Effects of CO2-mediated changes in paper birch and white pine chemistry on gypsy moth performance

We examined the effects of CO₂-mediated changes in the foliar chemistry of paper birch (Betula papyrifera) and white pine (Pinus strobus) on performance of the gypsy moth (Lymantria dispar). Trees were grown under ambient or enriched CO₂ conditions, and foliage was subjected to plant chemical assays and insect bioassays. Enriched CO₂ atmospheres reduced foliar nitrogen levels and increased condensed tannin levels in birch but not in pine. Foliar carbohydrate concentrations were not markedly altered by CO₂ environment. Gypsy moth performance was significantly affected by CO₂ level, species, and the CO₂ x species interaction. Under elevated CO₂ conditions, growth was reduced for larvae fed birch, while development was prolonged for larvae fed pine. Although gypsy moths performed better overall on birch than pine, birch-fed larvae were influenced more by CO₂-mediated changes in host quality.     

Boron uptake by ectomycorrhizas of silver birch

Boron (B) is an essential micronutrient for plants but it is thought not to be essential for fungi. We studied whether the extraradical mycelia of Paxillus involutus in symbiosis with silver birch (Betula pendula) take up B and transport it to the host plant. We grew mycorrhizal plants in flat microcosms with a partitioning wall, below which there was only extraradical mycelium. A boric acid solution enriched in ¹⁰B was applied to these mycelia. Increased ¹⁰B/¹¹B isotope ratios were subsequently measured in birch leaves, stems, and roots plus mycorrhizas in the upper compartment. Boron was therefore taken up by the mycorrhizal mycelia and transported to the host plant in this species combination.     

Maize root response to N in the greenhouse and field

Summary Root growth and morphology were compared between seven week old maize plants grown in the greenhouse and in the field. The plants were similar in shoot dry weight and the partioning of N and dry matter to roots were similar except for the field grown plants in 1983. Field grown plants had greater root mass per length and greater calculated diameter than greenhouse plants. Nitrogen fertilization decreased N and dry matter partitioning to the root system in all three environments.     

Carbon transfer associated with assimilation of organic nitrogen sources by silver birch (Betula pendula Roth.)

Summary Qualitative and quantitative aspects of heterotrophic carbon assimilation by mycorrhizal plants of birch (Betula pendula) were examined. Plants were grown aseptically from seed in the mycorrhizal condition with the fungus Hebeloma crustuliniforme and in the non-mycorrhizal condition, with protein as their sole exogenous nitrogen source. Yields and nitrogen contents were determined in some of the plants, while the roots of others were supplied with ¹⁴C-labelled protein and their shoots exposed for up to 72 h to different irradiance regimes. Only mycorrhizal plants utilised the organic nitrogen. Uptake of carbon associated with this utilisation and its translocation to the leaves was demonstrated directly by means of autoradiography. Amounts of activity transferred to shoots were greatest in low irradiance regimes. Calculation of net carbon gain from the heterotrophic source, based upon the assumption that breakdown products of protein are assimilated as amino-acids, indicates that over a 55-day growth period up to 9% of plant C may be derived from protein. The physiological and ecological significance of these findings are discussed.     

Estimation of canopy density and irradiance in 20- to 40-year-old birch stands (Betula pubescens Ehrh. andBetula pendula Roth)

Three different experiments in birch (Betula pubescens Ehrh. andBetula pendula Roth) stands were conducted during summer 1991: an evaluation of the accuracy of the vertical tube method measuring crown free projection (CFP) in four birch stands; a study of relative irradiance (RI; photosynthetically active radiation, PAR), in birch stands differing in stem density and basal area; and an estimation of the CFP in different types of birch stands and the correlation between RI and CFP. The results indicate that the number of observation points well distributed over an area of 0.1 ha can vary between 50 and 200 to achieve sufficient accuracy. There were no significant differences in the CFP estimates made on the same plot by different observers including an untrained observer. CFP was related to basal area, stem number and diameter sum in a non-linear regression, CFP = A^*e^-BX. The correlations between RI and basal area, density and diameter sum, respectively, were 0.54, 0.57 and 0.67 for PAR. The coefficients of determination for RI (PAR) and CFP were high (0.86).     

