Light Intensity and Substrate Availability in Relation to Tracheid Development in Picea sitchensis

Assimilation and growth of Picea sitchensis seedlings maintainedat three light intensities were examined in relation to previously-reporteddata on tracheid development in this species. Increases in photosynthetic efficiency with decreased lightlevel failed to compensate completely for reduced total amountsof incident radiation as judged from assimilate distributionpattern and growth rate. Incorporation of assimilate into reservesand new growth declined with decreased light level, while theextent of turnover materials generally increased. Most treatment differences in relative dry weight distributionappeared to result from a combination of differences in growthrate and changes in growth pattern. The proportion of dry weightin branches and roots increased with increased light intensitywhile that in stems and the hypocotyl decreased At the two highest light levels tested, both absolute stem growthrate and total wall accumulation appeared to be independentof substrate availability. This situation contrasts with thatobserved in older material and it is suggested that the initialindependence reflects the temporary existence of a high ratioof functional foliage to stem and cambial material during thefirst year of growth. Since tracheid diameter showed a consistent, positive relationshipwith assimilate status, it is suggested that substrate levelcan exert an important modifying influence on cell expansion.     

Daylength Effects on Growth, Tracheid Development, and Photosynthesis in Seedlings of Picea sitchensis and Pinus sylvestris

Effects of change in daylength on tracheid expansion and tracheidwall thickening are considered in relation to shoot and rootgrowth, assimilation rate, and starch content, in seedlingsof Picea sitchensis and Pinus sylvestris grown in controlledenviroments. Rates of wall thickening decreased in the first tracheids tobegin wall thickening after decrease in daylength. A sharp decreasein starch-grain size at the same time supports previous suggestionsthat wall thickness is related to available substrate; however,rates of assimilation were found to be far greater in shortdays than in long, suggesting that a surplus of carbohydratemay be produced in long days. It is pointed out that if availablesubstrate does limit wall thickening it is likely to determineto al accumulation of wall material; wall material per tracheidwould follow logistically from this depending on the numberof tracheids around the xylem, and wall thickness would dependalso on the radial tracheid diameter. Unexpectedly, rate of shoot growth accelerated after transferto short days before its final cessation with terminal-bud formation.Root growth declined in short days, but later increased againafter terminal bud formation. Rate of root growth did not appearto be associated with tracheid development in the shoot.     

Somatic embryogenesis in Sitka spruce (Picea sitchensis (Bong.) Carr.)

Embryonal-suspensor masses from immature embryos from cones of Sitka spruce (Picea sitchensis (Bong.) Carr.) proliferated on a modified Murashige & Skoog medium with N⁶-benzyl-aminopurine, kinetin, 2,4-dichlorophenoxyacetic acid and an organic nitrogen source. The slimy white embryonal-suspensor masses with proembryos were maintained on a solid proliferation medium with reduced amounts of growth regulators. Transfer of embryonal-suspensor masses to a non-woven polyester carrier with liquid maturation media containing ±2-cis-4-trans-abscisic acid and a reduced amount of inositol and organic nitrogen resulted in synchronized embryo formation. Further development was achieved on a medium without ±2-cis-4-trans-abscisic acid and organic nitrogen. Somatic embryos were successfully transferred ex vitrum.Abbreviations ABA ±2-cis-4-trans-abscisic acid - BAP N⁶-benzyl-aminopurine - ESM embryonal-suspensor masses - KIN kinetin - 2,4-D 2,4-dichlorophenoxyacetic acid     

Diurnal water storage in the stems of Picea sitchensis (Bong.) Carr.

Abstract. Two models of the relationship between diurnal variation in shoot water potential and transpiration in 14-year-old Picea sitchensis (Bong.) Carr. were compared. The first model was a physiologically based resistance-capacitance (R-C) analogue with its associated differential equations. The second was a non-physiological discrete-difference (D-D) or stochastic transfer function model. The RC model included only the effect of water storage in the phloem and bark while the D-D model implicity included all storage mechanisms. The R-C and D-D models explained similar fractions (62% and 68% respectively) of the variation in shoot water potential due to diurnal changes in transpiration rate. However, the D-D model had fewer parameters than the R-C model. The results from the D-D model showed that the resistance to flow from soil to shoots along the trunk, (RT), was 5 × 10³ MPa kg^-1s and the capacitance of the phloem and bark treated as a single store, (C_s), was 1.6 kg MPa^-1. It is suggested that the resistance to flow into storage (R_s) is much greater than R_T and can be disregarded. A non-linear version of the D-D model suggested [hat resistance to flow in the trunk increases with increasing transpiration rate.     

