Effects of salt spray and sand burial on Spinifex sericeus R. Br.

Abstract Spinifex sericeus, a common coastal sand dune grass, typically exhibits decreased vigour in the more stabilized section of the dunes when compared with the active foredune. These differences in vigour appear to be related to different environmental conditions across the dunes such as sand burial and salt spray deposition, both generally decreasing with distance inland. An experiment following the fate of foliar and root applications of ²²Na indicated that it may be taken up by the roots or the foliage and then translocated throughout the whole plant, and perhaps even extruded by the roots. Salt spray appeared to have a positive effect on the growth of S. sericeus when applied in conjunction with N and P but had no effect when N and P were not added. Adding acid-washed or non acid-washed foredune sand also resulted in a positive growth response. The results of these experiments indicate that the vigorous growth of S. sericeus on the dynamic sections of the foredunes is due to a stimulation of growth caused by sand deposition.     

Resource allocation patterns in Spinifex sericeus R.Br.: A dioecious perennial grass of coastal sand dunes

The resource allocation patterns within populations of Spinifex sericeus R.Br, were studied on the mid north coast of NSW. Sand burial and nutrient availability were two major factors influencing the allocation of resources to roots, culms, tillers and inflorescences, resulting in different growth forms in different sections of the dune. The data suggest that pollen availability may affect allocation to seeds late in the flowering season. Spinifex sericeus was found to have a greater below- than above-ground biomass, especially on the crest of the incipient foredune where sand accretion was high. The ability of culms of S. sericeus to grow upwards at a rate that generally prevents complete burial of the tillers is one mechanism which allows S. sericeus to vary resource allocation patterns in response to a varying environment. Differences in the inflorescence characteristics of males and females indicate their different functions. The much greater floret number of males indicated the importance of pollen dispersal. Female inflorescences consisted mainly of structures other than florets and suggested the importance of the female inflorescence in seed dispersal. Addition of nitrogen and phosphorus increased the number of spikelets and seeds but not the proportion of spikelets which produced seed.     

A cytogenetic study of R. constantinopolitanus and R. sericeus (Ranunculaceae) in Iran

With 600 species Ranunculus is the largest genus in Ranunculaceae, and has a broad global distribution. We studied the karyotypes of R. constantinopolitanus and R. sericeus species of Ranunculaceae and identified their symmetry level. New chromosome numbers of 2n = 21 (Nodeh woods population) and 2n ca. 63 (Javaherdeh population) are reported for R. constantinopolitanus. Two different populations of R. sericeus had two different chromosome results. We investigated morphological and karyological studies along with pollens micromorphology. Different populations of R. constantinopolitanus and R. sericeus, with different chromosome numbers showed morphological and micromorphological differences. Therefore, we considered the two populations of R. sericeus as cytotypes. There was a correlation between the studied morphological characters and pollen size with ploidy levels in the two R. constantinopolitanus populations.     

Nutlet morphology in Hemigenia R.Br. and Microcorys R.Br. (Lamiaceae)

Nutlets of Hemigenia R.Br. and Microcorys R.Br. were examined using SEM. Significant variation, mainly useful at the infrageneric level, was found in nutlet shape, nature of the attachment scar, nature of surface sculpturing, exocarp cell shape and sculpturing, and nature of the indumentum. Typical nutlets are ovoidal, strongly reticulate or rugose. The exocarp cells are isodiametric and convex to papillate. Also common are cylindrical nutlets, often with longitudinal ridging and papillate exocarp cells. Surface pitting and concave exocarp cells are rare. A cladistic analysis of nutlet characters suggests both Hemigenia and Microcorys are polyphyletic, and Microcorys paraphyletic with respect to Westringia Sm. Notwithstanding that, the infrageneric classification of Hemigenia was largely supported, while in Microcorys, there was support for sect. Hemigenioides, but sects Anisandra and Microcorys were not resolved as distinct.     

