Effects of high-temperature stress on microsporogenesis in heat-sensitive and heat-tolerant genotypes of Phaseolus vulgaris

High ambient temperature (32/27 °C, day/night, 12 h photoperiod) applied prior to anthesis to Phaseolus vulgaris plants results in abnormal pollen and anther development during microsporogenesis. Scanning and transmission electron microscopy were used to examine anther and pollen morphology and pollen wall architecture after heat stress was applied to two genotypes that differ with respect to yield potential under high‐temperature field conditions: one, a heat‐sensitive, Mesoamerican genotype, A55, the second, a heat‐tolerant, Andean genotype, G122. High‐temperature treatment of both genotypes was applied 1–13 d before anthesis. Under heat stress, the heat‐tolerant genotype showed anther and pollen characteristics that were generally similar to the low temperature controls. In contrast, after 9 d of heat treatment before anthesis, the anthers of the heat‐sensitive genotype were indehiscent and contained abnormal pollen. Pollen wall architecture was also affected in the 12 and 13 d treatments. In addition to the morphological changes, the heat‐sensitive genotype also experienced reduced pollen viability and reduced yield in high‐temperature experiments conducted in both the greenhouse and field.     

南水青冈属及壳斗科其他属花粉壁超微结构比较研究

对主要分布于南美和新西兰的南水青冈属Nothofagus 花粉外壁的超微结构进行了观察和研究, 同时与壳斗科其他属花粉外壁的结构进行比较,结果表明,南水青冈属花粉外壁的厚度、结构、萌发孔类 型以及花粉外壁表面的纹饰与壳斗科其他属花粉外壁的超微结构存在明显差别。主要表现为：南水青 冈属花粉外壁的柱状层和内层发育差,为颗粒状;基层和覆盖层无分化结构;覆盖层上为刺状纹饰;萌发 孔为5～8沟。壳斗科其他属花粉外壁的小柱发育好,形成明显的柱状层;覆盖层和基层常具一定的结 构;花粉表面较光滑,或为波状、颗粒或瘤状纹饰;内层发育较好;多数花粉具3孔沟,少数为3沟或3拟 孔沟。本研究认为南水青冈属花粉外壁的结构属于较原始类型,支持kuprianova等将南水青冈属独立为南壳斗科。     

库姆塔格柽柳沙包年层稳定碳同位素与气候环境变化

采用年层环境分析法,建立库姆塔格沙漠柽柳沙包年层稳定碳同位素序列,并利用记录的环境信息和附近气象资料,分析柽柳沙包稳定碳同位素与气候环境变化。结果表明:(1)柽柳沙包年层稳定碳同位素比率(δ13C)在20世纪40—60年代出现波动,80年代后趋于下降,δ13C序列变化符合全球树轮δ13C下降趋势,表明大气CO2浓度增加会对柽柳沙包年层δ13C造成影响。(2)柽柳沙包年层稳定碳同位素分辨率(Δ)与全球气候变化趋势相一致,120a以来,全球气候变暖,柽柳沙包Δ偏重,为干热的气候环境,19世纪80年代以前,气温偏低,柽柳沙包Δ值偏轻,代表冷湿的气候环境。(3)不同生境环境下柽柳沙包年层Δ值对气候环境要素产生不同的响应,高海拔的山前柽柳沙包Δ值与年降水、湿度及季节性气压、光照相关性显著,Δ值受多个气候要素的影响,其滞后作用不明显;低海拔的干旱沙漠区柽柳沙包Δ值对年气温及季节性降水、湿度特别敏感,Δ值存在明显的滞后效应。     

Zearalenone and flower bud formation in thin-cell layers of Nicotiana tabacum L.

Three lines of evidence indicated a connectionbetween zearalenone (ZEN) and flower bud formationin thin cell layer (TCL) explants of Nicotianatabacum L. cv. Samsun. (1) There were two peaks inthe endogenous ZEN level during the formation offlower buds. (2) The specific inhibitor of ZENbiosynthesis, malathion (MAL), inhibited thebiosynthesis of endogenous ZEN and at the same timeflower bud neoformation. (3) Exogenous ZEN inducedflower bud neoformation.     

