Localized, Cold-Induced Inhibition of Translocation in Mycelia and Strands of Serpula lacrimans

Thompson, W., Brownlee, C, Jennings, D. H. and Mortimer, A.M. 1987. Localized, cold-induce inhibition of translocationin mycelia and strands of Serpula lacrimans. —J. exp.Bot. 38: 889–899 The effect has been investigated of localized low temperatureon translocation of ³²P across myceliui of Serpula lacrimansusing two gas-flow detectors capable of recording radioactivitycontinuously. When the temperature of a band of mycelium wasreduced to 0 ? C, radioactivity ceased to accumulai and in factdeclined under the detector (number 2) separated from the sourceof radioactivity by tr cold-treated mycelium. In the myceliumbeneath the other detector (number 1), closest to the sourceradioactivity, the rate of accumulation of radioactivity increased.When the temperature was raised t 20 ?C, radioactivity beganto accumulate in the mycelium under detector 2 and, apart froma sma fluctuation, continued to accumulate at a uniform rate.In the mycelium under detector 1, the accumulation of radioactivitystopped for a short time but then recommenced at a rate similarto thi found at 0 ?C. In other experiments the distributionof radioactivity (¹⁴C) throughout the myceliui was measuredat the end in homogenized samples. In these experiments a bandof mycelium we subjected to 0 ?C or to 20 ?C for the whole experimentalperiod, or only after the mycelium had bee translocating radioactivityalready for 16 h. These experiments showed that the changesin the rate of accumulation of ³²P in living mycelium underthe two gas flow detectors used for in situ measurements werenot due to a reversal of the flow of translocation. The resultsare consistent with an hypothesis that a turgor-driven massflow of solution is the mechanism for translocation in thisfungus and are considered in relation to the results of similarexperiments on phloem translocation in higher plants. Key words: Serpula lacrimans, mycelium, translocation, low-temperature, phloem transport     

Cystolith Development and Structure in Pilea cadierei (Urticaceae)

Cystolith formation, structure and composition have been investigatedin leaves and stem internodes of Pilea cadierei (Urticaceae)using a variety of techniques at the light and electron microscopelevels. The development of lithocysts from epidermal cells hasbeen followed. These cells are cytoplasmically similar to otherepidermal cells but possess a much more active Golgi apparatusand more numerous mitochondria. The cystolith is a spindle-shapedbody composed of concentric layers of longitudinally orientatedcellulose microfibrils associated with pectins and other cellwall polysaccharides. At maturity it is heavily impregnatedwith calcium carbonate. Some cystoliths also contain siliconand are covered in a sheath of siliceous material. Cystolithformation occurs at the tip of a peg that grows in from thelithocyst wall. Evidence from ultrastructure suggests that thelithocytst cytoplasm transports carbohydrates to the cystolithvia Golgi vesicles, and organizes the deposition of cystolithcellulose microfibrils via a system of microtubules lying beneaththe plasma membrane that envelopes the growing cystolith. Thepeg is composed of heavily staining amorphous material likethat of an apoplastically sealed cell wall. It is incapableof supporting the migration of lanthanum ions into the cystolith.We conclude that cystoliths are isolated volumes of apoplastthat act as repositories for inorganic salts, principally calciumcarbonate. We propose that calcium ions move into the lithocystprotoplast from surrounding cells and are then transported acrossthe plasma membrane boundary into the cystolith. This proposalconflicts with previous suggestions that calcium enters by diffusionthrough the peg. Cystolith, lithocyst, cell wall, calcium, silicon, cytochemistry, electron probe analysis, Pilea cadierei     

Neurohormonal control of ecdysone production: Comparison of insects and crustaceans

Summary

Ecdysteroid synthesis is regulated in insects by prothoracicotropic hormone (PTTH) and in crustaceans by molt-inhibiting hormone (MIH). These neurohormones exert opposite effects on their respective target tissues, PTTH stimulating the prothoracic glands and MIH inhibiting the Y-organs. The present work reviews recent progress in the neurohormonal regulation of prothoracic gland and Y-organ function. The steroid products of these glands are briefly discussed, as is current information on the structures of PTTH and MIH. Focus is placed on the mechanism of action of these hormones at the cellular level, as well as developmental changes in cellular sensitivity to PTTH. Though exerting different effects on ecdysteroid secretion, both PTTH and MIH increase cyclic nucleotide second messengers, are influenced by alterations in cellular calcium, and are likely to activate protein kinases. The contrasting steroidogenic effects of PTTH and MIH probably arise from differences in the cellular kinase substrates. In insects, such substrates enhance ecdysteroid secretion, possibly by increasing the translation of glandular proteins. In crustaceans, MIH-stimulated changes lead to the inhibition of both protein synthesis and steroidogenesis.     