Germination and seedling survival in fens undergoing succession

We studied mechanisms of vegetation change in fens subject to succession from open water to floating mats and finally herbaceous rich-fens. Earlier research showed that these systems are characterized by transient seed banks. Our main question was whether seedlings of later successional fen stages are already present in earlier stages, remaining subordinate in the vegetation until conditions become suitable for them. If, however, conditions during succession change in a way that only a limited set of species can survive as seedlings during each of the successional stages, no seedling bank will exist. The transient character of the seeds would then imply that seeds will not germinate and will subsequently die and that seeds that have germinated in the “wrong” stage will not become established. We hypothesized that: (1) germination and seedling survival of fen species are significantly better in the successional fen stage for which these species are characteristic, (2) as a consequence no seedling banks occur in these fens. In a field experiment, seeds of five characteristic fen species in the standing vegetation of three successional fen stages i.e. raft fen, quaking fen and rich fen were sown in each of these stages in a turf pond in the Tienhoven area, The Netherlands. Germination and seedling survival were measured over two growing seasons together with environmental variables. Germination was higher in the “own” stage for all species groups as was survival for quaking fen species and rich fen species. For both these stages, percentage of germination and survival of four out of five characteristic species were significantly higher in the “own” stage. Germination and survival can be considered stage-dependent and it was concluded that seedling banks do not exist in these fens. Site-specific environmental variables act as a sieve and differentiate on species presence already during early life history stages. We found clues that the environmental sieve acts at the level of nutrient availability, tolerance for high sulphide concentration and light climate. Because of the transient seed bank and absence of a seedling bank in these fen wetlands, successful establishment of species necessitates a continuous dispersal of characteristic species until the environmental conditions permit establishment. This also implies that species of the whole successional sere should be present within dispersal distance.     

荔枝草花的形态发生

在体式显微镜系统观察的基础上,对唇形科鼠尾草属植物荔枝草(Salvia plebeiaR.Br.)的花发育过程进行了扫描电镜观察.发现荔枝草的轮伞花序由多数交互对生的聚伞花序单位组成,花器官发育形式为向心式",各部分花器官从外向内依次形成;共形成4个雄蕊原基,其中2个雄蕊原基在形成后不再发育,另2个雄蕊原基每个均发育出1可育药室和1不育药室,不育药室膨大连接,并在花成熟之前参与组成特殊杠杆结构;子房四深裂"的形成实际是由4个原基分别发育,而后相互靠拢而成.     

Biosystematic study ofRoegneria tenuispica, R. ciliaris andR. pendulina (Poaceae:Triticeae)

Morphological and cytological studies of three tetraploidRoegneria species,R. tenuispica, R. pendulina andR. ciliaris, and their artificial hybrids were carried out.Roegneria tenuispica was morphologically similar toR. pendulina. The general appearance of the interspecific hybrids was intermediate between the parents. The hybrids showed comparatively high chromosome pairing at meiosis, but were completely or almost completely sterile. The results indicate that the three independent species share two basic genomes (S_tY) and thatR. tenuispica is more closely related toR. pendulina than toR. ciliaris. The genomes ofR. tenuispica could be designated as S _t ^t Y^t.     

观赏草丽色画眉种子萌发特性研究

丽色画眉(Eragrostis spectabilis)在中国作为一种观赏草引种栽培,但有研究报道丽色画眉具有潜在的杂草入侵风险.通常成功的外来杂草有很强的繁殖能力,而丽色画眉种子的萌发特性如何,目前尚无人研究.本文通过培养皿和盆栽实验研究温度、光照、水分、土层深度对丽色画眉种子萌发的影响.以发芽率和发芽指数为评价指标的结果显示,丽色画眉种子最适萌发温度为35℃.应用种子萌发温度模型得出种子萌发温度范围为17.7 ～43.2℃,其中最适萌发温度为39.2℃.光照有利于种子萌发,与连续黑暗相比连续光照显著提高种子发芽率.PEG6000模拟的水分胁迫对丽色画眉种子的萌发有显著的抑制作用,水势降低到-0.8 Mpa时,种子已经不能完成萌发.0.5 cm是种子萌发的理想深度,0～1 cm的土层适宜色画眉种子的萌发,发芽率不低于60％,在土层1～4 cm范围内,随着土层深度的增加其萌发率显著降低.     

