Characteristics of spore germination and protonemal development in Hypnum pacleseens

The spore germination, protonemal development, and gametophyte differentiation of Hypnum pacleseens were observed in cultivation. Photomicrographs showed that spore germination of Hypnum pacleseens occured within the exospore. Its protonema is massive with filamentous chloronema formed inside. The terminal part of the chloronema differentiated into filamentous caulonema and its rhizoid was derived from the apical cell of the filamentous chloronema. The initial cell of gametophyte differentiated from chloronema and caulonema. Sporeling-type of Hypnum pacleseens is developmentally similar to Glyphmitrium-type.     

大帽藓(Encalypta ciliata Hedw.)原丝体发育特征的实验研究

在人工培养大帽藓(Encalypta ciliata Hedw．)孢子的基础上,对其孢子萌发、原丝体发育及配子体发生的全过程进行行了观察、描绘和照相。实验结果表明：在大帽藓的原丝体系统中主要包括两种成分,即：粗短的丝状绿丝体和细长的柳枝状轴丝体。丝状绿丝体一般由4～6个短粗柱状细胞组成,而轴丝体则是由多数细长柱形细胞构成,其上间隔分布有2～5个细胞组成的棒状体,初生假根有或者无。同时,还对大帽藓原丝体发育的特征进行了分析和讨论,初步确定大帽藓孢子萌发属于新的孢子萌发类型——大帽藓型(Encalypta-type)。     

大帽藓(Encalypta ciliata Hedw.)原丝体发育特征的实验研究

在人工培养大帽藓(Encalypta ciliata Hedw.)孢子的基础上,对其孢子萌发、原丝体发育及配子体发生的全过程进行了观察、描绘和照相。实验结果表明:在大帽藓的原丝体系统中主要包括两种成分,即:粗短的丝状绿丝体和细长的柳枝状轴丝体。丝状绿丝体一般由4～6个短粗柱状细胞组成;而轴丝体则是由多数细长柱形细胞构成,其上间隔分布有2～5个细胞组成的棒状体,初生假根有或者无。同时,还对大帽藓原丝体发育的特征进行了分析和讨论,初步确定大帽藓孢子萌发属于新的孢子萌发类型——大帽藓型(Encalypta-type)。     

梨蒴珠藓孢子萌发与原丝体发育特征研究

为了解梨蒴珠藓（Bartramia pomiformis）孢子萌发和原丝体发育特征,在显微镜下观察室内人工培养的梨蒴珠藓单倍配子体发育过程。结果表明,梨蒴珠藓孢子吸水膨胀5 d后,开始破壁萌发,原丝体系统以丝状绿丝体为主,轴丝体在绿丝体上分化产生。培养22 d后,配子体在轴丝体细胞上分化产生。参照Nishida的标准,梨蒴珠藓孢子萌发类型为真藓型（Bryum-type）。这为梨蒴珠藓的人工扩繁提供了发育学基础资料。     

尖叶拟船叶藓原丝体发育特征研究

将尖叶拟船叶藓[Dolichomitriopsis diversiformis(Mitt.)Nog.]孢子接种于Knop培养基上,置于恒温培养箱中培养,在光学显微镜下对其原丝体(protonema)发育特征进行了详细观察和记录。结果表明:孢子第2天就开始萌发,第6天时其萌发率达90%以上;原丝体系统由绿丝体(chloronema)和轴丝体(caulonema)构成,假根(rhizoides)产生于芽体基部,由轴丝体退化而成;配子枝原始细胞产生于绿丝体分枝的基部或轴丝体上的斜壁细胞;配子枝(game tophore)形成后其上各部位都可形成假根;孢子萌发类型为真藓型(Bryum-type)。     

碎米藓属两种藓类植物孢子萌发与原丝体发育特征研究

为获取其孢子萌发类型与该属植物系统发育、生态选择以及生殖策略选择的相关性,该研究通过室内人工培养的方式,在微米量级下观察并描述了碎米藓属(Fabronia)碎米藓(F.pusilla)和东亚碎米藓(F.matsumurae)两种藓类植物孢子萌发、原丝体发育和配子体发生的过程.结果表明:(1)两种藓类植物孢子均为壁外萌发...     

