Biological studies including population growth parameters of the predatory miteAmblyseius barkeri [Acarina.: Phytoseiidae] at 25°C in the laboratory

Amblyseius barkeri (Hughes) fed onThrips tabaci (Lind.) at 25°C showed an average duration of 2.2, 0.8 and 3.2 days for the egg, larval and nymphal stages, with mortalities at 1.0, 1.0 and 3.1%, respectively. Females represented 63% of the population and required multiple matings for optimal fertility. The oviposition period was 20.3 days and the average oviposition rate 2.3 eggs per day. The intrinsic rate of increase was 0.22 per day. The expected life span was 29.6 days for ♀♀ and 27.4 days for ♂♂.A. barkeri ♂♂ and ♀♀ both consumed 3.3 nymphs of thrips per day (mean value for the feeding stages). The larva does not take up food. In the absence of thripsA. barkeri was able to consume two-spotted spider mites,Tetranychus urticae (Koch), and their eggs, adult broad mites,Polyphagotarsonemus latus (Banks), and pollen of various plants. Cannibalism was observed when food was lacking. Certain morphological features, egglaying, mating and predatory behaviour are described.      

玉米花粉单倍体植株染色体上异染色质的变异

我们用Giemsa BSG C-带技术检查了玉米花药培养获得的花粉单倍体植株根尖细胞染色体上异染色质的变异,观察结果表明,有的植株所显示的C-带数目是与供体植株的相一致,有的植株所显示的C-带数目则发生了显著变化,其中有的增加,有的减少。并讨论了异染色质发生变异的可能原因。还相应地观察到间期核中染色中心的变化是与中期染色体上C-带数目的变化相一致。     

Effects of pollen donors on seed formation inEspeletia schultzii (Compositae) populations at different altitudes

The influence of different pollen donors on seed formation was investigated in three populations ofEspeletia schultzii that differ in environmental conditions and life history characteristics. Self pollen and pollen from different donors (< 15m apart) within each population was used in a diallel design in order to test the genetic base of seed set variation. Three measures of seed formation were used: (1) achene number; (2) proportion of filled achenes (fruits) that distinguishes between achenes with seeds and empty achenes; (3) proportion of aborted seeds that distinguishes between viable and aborted seeds. Self-pollinations resulted in empty achenes. Achene number did not vary between the different pollen donors. A bimodal pattern of filled achenes was found in two populations in two consecutive years. On the other hand, a unimodal pattern was found in crosses between more distant donors (> 30m). These patterns seems to be the results of a sporophytic incompatibility system. Seed abortion was highest at the higher elevations and seems to be correlated with elevation rather than with any genetic effect.     

City spore concentrations in the European Economic Community (EEC). VI. Poaceae (Grasses), 1982–1986

Summary Airborne grass-pollen concentrations in six cities in the EEC are compared, based on observations from five years, 1982–1986. Results show that there are quantitative differences both between the monitoring stations and between the years. Very provisionally, the average seasonal total of the European urban airborne grass-pollen concentration can be put at 4 to 5000 per m³ of air. Also qualitatively, regarding the seasonal fluctuations, there are differences between the stations, and between the years. Generally, the results confirm that June is the most typical grass-pollen month in northwestern Europe, whereas in mediterranean Europe May is the more prominent grass-pollen period. There seems to be little coherence between the starting dates of the grass-pollen season even at relatively nearby stations in northwestern Europe, suggestive for a great influence of the actual weather situation.     

Ontogeny of intruding non-periplasmodial tapetum in the wild chicory,Cichorium intybus (Compositae)

The tapetal development ofCichorium intybus L. is investigated using LM and TEM and discussed in relation to the development in other species. During the second meiotic division the tapetal cells become binucleate and lose their cell walls. They intrude the loculus at the time of microspore release from the meiotic callose walls, which means that a locular cavity is never present in this species. During pollen development they tightly junct the exine, especially near the tips of the spines. During the two-celled pollen grain stage they degenerate and most of their content turns into pollenkitt. Until anther dehiscence they keep their individuality, which means that these intruding tapetal cells never fuse to form a periplasmodium. The ultrastructural cytoplasmatic changes during this development are discussed in relation to possible functions.     

Nuclear DNA content and separation of Nicotiana sylvestris vegetative and generative nuclei at various stages of male gametogenesis

At all stages of male gametogenesis, generative and vegetative pollen nuclei of Nicotiana sylvestris can be distinguished without ambiguity after Feulgen or ethidium bromide staining. They differ by their morphology and their apparent DNA content, always lower in vegetative nuclei. These differences provide a basis for their separation by sedimentation and fluorometry. After elimination of the another somatic cells and after crushing the pollen, vegetative and generative nuclei are separated by two successive Percoll gradients (purity 80–90%). Analysis of the gradient fractions and final purification can be done with a cell sorter. DNAs of both types are isolated by a cetyltrimethylammonium method, followed by a RNase treatment. Yields are lower for vegetative than for generative nuclei, and decrease with the age of pollen. Molecular weights and digestibility by restriction enzymes are compatible with molecular analyses.     