Infectibility and sensitivity of UK raspberry, blackberry and hybrid berry cultivars to Rubus viruses

Six blackberry or hybrid berry cultivars and 19 raspberry cultivars were assessed for their infectibility with, and sensitivity to, graft inoculation with 10 distinct viruses found infecting Rubus in the UK. Cultivars were grafted with each of, two isolates of the pollen borne raspberry bushy dwarf virus (RBDV), five aphid borne viruses: black raspberry necrosis, raspberry leaf mottle (RLMV), raspberry leaf spot (RLSV), rubus yellow net and raspberry vein chlorosis (RVCV); and isolates of the nematode transmitted nepoviruses, arabis mosaic, raspberry ringspot, strawberry latent ringspot and tomato black ring. All tested cultivars were infectible with a resistance breaking isolate of RBDV but only about half of that number with the Scottish type isolate of the virus. The raspberry cvs Autumn Bliss, and occasionally Glen Garry and Glen Prosen, developed leaf yellowing symptoms following infection with RBDV, but none of the other infected cultivars showed obvious leaf symptoms when kept in a heated glasshouse during the growing season. All tested cultivars were infectible with each of the four viruses transmitted in nature by the aphid, Amphorophora idaei. Most were infected symptomlessly, but seven cultivars developed severe leaf spotting symptoms due to infection with RLMV or RLSV. All but one of the raspberry cultivars were infectible with RVCV, which is transmitted in nature by the aphid Aphis idaei, and almost all infected plants developed leaf symptoms; only one of the hybrid berry or blackberry cultivars tested was infected with RVCV. In tests with the four nepoviruses, all tested cultivars, except Tummelberry, were infectible with at least one or more of these viruses. However, cultivars responded differently to challenge inoculation with different isolates of individual nepoviruses. Several cultivars developed chlorotic leaf mottling following infection with some nepovirus isolates. The implications of these results for virus control are discussed in the light of the changing pattern of virus and virus vector incidence in the UK.     

Mandibular biomechanics of Crocuta crocuta,Canis lupus,and the late Miocene Dinocrocuta gigantea (Carnivora,Mammalia)

The relative simplicity of the mandible and its functional integration with the upper dentition in carnivorans makes it an ideal subject for functional morphological studies. To compare the mandibular biomechanics of two convergently evolved bone‐cracking ecomorphologies, we used finite element modelling to analyse mandibular corpus stress. The bone‐cracking spotted hyena Crocuta crocuta was used as a living analogue to the late Miocene percrocutid Dinocrocuta gigantea, using the grey wolf Canis lupus as a molar bone‐crushing outgroup. Mandibular stress values during p3, p4, and m1 tooth biting are found to be lowest in Cr. crocuta, and elevated in both Ca. lupus and D. gigantea. However, the stress‐dissipation patterns of the pre‐m1 corpus are similar between Cr. crocuta and D. gigantea. Lastly, D. gigantea has a relatively weaker corpus at the post‐m1 position than either Cr. crocuta or Ca. lupus. These findings suggest that even though stress patterns are similar amongst the bone‐cracking ecomorphs, the extinct D. gigantea had a weaker mandibular structure when performing a comparable bone‐cracking task as in Cr. crocuta because of its slender post‐m1 corpus. Ontogeny could potentially play an important role in strengthening the post‐m1 corpus by growth in the dorsoventral axis, and continuous increase in biting performance through adulthood in living Cr. crocuta suggests the possibility of a relatively more delayed development to full bone‐cracking capability in D. gigantea. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 683–696.     

The Effect of Carbon Dioxide Concentratioin, light Intensity and Isonicotinyl Hydrazide on the Photosynthetic Production of Glycollic Acid by Chlorella

Glycollic acid production by Chlorella was measured by colorimetricdetermination of the acid excreted into the medium. It was foundthat glycollic acid production showed a maximum at a low concentrationof carbon dioxide but tended toward zero as the rate of photosynthesisapproached carbon dioxide saturation. Glycollic acid productionbecame measurable at light intensities approaching that requiredto saturate photosynthesis and increased steadily with furtherincrease in intensity. Treatment with isonicotinyl hydrazideresulted in an approximately threefold stimulation of glycollicacid concentration over the range of conditions used. It issuggested that the precursor of glycollic acid is ribulose diphosphate,and that isonicotinyl hydrazide acts by inhibiting the furthermetabolism of glycollic acid.     