中华缩叶藓孢子萌发与原丝体发育特征研究

通过室内人工培养中华缩叶藓的孢子,在光学显微镜下详细观察了其孢子萌发、原丝体发育及配子体发生的全过程.结果表明:中华缩叶藓的孢子在壁内萌发,随后分裂产生块状原丝体;块状原丝体上可产生两种丝状体,一种是具疣的棒状原丝体,另一种是由长圆柱状细胞组成的轴丝体;配子体原始细胞只产生于块状原丝体上.根据中华缩叶藓的孢子萌发和原丝体发育特征,并参照Nishida对藓类植物孢子萌发类型的划分,确定中华缩叶藓的萌发孢子型应属于缩叶藓型(Ptychomitrium-type).     

仙鹤藓的孢子萌发及愈伤组织诱导

通过对采自河北雾灵山海拔1500m的仙鹤藓（Atrichum undulatum）的孢子萌发以及原丝体发育的观察,发现仙鹤藓孢子无休眠现象,孢子接种3天左右萌发：其原丝体发育分为绿丝体和轴丝体两个阶段。扩大培养实验结果表明。仙鹤藓茎叶体在添加2％葡萄糖的MS培养基上,置于25℃／20℃、14小时光照/10小时黑暗、36μmol·m^-2·s^-1条件下培养．产生新生茎叶体最多,且茎叶体长势最好,可以获得大量无菌材料。仙鹤藓愈伤组织诱导实验显示,形成愈伤组织的最佳培养基为添加2％葡萄糖和1．0mg·L^-16-BA的MS培养基。     

Unique Tissue-Specific Cell Cycle in Physcomitrella

Abstract: The moss Physcomitrella patens (Hedw.) B.S.G. is a novel tool in plant functional genomics as it has an inimitable high gene targeting efficiency facilitating the establishment of gene/function relationships.
Here we report, based on flow cytrometric (FCM) data, that the basic nuclear DNA content per cell of Physcomitrella is 0.53 pg, equating to a genome size of 1 C = 511 Mbp. Furthermore, we describe a unique tissue-specific cell cycle change in this plant. Young plants consisting of only one cell type (chloronema) displayed one single peak of fluorescence in FCM analyses. As soon as the second cell type (caulonema) developed from chloronema, a second peak of fluorescence at half the intensity of the previous one became detectable, indicating that caulonema cells were predominantly at the G1/S transition, whereas chloronema cells were mainly accumulating at the G2/M transition. This conclusion was validated by further evidence: i) The addition of ammonium tartrate arrested Physcomitrella in the chloronema state and in G2/M. ii) Two different developmental mutants, known to be arrested in the chloronema/caulonema transition, remained in G2/M, regardless of age and treatment. iii) The addition of auxin or cytokinin induced the formation of caulonema, as well as decreasing the amount of cells in G2/M phase. Additionally, plant growth regulators promoted endopolyploidisation.
Thus, cell cycle and cell differentiation are closely linked in Physcomitrella and effects of plant hormones and environmental factors on both processes can be analysed in a straight forward way. We speculate that this unique tissue-specific cell cycle arrest may be the reason for the uniquely high rate of homologous recombination found in the Physcomitrella nuclear DNA.     

On the formation of protonema ofDrummondia sinensis of the orthotrichaceae

In the present study, the mode of formation of the protonema ofDrummondia sinensis is recorded and the relationship between the sporeling type as a response to ecological adaptation is discussed. A spore germinates inside the stretched exospore, and later forms a massive protonema consisting of 8–20 cells. Soon after, the stretched spore coat ruptures and a mass of 5–6 cells protrdes from the broken exospore. In this species neither chloronema nor caulonema could be observed, although such is often seen in other species of Bryales. An initial cell of the leafy shoot is formed from the apical cell of the massive protonema.     