Evolution of hybrid taxa inNasturtium R.Br. (Brassicaceae)

Nasturtium officinale (2n=4x=32),N. microphyllum (2n=8x=64) andN. ×sterile (2n=6x=48) have been investigated by isozyme analyses to study evolutionary processes withinNasturtium. Four additional species assumed to be involved in the formation of the octoploidN. microphyllum (Rorippa amphibia, R. sylvestris, R. palustris, andCardamine amara) were also examined. A total of 641 individuals were analyzed for six isozyme systems (alcohol dehydrogenase, aspartate aminotransferase, glutamate dehydrogenase, leucine aminopeptidase, malate dehydrogenase, and phosphoglucoisomerase). Eleven gene complexes coding for 43 allozymes were detected. Fifteen alleles were observed inN. officinale, twelve of them being fixed. All alleles fixed inN. officinale were also present and fixed inN. microphyllum. Seven additional fixed alleles were observed inN. microphyllum. The presence of these seven alleles inRorippa taxa provide evidence for an allopolyploid origin ofN. microphyllum withN. officinale and aRorippa taxon involved.C. amara is not a parent species ofN. microphyllum. N. ×sterile showed a fixed banding pattern which was identical to that ofN. microphyllum. It is argued thatN. ×sterile is a hybrid betweenN. officinale andN. microphyllum. Human impact has played a major role in the evolution ofN. ×sterile. The formation and persistence of the hybrid were influenced by introducingN. officinale into the natural distribution area ofN. microphyllum and by creating ditches and ponds where due to its vegetative capabilitiesN.×sterile could establish.     

Germination, seedling morphology and establishment of Cotnbretum bauchiense Hutch. & Dalz. (Combretaceae)

ONYEKWELU, S. S. C, 1990. Germination, seedling morphology and establishment of Cotnbretum bauchiense Hutch. & Dalz. (Combretaceae). Cotnbretum bauchiense is a suffrutex with short, erect, usually herbaceous stems arising from a woody root stock. It appears in savanna soon after fire and (lowers within a few weeks. The fruits germinate in 5–6 days. The germination is cryptogeal. On germination the true radicle and the apparent radicle formed by fused cotyledon stalks push down into the soil, carrying the plumule with them. The cotyledon lamina and part of the fused cotyledon stalks remain above the soil. Both the apparent radicle and the true radicle produce roots. Below the soil at the joint of the apparent radicle and the true radicle the plumule produces 1–3 shoots which grow out to the surface of the soil. The underground portion of the shoot bears scale leaves, from which the plant regenerates when the aerial shoot is damaged by fire. This type of germination is an adaptation that ensures successful establishment in an environment that is subjected to fire.     

Genome constitutions of Roegneriaalashanica,R. elytrigioides,R. magnicaespes and R. grandis (Poaceae: Triticeae) via genomic in‐situ hybridization

The genomic constitutions of Roegneria alashanica, R. elytrigioides, R. magnicaespes and R. grandis were studied using GISH. DNA of Pseudoroegneria spicata (St), P. libanotica (St), P. stipifolia (St), R. ciliaris (StY), Lopophyllum elongatum (E^e), Agropyron cristatum (P) and Hordeum bogdanii (H) were used for probing, respectively. The results indicated that: 1) R. alashanica and R. magnicaespes contained one St genome, the other genome was unidentified, however, it was not an E, P, H or Y genome; 2) R. elytrigioides contained two St genomes and should on this basis be included in Pseudoroegneria; 3) R. grandis contained an St and an St^g genome. The St^g genome is suggested to be a modified form of the St genome of Pseudoroegneria and to be homoeologous with the Y genome. It might be an intermediate type between the St and Y genomes. Therefore, R. elytrigioides should be treated as Pseudoroegneriaelytrigioides.Roegneria alashanica, R. magnicaespes and R. grandis does apparently not belong in the genus Roegneria but further studies are needed to establish their correct taxonomic position.     