Effects of Light Intensity on Tracheid Dimensions in Picea sitchensis

In seedlings of Picea sitchensis grown in constant conditions,or within older trees in the field, light intensity had no neteffect on the wall thickness of tracheids produced at the samepoint in time. This appears to be due to a balanced regulatorysystem, effects of light intensity on rate of accumulation ofwall volume per leaf being offset by differences in rate ofxylem increment, and differences in wall material per tracheidbeing nullified in their effects on wall thickness by effectson tracheid diameter. Mean tracheid wall thickness across the growth ring increasedwith light intensity, due to increase in proportion of late-woodassociated with the longer duration of cambial activity at higherlight intensity, duration of wall thickening increasing duringthe season. Duration of wall thickening did not vary with lightintensity. The rate of increase in wall volume was limited by light intensity(and hence possibly by substrate availability) at all lightintensities in the field, but in seedlings in controlled conditionsthe rate of wall production was no greater at 20 000 lx thanat 6700 lx.     

Localised impact of Sitka spruce (Picea sitchensis (Bong.) Carr.) on soil permeability

A typical upland soil catena afforested with Sitka spruce (Picea sitchensis (Bong.) Carr.) was chosen to examine the localised effect of trees on soil permeability. A borehole permeameter was used to measure soil permeability at 0.2 m and approximately 2 m distance from the stem of 20 trees at a fixed measurement depth of 0.25 to 0.45 m. In the case of the near-tree measurements, this corresponded to soil beneath the main root plate of each conifer. Two principal elements of the soil catena: the ferric podzol of the mid-slope and histosol soil of the foot-slope were investigated.The preliminary data set shows that within the ferric podzol element, the permeability of the soil beneath individual conifers was a factor of 5.4 less than that of the adjacent soil. In contrast, within the histosol sub-tree permeabilities could not be distinguished from those of soil 2 m away from each tree. The decrease in sub-tree permeability within the podzol may be caused by sensitivity of the Bsl horizon to consolidation by tree weight or by enhanced illuviation resulting from changes in local soil chemistry. The histosol may be less sensitive to such processes. The results of a consolidation test applied to the Rawls and Brakensiek model of soil permeability supported the possible role of consolidation in the reduction of soil permeability beneath conifers in podzolic soil. Additional data on soil bulk density, porosity and texture are required to corroborate either the consolidation or illuviation hypotheses. As the Bsl horizon of ferric podzol soil is typically slowly permeable, a further decline may (i) restrict root development and thus, increase windthrow hazard, and (ii) increase the lateral flow of water within podzolic Eag horizons and thus affect stream acidification. Deep ploughing of a site prior to afforestation may mitigate such impacts.     

Intraspecific variation of DNA per cell between Picea sitchensis (Bong.) Carr. provenances

Quantitative intraspecific variation of DNA per cell was established by means of biochemical, double wavelength microspectrophotometry and micro-densitometric analyses of root tips from 7 seed sources of Picea sitchensis (Bong.) Carr. Northern seed sources possessed more DNA per cell than southern provenances. This, perhaps, is an indication of DNA adaptability through plasticity resulting from changing environmental stress over the natural range.     

The effect of applied heat on graft union formation in dormant Picea sitchensis (Bong.) Carr

The effect of application of heat on the development of graftunions in dormant Picea sitchensis (Bong.) Carr (Sitka spruce)was observed at monthly intervals from October to March. Noadvantage over controls was gained in terms of final graft successrates. It is suggested that this may have been a result of themild winter conditions during the course of the experiment,which enabled callus formation to occur in unheated controls.On the other hand, scions of grafts which had been heated for3 weeks, and then returned to ambient conditions showed considerablygreater growth than unheated controls during the following springand summer. The amount of extension depended on how late inthe winter the graft had been prepared and heated, with leastgrowth by grafts made in October, and most by grafts made inMarch. Microscopical examination showed that callus formationwas more rapid in heated grafts than in controls, although callusformation occurred in all control grafts examined. Heat alsoinduced cambial reactivation and tracheid formation, particularlyin the vicinity of needle or bud traces in the scion. In keepingwith this, it was found that the presence of needles and budswas essential for cambial reactivation in normal dormant stemsand that reactivation was restricted to the heated region. Key words: Grafting, Sitka spruce, callus, dormancy, differentiation     

