Carotenoid composition and metabolism in green and blue-green algal lichens in the field

The carotenoid composition of 33 species of green algal lichens and 5 species of blue-green algal lichens was examined and compared with that of the leaves of higher plants. As in higher plants, green algal lichen species which were found in both shade and full sunlight exhibited higher levels of the carotenoids involved in photoprotective thermal energy dissipation (zeaxanthin as well as the total xanthophyll cycle pool) in the sun than in the shade. This was particularly true when thalli were moist during exposure to high light, or presumably became desiccated in full sunlight. However, the reverse trend in the carotenoid composition of green algal lichens was also observed in those species which were found predominantly either in the shade or in full sunlight. In this case sun-exposed lichens often possessed lower levels of zeaxanthin and of the components of the xanthophyll cycle than lichens which were found in the shade. In contrast to higher plants, the lichens from all habitats exhibited a relatively high ratio of carotenoids to chlorophylls (more characteristic of sun leaves), very low levels of α-carotene (similar to that found in sun leaves), and a level of β-carotene similar to that found in shade leaves. Zeaxanthin, but not the expoxides of the xanthophyll cycle, was also frequently found in blue-green algal lichens. A trend for increasing levels of zeaxanthin with increasing growth light regime was observed inPeltigera rufescens, the species which was found to occur over the widest range of light environments. The level of zeaxanthin per chlorophylla in these blue-green algal lichens was in a range similar to that per chlorophylla+b in green algal lichens. However, zeaxanthin was also absent in one species,Collema cristatum, in full sunlight. Thus, the zeaxanthin content of the blue-green algal lichens can be similar to that of higher plants, or it can be rather dissimilar, as was also the case in the green algal lichen species. The presence of large amounts of ketocarotenoids in blue-green algal lichens is also noteworthy.     

Enhanced ethylene production by primary roots of Zea mays L. in response to sub-ambient partial pressures of oxygen

Ethylene production by primary roots of 72–h-old intact seedlings of Zea mays L. cv. LG11 was studied under ambient and sub-ambient oxygen partial pressures (pO₂) using a gas flow-through system linked to a photoacoustic laser detector. Despite precautions to minimize physical perturbation to seedlings while setting-up, ethylene production in air was faster during the first 6h than later, in association with a small temporary swelling of the roots. When roots were switched from air (20–8kPa O₂) to 3 or 5kPa O₂ after 6h, ethylene production increased within 2—3 h. When, the roots were returned to air 16 h later, ethylene production decreased within 2—3 h. The presence of 10kPa CO₂ did not interfere with the effect of 3kPa O₂. Transferring roots from air to 12–5kPa did not change ethylene production, while a reduction to 1 kPa O₂ induced a small increase. The extra ethylene formed in 3 and 5 kPa O₂ was associated with plagiotropism, swelling, root hair production, and after 72 h, increased amounts of intercellular space (aerenchyma) in the root cortex. Root extension was also slowed down, but the pattern of response to oxygen shortage did not always match that of ethylene production. On return to air, subsequent growth patterns became normal within a few hours. In the complete absence of oxygen, no ethylene production was detected, even when anaerobic roots were returned to air after 16 h.     

Distribution of microtubules during the growth of tobacco pollen tubes

Summary— The distribution of microtubules was investigated in Nicotiana tabacum pollen tubes at different stages of tube growth by immunofluorescence microscopy. Using specific antibodies, the presence of microtubules consisting of different tubulin isoforms was tested. α-, β- and tyrosinated α-tubulin were present within the tube, whereas the acetylated form was lacking. The presence of tubulin subunits in pollen tube extracts was also investigated by immunoblotting analyses. The use of a confocal laser scanning microscope integrated with computer-assisted imaging, allowed a detailed visualization of the microtubule distribution and organization. Cytoplasmic microtubules organized as short bundles with various orientations were detected at the apex of long tubes.     

Algal crust formation in the inland dune area,Laarder Wasmeer,the Netherlands

The aim of this study is to acquire insight in the initial vegetation development on active drifting sands in relation to geomorphological processes. For this purpose the algal vegetation and surface dynamics were monitored on a sand hill with active drifting sand, and on a bare slope within a terrain covered with Polytrichum piliferum located in the Laarder Wasmeer (The Netherlands).There is a successional development from an algal community dominated by the cyanobacterium Oscillatoria spp., through the crust in which initially the green alga Klebsormidium and later the cyanobacterium Synechococcus predominates, eventually succeeded by the green alga Zygogonium ericetorum. In this phase the sand is stabilized. The areal extent of algal crusts on the active drifting sand area is greatest during the winter, contrastingly highest biomass values are found during the summer and autumn in mature Zygogonium crusts.Substrate instability due to the action of wind clearly limits algal growth and vegetational development on the sand hill. The algal crust seldom reaches the stage of maturity. Near-flat ground is more easily stabilized. Unlike the algae found in coastal dune area and the initial pioneers in the Laarder Wasmeer area, the Zygogonium crust is water repellent when dry. Consequently increasing surface stability by algal crust development is accompanied by higher surface runoff on sloping areas.     