Computational Modeling of Orientation Tuning Dynamics in Monkey Primary Visual Cortex

In the primate visual pathway, orientation tuning of neurons is first observed in the primary visual cortex. The LGN cells that comprise the thalamic input to V1 are not orientation tuned, but some V1 neurons are quite selective. Two main classes of theoretical models have been offered to explain orientation selectivity: feedforward models, in which inputs from spatially aligned LGN cells are summed together by one cortical neuron; and feedback models, in which an initial weak orientation bias due to convergent LGN input is sharpened and amplified by intracortical feedback. Recent data on the dynamics of orientation tuning, obtained by a cross-correlation technique, may help to distinguish between these classes of models. To test this possibility, we simulated the measurement of orientation tuning dynamics on various receptive field models, including a simple Hubel-Wiesel type feedforward model: a linear spatiotemporal filter followed by an integrate-and-fire spike generator. The computational study reveals that simple feedforward models may account for some aspects of the experimental data but fail to explain many salient features of orientation tuning dynamics in V1 cells. A simple feedback model of interacting cells is also considered. This model is successful in explaining the appearance of Mexican-hat orientation profiles, but other features of the data continue to be unexplained.     

Pollen morphology of the tribe Rhinantheae (Orobanchaceae) and its systematic significances

Pollen morphology of 36 species representing 14 genera within the tribe Rhinantheae in the family Orobanchaceae was studied and illustrated with light microscopy (LM) and scanning electron microscopy (SEM). Five major pollen types were recognized on the basis of exine ornamentation. Within these major types, minor types (subtypes) were distinguished based on exine surface pattern, size, shape, amb form, colpi and colpus membrane. These types and subtypes are as follows: type I. retipilate: subtype Ia. regular retipilate: (1) pollen size < 27 μm, (2) pollen size > 27 μm, subtype Ib. irregular retipilate; type II. verrucate: subtype IIa. macro-verrucate, subtype IIb. verrucate, subtype IIc. sparse verrucate; type III. retirugulate; type IV. granulate; type V. micro-reticulate. A key to pollen morphology of genera studied within the Rhinantheae was made based on pollen morphology from our study and earlier work. Combining with other sources of information on the Rhinantheae, the systematic relationships of this tribe are discussed. Rhinantheae pollen displays considerable variation between genera and species, with taxonomically significant characters at genus and species level. Palynological characteristics provide evidence for interpreting the conflicting views concerning the “Pterygiella Complex”. The evolutionary trend in exine sculpture of Rhinantheae could be proposed, namely that retipilate sculpturing which is the most widespread type is more primitive than the other types (such as foveolate, granulate, regulate, reticulate, retirugulate and verrucate). The pollen data in present study and the view of Hong (1986), as well as the molecular data from Bennett and Mathews (2006) indicated that Asia and related regions were likely to the origin centre of the tribe Rhinantheae.     

Affinity cross-flow filtration: purification of IgG with a novel protein a affinity matrix prepared from two-dimensional protein crystals

In this article, we describe the use of 1- to 2-mum sized affinity microparticles for the isolation and purification of IgG from artificial IgG-human serum albumin mixtures and clarified hybridoma cell culture supernatants by affinity cross-flow filtration. Affinity microparticles were prepared from cell wall fragments of Clostridium thermohydrosulfuricum L111-69, in which the peptidoglycan-containing layer was completely covered with a hexagonally ordered S-layer lattice. After crosslinking the S-layer protein with glutaraldehyde, carboxyl groups from acidic amino acids were activated with carbodiimide and used for immobilization of Protein. A. Quantitative determination confirmed that Protein A molecules formed a monomolecular layer on the outermost surface of the S-layer lattice. Affinity microparticles were found to withstand high centrifugal and shear forces and revealed no Protein A leakage or S-layer protein release under cross-flow conditions between pH 2 to 12. The IgG-binding capacity of affinity microparticles was investigated under crossflow conditions and compared with that obtained in batch adsorption processes. (c) 1994 John Wiley & Sons, Inc.     

