Gametophyte development and reproduction of <Emphasis Type="Italic">Argyrochosma nivea</Emphasis> (Pteridaceae)

The gametophyte of Argyroschosma nivea was studied, mainly focusing in its morphological development, and in the apogamous production of sporophytes. Some observations on the spores were also made. As far as it is known, this is the second species of the genus whose gametophytes are studied. The germination pattern followed the Vittaria type. The subsequent developmental processes followed the Ceratopteris type. Some of the gametophytes reached an adult stage with a cordate, symmetric shape, but most of them developed as irregular, lobed prothalli. The sporophyte emerged from the anterior part of the prothallus, without formation of gametangia. First, a cell became active and originated a proliferating area of small cells. From this area, long glandular hairs were formed followed by a projected conical cluster of cells. The cluster elongated into a sporophytic structure and its apex became progressively spatulate and finally trilobulate, with marginal, glandular hairs, stomata and tracheids continuously produced. This sporophyte secreted granules of white farina from its beginnings. The production of farina in the sporophyte but not in the gametophyte could help to support the idea of the segregation of this species from its traditional location in Notholaena to Argyrochosma, as farinose gametophytes seem to be a synapomorphy of the notholenoids, group that includes Notholaena but not Argyroschoma.     

Gametophytic phase of Alsophila odonelliana (Cyatheaceae)

The gametophytic morphology and development of Alsophila odonelliana (Alston) Lehnert, have been studied through in vitro cultures. This species grows in southern Bolivia and northwestern Argentina. The spores are uniform in structure, but not in size; a certain percentage being smaller than the average. 16 spores per sporangium were found. The germination is of the Cyathea type. It was found that spores stored at 4°C can maintain their viability for over two years. The maximum value of germination depends on spore age. The filamentous gametophytes are 4–16 cells long. Young gametophytes have 1–2 branches that give rise to new gametophytes. Male, female, bisexual and neuter gametophytes were found. Propagules were frequently found in neuter gametophytes, and female and bisexual gametophytes were found to have chlorophyll containing scales. The antheridia are made up of five cells and produce non‐viable spermatozoids. The archegonia have necks formed by four columns with four cells each. Most of the gametophytic phase is documented with photomicrographs.     

下延叉蕨和芽胞叉蕨配子体发育的研究

利用光学显微镜详细观察了叉蕨属(Tectaria)下延叉蕨(Tectaria decurrens)和芽胞叉蕨(T.fauriei)的配子体发育过程,记录了配子体各发育阶段的特征。结果表明:(1)下延叉蕨和芽胞叉蕨的孢子均为单裂缝,具周壁,由周壁形成纹饰,孢子极面观椭圆形,赤道面观豆形或肾形。(2)孢子萌发方式为向心型。(3)原叶体发育方式为三叉蕨型。(4)成熟原叶体心脏形,两翼向斜上方扩展。(5)均具单细胞和多细胞毛状体,在丝状体或片状体阶段出现。研究认为,从配子体发育角度看,叉蕨属是较进化的陆生真蕨类;毛状体的类型、位置和出现时间等特征在叉蕨属种间存在差异,可作为该属种间分类的特征。     

EFFECTS OF BENLATE ON FERN GAMETOPHYTE DEVELOPMENT

The widely used fungicide, benlate, was tested for its effect(s) on gametophyte development in the fern Ceratopteris thalictroides (L.) Brongn. The active ingredient of benlate, benomyl, represents 50% of the fungicide by weight. Seven concentrations of benomyl were tested on C. thalictroides gametophytes: 0, 0.001, 0.01, 0.1, 1.0, 10.0 and 100 mg/l. Five developmental stages were observed for possible effects of benomyl. These were 1) germination, and the initiation of 2) antheridia, 3) notch meristems, 4) archegonia, and 5) sporophytes. Overall inhibition was greatest at 100 mg/l benomyl. At 10 mg/l and 100 mg/l, sporophyte initiation was completely blocked. This was probably the consequence of two characteristics found only on gametophytes growing on medium containing 10 mg/l and 100 mg/l benomyl. These characteristics were lack of sperm motility and production of callus growths in the areas proximal to the notch meristems, just proximal to the younger archegonia. Besides blocking the completion of sexual reproduction, the highest concentrations tested also produced smaller (cell number) and chlorotic gametophytes (especially at 100 mg/l). The bigametophyte population (made up of hermaphroditic and male gametophytes) was changed from 51% hermaphrodites (at 0 mg/l benomyl) to 26% hermaphrodites at 100 mg/l. This would, since only hermaphrodites possess archegonia, also decrease the potential for the production of sporophytes.     

