Mortality of pollen grains may result from errors of meiosis: study of pollen tetrads in Typha latifolia L

In the cattail Typha latifolia the four haploid products of meiosis remain attached and form the flat tetrad of pollen grains. Gametophytic lethals arisen de novo in diploid cells of sporophyte must manifest themselves as pollen tetrads with two dead grains. This could allow to estimate the rate of recessive lethals arresting pollen grain development. We studied pollen samples collected from 44 sprouts in two populations in the vicinity of Novosibirsk. The anomalous tetrads T1, T2, T3, and T4 carrying one, two, three, and four dead grains, respectively, were detected in each sampled individual. The mean frequency of all anomalous tetrads in the two populations was 3.4% and 8.7%. The frequencies of tetrad classes varied widely among the individuals with correlation coefficient up to 0.94, but their ratios remained nearly constant. The majority of anomalous tetrads were presented by T1 and T2 classes (their sum comprising 72.7 and 74.0% in two populations), T1 being a little more abundant. The observed pattern of frequencies of tetrads with dead grains can be explained by errors of male meiosis such as chromosome non-disjunction in both meiotic divisions. The tetrads with two dead pollen grains may result mostly from non-disjunction in anaphase I, and those with one pollen grain from non-disjunction in anaphase II, thus making tetrad analysis ineffective for estimating the rate of gametophytic lethals.     

Germination and ion leakage are linked with phase transitions: of membrane lipids during imbibition of Typha latifolia pollen

In previous studies on the causes of imbibitional leakage in dry polien we have presented data which suggest that the leakage is due to a gel to liquid crystalline phase transition in membrane phospholipids during the rehydration event. In the present study we greatly extend and confirm those results. A supplemented phase diagram for the hydration dependent transition temperature of membrane phospholipids in pollen is presented. In pollen containing > 0.05 g H₂O g⁻¹ dry weight at the time of imbibition, this phase diagram for the phospholipids precisely predicts the conditions for rehydration under which germination is maximal and leakage is minimal. However, in extremely dry pollen, containing < 0.05 g H₂O g⁻¹ dry weight the predictive value of the phase diagram for phospholipids in the pollen is not in agreement with data for germination and leakage. Thus, an alternative explanation must be sought for leakage in these circumstances. We examined the available evidence and suggest here that a modified form of the non-bilayer phase hypothesis proposed by Simon (1974) may apply in the specialized case of extremely dry cells.     

Long-term competitive displacement of Typha latifolia by Typha angustifolia in a eutrophic lake

This study follows the outcome of long-term competition between a broad-leaved and a narrowleaved Typha species, T. latifolia and T. angustifolia respectively, in a eutrophic lake. The lake was bordered by a zone of T. latifolia, at one location interrupted by a T. angustifolia stand. Distributional changes of the T. angustifolia stand and the adjacent zone of T. latifolia were measured on aerial photographs (13 years) and along ground-level transects (6 years). A second stand of T. angustifolia was established with transplanted ramets within a formerly homogeneous zone of T. latifolia, and displacement between the two species was measured along ground-level transects after 6 years. Differences between the species in shoot performance were investigated to help explain the relative competitive abilities of the two Typha species. T. angustifolia expanded at the expense of T. latifolia at all water depths where both species occurred, except in very shallow water. Expansion rates suggest that T. angustifolia was not affected by the presence of T. latifolia in water depths exceeding 0.25 m. The Typha species were significantly negatively associated according to rank correlations of shoot densities, and changes of shoot densities, along the transects. These results suggest that T. angustifolia is competitively superior to T. latifolia, contradicting earlier studies. The higher competitive ability of T. angustifolia is consistent with its having taller shoots and a higher standing crop in early summer. Further, shoot height distributions indicated a closer integration of shoot emergence during spring in T. angustifolia than in T. latifolia. A high leaf area/shoot weight ratio suggest that T. latifolia may instead be relatively fast-growing, achieving competitive superiority over narrower-leaved Typha species during a transient period after simultaneous seedling establishment.     

