Chemical treatments for control of decay in pruning wounds

Wound treatments were evaluated, in the laboratory and the field, for their effect on beech and poplar tissue (phytotoxicity) and on the growth and colonisation pattern of micro-organisms. Three types of treatment were examined: a physical barrier or sealant, a sealant plus fungicide and a fungicide alone. Greatest phytotoxicity was shown by materials normally employed as timber preservatives and the least by sealants. Generally colonisation by fungi and bacteria was little delayed by most treatments with the exceptions of Santar (sealant plus mercuric oxide) and Australian Arborseal (sealant plus captafol). However, colonisation by basidiomycetes was generally delayed by treatment, but its overall intensity was reduced only by Santar and Lac Balsam (sealant). Some treatments had a selective effect on the species of micro-organisms colonising a wound - thus wounds treated with carbendazim derivatives were most likely to be colonised by basidiomycetes and Alternaria spp. Treatment with Santar discouraged most micro-organisms with the exception of Phoma spp. No sealant provided a visually intact cover for longer than 12 months: even wounds with apparently intact cover occasionally had fruit bodies of decay fungi present on them. The chemicals triadimenol, triadimefon, carbendazim and thiophanate methyl were still present in fungicidal amounts in wounds up to at least 157 days. Both Santar and triadimenol prevented the growth of Trametes versicolor from inoculum plugs in wounds of apple trees.     

An Examination of Scale-Dependent Resource Use by Eastern Hognose Snakes in Southcentral New Hampshire

ABSTRACT The decline of many snake populations is attributable to habitat loss, and knowledge of habitat use is critical to their conservation. Resource characteristics (e.g., relative availability of different habitat types, soils, and slopes) within a landscape are scale-dependent and may not be equal across multiple spatial scales. Thus, it is important to identify the relevant spatial scales at which resource selection occurs. We conducted a radiotelemetry study of eastern hognose snake (Heterodon platirhinos) home range size and resource use at different hierarchical spatial scales. We present the results for 8 snakes radiotracked during a 2-year study at New Boston Air Force Station (NBAFS) in southern New Hampshire, USA, where the species is listed by the state as endangered. Mean home range size (minimum convex polygon) at NBAFS (51.7 ± 14.7 ha) was similar to that reported in other parts of the species’ range. Radiotracked snakes exhibited different patterns of resource use at different spatial scales. At the landscape scale (selection of locations within the landscape), snakes overutilized old-field and forest edge habitats and underutilized forested habitats and wetlands relative to availability. At this scale, snakes also overutilized areas containing sandy loam soils and areas with lower slope (mean slope = 5.2% at snake locations vs. 6.7% at random locations). We failed to detect some of these patterns of resource use at the home range scale (i.e., within the home range). Our ability to detect resource selection by the snakes only at the landscape scale is likely the result of greater heterogeneity in macrohabitat features at the broader landscape scale. From a management perspective, future studies of habitat selection for rare species should include measurement of available habitat at spatial scales larger than the home range. We suggest that the maintenance of open early successional habitats as a component of forested landscapes will be critical for the persistence of eastern hognose snake populations in the northeastern United States.     

Alavesia Waters and Arillo–a Cretaceous‐era genus discovered extant on the Brandberg Massif,Namibia (Diptera: Atelestidae)

Two new extant species of the fossil genus Alavesia Waters & Arillo (A. brandbergensis sp.n. and A. daura sp.n. ) are described from the Brandberg Massif, Namibia. The genus is reassigned to the family Atelestidae (subfamily Atelestinae) on the basis of male terminalia (elongate gonocoxal apodemes, ventral apodemes, subapical surstylus), female terminalia (absence of tergum 10) and a three‐articled stylus. This is the first record of Atelestidae from the Afrotropical Region. A genus‐level phylogeny of the Atelestidae is resolved, in which Alavesia is the sister genus to the remaining genera of the Atelestinae. The biogeographic history of the genus is briefly discussed, as is the significance of this and other relict Diptera on the Brandberg.     

The Effect of Temperature on the Initiation of Leaf Primordia in Developing Potato Sprouts

Kirk, W W., Davies, H. V. and Marshall, B. 1985. The effectof temperature on the initiation of leaf primordia in developingpotato sprouts.—J. exp. Bot. 36: 1634–1643. Initiation of leaf primordia in potato sprouted out of soilin light was an asymptotic function of thermal time and thebase temperature for the process was 3.6 °C. The parametervalues of the asymptotic function were universal for cv. MarisPiper. The estimated rate of leaf primordium initiation decreasedlinearly from 0.033 leaf pnmordia (K day)^–1 when abouteight leaf primordia were present to zero after a maximum numberof 24 leaf primordia had been initiated. The decrease in rateof development with increasing number of primordia may be dueto depletion of mother tuber resources. The transition of theapex from a vegetative to a reproductive state was not the factorlimiting the initiation of additional leaf primordia. Key words: Potato, Solanum tuberosum L., leaf primordia initiation, temperature, thermal time, development     