Comparative development of gametophytes ofOsmunda lancea andO. japonica (osmundaceae): Adaptation of rheophilous fern gametophyte

Development of the gametophytes of a rehophytic fernOsmunda lancea and a related dryland speciesO. japonica was examined, and adaptation ofO. lancea gametophytes to rheophytic habitat was discussed. The spores ofO. lancea were larger in size and contained larger oil droplets than those ofO. japonica. The germination rate was similar. In agar culture,O. lancea gametophytes grew more rapidly and reached reprudctive maturity earlier thanO. japonica, although there was no prominent gross-morphological difference in developing and mature gametophytes. Sporophyte formation ofO. lancea took place at roughly two times higher rate than that ofO. japonica. TheO. lancea gametophytes might be adapted to the periodically flooded habitat by shortening its life, which is a different strategy from that of the sporophytic generation.     

Mycothallic/mycorrhizal symbiosis of chlorophyllous gametophytes and sporophytes of a fern, Pellaea viridis (Forsk.) Prantl (Pellaeaceae, Pteridales)

Gametophytes of Pellaea viridis that appeared spontaneously on the surface of substratum originating from an ultramafic area were found to form mycothallic symbiosis with arbuscular mycorrhizal fungi (AMF) under laboratory conditions. In gametophytes and sporophytes grown with Glomus tenue, abundant arbuscule formation was observed at both stages. In gametophytes, the fungus was found in the region where the rhizoids are initiated. If G. intraradices was added to the soil, the gametophytes were colonised mostly by G. tenue, and roots of sporophytes were colonised by G. intraradices. The presence of AM fungi in both gametophytes and sporophytes of P. viridis resulted in the development of larger leaf area and root length of the sporophyte. The analysis of gametophytes from the Botanical Garden in Krakow (Poland) showed that cordate gametophytes of Pteridales, namely Pellaea viridis (Pellaeaceae), Adiantum raddianum and A. formosum (Adiantaceae), were also mycothallic.     

Morphology and life history of Scytosiphon canaliculatus comb. nov. (Scytosiphonales,Phaeophyceae) from Japan*

Morphology of field material and life history in culture were studied in Scytosiphon canaliculatus (Setchell et Gardner) comb. nov. from northern Japan. Erect gametophytes of S. canaliculatus are cylindrical, tubular, up to 7 mm wide and 40 cm long, and without regular constrictions. S. canaliculatus has pronounced anisogamy and ascocysts accompanied with plurilocular gametangia. The life history of S. canaliculatus showed an alternation between erect gametophytes and crustose prostrate sporophytes bearing unilocular sporangia. Since field sporophytes of S. canaliculatus were found to be identical with Hapterophycus canaliculatus Setchell et Gardner (Ralfsiaceae, Phaeophyceae), it is proposed to transfer H. canaliculatus to the genus Scytosiphon. In the field, gametophytes with plurilocular gametangia appeared in spring and disappeared in summer. Sporophytes with unilocular sporangia were collected in late autumn and winter. Unilocular sporangia were produced at 15°C in short-day culture conditions and unispores developed into erect gametophytes at 5–15°C. It is suggested that the seasonal Occurrence of gametophytes in the field is due to the seasonal formation of unilocular sporangia, which is regulated by temperature and photoperiod.     

Embryological observations on Tipuana tipu (Benth.) O. Kuntze (Dalbergieae,Papilionaceae)

Abstract

The anther and ovule development of Tipuana tipu is described. Some embryological aspects previously not reported for the family have been pointed out, i.e. the Basic type of anther wall development; the constant occurrence of several megasporo-cytes undergoing meiosis, the concurrent development of more than one megaspore and finally the coexistence of three or four mature gametophytes in the same ovule.     

Growth,radicle and root hair development ofDeschampsia flexuosa (L.) Trin. seedlings in relation to soil acidity

Deschampsia flexuosa (L.) Trin. is an abundant grass species in the ground flora of acidic beech forests in southern Sweden. Generally, the species is restricted to a limited soil pH range (pH 4–5). The main objective was to study the influence of different soil acidities on germination, initial root development and on the growth of the species. The experiments were carried out under controlled conditions and designed to simulate the physico-chemical conditions present in the field. By using forest soils within the pH range 4.0 to 8.3 and artificial variation in pH (3.2 to 7.6) of soil-water extracts, it was possible to evaluate the influence of soil reaction and the H⁺ per se. In all experiments seeds have been used. Germination was significantly delayed in the very acid soil (pH 4.0) in comparison to the germination in soils within the pH range (4.4 to 6.4). Soil substances, other than the H⁺, might be responsible for this delay in germination, whereas development of the radicle was markedly affected by increasing H⁺ concentrations. Especially the development of root hairs was sensitive to H⁺ and was significantly reduced at a pH<-3.8. By increasing soil acidity the injury symptoms, including curling and discolouring, became more intense and at the highest acidity (pH 3.2) the radicles appeared brown, stunted and the root hairs were lacking. Most favourable growth was obtained at pH 4.4 and 5.0. Soil pH levels above and below this range limited both shoot and root growth. The results showed very good correspondence with observations made in Beech forest soils in southern Sweden, where the species was growing in soils within the pH range 3.9 to 5.1 with a peak growth at pH 4.3. This study shows that in soils at pH≤3.8, the poor development of the radicle may be crucial in the establishment ofDeschampsia flexuosa. Root hair development was more sensitive to soil acidity than radicle elongation. Germination was delayed in very acid Beech forest soils but other factors than the H-ion per se may be responsible for this delay.     