A New Type of Phytase from Pollen of Typha latifolia L.

A phytase was isolated and partially purified from pollen of cattail, Typha latifolia. Its maximum activity was at pH 8.0 and its Km value was 1.7 × 10^?5 m for phytic acid in the presence of Ca²⁺. Among divalent cations tested only Ca²⁺ affected the activity, increasing it by about 120%, but an excess was inhibitory. The enzyme was specific for phytic acid except for 6% activity for p-nitrophenylphosphate. It seems to be a new type of phytase because it cleaved almost 50% of the total phosphate esters in phytic acid and was product-specific, yielding an inositol triphosphate as a final product.     

X-ray diffraction studies of lipid phase transitions in cholesterol-rich membranes at sub-zero temperatures

In X-ray diffraction studies of hydrated (greater than 60%) cholesterol/dioleoylphosphatidylcholine mixtures the lipid packing band showed an abrupt transition from liquid crystal-type to gel-type position and definition at a temperature which decreased progressively to almost -50 degrees C as the proportion of cholesterol was increased to a saturation level of about 50 mol%. Plots of transition temperature against composition (mol% cholesterol) and of peak position against composition provided evidence of a significant change in phospholipid configuration at about 20 mol% cholesterol. However, the data overall suggested a uniform dispersion of the cholesterol molecules in the phospholipid bilayer at all concentrations up to the saturation point. Parallel studies of hydrated lipid extract of erythrocyte membranes and of several cholesterol-rich membrane preparations showed a similar overall change from liquid crystal-type packing at +20 degrees C to a gel-type packing at -30 degrees C to -40 degrees C but without displaying a defined transition temperature.     

Preliminary X-ray diffraction analysis of crystalline lectins from the seeds and leaves of Sophora japonica

The Japanese Pogada Tree (Sophora japonica) contains at least four distinct lectins distributed among seeds, bark, and leaf tissues of the plant. All of these lectins are N-acetylgalactosamine-specific, have molecular weights of about 130,000, are glycoproteins and possess substantial sequence homology. However, they are products of distinct genes. We have crystallized Sophora lectins from bark, seeds, and two different lectins from leaves. Multiple crystal forms of each variety have been obtained by vapor diffusion with polyethylene glycol 4,000 solutions, and five of the crystal forms have been characterized by X-ray diffraction. The data demonstrates that at least in the case of leaf lectin II, the tetrameric molecule contains at least one exact dyad axis. Several of the crystals appear suitable for high resolution structure analysis.     

外源铁对铅污染土壤中宽叶香蒲铅积累的影响

采用温室盆栽方法,研究添加外源铁对不同铅浓度(0、100、500和1000 mg·kg-1)污染土壤中宽叶香蒲铅积累的影响.结果表明:各铅浓度条件下,与添加100 mg Fe·kg-1相比,添加500 mg Fe·kg-1处理的宽叶香蒲地上部和根的铅含量均增高.土壤铅浓度为1000mg·kg-1时,添加500 mg Fe·kg-1处理根的铅含量比100 mg Fe·kg-1处理增加33.7％,地上部铅含量增加50.5％.添加500 mg Fe·kg-1处理的根际土壤中可交换态铅比100mg Fe·kg-1处理增加77.0％～114.6％.除500 mg·kg-1铅浓度外,各铅浓度条件下添加500mg Fe·kg-1处理根干质量均显著低于100 mg Fe·kg-1处理.在铅污染的湿地环境中添加适量铁可以提高铅的有效性,促进铅积累.     

A time-resolved synchrotron X-ray study of a crystalline phase bilayer transition and packing in a saturated monogalactosyldiacylglycerol-water system

The structural changes associated with a phase transition between the gel-phase bilayer (L_β) in which the acyl chains pack in a hexagonal subcell, and a crystalline bilayer phase (L_C1) where the acyl chains are packed in an orthorhombic subcell in a saturated monogalactosyldiacylglycero-water system are reported. The phase change is cooperative and takes place isothermally after the lamellar-gel phase has been held at 20°C for about 8 min. The transformation of the acyl chain subcell from hexagonal to orthorhombic induces a change in diffraction maxima observed in the region 0.6–0.7 nm which is interpreted as a change in packing of the galactose residues from an orthorhombic to hexagonal subcell. We conclude that the rearrangement of the acyl chains into a more closely packed subcell requires the head groups to reorient to reduce the steric hindrance between the bulky galactose residues.     