The Induction of Root Dormancy in Picea sitchensis (Bong.) Carr. by Abscisic Acid

Abscisic acid at 10⁴ M inhibited elongation and induced dormancyin roots of Sitka spruce cuttings growing in solution culture.The dormancy was characterized by superficial browning whichprogressed towards the root tip and by the development of alayer of lignified and suberized cells around the root apex.The dormant roots remained alive and resumed growth on transferto ABA-free solutions. The induction of dormancy was confinedto those roots actually bathed in the ABA solution and a rangeof conditions which affected shoot activity did not alter theresponse. By contrast, the time for which the roots had beenelongating strongly influenced root dormancy since it was notinduced in roots which had recently begun to elongate in solutionculture. The possible role of ABA in inducing root dormancyunder adverse conditions is discussed.     

Development of a set of highly polymorphic genomic microsatellites (gSSRs) in Sitka spruce (Picea sitchensis (Bong.) Carr.)

Robust, polymorphic microsatellite DNA markers (simple sequence repeats—SSRs) are valuable tools for a range of tree conservation and breeding applications. SSRs are routinely used in the study of population genetic structure and diversity, pedigree reconstruction and genetic linkage mapping. Their abundance in the genome, co-dominant inheritance and potential for cross-species amplification make microsatellites highly prized markers. This paper characterises 22 novel genomic polymorphic microsatellite loci for Sitka spruce (Picea sitchensis (Bong.) Carr.). Amplification of DNA from Sitka spruce material was carried out both with a set of unrelated trees to obtain diversity statistics for each locus, and with the progeny of a full-sib family to test simple Mendelian inheritance. Observed heterozygosity ranged from 0.38 to 0.91 and allele number per locus ranged from 6 to 21, with a mean of 12.2. In addition, the primer pairs were tested with DNA from Norway spruce (P. abies) and white spruce (P. glauca) to investigate their potential for cross-species amplification and ten loci amplified in all three species. The results from these genomic microsatellites are compared to data generated from microsatellites derived from Picea EST libraries. In summary, this novel, highly polymorphic markers represent a significant addition to the rapidly expanding Picea genomics tool-box. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effects of Growth Hormone Application on the Secondary Growth of Roots and Stems in Picea sitchensis (Bong.) Carr

Indol-3-ylacetic acid (IAA), gibberellin A3 (GA) and 6 benzylaminopurine(BAP) were applied factorially each at 3x10^–2 M in lanolinto the roots and stems of Sitka spruce seedlings and the activityof the two secondary meristems, the vascular cambium and phellogen,and of the parenchymatous tissues between them, was examined.All the treatments, with the exception of GA produced a localizedstimulation of radial growth at the point of application andthere was a similarity in the response of the various tissuesin both the root and stem. Radial growth of the xylem was notsignificantly affected in the roots whereas in the stems BAPand IAA stimulated growth. In the phloem BAP produced significantstimulation in both roots and stems and IAA stimulated growthin the roots. Growth of the parenchyma and periderm externalto the phloem was also strongly stimulated by both BAP, andIAA in roots and stems. In roots and stems the application of BAP altered the derivativesproduced by the vascular cambium, resulting in the productionof large multiseriate rays in the xylem, and giving rise toan overall increase in the proportion of ray tissue. Picea sitchensis (Bong.) Carr, Sitka spruce, secondary growth, xylem, phloem, periderm, wood rays, Indol-3-ylacetic acid, gibberellin A3, 6 benzylaminopurine, growth hormones     

Effect of carbenicillin and cefotaxime on somatic embryogenesis of Sitka spruce (Picea sitchensis (Bong.) Carr.)