On the glandular hairs of Cistus laurifolius L. (Cistaceae)

Abstract

Two types of glandular hairs have been found in Cistus laurifolius L. (Cistaceae). Both types present a great degree of morphological and histochemical variability, not only at population level but even within a single plant. This fact excludes that the hairs of C. laurifolius could be given a diagnostic value. The two hair types have a mixed hydrophilous and lipophilous secretion in which we have identified, especially in one type of them, cathecolic tannins. The powerful antimycotic activity of such tannins, makes the hairs particularly interesting for the possible ecological implications.     

Carbohydrate Composition during Germination and Outgrowth of Ascospores of Saccharomyces cerevisiae

Single spores of Saccharomyces cerevisiae were examined to distinguish changes in the synthesis and degradation of intracellular and wall carbohydrates during germination and outgrowth. Intracellular carbohydrate was fractionated into trehalose and glycogen. Trehalose degradation occurred during germination and outgrowth. The intracellular glycogen was degraded during germination and then synthesized during outgrowth. Wall carbohydrate was fractionated into glycogen, glucan and mannan. The wall glycogen and the KOH-soluble glucan were degraded during germination and then synthesized prior to and during outgrowth, respectively. The major component of the KOH-insoluble glucan in the wall is β-1,3-glucan. The glucan and mannan were synthesized during outgrowth.

The study revealed that the development of a vegetative cell from a spore follows rapid decreases in the amounts of trehalose, glycogen and KOH-soluble glucan during germination, and great increases in the amounts of glycogen, β-1,3-glucan and mannan during outgrowth.     

A comparison between two populations of Lessonia trabeculata (Phaeophyta: Laminariales) microscopic stages

Lessonia trabeculata is the most important brown seaweed in northern Chilean subtidal environments. It usually grows in areas with high to moderately high water movement, and only occasionally in sheltered habitats. These different hydrodynamic environments produce morphologically and physiologically distinct plants. The purpose of this study was to determine probable differences in reproductive features between two L. trabeculata populations exposed to different water movement intensities. The zoospore production, settlement, germination, gametophyte fertility and survival were studied.Zoospore release and spore attachment capacity were higher from blades from El Francés Beach, the locality with higher water movement energy. Germination at 24 hours was higher in the germlings from El Francés Beach than those from La Herradura Bay. However, after 4 days of culture germination rates were similar. Average survival rates of gametophytes were similar for both populations. After 20 days culturing gametophytes from El Francés Beach fertilization was observed, while in samples from La Herradura Bay the sporophytes were seen at 27d.The results suggest a higher reproductive vitality in plants of Lessonia trabeculata living in an environment with an active water movement, than plants growing in a sheltered environment.     

Gametophyte development of Woodwardia radicans (L.) Sm.: Effect of population density and antheridiogen on sex expression

Abstract

Gametophyte development of Woorwardia radicans was studied in controlled culture conditions, as well as the effect of population density and antheridiogen on sex expression. The pattern of gametophyte development is not affected by temperature, while sex expression of gametophytes is affected by sowing density, by the presence in the culture medium of «antheridiogen» and by the nutritional conditions of gametophytes. The probable effects of antheridiogen and population density on the observed developmental pattern are considered.     

Efficient induction of apospory and apogamy in vitro in silver fern (Pityrogramma calomelanos L.)

Silver fern (Pityrogramma calomelanos L.) is a terrestrial or lithophytic herbaceous fern used for ornamental and medicinal purposes. In its farina it produces the cytotoxic and anticancer compound dihydrochalcone. In vitro induction of apospory and apogamy, and direct field establishment of aposporous gametophytes and subsequent sporophyte development has been accomplished. Half-strength Murashige and Skoog (MS) medium with 3.33 μM N⁶-benzyladenine (BA) and 2.32 μM kinetin (Kn) showed earlier development and produced higher numbers of aposporous gametophytes than half-strength MS basal medium. Crozier explants developed higher numbers (mean value 29.2) of gametophytes, but were slower than frond explants (mean value 23.2). The gametophytes originated from the epidermal hairs progressed from uniseriate filamentous to cordate through bi-, tri- and multiseriate and spatulate stage with the development of antheridia. Reduction in the nutrient and sucrose concentrations in the media favoured apogamy. Sucrose-free 1/10 strength MS medium and agar plates developed a mean of 30.4 and 29.9 sporophytes, respectively in the light. The greenhouse-established gametophytes developed sporophytes. The established sporophytes ex vitro showed 95% survival rate. Apogamous sporophytes and the source plant showed the same chromosome numbers (2n=116). The established protocol accomplishes apogamy and apospory in silver fern, and the aposporous gametophytes can be used for genetic transformation and development of transgenic silver fern.     