An X-ray diffraction analysis of oriented lipid multilayers containing basic proteins

X-ray diffraction techniques have been used to study the structures of lipid bilayers containing basic proteins. Highly ordered multilayer specimens have been formed by using the Langmuir-Blodgett method in which a solid support is passed through a lipid monolayer held at constant surface pressure at an air/water interface. If the lipid monolayer contains acidic lipids then basic proteins in the aqueous subphase are transferred with the monolayer and incorporated into the multi-membrane stack. X-ray diffraction patterns have been recorded from multilayers of cerebroside sulphate and 40% (molar) cholesterol both with and without polylysine, cytochrome c and the basic protein from central nervous system myelin. Electron density profiles across the membranes have been derived at between 6 A and 12 A resolution. All of the membrane profiles have been placed on an absolute scale of electron density by the isomorphous exchange of cholesterol with a brominated cholesterol analog. The distributions and conformations of the various basic proteins incorporated within the cerebroside sulphate/cholesterol bilayer are very different. Polylysine attaches to the surface of the lipid bilayer as a fully extended chain while cytochrome c maintains its native structure and attaches to the bilayer surface with its short axis approximately perpendicular to the membrane plane. The myelin basic protein associates intimately with the lipid headgroups in the form of an extended molecule, yet its dimension perpendicular to the plane of the membrane of approx. 15 A is consistent with the considerable degree of secondary structure found in solution. In the membrane plane, the myelin basic protein extends to cover an area of about 2500 A2. There is no significant penetration of the protein into the hydrocarbon region of the bilayer or, indeed, beyond the position of the sulphate group of the cerebroside sulphate molecule.     

Characterization of the L lambda phase in trehalose-stabilized dry membranes by solid-state NMR and X-ray diffraction

Solid-state nuclear magnetic resonance (NMR) spectroscopy and X-ray powder diffraction were used to investigate the mechanism of trehalose (TRE) stabilization of lipid bilayers. Calorimetric investigation of dry TRE-stabilized bilayers reveals a first-order phase transition (L kappa----L lambda) at temperatures similar to the L beta'----(P beta')----L alpha transition of hydrated lipid bilayers. X-ray diffraction studies show that dry mixtures of TRE and 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) have a lamellar structure with excess crystalline TRE being present. The L kappa phase shows typical gel-phase X-ray diffraction patterns. In contrast, the L lambda-phase diffraction patterns indicate disordered hydrocarbon chains. 2H NMR of specifically 2H chain-labeled DPPC confirmed that the acyl chains are disordered in the L lambda phase over their entire lengths. 2H spectra of the choline headgroup show hindered molecular motions as compared to dry DPPC alone, and 13C spectra of the sn-2-carbonyl show rigid lattice powder patterns indicating very little motion at the headgroup and interfacial regions. Thus, the sugar interacts extensively with the hydrophilic regions of the lipid, from the choline and the phosphate moieties in the headgroup to the glycerol and carbonyls in the interfacial region. We postulate that the sugar and the lipid form an extensive hydrogen-bonded network with the sugar acting as a spacer to expand the distance between lipids in the bilayer. The fluidity of the hydrophobic region in the L lambda phase together with the bilayer stabilization at the headgroup contributes to membrane viability in anhydrobiotic organisms.     

X-ray diffraction studies of lipid phase transitions in hydrated mixtures of cholesterol and diacylphosphatidylcholines and their relevance to the structure of biological membranes

Previous X-ray diffraction data on the effects of temperature on hydrated cholesterol/dimyristoylphosphatidylcholine mixtures have been confirmed and equivalent new data on cholesterol/stearolyoleoylphosphatidylcholine obtained. Molecular interpretations are discussed and related to previous studies of cholesterol/dioleoylphosphatidylcholine and of cholesterol-rich biological membranes.     

