液体培养基条件下乌毛蕨配子体发育的研究

在液体培养基条件下对中国产乌毛蕨(Blechnum orientaleL.)配子体发育进行了观察。结果表明:乌毛蕨的孢子为两面体型,两侧对称,极面观为椭圆形,赤道面观为半圆形或豆形,周壁具脊状褶皱;孢子萌发为书带蕨型;原叶体发育为三叉蕨型,成熟原叶体为对称的心脏形。经比较分析,蕨类植物孢子繁殖时采用混合土培养较适宜;液体培养基和混合土在研究蕨类植物配子体发育时同样具有可行性。孢子形态和配子体发育的观察结果表明,乌毛蕨是蕨类植物中较进化的种类;乌毛蕨科与鳞毛蕨科亲缘关系较近。     

Gametophytes,embryogeny and pericarp ofMicrostylis wallichii lindl. (Orchidaceae)

The anther wall is 4-layered thick. Its development is of the Monocotyledonous type. Simultaneous cytokinesis results in decussate, isobilateral, linear and tetrahedral tetrads. At anthesis, the microspores are 2-celled. The mature ovules are anatropous, bitegmic and tenuinucellate. Both the integuments are dermal in origin and 2-layered. The inner integument alone forms the micropyle. Development of the female gametophyte is of the Monosporic type. Double fertilization occurs but the primary endosperm nucleus degenerates without any division. Development of embryo corresponds to the variation of the Onagrad type. The mature embryo lacks differentiation. The seeds are minute and non-endospermic. The seed coat is formed entirely by the outer layer of outer integument. There are three sterile and three fertile valves in the ovary. In the prefertilization stages valves consist of parenchymatous cells. After fertilization, the sterile valves become sclerenchymatous whereas the fertile valves remain parenchymatous.     

T-DNA mediated disruption of essential gametophytic genes in Arabidopsis is unexpectedly rare and cannot be inferred from segregation distortion alone

Many genes are thought to be expressed during the haploid phase in plants, however, very few haploid-specific genes have been isolated so far. T-DNA insertion mutagenesis is a powerful tool for generating mutations that affect gametophyte viability and function, as disruption of a gene essential for these processes should lead to a defect in the transmission of the gametes. Mutants can therefore be screened on the basis of segregation distortion for a reporter resistance gene contained in the T-DNA. We have screened the Versailles collection of Arabidopsis transformants for 1:1 Kan^R:Kan^S segregation after selfing, focussing on gametophyte mutations which show normal transmission through one gametophyte and cause lethality or dysfunction of the other. Only 1.3% (207) of the 16,000 lines screened were scored as good candidates. Thorough genetic analysis of 38 putative T-DNA transmission defect lines (Ttd) identified 8 defective gametophyte mutants, which all showed 0 to 1% T-DNA transmission through the pollen. During the screen, we observed a high background of low-penetrance mutations, often affecting the function of both gametophytes, and many lines which were likely to carry chromosomal rearrangements. The reasons for the small number of retained lines (all male gametophytic) are discussed, as well as the finding that, for most of them, residual T-DNA transmission is obtained through the affected gametophyte. Received: 27 July 1998 / Accepted: 16 September 1998     

Gametophyte contribution to sporophyte growth on the basis of carbon gain in the fern <Emphasis Type="Italic">Thelypteris palustris</Emphasis>: effect of gametophyte organic-matter production on sporophytes

At an early stage of growth gametophytes support the sporophytes of ferns. Young sporophytes become independent of gametophytes when the first leaves develop. Although large fern gametophytes produce multiple archegonia simultaneously, only one sporophyte is typically established on one gametophyte. The number of sporophytes is believed to be controlled in two possible directions, from gametophyte to sporophyte or from preceding sporophyte to another sporophyte. To investigate the effects of gametophytes on their sporophytes, we studied the relationship between organic matter production by gametophytes and the growth of young sporophytes of Thelypteris palustris. We cut gametophytes in half (CGs) to reduce the gametophytes’ production of matter. There was no significant difference between the growth of sporophytes on intact gametophytes (IGs) and that on CGs. According to our estimates, based on the rate of organic matter production, the large gametophyte was able to produce two or more sporophytes. The resources required for CGs to make similar-sized sporophytes was twice that for IGs. In polyembryony each of the multiple sporophytes was similar in size to the single sporophytes. Resource limitation does not seem to explain why fern gametophytes establish single sporophytes.     

东北蕨类植物配子体发育的研究Ⅷ铁角蕨科

本文研究了过山蕨配子体的发育过程。孢子左右对称,单裂缝,具周壁,孢子萌发为书带蕨型,丝状体２－７个细胞长,原叶体发育为三叉蕨型,原叶体的毛状体形状多样。性器官较小,在配子体上的此等特征说明过山蕨为进化的类型。     

Regeneration of drought-stressed gametophytes of the epiphytic fern, Pyrrosia pilosellodes (L.) Price

The epiphytic habitat represents a highly dynamic environment, and water deficit is one of the common factors that affects growth and development of epiphytes. Gametophytes of the epiphytic fern, Pyrrosia piloselloides (L.) Price, were able to tolerate up to 50 days of drought. Upon rehydration, cells that recovered from water stress were capable of forming new gametophytes. The ability of gametophytes to recover from desiccation plays an important role in the survival and growth of the fern species under natural conditions. Received: 20 May 1998 / Revision received: 5 August 1998 / Accepted: 21 August 1998