Bleomycin-Iron Damage To Dna With Formation Of 8-Hydroxydeoxyguanosine and Base Propenals. Indications That Xanthine Oxidase Generates Superoxide From Dna Degradation Products

Bleomycin, in the presence of ferric salts, oxygen and a suitable reductant, degrades DNA with the release of base propenals, detected as thiobarbituric acid (TBA) reactivity, and the formation of 8-hydroxydeo-xyguanosine (80HdG) detected by HPLC. When xanthine oxidase is added to the incubated mixture of DNA degradation products, TBA-reactivity is destroyed but 80HdG formation is increased. EPR Spin trapping experiments show that hydroxyl radicals (OH) are formed in the reaction mixture and can be inhibited by the inclusion of either superoxide dismutase or catalase. These findings suggest that the base propenals and possibly malondialdehyde, formed from them, are aldehydic substrates for xanthine oxidase and, the product of this reaction is superoxide (O₂^-) and hydrogen peroxide (H₂O₂). Thus, TBA reactivity is destroyed in the formation of O₂^- and H₂O₂ which stimulate further oxidative damage to DNA resulting in increased 8OHdG formation.     

Detection of Myoglobin-Derived Radicals On Reaction of Metmyoglobin With Hydrogen Peroxide and Other Peroxidic Compounds

The reaction of metmyoglobin with equimolar concentrations of hydrogen peroxide has been studied using both electron spin resonance (e.s.r.) and optical spectroscopy. Using the former technique a strong anisotropic e.s.r. signal is observed, in the presence of the spin trap DMPO, which decays relatively rapidly. This previously unobserved signal, which is also observed on reaction of metmyoglobin with a number of other powerful oxidants (peracetic acid, 3-chloroperoxybenzoic acid, monoperoxyphthalic acid, iodosyl benzene, ¹BuOOH and cumene hydroperoxide) is assigned to a slowly-tumbling, metmyoglobin-derived, spin adduct. The parameters of this signal (a_N 1. 45, a_H 0.83 mT) are consistent with the trapped radical having a heteroatom centre; this is believed to be oxygen. The concentration of this species is not affected by compounds such as 2-deoxyribose, mannitol and phenylalanine which are all efficient hydroxyl radical scavengers, demonstrating that the formation of this radical is not due to reaction of “free” HO· generated by breakdown of H₂O₂, by released iron ions. The concentration of this species is however decreased by desferal, ascorbate, Trolox C, salicylate and, to a lesser extent, linoleic acid; with the first three of these compounds further substrate-derived radicals are also observed. Examination of similar reaction systems (though in the absence of DMPO) by optical spectroscopy shows that the myoglobin (IV) species is formed and that this species behaves in a somewhat different manner with these added compounds. These results suggest that the radical trapped in the e.s.r. experiments is a myoglobin-derived species, probably a tyrosine peroxyl radical, arising from oxidative damage to the globin moiety.

The diminution of both the e.s.r. signal of the spin adduct and the optical absorption of the myoglobin (IV) species in the presence of linoleic acid suggests that these myoglobin-derived species can initiate oxidative damage but that this process can be ameliorated by the presence of a number of water-soluble compounds such as ascorbate, Trolox C, desferal and salicylate.     

Free Radical Formation by Ultrasound in Aqueous Solutions. A Spin Trapping Study

Our recent spin trapping studies of free radical generation by ultrasound in aqueous solutions are reviewed. The very high temperatures and pressures induced by acoustic cavitation in collapsing gas bubbles in aqueous solutions exposed to ultrasound lead to the thermal dissociation of water vapor into H atoms and OH radicals. Their formation has been confirmed by spin trapping. Sonochemical reactions occur in the gas phase (pyrolysis reactions), in the gas-liquid interfacial region, and in the bulk of the solution (radiation-chemistry reactions). The high temperature gradients in the interfacial regions lead to pyrolysis products from non-volatile solutes present at sufficiently high concentrations. The sonochemically generated radicals from carboxylic acids, amino acids, dipeptides. sugars, pyrimidine bases. nucleosides and nucleo-tides were identified by spin trapping with the non-volatile spin trap 3.5-dibromo-2.6-dideuterio-4-nitrosobenzenesulfonate. At low concentrations of the non-volatile solutes. the spin-trapped radicals produced by sonolysis are due to H atom and OH radical reactions. At higher concentrations of these non-volatile solutes, sonolysis leads to the formation of additional radicals due to pyrolysis processes (typically methyl radicals). A preferred localization of non-volatile surfactants (compared to analogous non-surfactant solutes) was demonstrated by the detection of pyrolysis radicals at 500-fold lower concentrations. Pyrolysis radicals were also found in the sonolysis of aqueous solutions containing only certain nitrone spin traps. The more hydrophobic the spin trap, the lower the concentration at which the pyrolysis radicals can be observed. The effect of varying the temperature of collapsing transient cavities in aqueous solutions of different rare gases and of N₂O on radical yields and on cell lysis of mammalian cells was investigated.