Prevention of the flowering of a tree,silver birch

Genetic modification of trees presents great advantages but it is hampered by the possible spread of introduced genes to native populations. However, the spread would be prevented if the modified trees would be sterile. We have previously shown that the induction of sterility by the prevention of flowering is possible in tobacco and Arabidopsis by introducing a gene construct composed of the ribonuclease gene BARNASE ligated to the flower-specific promoter of the birch gene BpMADS1. In the present study, we test this gene construct in silver birch (Betula pendula Roth). When this gene construct was introduced into very early-flowering birch clones, 81 kanamycin resistant lines were obtained. In 38 lines, the vegetative development was disturbed, e.g., the leaves were small and the plants were short and bushy or the growth of plants was weak. More importantly, in 7 other lines no male inflorescences formed or they aborted early. If male inflorescences were formed, they did not contain any stamens. The initial growth of these lines was similar to the non-transgenic control lines. Later, however, the growth of the non-flowering lines differed from that of the controls in showing some dichotomic branching and a reduced number of branches. Preliminary results showed that the gene construct can prevent the development of female inflorescences as well. The results show clearly that BpMADS1::BARNASE can prevent the flowering in a tree but the prevention of flowering may cause some side effects. Studies with ordinary birch clones will show whether the side effects are a property of the early flowering clones or all birches.     

Epirrita autumnata induced VOC emission of silver birch differ from emission induced by leaf fungal pathogen

The production of volatile organic compounds (VOCs) through the activation of different signal-transduction pathways may be induced in various biotic and abiotic stress situations having importance e.g. in insect and disease resistance. We compared the emission of VOCs emitted from silver birch Betula pendula Roth (clones 4 and 80) twigs damaged either by larvae of Epirrita autumnata, or infected with pathogenic leaf spot causing fungus Marssonina betulae. We also analysed whether local herbivore damage can systemically induce the release of VOCs from the undamaged top of same sapling. The emissions of methylsalicylate (MeSA), (Z)-ocimene, (E)-β-ocimene, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and linalool were induced from the twigs after 72 h feeding damage by E. autumnata larvae. However, 48 h feeding damage did not induce rapid systemic release of VOCs from undamaged top leaves of the same twigs. Pathogen-infected birch twigs had significantly greater emission of (Z)-ocimene and (E)-β-ocimene than intact control twigs. The emission of DMNT was not significantly induced and MeSA was not found at all after pathogen infection, both being significantly different from herbivore damaged twigs. According to our results leaf fungal pathogen induces VOC emission profile differs from that of arthropod herbivore-damaged leaves, suggesting that birch is able to transmit parasite-specific information via VOC emissions to conspecifics and natural enemies of herbivores. Handling editor: Yvan Rahbé     

Mutual use of leaf-shelters by lepidopteran larvae on paper birch

Abstract.

• 1 Many species of birch-feeding Lepidoptera make leaf-shelters by tying leaves together with silk. Several species, or several instars of a single species, may be found together within a single leaf-shelter.
• 2 Shelters made in June by the birch tube-maker Acrobasis betulella (Pyralidae) are colonized throughout the season by other Lepidoptera. Artificial A.betulella shelters, made by tying leaves together with string, were colonized at a greater rate than nearby control foliage, indicating that secondary species are indeed responding to the presence of the shelter, and not to some other aspect of plant quality.
• 3 Several species in the families Oecophoridae, Gelichiidae and Stenomidae make ‘leaf-sandwiches’ by tying two leaves together; these are later colonized by oviposition from adult A.betulella. Artificial sandwiches made by joining leaves together with paperclips were colonized by several species of sandwich-makers, as well as by A.betulella. Colonization occurred mainly via oviposition, although some sandwiches may have been colonized by wandering larvae.
• 4 First instar A.betulella, which cannot form their own shelter, enjoyed greater survivorship when placed in artificial leaf-sandwiches than when placed on leaves without sandwiches.