垂蒴真藓原丝体发育特征的研究

在室内培养垂蒴真藓(Bryum uliginosum)孢子的基础上,对其孢子萌发、原丝体发育及配子体发生的全过程进行了跟踪观察。结果表明：该种孢子萌发后直接产生绿丝体。而轴丝体和假根仅在绿丝体上产生;配子体原始细胞产生于绿丝体基部细胞或轴丝体上。由此可以看出：垂蒴真藓属于真藓型孢子萌发型(Bryum-type)。     

Occurrence and biosynthesis of auxin in protonema of the moss Funaria hygrometrica

We have investigated the presence of auxin and the ability of chloronema cells to synthesize indole-3-acetic acid (IAA) in axenic protonema cell cultures of the moss Funaria hygrometrica. The endogenous level of auxin activity was 4 and 7μg-IAA equivalents/kg in caulonema and chloronema cell types, respectively. Based on an indole-α-pyrone fluorometric assay, the level of putative IAA was observed to be 5.0 and 1.9.μg/kg in caulonema and chloronema cells, respectively. [³H]Tryptophan was metabolized into IAA via the indole-pyruvate pathway by intact chloronema cells and also by the cell free homogenates. More [³H]IAA accumulated when homogenates from cells pre-grown at low cell densities (< 0.5 mg/ml) as compared to those at high cell densities ( > 0.5 mg/ml) were used. Since the activities of peroxidase and IAA-oxidase are known to be high at high cell densities, the lack of accumulation of radioactivity in IAA at high densities can be attributed to a high level of IAA-oxidizing enzymes. Our results suggest a possible relationship between IAA accumulation and caulonema differentiation.     

Jasmonic acid promotes division of fern protoplasts, elongation of rhizoids and early development of gametophytes

The effects of jasmonic acid (JA) on spore germination, early gametophyte development and sporophytic protoplast culture of the fern Platycerium bifurcalum (Cav.) C. Chr. were investigated. JA and no influence on spore germination and primary rhizoid initiation, but significantly promoted early gametophyte development, which was evident from the longer primary rhizoids as well as the higher number of rhizoids and cells per gametophyte. Jasmonic acid (1 μ M ) also promoted the transition of gametophytes from a filamentous to a planar growth. Optimal primary rhizoid elongation and highest cell division activities in the gametophytes were observed at 0.01–1 μ M JA, while the highest number of rhizoids on gametophytes was obtained at 0.1–1 μ M JA. Jasmonic acid (0.01 μ M ) also stimulated initial protoplast divisions. Except for the experiment in which the effect of JA on germination was tested. JA concentrations exceeding 1 μ M did not promote cell elongation or cell division but were instead inhibitory. On the basis of these findings, we propose that JA may be involved in early stages of P. bifurcatum development.     

阔叶鳞盖蕨和粗毛鳞盖蕨(碗蕨科)配子体发育的研究

以腐殖土为基质,对阔叶鳞盖蕨Microlepia patyphylla（D．Don）J．Sm．和粗毛鳞盖蕨M.strigosa（Thunb．）Presl进行了孢子繁殖;利用光学显微镜观察和记录了它们的孢子萌发和配子体发育过程。结果表明,两者的孢子及配子体性状极为相似：孢子同型,三裂缝,萌发慢;孢子萌发需要光,萌发方式为书带蕨型Vittaria-type;配子体生长慢,发育类型为铁线蕨型Adiantum—type;原叶体心形或其他形状,无毛状体,多数为雌雄异株。性器类型为薄囊蕨型Leptosporangiate-type。它们既具有大量的原始性状,也具有少数进化性状。与阔叶鳞盖蕨相比,粗毛鳞盖蕨的配子体发育特征更为原始。说明粗己鳞盖蕨的系统位置更加低下。首次观察到阔叶鳞盖蕨中细胞自然死亡时的叶绿体聚集现象。粗毛鳞盖蕨原叶体老化时叶绿体呈现规则的、相互镶嵌的多边形的形状以及在正常光照下粗毛鳞盖蕨某些细胞中的部分叶绿体成链珠状排列等现象。     

Cytokinin induces the developmentally restricted synthesis of an extracellular protein in Physcomitrella patens

Early development of the moss Physcomitrella patens follows a simple course leading to the formation of a filamentous protonema containing only two cell-types, chloronema and caulonema. The addition of the hormone cytokinin leads to the induction of multicellular buds from such protonema. The spectrum of extracellular proteins (ECPs) synthesized by P. patens has been investigated at defined stages of development and under defined hormone treatments. It is found that in contrast to the limited changes in intracellular protein synthesis detectable, in the extracellular environment major and specific changes in the patterns of proteins synthesized occur. For example, the presence of caulonema cells is characterized by the synthesis of a 25 kDa ECP whereas early chloronema differentiation is distinguished by the presence of a 38 kDa ECP. The analysis of the pattern of ECPs synthesized by developmental mutants altered in bud formation, and in response to cytokinin in tunicamycin treated protonema (in which bud induction is blocked) indicate that the synthesis of a 14 kDa ECP is specifically induced by cytokinin. This protein represents a novel cytokinin-induced ECP. These data show that the differentiation of particular cell types in plants is associated with the synthesis of particular ECPs, and suggest that hormones which induce specific morphogenic events may do so via the synthesis of specific ECPs.     