Carbenicillin prevented the development of mature somatic embryos,reduced early stage embryos by >90% and tissue growth by50%. Cefotaxime had no effect on overall tissue growth, butreduced the development of early and mature embryos by 20% and66–80%, respectively. Carbenicillin should not be usedfor transformation of Sitka spruce. Key words: Sitka spruce, somatic embryogenesis, antibiotic sensitivity     

Ectomycorrhizal colonisation of Sitka spruce [Picea sitchensis (Bong.) Carr] seedlings in a Scottish plantation forest

 The ectomycorrhizal (ECM) colonisation of seedling Sitka spruce (Picea sitchensis) was examined in an uneven-aged plantation forest in southern Scotland. The extent of ECM colonisation of individual seedlings was 43.8–97.2%, with an overall mean of 80.3 ± 1.1%. A total of 13 ECM morphotypes were differentiated, with 1–4 ECM types colonising an individual seedling. ECM colonisation was dominated by a single species, Tylospora fibrillosa, which accounted for 72.4–97.7% of the ECM colonisation recorded, on a plot mean basis. Other ECM types appeared to be distributed very patchily, only two types (Lactarius sp. and Mycelium radicis atrovirens Melin) exceeding a mean of 10% colonisation in any one plot. No significant correlations were recorded between ECM colonisation and seedling growth, or between ECM colonisation and soil pH, loss-on-ignition, or water content. Accepted: 16 October 1997     

The Effect of Explant Type on the Establishment of Sitka Spruce [Picea sitchensis (Bong.) Carr.] in Culture

Five different types of shoot tip explant from three-year-oldand 13-year-old Sitka spruce trees were established on a rangeof media and shoot growth was recorded. While Schenk and Hildebrandtmedium gave the greatest shoot elongation, Webb and Street mediumproduced the healthiest-looking shoots. Poorest growth was recordedfor the explants cultured without the crown or any vasculartissues from the previous year's growth. [¹⁴C]sucrose tracerstudies indicated that poor uptake was not responsible for thereduced growth and it was suggested that damage due to inadequatewater uptake may be responsible. Results demonstrated that peelingthe protective scales from resting buds and trimming the shoottissues below the crown to a wedge shape and excluding the barkwas a reliable method of explant preparation for establishingmature and juvenile Sitka spruce in culture. Picea sitchensis, Sitka spruce, mature, juvenile, crown, [¹⁴C]sucrose, micropropagation     

Abrasive damage by wind to the needle surfaces of Picea sitchensis (Bong.) Carr. and Pinus sylvestris L.

Abstract. After a period of one week at 11m s⁻¹ in a wind tunnel, the leaf surface of Picea sitchensis and Pinus sylvestris had undergone structural modification. Low-temperature scanning electron microscopy was used to examine these changes. Picea showed flattening and smearing of wax crystals, as well as cracks in some of the wax structures filling the stomatal antechambers. In Pinus , most damage was on the cells surrounding the stomatal antechamber or on needle ridges. Artificially abraded surfaces were of similar appearance. Minimum epidermal conductance to water vapour ( g _e^MIN) was determined gravimetrically. In Picea g _c^MIN was more than doubled by wind treatment and increased eightfold by rubbing. Similar but less extreme increases occurred in Pinus. Neither species showed recovery of g _e^MIN after 1 week at low windspeed.     

Studies of Growth and Flowering in Picea sitchensis (Bong.) Carr. 1. Effects of Growth Regulator Applications to Mature Scions on Seedling Rootstocks

Effects of growth regulator applications on the flowering of5-years-grafted mature scions of Picea sitchensis (Bong.) Carr.were assessed. Growth regulators were applied to the bud surfacein droplets of ethanol during July, August and September ina polythene house or glasshouse. A mixture of gibberellins A₄and A₇ applied alone, and in combination with gibberellins A₃and A₅, significantly increased numbers by up to seven timesfor male and by up to eight times for female strobili, gibberellinA, gave relatively the strongest response, and gibberellin A₄was inactive. Phosphon D and abscisic acid each reversed thepromotion of flowering by gibberellins, whilst kinetin and N,N-diphenylureahad no effect. The number of female strobili was negativelycorrelated with vegetative shoot length in the year after treatment. Under field conditions hormones were applied in July and Augustunder flaps of bark on the branches of 10-years-grafted maturescions. Gibberellin applications caused a 5-fold increase inflowering and N⁶-benzyladenine further increased the response.Naphth-lyl-acetic acid reduced female and increased male flowering.Bark removal near the base of the branch further enhanced hormone-inducedstrobilus production. The usefulness of these findings for thebreeding of Picea sitchensis is discussed.