     

Response of cassava to VA mycorrhizal inoculation and phosphorus application in greenhouse and field experiments

Cassava (Manihot esculenta Crantz) was grown in the greenhouse and in the field at different levels of phosphorus applied, with or without inoculation with VA mycorrhiza in sterilized or unsterilized soil. When grown in a sterilized soil to which eight levels of P had been applied the non-inoculated plants required the application of 3200 kg P ha⁻¹ to reach near-maximum yield of plant dry matter (DM) at 3 months. Inoculated plants, however, showed only a minor response to applied P. Mycorrhizal inoculation in the P check increased top growth over 80 fold and total P uptake over 100 fold. Relating dry matter produced to the available P concentration in the soil (Bray II), a critical level of 15 ppm P was obtained for mycorrhizal and 190 ppm P for non-mycorrhizal plants. This indicates that the determination of critical levels of P in the soil is highly dependent on the degree of mycorrhizal infection of the root system. In a second greenhouse trial with two sterilized and non-sterilized soils it was found that in both sterilized soils, inoculation was most effective at intermediate levels of applied P resulting in a 15–30 fold increase in DM at 100 kg P ha⁻¹. In the unsterilized soil inoculation had no significant effect in the quilichao soil, but increased DM over 3 fold in the Carimagua soil, indicating that the latter had a native mycorrhizal population less effective than the former. When cassava was grown in the field in plots with 11 levels of P applied, uninoculated plants grown in sterilized soil remained extremely P deficient for 4–5 months after which they recuperated through mycorrhizal infection from unsterilized borders or subsoil. Still, after 11 months inoculation had increased root yields by 40%. In the non-sterilized soil inoculation had no significant effect as the introduced strain was equally as effective as the native mycorrhizal population. These trials indicate that cassava is extremely dependent on an effective mycorrhizal association for normal growth in low-P soils, but that in most natural soils this association is rapidly established and inoculation of cassava in the field can only be effective in soils with a low quantity and quality of native mycorrhiza. In that case, plants should be inoculated with highly effective strains.     

Restoration of secondary metabolism in birch seedlings relieved from PAL-inhibitor

Phenylalanine ammonia lyase (PAL) plays a key role in phenylpropanoid metabolism, catalyzing the deamination of phenylalanine (Phe) to form trans-cinnamic acid. Inhibitors of PAL have been used to study the physiological role of the different compounds derived from trans-cinnamic acid, and to test theories about a trade-off between growth and defence in plants. In a previous study with birch (Betula pubescens Ehrh.) seedlings, the PAL inhibitor 2-aminoindane-2-phosphonic acid monohydrate (AIP) caused an accumulation of Phe and a strong decrease in the quantity of simple phenolics, soluble condensed tannins and growth, whereas flavonol glycosides were generally not affected. The present study demonstrates restoration of secondary metabolism in the previously AIP treated birch seedlings. Our results indicate that Phe accumulated during PAL inhibition could be partly used to increase the content of the phenolic acids, flavan-3-ols and to some extent the soluble condensed tannins. Seedling growth also increased when the supply of PAL inhibitor ceased. We thereby show that the inhibition of PAL by AIP in vivo is reversible, at least for moderate AIP concentrations and the rate of restoration is dependent on the inhibitor concentration.     

Plantlet differentiation in leaf and root cultures of birch (Betula Pendula roth.)

The newly-formed leaves on plantlets differentiated from shoot bud cultures of Betula pendula, when excised and grown on a fresh medium produced callus from the margins or regenerated leafy shoots, roots and plantlets. After 4 weeks, upon transfer to murashige and Skoog (MS) medium supplemented with 3-indoleacetic acid (IAA) + 6-(4-hydroxy-3-methyl-trans-2-enyl)aminopurine (zeatin) + 6-aminopurine (adenine), 15–20 plantlets were produced from each explant. Likewise, the roots also showed meristematic activity at several sites, and produced nodulated callus on MS + α-naphthaleneacetic acid (NAA) + 6-(3-methyl-2-butenyl-amino)purine (2-iP) + adenine, and ultimately differentiated plantlets. Anatomical studies showed that initiation of callus takes place by meristematic activity in epidermal cells of leaves, and cortical cells of roots. Cytological investigations revealed no change in chromosomal complement.     

Prevention of flower development in birch and other plants using a BpFULL1::BARNASE construct

The prevention of flower formation is important for avoiding the spread of transgenes from genetically modified plants into wild populations. Moreover, the resources not expended for the generation of flowers and fruits might be allocated to increased vegetative growth. We have been developing methods for preventing flower formation in silver birch (Betula pendula), a tree species of considerable economical importance in the boreal region. Here we study the suitability of the promoter of BpFRUITFULL-LIKE1 (BpFULL1, formerly BpMADS5) for tissue-specific ablation of inflorescences in Arabidopsis, tobacco and birch. With all these species, the development of inflorescences was successfully prevented. The results show that the BpFULL1::BARNASE construct has potential biotechnological applications in different plant species.This revised version was published online in March 2005 because the name of the second author (M. Hassinen) was missing.     