Immunolabeled microtubules and microfilaments are visible in multiple cell layers of rye root tip sections

Summary A protocol was developed to observe plant microtubules and actin microfilaments in large tissue samples without physical sectioning. Rye (Secale cereale L. cv. Rymin) root tip pieces from two-day-old seedlings were fixed and processed for immunolabeling. Incubation times of 24–48 h were required to insure adequate penetration of fixatives, antibodies, and washing buffers. Clearing of the tissue with methyl salicylate reduced background auto-fluorescence that would otherwise interfere with the resolution of cytoskeletal structures. Microtubules or microfilaments in 5–7 cell layers were visualized using the optical-sectioning capability of laser scanning confocal microscopy (LSCM) and projected as three-dimensional images. The three-dimensional character of the cytoskeletal elements is retained when viewing stained cells of intact tissue. The net-like character of a microfilament array radiating out from a single point into the cytoplasm is maintained when the cells are stained in intact root tip pieces and imaging is accomplished in situ.Abbreviations Cy3 cyanine 3.18-conjugated goat anti-mouse IgG - FITC-M fluorescein isothiocyanate conjugated anti-mouse IgG - IFB immunofluorescence buffer - LSCM laser scanning confoeal microscopy - TPBS phosphate-buffered saline with 0.1% Triton X-100     

The accumulation and metabolism of plant growth regulators during organogenesis in cultures of thin cell layers of Nicotiana tabacum

The accumulation and metabolism of exogenously applied and endogenously produced auxins and cytokinins were studied in relation to organogenesis in thin cell layers of Nicotiana tabacum L. It was shown that, in order to obtain maximal flower bud formation, both exogenous auxin and cytokinin needed to be present during the first 4 days of culture (to the formation of a subepidermal meristematic zone) whereas cytokinins needed to be present for at least 4 days more (until formation of organogenic centres). Explants taken from floral branches have higher endogenous indole-3-acetic acid (IAA) levels compared with explants from the basal part of the stem which form only vegetative buds. This might be related to a different IAA metabolism in these two types of explants as was shown by the different accumulation of exogenously applied IAA. Both 'floral' and 'vegetative' cells layers contained comparable amounts of zeatin riboside (ZR) as their major cytokinin. Free bases, zeatin (Z) and dihydrozeatin [(diH)Z], given exogenously, were largely metabolised to their respective ribosides. The observation that Z was less effective than (diH)Z in the induction of flower buds could be related to (diH)ZR apparently not being a substrate for cytokinin oxidase.     

Root histogenesis from tobacco thin cell layers

Summary Internode stem expiants ofNicotiana tabacum cv. Samsun, consisting of eight cell layers: epidermis, subepidermal chlorenchyma, collenchyma and cortical parenchyma (i.e., thin cell layers), were cultured under conditions inducing rhizogenesis. The aim was to investigate the histological sequence of adventitious root formation in this system. The earliest cytological events in culture (12 h) were nucleolar extrusions and amitotic nuclear divisions. Though not restricted to a specific cell layer, the two phenomena were more frequent in the subepidermal chlorenchyma, and characterized the first phases (12-96 h) of cell proliferation mainly occurring in this layer. Amitoses were followed by the formation of thin walls within the original cells, resulting in the formation of intracellular clusters. These subepidermal clusters were separated by enlarged cells of the parent tissue, whose nuclei showed nucleolar extrusion. At day 3 the first mitoses were observed in cells having abundant starch inclusions. Amitotic divisions also continued, but less frequently. The increasing frequency of mitoses in the subepidermal chlorenchyma (day 4), as well as in the two underlying collenchymatous layers, contributed to the growth of the superficial clusters, in which small clumps of meristematic cells were formed; these, later (day 9), gave rise to root domes. The 5th cell layer remained undivided for a relatively long time (two weeks). The 6th and 7th layers proliferated mitotically later (from day 8 onwards) than the superficial layers and formed root domes following the same histological sequence. Wound callus, generated by the innermost layer, increased markedly in the last two weeks of culture and concomitantly formed vascular clumps surrounded by meristematic layers; these produced root primordia which were frequently anomalous (day 26–27). Regardless of its origin (i.e., superficial or deep layers of the expiant, or wound callus cells), root tip formation was always preceded by the differentiation of a sheath of starch-containing cells, from which the root cap developed.Abbreviations LS longitudinal section - S.E. standard error - TVS transverse section