore germination, photoinduction, phytochrome     

Inhibition of Spore Germination in the Cellular Slime Moulds

The phenomenon of auto-inhibition of spore germination has beendemonstrated in the slime moulds Dictyostelium purpureum, strainno. 2; Dictyostelium discoideum, strain no. 1; Dictyosteliummucoroides, strain no. 2; and Polysphondy-Iium violeceum, strainno. 6. A water-soluble substance present in spores was shownto cause this self-inhibition. The substance was isolated fromeach species studied. Evidence as presented indicates that thesame substance occurs in each species of Dictyostelium, butthat it differs from that found in Pv6. An attempt was alsomade to relate this inhibitory substance to the phenomenon of'differential inhibition' in Dp2, Dd, Dm2, and Pu6. An explanationbased on evidence for differential sensitivity to a common inhibitorof spore germination in Dictyostelium and an inhibition in otherthan the spore stage in Pu6 is presented. Apparent differentialproduction of a common inhibitor in Dictyostelium is also reported.     

Changes in Microsporum gypseum Mycelial Wall and Spore Coat Glycoproteins During Sporulation and Spore Germination

Ethylenediamine-soluble glycoproteins were extracted from isolated Microsporum gypseum hyphal walls during sporulation and from spore coats before and after germination. This study was carried out to identify a sporulation-specific cell wall protein that possibly served as a substrate for the alkaline protease which initiated the macroconidial germination of this fungus. Analyses revealed that water-insoluble glycoprotein accounted for 10% of the ungerminated spore coat but only for 4 to 5% of the mycelial wall dry weight. This fraction was modified in its amino acid composition during sporulation, and it decreased in protein content during spore germination. Water-soluble glycoprotein, which accounted for approximately 3 to 3.5% of either the spore coat or mycelial wall dry weight, was of similar amino acid composition from both sources and did not decrease in protein content upon spore germination. The water-insoluble glycoprotein was found to be rich in leucine, aspartic acid, glycine, glutamic acid, and phenylalanine residues. The water-soluble glycoprotein was rich in proline, threonine, glycine, serine, glutamic acid, and alanine.     

Spore Germination in the True Slime Mold Didymium nigripes1

The morphology of spore germination in Didymium nigripes was studied using scanning electron microscopy and Nomarski phase optics. First, the outer spore wall splits, revealing a fibrillar inner wall. Remnants of the inner wall continue to cover the newly emerged amoeba. A single nucleus and a prominent vacuole are visible throughout germination. Germination is more rapid in glucose-peptone-yeast extract than in phosphate buffer. Germination is completely inhibited at 4°C, and is very slow at 18°C. Germination is most rapid at 26°C; at 21°C or 32°C it is slightly slower. Germination is reversibly inhibited by 20 μ/ml cycloheximide, but not by 200 μ/ml 5-fluoro uracil or 200 μ/ml proflavin. It is completely inhibited by 10^-3 M Na azide.