Effects of leguminous ground cover competition on red birch and soil nutrient status in the nursery

Legumes as ground cover are regularly planted to increase nitrogen economy of crops and to improve soil. In the present study various clover species were evaluated as vegetative ground cover in nursery field production of micropropagated red birch (Betula pubescensEhrh. f. rubraUlvinen f. nova) in two 2-year experiments. The clover species and cultivars, Trifolium pratenseL. ‘Bjursele’, T. repens L. ‘Jogeva’, T. repens L. ‘Sonja’, T. hybridum L. ‘Frida’, T. incarnatum L. ‘Opolska’, T. resupinatum L. and T. subterraneum L. were compared to grass sod Festuca rubra L. ‘Ensylva’ and to a coverless ground (control). The last one was kept weed free by hand hoeing. Birch (leaves, stems, branches and roots) and soil nutrient concentrations (N, P, K, Ca, Mg and Fe) were analysed and nutrient ratios in birch determined. The annual clovers, T. incarnatumL., T. resupinatumL. and T. subterraneumL., provided about the same nutrient status in birch as did the control. Perennial clovers and grass were strong competitors with trees. High levels of P and Mg in birch leaves relative to N concentration were typical for poorly growing seedlings. Neither annual nor perennial clovers did generally improve soil nutrient status. This revised version was published online in June 2006 with corrections to the Cover Date.     

Light quality affects photosynthesis and leaf anatomy of birch plantlets in vitro

Cultures in vitro of Betula pendula Roth were subjected to light of different spectral qualities. Photosynthetic capacity was highest when the plantlets were exposed to blue light (max recorded photosynthesis, 82 mol CO₂ dm^–2 h^–1) and lowest when irradiated with light high in red and/or far-red wave lengths (max recorded photosynthesis, 40 mol CO₂ dm^–2 h^–1). Highest chlorophyll content (2.2 mg dm^–2 leaf area) was found in cultures irradiated with blue light, which also enhanced the leaf area. Morphometric analysis of light micrographs showed that the epidermal cell areas were largest in plantlets subjected to blue light and smallest in those subjected to red light. Morphometric analysis of electron micrographs of palisade cells, showed that the functional chloroplast area was largest in chloroplasts of leaves subjected to blue light and smallest in those exposed to red light. We suggest that light quality affects photosynthesis both through effects on the composition of the photosynthetic apparatus and on translocation of carbohydrates from chloroplasts.     

Demography of Betula pubescens ssp. tortuosa sown in contrasting habitats close to the birch tree-limit in Central Sweden

Seeds of mountain birch (Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman) were sown on permanent plots in three contrasting habitats close to the birch tree-limit in Central Sweden. The habitats differed mainly in regard to the length of the growth period, as determined by the pattern of local snow-accumulation. Germination success, seedling demography (1981–1983) and related aspects of the early stages were studied. Germination was found to start shortly after snowmelt in the year after ripening, in all three habitats. The conclusion is that germination is not the crucial phase of the life-cycle. In the habitat with the longest growth period, and where spontaneous birch stands are present, mortality mainly occurred in summer, evidently caused by soil drought. With shortening of the growth period, however, mortality during the winter became increasingly important. Survival was clearly correlated with the length of the growth period and the autumn height of seedlings. Factors which affect ecesis determine the altitude of the tree-limit and the long-term stability of the mountain birch forest ecosystem.     

Growth and nutrition of birch seedlings in relation to potassium supply rate

Summary Growth of hydroponically cultivated birch seedlings (Betula pendula Roth.) at sub- and supra-optimum potassium supply rates was investigated. Potassium was supplied either as a relative addition rate (r _k = 5, 10, 15 and 20% increase day^-1) or as fixed concentrations (0.2, 3, 6, 12 and 15 mM) in the culture solution. After an acclimation period the growth rate of the seedlings in the suboptimum treatments reached values close to the treatment variable, the relative rate of K-addition. Deficiency symptoms, in the form of chlorosis and necroses along the leaf margins, developed initially in all suboptimum treatments, but very few new symptoms appeared once the seedlings had reached the phase of steady-state nutrition and growth. At supra-optimum K-supply levels, i.e. at 0.2–15 mM K in the culture solution, no symptoms of deficiency or toxicity developed, and the relative growth rate of the seedlings remained maximum. The relative growth rate of the seedlings was linearly related to the plant K-status for K contents ranging from 0.2 to 1.0% of dry weight (DW). At higher internal K-concentrations, 1.0–3.0% DW, no further increase in relative growth rate was achieved. A shortage of K resulted in a decrease in the net assimilation rate. This effect was counterbalanced by the absence of shift in he leaf weight ratio as well as by the production of relatively thin leaves. The fraction of dry matter allocated to roots decreased in K-limited plants, as did the leaf contents of soluble carbohydrates and starch.     

