Variances of tracheid lengths in tropical pines from central Africa     

Jeffery Burley  Philip G. Adlard  Penelope Waters 《Wood Science and Technology》1970,4(1):36-44

Summary Individual tracheid lengths were measured in macerated tissue samples of Pinus merkussii Jungh. and de Vries, P. kesiya Royle ex Gordon (syn. P. khasya Royle) and P. patula Schiede and Deppe. The sample trees were selected from stands of different ages, treatments and sites in central Africa.A sampling unit of 50 tracheids, measured for convenience on two microscope slides, was chosen on the basis of an earlier study. The variation in individual tracheid length and the variation of within-slide variance was studied by means of analysis of variance and variance components. This indicated the nunber of samples required in the different sampling categories to give maximum sampling efficiency. Sampling categories included both random factors (individual tracheids, number of slides, radii in discs) and fixed factors (annual rings, tree classes, thinning treatments, etc.).While large effects were attributable to fixed factors more than half the total variation was explained by random factors. The effect of the number of slides was rarely important and two slides need be used only to facilitate the location of the required number of tracheids and to provide a check on operator consistency. The sample unit of 50 tracheids can detect differences in tracheid length of 0.20 ... 0.34 mm thus confirming the routine used in this laboratory as a practical and meaningful procedure.Laboratory work was carried out in Kitwe, computing at Oxford. Paper published with permission of Professor of Forest Science, Oxford and Director, Agricultural Research Council of Zambia.  相似文献   

Anatomy of the primary-secondary transition zone in stems of Populus deltoides     

Philip R. Larson  J. G. Isebrands 《Wood Science and Technology》1974,8(1):11-26

Summary The transition from primary to secondary stem tissues occurs as a continuum, and a precise anatomical definition of the transition does not exist. A definition was derived for Populus deltoides based on the birefringent properties of the fiber wall. This definition was quantitatively reproducible in the 9 plants tested, and the secondary transition was found to occur in the internode associated with the first mature leaf from the apex. The primary-secondary transition did not occur uniformly around the periphery. It was first observed in the vascular bundles opposite the incoming trace, and from there it progressed in a counter-clockwise direction. Within the transition internode, each vascular bundle and each tissue comprising the bundle differentiated in accord with the physiological age and the phyllotactic disposition of the developing leaf to which it led. Within any one vascular bundle, differentiation occurred first in the metaxylem vessels and associated fibers, followed closely by extension of fibers into the interfascicular regions and centripetal differentiation of the phloem fibers. The ontogenetic sequence of differentiation for each of the principal tissues of the secondary transition zone is described.The technical assistance of Mr. Gary Buchschacher with the ultramicrotomy and photomicrography is gratefully acknowledged.  相似文献   

Planted conifer seedling growth under two soil thermal regimes in high-elevation forest openings in interior British Columbia     

Balisky  Allen C.  Burton  Philip 《New Forests》1997,14(1):63-82

A field trial was conducted investigating the single season growth response of 1+0 313 PSB Engelmann spruce (Picea engelmannii Parry ex Engelm.) and lodgepole pine (Pinus contorta Dougl. ex Loud.) seedlings planted into two different soil thermal regimes at three high-elevation locations spanning 200 km in the Engelmann Spruce-Subalpine Fir (ESSF) biogeoclimatic zone in the Cariboo Mountains of central British Columbia. Temperature treatments represented the extremes of soil temperature commonly found in high-elevation clear-cuts. A warm soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 18 to 25 °C at –10 cm) consisting of a bare mineral soil hummock (average dimensions of 100 cm × 100 cm × 40 cm) was contrasted with a cool soil treatment (clear day, mid-afternoon soil temperature in mid-summer of 10 to 13 °C at –10 cm) comprised of organic forest floor overlying mineral soil. By the end of the growing season, seedlings of both species planted into the warm treatment generally exhibited greater root, stem, foliage, and total seedling biomass than cool treatment seedlings. Measurements of root growth at 30, 60, and 90 days after planting showed that total root number and total root length were consistently greater for warm treatment seedlings than for cool treatment seedlings. Root growth was greater from the bottom rather than from the side of the root plug for all seedlings. These results suggest that the effect of low soil temperatures on outplanted styroblock conifer seedlings is pronounced and may be limiting growth performance in high-elevation plantations in British Columbia. We recommend silvicultural treatments that secure natural regeneration, ensure that warmer microsites are always planted, and utilize seedling stocktypes able to make rapid lateral root growth into warmer surface organic horizons.  相似文献   