穴位激光照射对兔子宫类固醇激素受体的影响

对兔用Ｈｅ－Ｎｅ激光照射穴位,照射外生殖器,用类固醇激素受体测定法测定子宫雌二醇受体（ＥＲ）和孕酮受体（ＰＲ）含量。照射穴位后部分实验组的ＥＲ和ＰＲ浓度上升,与正常对照组相比较有显著或极显著差别（Ｐ＜０．０５,Ｐ＜０．０１）,ＥＲ提高１．７－３．２倍,ＰＲ提高２．７－３．７倍。实验结果提示激光可通过类固醇激素受体浓度的提高,在受体水平上影响机体代谢。     

A New Histochemical Double-Stain Method Using Three-Dimensional Analysis with Confocal laser Scanning Microscopy

We describe a new technique for immunohistochemical and enzyme-histochemi-cal double staining using confocal laser scanning microscopy in the reflection mode. As an example, we investigated the immunoreactivity for Spot 35-calbindin-D_28K, a vitamin D-dependent calcium binding protein, and the enzyme activity for ma⁺-ATPase in the rat kidney. The lead precipitation method for Ca²⁺-ATPase was initially used to process kidney slices. Each specimen was then dehydrated and embedded in a water soluble resin. Thin sections were cut from the resin block, and an indirect immunocolloidal gold method with silver enhancement for Spot 35-calbindin-D_28K antigen was carried out on the glass slides. Results were then observed by confocal laser scanning microscopy in the reflection mode. The three-dimensional distribution of the reaction products was detected by serial optic slice images. Lead phosphate particles, which represented the location of Ca²⁺-ATPase, were distributed deep in the section. The most intense signals from the silver partkles were detected from the surface slice of the section. A stereoscopic image generated from the serial optic slices clearly showed the differences in their distribution.     

Confocal laser scanning light microscopy of the extra-thecal epithelia of undecalcified scleractinian corals

The extra-thecal epithelia of cryofixed undecalcified, freeze-substituted polyps of the scleractinian corals Galaxea fascicularis and Tubastrea faulkneri and axial and basal polyps of Acropora formosa have been examined, in anhydrously prepared thick slices, by confocal laser scanning light microscopy. The avoidance of chemical fixation and decalcification makes it possible to determine whether previously seen structures are real or artefactual products of swelling, shrinkage and distortion. All of the epithelia of all the corals examined are characterised by well defined intercellular spaces. Mucocytes are present in all cell layers in Galaxea and Tubastrea but are not present in any cell layers in the axial polyp of Acropora although they are abundant in the oral ectoderm of the basal polyps in this coral. Zooxanthellae are absent in Tubastrea, the epithelia of the exert septa of Galaxea and the axial polyp of Acropora. The calicoblastic ectoderm is generally composed of thin squamous cells with large intercellular spaces. At rapidly calcifying regions such as the tips of the exert septa of Galaxea, the calicoblastic cells are elongated with extensive arborisation of the basal regions of the cells. They are separated by large intercellular spaces and contain numerous fluorescent granules. The apical regions of these cells appear to be closely applied to the surface of the skeleton. There is no evidence of a space between the apical region of the calicoblastic cells and the skeleton.     

低剂量CO2激光对茄子,青椒叶绿体超微结构影响的初步观察

本试验用功率密度为825mw/cm~2的CO_2激光照射茄子干种子(含水量8.33％)13s、青椒干种子(含水量5.4％)3s,分别以Os为对照(ck)。照射后播于生长箱内,出苗10天分苗于玻璃温室内,于四叶期取样观察成熟叶片叶绿体的超微结构。发现激光照射处理的茄子、青椒的叶绿体的基质片层、基粒片层有明显的吸胀现象。     

番茄种子经激光和咖啡因处理后其当代生物效应的研究

咖啡因具有抑制一些酶的活性,可减弱或消除生物体自身对激光引起的生物效应的修复作用。试验证明咖啡因对番茄种子萌发有强烈的抑制作用,咖啡因和激光复合处理生物效应显著,可降低番茄种子的发芽,并促进番茄果实增大和生长前期速率加快。     

Damage to living trees contributes to almost half of the biomass losses in tropical forests

Accurate estimates of forest biomass stocks and fluxes are needed to quantify global carbon budgets and assess the response of forests to climate change. However, most forest inventories consider tree mortality as the only aboveground biomass (AGB) loss without accounting for losses via damage to living trees: branchfall, trunk breakage, and wood decay. Here, we use ~151,000 annual records of tree survival and structural completeness to compare AGB loss via damage to living trees to total AGB loss (mortality + damage) in seven tropical forests widely distributed across environmental conditions. We find that 42% (3.62 Mg ha⁻¹ year⁻¹; 95% confidence interval [CI] 2.36–5.25) of total AGB loss (8.72 Mg ha⁻¹ year⁻¹; CI 5.57–12.86) is due to damage to living trees. Total AGB loss was highly variable among forests, but these differences were mainly caused by site variability in damage-related AGB losses rather than by mortality-related AGB losses. We show that conventional forest inventories overestimate stand-level AGB stocks by 4% (1%–17% range across forests) because assume structurally complete trees, underestimate total AGB loss by 29% (6%–57% range across forests) due to overlooked damage-related AGB losses, and overestimate AGB loss via mortality by 22% (7%–80% range across forests) because of the assumption that trees are undamaged before dying. Our results indicate that forest carbon fluxes are higher than previously thought. Damage on living trees is an underappreciated component of the forest carbon cycle that is likely to become even more important as the frequency and severity of forest disturbances increase.