Soil and Hydrological Drivers of Typha latifolia Encroachment in a Marl Wetland

Aggressive species competition by Typha latifolia in wetland systems on marl-derived soils may threaten the unique vegetation in these areas. We examined historic water and land use, soil chemistry, soil genesis, and topography in a wetland (Harewood Marsh) that is under encroachment by T. latifolia. An earthen road that bisects the wetland and active pastures in and around the wetland were also considered in the study due to their potential influence on wetland hydrology and nutrient inputs. Historic land uses and trends in surface water patterns were determined via aerial photography. In addition local landowners and city officials were contacted for information about historic water use in the area around the marsh. Soils were augered and sampled in seven locations in the wetland, and at each auger site, vegetation was described. Six wells were installed near the earthen road and weekly water depth measurements were taken from January 2002 to January 2003. In February 2002, 10 A-horizon soil samples (per transect) were taken from three 150-m transects that spanned areas with and without T. latifolia. Results indicate that T. latifolia encroachment is facilitated by a rising water table (the result of the termination of a local municipal water supply source) and N and P inputs, most likely from cattle grazing on the wetland. An increase in the numbers of rare plant species associated with marl wetland habitats appears to have also occurred and is believed partly due to current wetter conditions. Our study provides insight into the dynamics of T. latifolia encroachment in a unique marl wetland habitat and demonstrates how local factors controlling nutrient and hydrologic dynamics can have significant effects on changes in plant community composition.     

Variations in growth and reproduction within populations of two rhizomatous plant species: Typha latifolia and Typha angustifolia

Summary The whitespotted swayer Monochamus scutellatus (Say) (Coleoptera: Cerambycidae) breeds in recently killed conifers in northeastern North America, especially white pine Pinus strobus L. We cut down 4 white pines in Pocahontas County, West Virginia, in June 1981, in order to study the behavior of sawyers attracted to the trees. Far greater numbers of both male and female sawyers were attracted to the largest of the trees cut. At all trees, females preferred the parts of the tree of greater circumference. These preferences may be related to greater larval survival in large-circumference regions. Male and female numbers at breeding site peaked at about 1200–1500 h EST; at this time, males generally outnumbered females by about 2:1. We placed males in 3 size classes: L (>2.0 cm), M (2.0 cm, 1.8 cm), and S (<1.8 cm). At the largest of our 4 trees, L males disproportionately frequented the portion of the trunk preferred by females. L males were far more successful than M and S males in mating and in agonistic encounters with other males. L males were thus apparently able to exclude smaller males from the preferred region to some extent.     

Storage behavior of Typha latifolia pollen at low water contents: Interpretation on the basis of water activity and glass concepts

Germplasm must be stored under optimal conditions to maximize longevity and efficiently maintain genetic resources. In order to identify optimal storage conditions, we investigated the effects of temperature (−5 to 45°C) and water content (<0.17 g H₂O g⁻¹ dry weight) on longevity of Typha latifolia L. pollen. Longevity was highest at water contents corresponding to storage relative humidity (RH) of 11‐15% which corresponded to the shoulder of water sorption isotherms. Also coinciding with this shoulder were abrupt changes in heat capacity of water present in the pollen. Consistent with changes in isotherms with temperature and the concept of critical RH for storage, optimum water contents increased with decreasing temperature. An attempt was made to explain the aging behavior according to the glass concept. The water content‐temperature combinations of optimal storage were found to be below the glass transition curve, indicating that optimum storage conditions are achieved when intracellular glasses are present. We also found a change in activation energy of aging in Arrhenius plots around T_g, demonstrating a change in aging kinetics when the glassy state is lost. We concluL that T_g curves cannot be used solely to predict precise conditions of optimum storage, but might be useful for predictions of storage longevity above optimum water contents. The data imply that too much drying reduces longevity and should be avoided, particularly when cryogenic storage is considered.     