Epacris crassifolia R. Br. (Epacridaceae) - A Reappraisal

Epacris crassifolia R. Br.s. lat.,as represented in collectionsat G, BM, HO, NSW, MEL, CBG and CAN, has been redefined as threeseparate species. The common lax, prostrate form includes twosubspecies,E. crassifoliassp.crassifoliaR. Br.stat. nov. andE.crassifoliassp.macrofloraCrowden et Menaduessp. nov.separatedon floral morphology.E. pinoideaCrowden et Menaduesp. nov.andE.lithophilaCrowden et Menaduesp. nov.are erect and woody, beingdistinguished on leaf and floral characters. Epacridaceae; Epacris crassifolia ; Epacris lithophila; Epacris pinoidea; new species     

The genus Sarcostemma R.Br. (Asclepiadaceae) in Madagascar

The Madagascar! representatives of the genus Sarcostemma are investigated. All Malagasy material studied can be assigned to four taxa. S. viminale ssp. viminale occurs in Madagascar as well as on other islands along the African coast and on the African mainland: the other three species are endemic to Madagascar. All four species occur in the southern, arid part of the island, to which S. decorsei is endemic. S. membranaceum and S. elachistemmoides are new. All species are described and illustrated and a key and distribution maps are presented.     

Cytological Studies of Hybrids of Roegneria ciliaris with R.alashanica and R.magnicaespes(Poaceae:Triticeae)

In order to investigate the relationships between Roegneria.ciliaris(Trin.)Nevski and R.alashanica Keng,and between R.ciliaris and R.magnicaespes D.F.Cui.R.ciliaris(Trin.)Nevski was crossed with the other two species,through the aid of embryo rescue. Hybrids were obtained from these two combinations.Chromosome pairing behavior of parents an dhybrids was observed at metaphase I of pollen mother cells. Meiotic configuratons were 10.62Ⅰ＋8.17Ⅱ＋0.32Ⅲ＋0.02Ⅳ for R.ciliaris×R.magnicaespes and 18.00Ⅰ＋4.76Ⅱ＋0.16Ⅲ for R.ciliaris ×R.magnicaespes;c-value of the two hybrids were 0.44 and 0.21,respectively.     

纤毛鹅观草同阿拉善鹅观草、大丛鹅观草间杂种细胞学研究

为了探索阿拉善鹅观草RoegneriaalashanicaKeng、大丛鹅观草RoegneriamagnicaespesD .F .Cui与纤毛鹅观草Roegneriaciliaris (Trin .)Nevski间的相互关系 ,将其进行了远缘杂交 ,通过幼胚离体培养 ,两个组合均成功合成了杂种。对亲本及杂种F1 花粉母细胞减数分裂中期Ⅰ染色体配对行为及形态学进行了统计分析。结果表明 ,上述物种的种间杂交较难进行 ,杂种F1 减数分裂染色体平均构型分别为 :R ciliaris×R alashanica 10 6 2Ⅰ 8 17Ⅱ 0 32Ⅲ 0 0 2Ⅳ (c -值 =0 4 4 ) ,R ciliaris×R magnicaespes 18 0 0Ⅰ 4 76Ⅱ 0 16Ⅲ (c -值 =0 2 1) ;杂种穗部特征多数介于双亲之间。阿拉善鹅观草、大丛鹅观草与纤毛鹅观草间至少有一个基因组具有较高的同源性 ,即为S基因组 ,本文对它们在分类中的地位也进行了讨论。