The supraspecific taxonomy and evolution of the fern genusAzolla (Azollaceae)

The systematics of the aquatic fern genusAzolla Lam. is revised at the supraspecific level. Published morphological data are reviewed, and cytological and cladistic analyses of the genus conducted, enabling a discussion of the putative evolutionary trends in the genus, and a revision of the current taxonomy. A phylogenetically more acceptable subgeneric and sectional classification is proposed, viz. subg.Azolla sect.Azolla (comprisingA. filiculoides Lam.,A. rubra R. Br.,A caroliniana auct. nonWilld.,A. microphylla auct. nonKaulf. andA. mexicana Presl), subg.Azolla sect.Rhizosperma (Mey.)Mett. (comprisingA. pinnata R. Br.), and subg.Tetrasporocarpia subg. nov. (comprisingA. nilotica Decne. exMett.).     

Cell expansion in the filamentous gametophyte of the fernOnoclea sensibilis L.

Filamentous gametophytes of the fernO. sensibilis were exposed to paired combinations of light of different qualities, hormones and cations in the attempt to elucidate the underlying processes that regulate cell expansion. Simultaneous treatments with high-pH buffers or the auxin antagonistp-chlorophenoxyisobutyric acid abolished blue-light-mediated expansion but did not influence growth in red light. In contrast, the red-light response was preferentially altered by the ethylene absorbant KMnO₄ or the Ca²⁺ chelator ethyleneglycol-bis(-aminoethyl ether) N,N-tetraacetic acid. The Ca²⁺ ionophore A23187 caused a significant reduction in cell expansion under both blue and red irradiation. A marked promotion of expansion was mediated by high concentrations of indole-3-acetic acid, but this effect was dependent on the presence of low-pH buffers. The ethylene-generating agent 2-chloroethylphosphonic acid decreased the magnitudes of both photoresponses; this inhibition was further enhanced by high Ca²⁺ concentrations. These findings and those with other plants are interpreted in terms of two independent control mechanisms for cell expansion: 1) a blue light photoreceptor-auxin-hydrogen ion system, and 2) a phytochrome-ethylene-calcium ion system.Abbreviations APW-X artificial pond water (the associated number designates pH) - CEPA 2-chloroethylphosphonic acid - EGTA ethyleneglycol-bis(-aminoethyl ether)N,N-tetraacetic acid - IAA indole-3-acetic acid - PCIB p-chlorophenoxyisobutyric acid     

25种中国蕨类植物的细胞学观察

本文报道了四川峨眉山、云南点苍山和北京雾灵山产的25种蕨类植物的染色体数目,其中15种的染色体数目和4个种的细胞型是首次记载。此外,还对荚囊蕨属(Struthiote-ris)和水龙骨属(Ppolypodiodes)等属的染色体基数进行了讨论。     

海南尖峰岭自然保护区蕨类植物区系分析

对海南尖峰岭国家级自然保护区的蕨类植物区系进行了分析。结果表明：自然保护区内共有蕨类植物165种,隶属于41科84属,优势科有7科,分别为水龙骨科、铁角蕨科、金星蕨科、蹄盖蕨科、叉蕨科、膜蕨科、鳞毛蕨科,含5种以上的优势属有7属,分别为铁角蕨属Asplenium、卷柏属Selaginella、观音座莲属Angiopteris、鳞始蕨属Lindsaea、凤尾蕨属Pteris、短肠蕨属Allantodia、鳞毛蕨属Dryopteris;根据植物的现代地理分布,本区蕨类植物科、属、种的热带成分分别占非世界分布的96.6%、90.4%、72.2%,表明本区蕨类植物区系具有较强的热带性质;本区蕨类植物的属内种类贫乏,含1种的属占63.1%,含2～3种的属占21.4%;生态类型多样,主要有土生蕨类、石生和附生蕨类;苏铁蕨Brainea insignis、水蕨Certopteris thalictroides、金毛狗Cibotium barometz、桫椤Alsophila spinulosa、黑桫椤Gymnasphaera podophylla、大叶黑桫椤Gymnasphaera gigantea是本区国家重点二级保护珍稀濒危蕨类植物,应采取措施加强保护。     

Effect of high-light treatments in inducing photoinhibition of photosynthesis in intact leaves of low-light grown Phaseolus vulgaris and Lastreopsis microsora

Photoinhibition studies, using gas-exchange techniques, were conducted with leaflets of Phaseolus vulgaris L. plants that were grown under low photonfluence rates. Comparative measurements were made on attached, intact leaflets and in subsequently isolated chloroplasts. Photoinhibition studies were also conducted with attached fronds of the deep-shade fern Lastreopsis microsora (Endl.) Tindale. Leaflets of lowlight-grown Phaseolus vulgaris and fronds of the shade fern were found to be subject to similar photoinhibition when exposed to photon-fluence rates in excess of those at which they were grown. Photoinhibition following exposure to a photon fluence-rate approximating full sunlight is manifested as a reduction in the capacity for both light-saturated and light-limited carbon uptake and is reflected at the chloroplast level as substantial inhibition of electron flow through photosystem (PS) II, with little effect on PS I. The extent of photoinhibition is markedly dependent on the length of exposure to a high-light regime and on the actual photon-fluence rate maintained during treatment. A greater degree of photoinhibition is evident if carbon metabolism is prevented by the removal of CO₂ than when maximum rates of CO₂ uptake prevail throughout the exposure to a high photonfluence rate. Apparently a certain level of CO₂ turnover is beneficial in providing a sink for photochemically generated energy. When leaf material is exposed to photon-fluence rates well in excess of the rate present during growth apparently the potentials of the various biophysical and photochemical means of dissipating excitation energy are exceeded and photoinhibition of photosynthesis results.Abbreviation PFR photon fluence rate     

