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1.
Nitrogen-fixing cyanobacteria inhabit the zone between the inner and outer cortex of cycad coralloid roots. In the growing tip of such roots the cyanobacterial heterocyst frequency, nitrogenase activity (C2H2-reduction) and glutamine synthetase activity (both transferase and biosynthetic) were comparable to those found in freeliving cyanobacteria. The relative level of glutamine synthetase protein and its pattern of cellular/subcellular localization in heterocysts and vegetative cells were also similar to those of free-living cyanobacteria. However, there was a progressive decline in nitrogenase activity along the coralloid root with maximum reduction occurring in the regions farthest from the growing tip. A similar but less pronounced pattern was observed for glutamine synthetase activity. Distribution of glutamine synthetase protein in cyanobacteria in the first 2–3 mm of the root tip indicated a slight decrease in the heterocysts and vegetative cells. However, the overall level of cyanobacterial glutamine synthetase protein did not change because of a drastic increase in the numbers of heterocysts, which contain a proportionally higher level of glutamine synthetase than the vegetative cells.Abbreviation GS
glutamine synthetase 相似文献
2.
MIGUEL A. PÉREZ-FARRERA REW P. VOVIDES CARLOS G. IGLESIAS 《Botanical journal of the Linnean Society. Linnean Society of London》2001,137(1):77-80
Ceratozamia zoquorum sp. nov. from the northern mountains of Chiapas, Mexico, is described and illustrated. It has affinities with C. miqueliana Wendl. from Veracruz, but differs in leaf, male female cone and trunk morphology. 相似文献
3.
The cycad Cycas armstrongii is endemic to the north-western corner of the Northern Territory in Australia. Here we provide data on its life history and
population structure from four populations across its range. Few plants reproduced before they were 1 m in height. There was
considerable variation in the proportion of reproductive plants between sites and years, but the sex ratio in all populations
was close to 1:1. The growth rate of plants was approximately 4.5 cm year−1 which indicates that most plants are less than 100 years old and that the tallest individuals are likely to be little older
than this. The annual fecundity of female plants ranged from 12 to 80 seeds; there was no evidence that fecundity varied with
plant height. Dispersal was restricted generally to less than 1 m and the distribution of dispersal distances was fitted well
by a gamma distribution. Recruitment occurred through both seedlings and vegetative sprouts and the proportion of juveniles
(plants without trunks) in the populations varied between one-quarter and two-thirds. The data indicate that recruitment is
episodic, but occurs more frequently under the current fire regime than amongst the canopy trees. It is shown that there is
considerable variation in the dynamics of populations between sites and that the long term dynamics of a population cannot
readily be inferred from an examination of the size structure at a single point in time.
Received: 4 January 1997 / Accepted: 1 March 1997 相似文献
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The roots of 27 species of South Florida plants in 15 families (including one cycad, six palms, one Smilax, and 19 dicotyledons) native to pine rockland and tropical hardwood hammock communities were examined for arbuscular mycorrhizal
fungi (AMF). These plants grow in the biologically diverse but endangered Greater Everglades habitat. Roots from field-grown
and potted plants were cleared and stained. All 27 species had AMF and include 14 species having an endangered or threatened
status. The Paris-type colonization occurred in two species in the families Annonaceae and Smilacaceae. The Arum-type occurred in 22 species in the families Anacardiaceae, Arecaceae (Palmae), Boraginaceae, Cactaceae (questionable), Euphorbiaceae,
Fabaceae, Lauraceae, Melastomataceae, Polygalaceae, Rubiaceae, Simaroubaceae, Ulmaceae, and Zamiaceae. Three species in the
families Fabaceae, Lauraceae, and Simaroubaceae had a mix of Paris- and Arum-types. The results have implications for the restoration of these endangered plant communities in the Everglades. 相似文献
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Comparison of DNA restriction fragment length polymorphisms of Nostoc strains in and from cycads 总被引:2,自引:0,他引:2
Peter Lindblad Robert Haselkorn Birgitta Bergman Sandra A. Nierzwicki-Bauer 《Archives of microbiology》1989,152(1):20-24
DNA was prepared from cyanobacteria freshly isolated from coralloid roots of natural populations of five cycad species: Ceratozamia mexicana mexicana (Mexico), C. mexicana robusta (Mexico), Dioon spinulosum (Mexico), Zamia furfuraceae (Mexico) and Z. skinneri (Costa Rica). Using the Southern blot technique and cloned Anabaena PCC 7120 nifK and glnA genes as probes, restriction fragment length polymorphisms of these cyanobacterial symbionts were compared. The five cyanobacterial preparations showed differences in the sizes of their DNA fragments hybridizing with both probes, indicating that different cyanobacterial species and/or strains were in the symbiotic associations. On the other hand, a similar comparison of cyanobacteria freshly collected from a single Encephalartos altensteinii coralloid root and from three independently subcultured isolates from the same coralloid root revealed that these were likely to be one and the same organism. Moreover, the complexity of restriction patterns shows that a mixture of Nostoc strains can associate with a single cycad species although a single cyanobacterial strain can predominate in the root of a single cycad plant. Thus, a wide range of Nostoc strains appear to associate with the coralloid roots of cycads.Non-standard abbreviations bp
base pairs
- kbp
kilobase pairs
- RFLP's
restriction fragment length polymorphisms 相似文献
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The genus Cycas (Cycadaceae; gymnosperm) have circumstantially been considered to be wind-pollinated. The cones of Cycas revoluta Thunb., however, emit a strong unpleasant odor. The chemical profiles of floral scents often correlate with various pollination modes (pollinators). We collected and analyzed the volatiles emitted from male and female cones of C. revoluta native to Iriomote and Yonaguni Islands, Japan. The analyses indicated that estragole (4-allylanisole) dominated in the volatiles (67.0–92.7%), with small amounts of other benzenoids, e.g., anethole, methyl salicylate, methyl eugenol, and ethyl benzoate. Several fatty acid esters were also detected in the samples from Iriomote Island. The function of estragole in the reproductive biology of C. revoluta is discussed. 相似文献
10.
ANDREW P. VOVIDES MIGUEL A. PÉREZ-FARRERA JORGE GONZÁLEZ-ASTORGA CARLOS IGLESIAS 《Botanical journal of the Linnean Society. Linnean Society of London》2008,157(2):169-175
Ceratozamia chimalapensis sp. nov. is described and illustrated. It is related to C. mirandae Vovides, Pérez-Farrera & Iglesias from Chiapas, but differs in trunk and peduncle size as well as in diameter of both megastrobili and microstrobili. Petiole, megasporophyll and indument colour also differ from that of C. mirandae . Ceratozamia chimalapensis forms part of the C. norstogii D.W.Stev. species complex, a group of ceratozamias with narrow leaflets growing in the herbaceous layer of oak forests in southern Mexico. These forests were severely affected by forest fires during 1998 and we recommend an IUCN Red List Category of CR B.1. Speciation in Ceratozamia has been discussed in the light of floristic refugia. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 169–175. 相似文献