Phylogeny of Paussus L. (Carabidae: Paussinae): unravelling morphological convergence associated with myrmecophilous life histories

Ant nest beetles (Paussus L.) are ecologically fascinating and phenotypically bizarre. Obligate myrmecophiles, Paussus have undergone extreme adaptations for life with ants and their profound range of phenotypic diversity has been difficult to reconcile in a systematic framework. We conducted a detailed morphological study of Paussus utilizing novel techniques and character systems in order to discover anatomical apomorphies diagnostic of the major clades of Paussus strongly supported by molecular data. Bayesian inference (BI) of molecules alone, morphology alone and varying combinations of the two data types reveal that morphology is informative for placing Paussus species, despite the extreme phenotypic diversity and convergence prevalent in the group. We propose a new classification for Paussus based on this phylogeny. The genus Paussus is revised to include all genera, subgenera and species formerly classified as Paussus by Nagel (2003) in addition to Hylopaussus syn.n. , Hylotorus syn.n. and Granulopaussus syn.n. The following species are transferred to Paussus: Paussus sebakuanus (Péringuey) comb.n. , Paussus gracilis (Reichensperger) comb.n. , Paussus bucephalus Gyllenhal, Paussus caroli (Reichensperger) comb.n. , Paussus uelensis (Reichensperger) comb.n. , Paussus hottentottus (Westwood) comb.n. , Paussus blanchardi (Raffray) comb.n. , Paussus basilewskyi (Luna de Carvalho) comb.n. , Paussus granulatus Westwood, Paussus sankuruensis Reichensperger, Paussus leleupi (Reichensperger) comb.n. , Paussus reichenspergeri (Luna de Carvalho) comb.n. We formally delineate and diagnose the following major subgroups of Paussus: Paussus I series, comprising the subgenera Bohemanipaussus Luna de Carvalho stat. rev. sensu n. , Bathypaussus Wasmann stat. rev. sensu n. , and Edaphopaussus Kolbe stat. rev. sensu n. ; the Paussus II series comprising the subgenera Paussus L. stat. rev. sensu n. , Klugipaussus Kolbe stat. rev. sensu n. , Scaphipaussus Fowler stat. rev. sensu n. , Hylotorus Dalman stat.n. sensu n. , and Anapaussus Wasmann stat. rev. sensu n. ; and the Paussus III series comprising the subgenera Lineatopaussus Kolbe stat. rev. sensu n. and Shuckardipaussus Kolbe stat. rev. sensu n.     

Dormancy in Cereal Seeds: I. THE EFFECTS OF OXYGEN AND RESPIRATORY INHIBITORS

A wide spectrum of respiratory inhibitors has been found tostimulate the breaking of dormancy in barley. These includecarbon monoxide, cyanide, azide, hydrogen sulphide, sodium sulphide,hydroxylamine, diethyldithiocarbamate (DIECA), fluoride, iodoacetate,malonate, monofluoroacetate, and 2,4-dinitrophenol (DNP). Inrice, only the first six of these have been shown to be effective.Apart from CO, all the above inhibitors were tested on winteroats, but in this material only cyanide, azide, and hydroxylaminewere found to increase the germination of dormant seeds. Allthe terminal-oxidase inhibitors except CO were tested on perennialryegrass, but in this case only cyanide was found to break dormancy. As compared with air, an atmosphere of 96 per cent oxygen appliedto barley during the first 24 h after the seeds have been setto germinate stimulates the breaking of dormancy. When appliedat later stages, this high oxygen tension inhibits the germinationof dormant seeds although it has no effect on nondormant seeds.Paradoxically, the stimulatory effects of respiratory inhibitorsapplied during the initial stages of germination are relatedto their ability to inhibit oxygen uptake. Thus cyanide, azide,malonate, and monofluoroacetate, while stimulating the breakingof dormancy in barley, also inhibit oxygen uptake. In rice,cyanide and azide had similar effects, but fluoride, which hadno effect on dormancy, also had no effect on the oxygen uptakeof dormant seeds. These results are compatible with the hypothesis that some oxidationreaction is necessary for germination. This oxidation is notpart of the normal respiratory pathway, and does not proceedsatisfactorily in dormant seeds. It may be stimulated, however,by increasing the oxygen tension or by reducing normal respiratorycompetition with respiratory inhibitors.