Structural basis for the red light induced repolarization of tip growth in caulonema cells ofCeratodon purpureus

Summary Two dynamic changes are associated with the phytochrome-regulated phototropic response in tip cells of the mossCeratodon purpureus: a tip-located gradient shift of chlortetracy-cline (CTC)-stained calcium and a structural reorganization of apical microfilaments (MFs). We examined the interdependence of these processes. Cells were treated with the antimicrotubule drug oryzalin, the antimicrofilament drug cytochalasin-D, and the calcium channel blocker nifedipine. respectively. The effects on phototropic growth, on the structural alignment of the cytoskeleton (microtubules, MTs; microfilaments) and on the distribution of CTC-stained calcium were studied under each of these conditions. In gravitropically growing tip cells the apical MFs form a cortical collar-like structure, consisting of actin bundles with a parallel axial alignment. These MFs point towards the presumptive growing point, a weakly stained region in the tip of the cell from which bundles are absent. MTs are present in the cortex and in the endoplasm of the tip, predominantly oriented longitudinally. The MTs converge within the central apex. The cells show a steep tip-to-base CTC-calcium gradient with its highest signal in the central apex. Destruction of MTs by 1 M oryzalin induces several translocational effects: (i) the growing zone and phototropic outgrowth shift from the apex to subapical parts of the cell; (ii) the structural integrity of the apical MFs and the tip-to-base alignment of the CTC-calcium gradient are disturbed; and (iii) the red light induced gradient shift and the reorientation of MFs proceed in an expanded area spanning from the tip to subapical parts of the cell. Cytochalasin-D (10 g/ml) destroys the MFs. Under these conditions tip growth stops and the phototropic outgrowth is suppressed. The apical MT-structure and the CTC-calcium gradient are not influenced by the agent. Unilateral red light still induces the light-directed translocation of the gradient. Tip cells memorize a unilateral irradiation applied during growth inhibition with cytochalasin-D. After recovery in darkness the cells start to grow in the former light direction. The restoration of the MFs precedes the outgrowth. The structural alignment of the rebuilt actin bundles indicates the future growth direction. The calcium channel blocker nifedipine (10 M) also inhibits tip growth and concurrently phototropic outgrowth. Nifedipine destroys the CTC-calcium gradient and apical MFs; MTs are not influenced by the channel blocker.Abbreviations CTC chlortetracycline - DIC differential interference contrast - DMSO dimethyl sulfoxide - EGTA ethyleneglycol-bis-(-aminoethylether) N,N,N-N-tetraacetic acid - MBS 3-maleimidobenzoic acid N-hydroxysuccimide ester - MF microfilament - MT microtubule - MTSB microtubule stabilizing buffer - PIPES piperazine-N,N-bis(2-ethane-sulfonic acid) - RP rhodamine labeled phalloidin     

The cephalic morphology of the Gondwanan key taxon Hackeriella (Coleorrhyncha,Hemiptera)

External and internal head structures of Coleorrhyncha, a key-taxon within the Hemiptera, are described in detail and documented using modern techniques. The main focus is on Hackeriella veitchi, but two additional representatives of the Gondwanan relict group were also examined, and also head structures of Enicocephalidae, a member of a potentially basal heteropteran lineage. Features were compared to those documented in literature for the Sternorrhyncha, Auchenorrhyncha, and Heteroptera. Coleorrhyncha are characterized by highly modified head structures and correspondingly an entire series of autapomorphies, such as for instance a strongly flattened head capsule with fenestrations. However, they also display features that are likely plesiomorphic compared to members of other hemipteran groups. These include the almost complete tentorium and the lack of the gula. The sistergroup relationship between Coleorrhyncha and Heteroptera is well supported by cephalic features. Potential synapomorphies are the presence of a distinct mandibular sulcus, the reduced number of antennomeres, the absence of clasping organs in the labial groove, coiled accessory salivary ducts, the presence of a small cervical muscle M1a (M. pronotopostoccipitalis medialis), the presence of a second mandibular promotor M14 (M. zygomaticus mandibulae), the presence of M28 (M. verticopharyngalis), and M30 (M. frontobuccalis posterior).     

Aerobryum brevicuspis S.He (Brachytheciaceae), a new species from northern Vietnam

A new species of Aerobryum Dozy & Molk. (Brachytheciaceae), A. brevicuspis S.He from Lao Cai Province, northern Vietnam is described and illustrated. The new species resembles epiphytic A. speciosum Dozy & Molk. in the presence of pendent, sparsely branched stems, similar shape of leaves and areolation, but differs by its apiculate to cuspidate leaf apices, a single, faint or sometimes double costae in branch leaves, rather differentiated alar cells, the presence of a central strand in the stems, and numerous clustered axillary hairs that are often 5-8(-10) cells long.     