金毛狗对重金属的富集特性的研究

为探讨金毛狗[Cibotium barometz(L.) J. Sm.]对重金属的富集能力,在广东省选取6个样点(南岭、南昆山、白云山、大岭山、梧桐山、西樵山)采集金毛狗的叶片、根状茎和根际土壤,采用ICP-MS测定9种重金属元素(Cr、Mn、Ni、Cu、Zn、As、Cd、Hg、Pb)的含量。结果表明,样地土壤已受到不同程度的重金属污染,土壤中Cd和Hg含量均高于广东省土壤背景值,分别为背景值的1.61~4.82倍和4.74~11.79倍。西樵山土壤中Cd含量最大,南岭土壤中Hg含量最大。在9种元素中,金毛狗对Hg的转运系数最高,达4.8,对Cd的富集系数最高,达2.2,Cu和Cd元素的转运系数和富集系数均大于1。这说明金毛狗对重金属元素的富集能力较弱而转运能力较强。     

Some New Species of Pteridophytes from Hengduan Mountains

Thirteen new species of pteridophytes are described from the Hengduan Mountains, China. They are Selaginella laxistrobila Shing, S. trichophylla Shing, Hypodematium daochengense Shing, Stegnogramma latipinna Ching, Pseudocyclosorus pseudorepens Ching et Y. X. Lin, P. subfalcilobus Ching, Pyrrosia pseudodrakeana Shing, Lepisorus neolewisii Shing, L. bilouensis Ching et Y. X. Lin, Polypodium muliense Ching, P. nervopilosum Shing, P. intermediumChing et S. K. Wu and P. daochengense Ching et S. K. Wu.     

广东古兜山自然保护区蕨类植物群落的特征

通过对广东新会古兜山自然保护区中108个5m ×5m的蕨类植物样方调查,初步分析了样方中蕨类植物的种类组成和区系特点及种群的多度、频度、重要值、蕨类的生长型、叶的性质和群落的外貌、季相等群落学特征。结果表明:(1)古兜山自然保护区的蕨类植物种类具有典型的南亚热带植物区系特点,热带亚洲植物区系成分对古兜山蕨类植物区系有强烈影响;(2)由于蕨类植物种群的随机分布和环境因子的异质性,种群的多度和重要值分布表现出明显的正态分布规律;(3)样方中蕨类植物的形态外貌、叶的性质及其群落的外貌和季相均表现出典型的南亚热带蕨类植物群落特征;古兜山自然保护区的蕨类植物可划分为花篮状蕨类、树蕨类、匍匐类、攀援类、附生类5种生长型类型。     

Partial purification and characterization of L-myo-inositol-1-phosphate synthase of pteridophytic origin

Myo-Inositol is an important metabolite for normal growth and development of all living organisms. The cellular level of myo-inositol is controlled by the enzyme L-myo- inositol-1-phosphate synthase (MIPS) [EC 5.5.1.4]. Appreciable level of MIPS activity was detected from the common pteridophytes like Dicranopteris, Diplazium, Diplopterygium, Equisetum, Lycopodium, Polypodium, Pteridium, Selaginella etc. available in Darjeeling Himalayas. The enzyme was partially purified from the reproductive pinnules of Diplopterygium glaucum (Thunb.) Nakai. The purification obtained was about 81 fold and the recovery was about 13.5 %. The final enzyme preparation specifically utilized D-Glucose-6-phosphate and NAD+ as its substrate and co-factor respectively. It shows pH optima between 7.0 and 7.5 while the temperature maximum was at 35 °C. The enzyme activity was slightly inhibited by Na⁺ and Cd²⁺ and highly inhibited by Li⁺ and Hg²⁺. The K _rn values for D-glucose-6-phosphate and NAD+ was found to be as 0.83 mM and 0.44 mM respectively while the V _max values were 1.42 mM and 1.8 mM for D-glucose-6-phosphate and NAD+ respectively. The present study indicates the universal occurrence of this enzyme in all plant groups.     

广东潮州凤凰山的蕨类植物

经实地调查和标本研究,广东潮州凤凰山蕨类植物共有96种,隶属于31科58属。区系分析表明:该地蕨类植物具有较强的热带性质,科、属、种的分布区类型均以热带、亚热带分布型为主。热带、亚热带分布的科有13科,占41.94%,属有36属,占62.08%,其中泛热带分布属(22属,占37.93%)是最重要的分布类型;世界分布属占24.14%,温带分布属不明显,占13.79%,显示出该区蕨类植物区系从热带向亚热带的渗透和过渡性质;热带、亚热带分布的种所占比例最大(52种,占54.17%),其中以热带亚洲性质的占优势(38种,占39.58%);温带成分次之(36种,占37.5%),其中中国-日本分布性质的占优势(30种,占31.25%)。按生长基质的不同,将凤凰山蕨类植物划分为土生、石生、附生三种生态类型,其中以土生为主。按蕨类植物多样性的应用性,又可分为药用、观赏和食用蕨类植物等。