Differential effects of carotenoids on lipid peroxidation due to membrane interactions: X-ray diffraction analysis

The biological benefits of certain carotenoids may be due to their potent antioxidant properties attributed to specific physico-chemical interactions with membranes. To test this hypothesis, we measured the effects of various carotenoids on rates of lipid peroxidation and correlated these findings with their membrane interactions, as determined by small angle X-ray diffraction approaches. The effects of the homochiral carotenoids (astaxanthin, zeaxanthin, lutein, β-carotene, lycopene) on lipid hydroperoxide (LOOH) generation were evaluated in membranes enriched with polyunsaturated fatty acids. Apolar carotenoids, such as lycopene and β-carotene, disordered the membrane bilayer and showed a potent pro-oxidant effect (> 85% increase in LOOH levels) while astaxanthin preserved membrane structure and exhibited significant antioxidant activity (40% decrease in LOOH levels). These findings indicate distinct effects of carotenoids on lipid peroxidation due to membrane structure changes. These contrasting effects of carotenoids on lipid peroxidation may explain differences in their biological activity.     

Differential effects of carotenoids on lipid peroxidation due to membrane interactions: X-ray diffraction analysis

The biological benefits of certain carotenoids may be due to their potent antioxidant properties attributed to specific physico-chemical interactions with membranes. To test this hypothesis, we measured the effects of various carotenoids on rates of lipid peroxidation and correlated these findings with their membrane interactions, as determined by small angle X-ray diffraction approaches. The effects of the homochiral carotenoids (astaxanthin, zeaxanthin, lutein, beta-carotene, lycopene) on lipid hydroperoxide (LOOH) generation were evaluated in membranes enriched with polyunsaturated fatty acids. Apolar carotenoids, such as lycopene and beta-carotene, disordered the membrane bilayer and showed a potent pro-oxidant effect (>85% increase in LOOH levels) while astaxanthin preserved membrane structure and exhibited significant antioxidant activity (40% decrease in LOOH levels). These findings indicate distinct effects of carotenoids on lipid peroxidation due to membrane structure changes. These contrasting effects of carotenoids on lipid peroxidation may explain differences in their biological activity.     

Acyl-chain correlation in membrane fusion intermediates: x-ray diffraction from the rhombohedral lipid phase

We have studied the acyl-chain conformation in stalk phases of model membranes by x-ray diffraction from oriented samples. As an equilibrium lipid phase induced by dehydration, the stalk or rhombohedral phase exhibits lipidic passages (stalks) between adjacent bilayers, representing a presumed intermediate state in membrane fusion. From the detailed analysis of the acyl-chain correlation peak, we deduce the structural parameters of the acyl-chain fluid above, at, and below the transition from the lamellar to rhombohedral state, at the molecular level.     

Phospholipid Motional Characteristics in a Dry Biological System : A P-Nuclear Magnetic Resonance Study of Hydrating Typha latifolia Pollen

Analysis of the proton-decoupled ³¹P-nuclear magnetic resonance (NMR) spectrum of fully hydrated Typha latifolia pollen revealed the presence of two main peaks: A broad asymmetrical component of a `bilayer' lineshape and a much narrower symmetrical component originating from phosphorus compounds undergoing rapid isotropic motion. From (a) ³¹P-NMR experiments on the hydrated total pollen phospholipids, (b) saturation transfer ³¹P-NMR experiments, and (c) the fraction of lipid phosphate in the pollen, it can be concluded that the great majority of the endogenous phospholipids are arranged in extended bilayers in which the lipid phosphates undergo fast (τ_c < 10⁻⁶ second) long axis rotation. This bilayer arrangement of phospholipids was observed in the pollen down to hydration levels of at least 10.9% moisture content. At the lowest level of pollen hydration examined (5.2%) the ³¹P-NMR spectrum had a solid state lineshape demonstrating that all the phosphorus-containing compounds (including the phospholipids) were virtually immobile.