Chemical characterization of cell-wall polysaccharides from tank-cultivated and wild plants ofDelesseria sanguinea (Hudson) Lamouroux (Ceramiales,delesseriaceae): culture patterns and potent anticoagulant activity

Tank cultivation ofDelesseria sanguinea was investigated in order to manipulate conditions for vegetative growth and to provide biomass for the analysis of cell wall polysaccharides. Seasonality is subject to short-day photoperiodic control. Night-break or long-day conditions prevented fertility in tetrasporophytes and gametophytes and triggered outgrowth of new blades. Long-day illuminations allowed a 1% daily growth rate. Seawater temperature below 13 °C was necessary for inducing formation of new blades. Both wild and cultivated ofD. sanguinea plants contained a non gelling sulfated heteropolysaccharide composed of a galactosyl backbone branched with xylosyl residues. The hot water extract at neutral pH displayed the highest anticoagulant activity (5 μg ml^-1 polysaccharide concentration in APTT clotting assay). No obvious differences were found in polysaccharide chemical composition and properties between gametophytes and sporophytes or between cultivated and wild plants.     

Effect of temperature and photon fluence rate on gametophytes and young sporophytes of Laminaria ochroleuca Pylaie

We analysed the effects of temperature and photon fluence rate on meiospore germination, growth and fertility of gametophytes, and growth of young sporophytes of Laminaria ochroleuca. Maximum percentages of germination (91–98%) were obtained at 15°C and 18°C, independent of photon fluence rate. Optimal development of female gametophyte and maximum fecundity and reproductive success of gametophytes occurred at 15°C and 18°C and at 20 and 40 μmol m^–2 s^–1. Maximum relative growth rate of young sporophytes after 2 weeks of culture was achieved under the same conditions. L. ochroleuca gametophytes cannot reproduce and growth of its sporophytes is not competitive at temperatures close to 10°C. Received in revised form: 31 August 2001 Electronic Publication     

环境因子对中华双扇蕨孢子萌发的影响

为了解珍稀濒危植物中华双扇蕨(Dipteris chinensis)濒危原因,研究了温度和湿度对其孢子萌发的影响.结果表明,中华双扇蕨孢子萌发能力较强,萌发方式为Vittaria型,配子体萌发为Marattia型.中华双扇蕨孢子繁殖不受温度影响,而湿度显著影响孢子繁殖过程,湿润环境中孢子正常萌发,并形成心形配子体,顺利...     

Phenology of Paralemanea mexicana (Batrachospermales,Rhodophyta) in a high‐altitude stream in central Mexico

The morphology and phenology of Paralemanea mexicana (Kützing) Vis et Sheath was evaluated seasonally in a fifth order high‐altitude stream in central Mexico. The gametophytes grew during oligotrophic and eutrophic conditions, and during particular microhabitat conditions: high current velocity (40–240 cm s^?1), low to medium irradiance (5–973 μmol photons m^?2 s^?1), and shallow depth (1–30 cm). The abundance of gametophytes was positively correlated with low temperature, high current velocity and concentrations of soluble reactive phosphorus. Interestingly, monoecious gametophytes formed two types of branches, true branches with sympodial pattern originating from meristematic cells in variable number, and abundant false branches produced during the development of the ‘Chantransia’ stage in the surface of the gametophyte or by uniseriate filaments arising within the thallus lumen. These filaments generally produce gametophytes and suggest that they could support the germination of carpospores. The frequently whorled branches are the result of a false branching pattern and are exclusive to P. mexicana. These morphological and reproductive characteristics appear to be biomechanical adaptations to avoid detachment and increase reproductive success. Efficient reproductive strategies of P. mexicana observed in this study can be interpreted as adaptations to successfully colonize streams; however, these features may not have been common in the study region due to restricted microhabitat conditions and geographic isolation.     

东北蕨类植物配子体发育的研究X.岩蕨科

在室内培养条件下,详尽地比较观察了我国东北产的岩蕨科２属４种的配子体发育过程,了解该科在配子体发育上的特征,来说明建立岩蕨科的合理性和种属间的区别。