Floodwater Oxygen Content, Ethylene Production and Lenticel Hypertrophy in Flooded Mango (Mangifera indica L.) Trees

A system was developed to test the effects of floodwater O₂concentration on ethylene evolution and stem lenticel hypertrophy,and the effects of exogenous ethylene on stem lenticel hypertrophyin mango (Mangifera indica L.) trees. Dissolved O₂ concentrationsof 1–7x10^–9 m³ m^–3 generally resulted in hypertrophyof stem lenticels within about 6 d of flooding, whereas floodwaterO₂ concentrations of 13–15 x 10^–9 m³ m^–3 delayedhypertrophy until about day 9. After 14d of flooding, therewere more than twice the number of hypertrophied lenticels pertree with floodwater O₂ concentrations of 1–7 x 10^–9m³ m^–3 than with floodwater O₂ concentrations of 15 x10^–9 m³ m^–3. Ethylene evolution from stem tissueimmediately above the floodline increased 4- to 8-fold in treesexposed to floodwater O₂ concentrations of 1–2 x 10^–9m³ m^–3, increased 2-fold for trees exposed to floodwaterO₂ concentrations of 6–7 x 10^–9 m³ m^–3, butremained constant with floodwater O₂ concentrations of 13–15x 10^–9 m³ m^–3. Plants maintained in highly oxygenatedfloodwater (13–15 x 10^–9 m³ m^–3), and givenexogenous ethylene developed many hypertrophied lenticels, whereasplants in highly oxygenated water and not given ethylene developedfewer or nohypertrophied lenticels. These data suggest thatethylene plays a role in promotion of stem lenticel hypertrophyin flooded mango trees, and that floodwater dissolved oxygenconcentration can regulate stem lenticel hypertrophy and ethyleneevolution in this species. Key words: Flooding, hypoxia, hypertrophic cell swelling     

INTERACTION OF ASTRINGENCY AND TASTE CHARACTERISTICS1

The perception of astringency and basic taste in mixtures and their interaction effects were investigated by two procedures. In Experiment 1, focused and nonfocused testing procedures were compared using mixtures of low and high concentrations of alum and basic taste solutions. Both procedures yielded taste and astringency intensities that were modality‐dependent. Nonfocused testing was used in Experiment 2 to investigate the interactions of astringent phenolic (tannic acid) and nonphenolic (alum) compounds with each basic taste. Sweetness of sucrose increased with increased concentration with or without alum or tannin present. Changes in salty, bitter, and sour taste intensities were modality‐dependent. Astringency either remained unchanged or decreased with the addition of sucrose, sodium chloride, citric acid, or caffeine depending upon the taste concentration. Bitterness of tannin and alum at high concentrations was suppressed by the addition of sucrose, sodium chloride, or citric acid; sourness also decreased in the presence of sucrose or sodium chloride as well as a high level of caffeine.     

The oxygen consumption of the microspores of Trillium in relation to the mitotic cycle

The oxygen consumption of 265 single Trillium erectum anthers was measured before and during the mitotic cycle of the microspores using a modified differential microrespirometer. The results show a rising oxygen consumption of the anther in the premitotic stages followed by a sharp drop immediately preceding and during active division. It is suggested from these results that active division may be associated with anaerobic behavior and that the rapid uptake of molecular oxygen commonly associated with proliferating tissues is probably characteristic of premitotic development.     

Reproduction of Lumbricillus rivalis (Levinsen) in laboratory cultures and in decaying seaweed

The cocoon production of 144 Lumbricillus rivalis cultured in pairs at 10 ± 1 °C was high over the first 2 weeks of breeding activity and then declined, chiefly because of high mortality. Cocoon deposition lasted for between 1 and 16 weeks, eight pairs of worms producing cocoons for 9 weeks and one pair for 16 weeks. During the total period of cocoon deposition over 9000 eggs (mean 17·4 per cocoon) were deposited. Two decaying wrack bed populations of L. rivalis showed a low level of cocoon and egg production in autumn, rising to an annual maximum in late winter/early spring. In these populations the mean egg content varied seasonally from 17·1 to 47·8 eggs per cocoon. When cocoons in the laboratory were transferred from the site of deposition to incubation dishes 31% hatched, but those left in the substrate showed a 92% hatch. In the naturally occurring populations 19% of the cocoons detached from seaweed fronds hatched, but 62% of those left in situ. Eggs and worm embryos developed to relatively late stages in most cocoons, whatever the rate of hatching; development often continued for up to 2 months after deposition without hatching. Over 50% of the fertile eggs in cocoons from decaying wrack hatched and developed to 5 mm worms.