A Preliminary Study of Silver Sodium Zirconium Phosphate Polyurethane Foam Wound Dressing on Wounds of the Distal Aspect of the Forelimb in Horses          下载免费PDF全文

Maureen E. Kelleher DVM  Diplomate ACVS  Isabelle Kilcoyne MVB  Julie E. Dechant DVM  MS  Diplomate ACVS & ACVECC  Emma Hummer BS  Philip H. Kass DVM  PhD  Diplomate ACVPM  Jack R. Snyder DVM  PhD  Diplomate ACVS 《Veterinary surgery : VS》2015,44(3):359-365

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The Impact of Egg Ozonation on Hatching Success,Larval Growth,and Survival of Atlantic Cod,Atlantic Salmon,and Rainbow Trout     

Jessica Fry  Juan Pérez Casanova  Lynn Lush  Andy Walsh  Cyr Couturier 《Journal of aquatic animal health》2015,27(1):57-64

The direct exposure of fish eggs to ozonated water has generated interest as a means of ensuring pathogen-free eggs without the use of harsh chemicals. However, there are numerous knowledge gaps, including safe contact times, exposure levels, and potential long-term effects on aquaculture species in both freshwater and seawater. The effect of different ozone (O₃) doses (0.5–1.0, 1.5–2.0, and 2.5–3.0 mg of O₃/L for 90 s) on recently fertilized eggs of Atlantic Cod Gadus morhua and eyed eggs of Atlantic Salmon Salmo salar and Rainbow Trout Oncorhynchus mykiss was evaluated in comparison with the effects of two commercial disinfectants: Perosan (0.004 mg/L) and Ovadine (100 mg/L). The impact of ozone application was evaluated based on hatching success, larval nucleic acid concentration, larval growth, and survival. Overall, results indicated that ozonation of Atlantic Cod eggs at a dose less than 3.0 mg/L for 90 s produced no negative effect on the larvae up to 30 d posthatch. Furthermore, ozonation of Atlantic Salmon and Rainbow Trout eggs generated no negative effect on the larvae, based on monitoring until 85% yolk sac re-absorption (16 d posthatch).

Received May 6, 2014; accepted October 24, 2014  相似文献   

Use of pyrethroid analogues to identify key structural features for enhanced esterase resistance in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)     

Gunning RV  Moores GD  Jewess P  Boyes AL  Devonshire AL  Khambay BP 《Pest management science》2007,63(6):569-575

It has been reported previously that the major resistance mechanism to pyrethroid insecticides by the cotton bollworm Helicoverpa armigera (Hübner) in Australia is a consequence of overproduction of esterase isoenzymes. This paper reports structure-activity relationships that support such a view, based on in vivo bioassays conducted with a range of pyrethroid structures containing a variety of acid and alcohol moieties and the correlation with in vitro esterase inhibition assays against the same structures, and identifies the critical regions of the molecule with regard to esterase inhibition, and hence resistance. The implications of this work in terms of possible resistance management are evaluated and discussed.  相似文献   

Vascular-Streak Dieback: A New Encounter Disease of Cacao in Papua New Guinea and Southeast Asia Caused by the Obligate Basidiomycete Oncobasidium theobromae     