Cadmium and copper interactions on the accumulation and distribution of Cd and Cu in birch (Betula pendula Roth) seedlings

The effect of different external cadmium (Cd) and copper (Cu) regimes on the concentration of Cd and Cu in roots and shoots of birch (Betula pendula Roth.) seedlings was investigated. The seedlings were grown for 12 days in a weak nutrient solution (containing all essential nutrient elements including 0.025 µM Cu) at pH 4.2 with combinations of additional 0–2 µM CdCl₂ and 0–2 µM CuCl₂. Root and shoot concentrations of Cu were decreased by Cd in all treatments which included 0.1–2 µM of additional Cu in the treatment solution. When no extra Cu was added, only the shoot concentration of Cu was decreased by Cd whereas the root concentration was not affected. The shoot concentration of Cd was decreased by 0.5 and 2 µM of additional Cu in the treatment solution. The root concentration of Cd was decreased by Cu only when the concentration of additional Cu in the treatment solution was equal to or exceeded the concentration of Cd.     

Applicability of the co-inoculation technique using Agrobacterium tumefaciens shooty-tumour strain 82.139 in silver birch

In the co-inoculation technique, genetic transformation is performed using a mixture of Agrobacterium strains – shoot regeneration is induced by the wild-type strain 82.139, while the transferable genes are provided in a binary plasmid by another, non-oncogenic Agrobacterium strain. The aim of the present work was to study the applicability of co-inoculation under both in vitro and greenhouse conditions for in planta transformation in silver birch (Betula pendula Roth). In addition to the original method, several modifications of the technique including an genetically engineered 82.139 strain harbouring the binary pGUSINT were tested. The co-inoculations resulted in a gall formation frequency of 52–94% with greenhouse seedlings, and 4–63% with tissue-cultured plantlets, the shoot induction percentage varying by 0–13 in the greenhouse and 42–75 in vitro. PCR analysis verified that the majority of the regenerated material was non-transgenic, with a few individuals showing integration of the oncogenic T-DNA. According to the histochemical tests, however, some of the numerous differentiating buds and small shoots on gall tissues were transgenic, and contained the GUS reporter gene. The results show that it would have been necessary to apply selection pressure during differentiation in order to recover shoots transformed with the desired genes from the binary plasmid. The morphology and growth of all the regenerated plantlets was normal, suggesting that the oncogenic T-DNA was not expressed even though it was present. In conclusion, it was possible to obtain transgenic silver birch plantlets using the A. tumefaciens strain 82.139, but the co-inoculation method is not directly applicable as in planta transformation protocol.     

Yield response and availability of various phosphate fertilizer types as estimated by EUF

Summary The solubility of various phosphate fertilizers (Superphosphate, Rhenania phosphate, Novaphos, Carolon phosphate and Hyperphosphate) was studied in an incubation experiment, and the uptake of P from these fertilizers and their effects on wheat yields were investigated in a pot experiment. The soil used was a carbonate-free, brown podsolic soil (C horizon) with a neutral pH and low in available phosphate and humus.The quantities of P extracted from the soil by the EUF technique decreased with an increase of the unacidulated portion of the P fertilizer. This clear differentiation in the solubility of the various P fertilizers was not obtained with a DL extraction. Uptake of P by plants was highly correlated with quantity of P extracted by EUF (r=0.95^***), while the correlation between P uptake and P extracted by DL was less narrow (r=0.64^*). Yield, particularly grain yield, decreased with increasing portion of unacidulated P in the fertilizers tested. Grain yield and EUF-extractable P were highly correlated (r=0.86^***), whereas the relationship between grain yield and DL-extractable P was poorer (r=0.62^*). The experiments showed that mainly the easily soluble phosphate is of importance for the P nutrition of crops.