Connection between the Synthesis of Differentiation Specific Proteins and the Capacity of Cells to Respond to Cytokinin in the Moss Funaria

The differentiation stage of the caulonema in Funaria hygrometrica protonema is distinguished from the chloronema stage by three additional protein bands (CSP) in the soluble protein fraction. During the change of caulonema to chloronema, which is induced by isolation of single filaments (regeneration), the CSP disappear. This is not the consequence of an accelerated degradation or turnover but of a gradual termination in the de novo synthesis of CSP during regeneration as demonstrated by pulse-chase experiments with l -[4,5–³H] leucine. Cytokinin inhibits the termination of the synthesis of CSP. The decrease in synthesis parallels the decrease in ability of the isolated caulonema cells to respond to cytokinin via bud formation. It is therefore concluded that the CSP are involved in the competence of caulonema cells to respond to cytokinins.     

Both chloronemal and caulonemal cells expand by tip growth in the moss Physcomitrella patens

Tip growth is a mode of cell expansion in which all growth is restricted to a small area that forms a tip in an elongating cell. In green plants, tip growth has been shown to occur in root hairs, pollen tubes, rhizoids, and caulonema. Each of these cell types has a longitudinally elongated shape, longitudinally oriented microtubules and actin microfilaments, and a characteristic cytoplasmic organization at the growing tip which is required for growth. Chloronema are elongated cylindrical shaped cells that form during the development of the moss protonema. Since there are no published reports on the precise mode of chloronema elongation and conflicting interpretations of its cytology, the mechanism of cell growth has remained unclear. To determine if chloronema elongate by tip or diffuse growth, time-lapse light microscopy was employed to follow the movement of fluorescent microspheres attached to the surface of growing cells. It is shown here that chloronemal cells elongate by a form of tip growth. However, the slower growth of chloronema compared with caulonema is probably the result of differences in cytological organization of the growing tip.     

Distribution of activated calmodulin in the chloronema tip cells of the moss Funaria hygrometrica

Auxin (indole-3-acetic acid) regulates caulonema differentiation as a result of gradual transitional events in the chloronema tip cells in moss protonema. This auxin action in the moss Funaria hygrometrica involves a rapid influx of calcium ions from the extracellular medium. This investigation demonstrates spatial and temporal changes in calmodulin (CaM) activation (formation of Ca(2+)-CaM complex) in the chloronema tip cells subjected to auxin treatment. Photomicroscopic localisation of the fluorescence (excitation at 365 nm and emission of 397 nm) from the tricomplex of Ca(2+)-CaM with trifluoperazine (TFP, a blocker of Ca(2+)-CaM action) shows a tip to base (tip high) gradient of Ca(2+)-CaM in the chloronema tip cells. Comparison of Ca(2+)-CaM-TFP fluorescence over time in the chloronema tip cells of wild type Funaria with the response in an auxin overproducer mutant (86.1) and an auxin deficient mutant (87.13) reveals the involvement of auxin in calmodulin activation as a rapid response prior to cell differentiation.     

金灰藓(Pylaisiella polyantha)配子体发生的实验观察

金灰藓Pylaisiella polyantha (Hedw．)Grout孢子在光照培养箱中进行培养,实验组为含有Knop培养液的琼脂培养基质,对照组为无营养成分的琼脂培养基质。在光学显微镜下对配子体发生进行了观察、描绘和照相。结果表明：实验组和对照组孢子萌发所需时间相同,均为53．5h,萌发极相为1～4极。4d时,实验组萌发率为85．4％,对照组为54．1％;20d时,开始形成配子体芽原基;40d时,形成具假根、茎、叶的配子体,并形成两性器官。并对配子体发生过程的特点进行了分析和讨论。