Guest D  Keane P 《Phytopathology》2007,97(12):1654-1657

ABSTRACT The basidiomycete Oncobasidium theobromae was identified as the cause of a devastating disease of cacao named vascular-streak dieback (VSD) in Papua New Guinea in the 1960s. VSD now causes losses among cacao seedlings and kills branches in mature cacao trees throughout Southeast Asia and parts of Melanesia. The characteristic symptoms include a green-spotted chlorosis and fall of leaves beginning on the second or third flush behind the stem apex, raised lenticels, and darkening of vascular traces at the leaf scars and infected xylem. Eventually complete defoliation occurs and, if the fungus spreads to the trunk, the tree will die. O. theobromae is a highly specialized, near-obligate parasite of cocoa. It is a windborne, leaf-penetrating, vascular pathogen, and may have evolved as an endophyte on an as yet unidentified indigenous host. The rate of disease spread on cocoa is limited because basidiocarps develop only on fresh leaf scars during wet weather, and basidiospores remain viable for a few hours on the night they are shed. Consequently, very few new infections occur beyond 80-m from diseased trees. Transmission of the disease through seed or infected cuttings has not been demonstrated. Strict quarantine measures applied to the movement of intact plants are crucial in reducing spread of the disease. Integrated management, including the planting of less susceptible genotypes, nursery construction and management, canopy pruning and shade management, provides effective control.  相似文献   

Timing and order of different insecticide classes drive control of Drosophila suzukii; a modeling approach     

Mermer  Serhan  Pfab  Ferdinand  Tait  Gabriella  Isaacs  Rufus  Fanning  Philip D.  Van Timmeren  Steven  Loeb  Gregory M.  Hesler  Stephen P.  Sial  Ashfaq A.  Hunter  Jamal H.  Bal  Harit Kaur  Drummond  Francis  Ballman  Elissa  Collins  Judith  Xue  Lan  Jiang  Duo  Walton  Vaughn M. 《Journal of pest science》2021,94(3):743-755

The spotted-wing drosophila, Drosophila suzukii Matsumura, is an invasive pest causing significant damage to soft skinned fruits. Control of D. suzukii is critical since there is no tolerance for infested fruit in the market. While most insecticides control one or more D. suzukii life-stages (e.g., egg, larvae, and adult), the impact of insecticides that are toxic to immature stages  is unclear on the subsequent generation of a field population. Insecticides were applied at field recommended rates on cherries and blueberries in the laboratory to determine immature D. suzukii mortality. Spinetoram, cyantraniliprole, malathion, methomyl, spinosad, and phosmet resulted in relatively high mortality of all immature life stages. Zeta-cypermethrin, cyclaniliprole, and fenpropathrin resulted in lower mortality of egg and all larval instars. Malathion was also applied to lowbush blueberries with different fruit sizes (small, medium, and large) in the laboratory and there was no statistical difference in mortality rates depending on fruit sizes. Mortality data from the laboratory experiments were used to parameterize a refined D. suzukii population model. The model revealed that the timing and order of different insecticide classes are important to control D. suzukii population. Model runs that included early applications of more effective insecticides resulted in high immature mortality and greater reduction of D. suzukii populations compared to treatments applied later.

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Mechanisms and management of acaricide resistance for Tetranychus urticae in agroecosystems     

Adesanya  Adekunle W.  Lavine  Mark D.  Moural  Timothy W.  Lavine  Laura C.  Zhu  Fang  Walsh  Douglas B. 《Journal of pest science》2021,94(3):639-663

Journal of Pest Science - The two-spotted spider mite, Tetranychus urticae Koch, is a constant threat to sustainable production of numerous economically important crops globally. Management of T....  相似文献   

Blue light from individual light masks directed at a single eye advances the breeding season in mares     

B. A. Murphy  C. M. Walsh  E. M. Woodward  R. L. Prendergast  J. P. Ryle  L. H. Fallon  M. H. T. Troedsson 《Equine veterinary journal》2014,46(5):601-605

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