Pleurozium schreberi as an ecological indicator of polybrominated diphenyl ethers (PBDEs) in a heavily industrialized urban area

Polybrominated diphenyl ethers (PBDEs) are toxic contaminants with a persistent character and adverse effects on humans and wildlife. Therefore, the deposition of these chemicals in vegetation must be carefully controlled. Our objective was to determine PBDE concentrations (BDEs 28, 47, 66, 85, 99, 100, 153, 154, 183 and 209) in Pleurozium schreberi collected in a heavily industrialized urban agglomeration. High PBDE concentrations in the moss confirm the presence of active sources of atmospheric pollution in an area tested. The distribution of these xenobiotics was related to the vegetation cover being lower in sites surrounded by forests which indicates that PBDEs may have a tendency to be trapped from the air by tree leaves and needles. Congener profiles in P. schreberi were dominated by BDE 209 which was for 79% (in case of the coke smelter) to 95% (in case of the chemical plant) part of the total PBDE burden in this moss. The principal component and classification analysis classifying the concentration of PBDEs in P. schreberi allowed us to distinguish the pattern of these compounds characteristic for the origin of pollution. P. schreberi may be used as a bioindicator for PBDEs in areas contaminated with these chemicals.     

南极地区苔藓地衣植物的地球化学元素营养富集特征

研究南极苔藓地衣中地球化学元素的营养富集特征,发现K,Ca为苔藓地衣中最活跃元素,主要以主动吸收的方式累积于苔藓地衣植物中,P极易富集在地衣的藻层,参与藻类的有机合成过程,苔藓容易富集环境中的S,Al,Si以被动吸收的方式累积于地衣中,同时Fe,Mg以被动吸收的方式累积于苔藓体内,根据元素的含量和营养作用,研究认为K,Ca苔地衣的大量无机营养元素,S,P为苔藓地衣的中等营养元素,Al,Si为苔藓地衣的环境累积元素。     

Mapping of the Physcomitrella patens proteome

The moss Physcomitrella patens is unique among land plants due to the high rate of homologous recombination in its nuclear DNA. The feasibility of gene targeting makes Physcomitrella an unrivalled model organism in the field of plant functional genomics. To further extend the potentialities of this seed-less plant we aimed at exploring the P. patens proteome. Experimental conditions had to be adopted to meet the special requirements connected to the investigations of this moss. Here we describe the identification of 306 proteins from the protonema of Physcomitrella. Proteins were separated by two dimensional electrophoresis, excised form the gel and analysed by means of mass spectrometry. This reference map will lay the basis for further profound studies in the field of Physcomitrella proteomics.     

三峡库区三种林下地被物储水特性

通过对三峡库区3种森林类型(松栎混交林、栓皮栎纯林、马尾松纯林)林下地被物调查及其持水试验,分别得到3种森林类型林下地被物最大储水量、吸水速率等水文特征参数,结果表明,栓皮栎纯林林下苔藓层储水量最大,为其风干重的303．1％,松栎混交林林下的为283．8％,马尾松纯林林下的为242．3％．松栎混交林林下枯落物最大储水量为其风干重的282.2％,栓皮栎纯林林下的为262．5％,马尾松纯林林下的为239．3％。经分析拟合,得到林下苔藓层、林下枯落物吸水速率与浸泡时间之间关系式为S=kt^n,在同为中龄林条件下,3种森林类型林下苔藓层储水量均高于林下枯落物储水量,而林下地被物储水量随时间变化过程与森林类型无关。     

禁牧对锡林郭勒典型草原物种多样性的影响

为了研究禁牧对典型草原物种多样性的影响,对自由放牧和不同时间(1987、1997和2003年)禁牧的典型草原的物种组成进行了调查.结果表明:禁牧并未使典型草原的主要物种组成发生明显的改变,但使物种的相对重要性发生了明显变化,优势种的优势更加明显;同时,禁牧在一定的时间内可以提高典型草原的物种多样性,但随着禁牧时间的延长,典型草原的物种多样性和丰富度都表现出一种先上升后下降的趋势;在相同的禁牧或放牧条件下,水分条件较好的典型草原具有更高的物种多样性.可见,合理的禁牧时间与优越的水分条件有利于典型草原维持较高的物种多样性.典型草原物种多样性下降可能是人为干扰与干旱环境条件共同作用的结果.