Jana Albrechtová

Applicability of the PROSPECT model for Norway spruce needles

The potential applicability of the leaf radiative transfer model PROSPECT (version 3.01) was tested for Norway spruce (Picea abies (L.) Karst.) needles collected from stress resistant and resilient trees. Direct comparison of the measured and simulated leaf optical properties between 450–1000 nm revealed the requirement to recalibrate the PROSPECT chlorophyll and dry matter specific absorption coefficients k ab(λ) and k m(λ). The subsequent validation of the modified PROSPECT (version 3.01.S) showed close agreement with the spectral measurements of all three needle age‐classes tested; the root mean square error (RMSE) of all reflectance (ρ) values within the interval of 450–1000 nm was equal to 1.74%, for transmittance (τ) it was 1.53% and for absorbance (α) it was 2.91%. The total chlorophyll concentration, dry matter content, and leaf water content were simultaneously retrieved by a constrained inversion of the original PROSPECT 3.01 and the adjusted PROSPECT 3.01.S. The chlorophyll concentration estimated by inversion of both model versions was similar, but the inversion accuracy of the dry matter and water content was significantly improved. Decreases in RMSE from 0.0079 g cm−2 to 0.0019 g cm−2 for dry matter and from 0.0019 cm to 0.0006 cm for leaf water content proved the improved performance of the recalibrated PROSPECT version 3.01.S.

Detection of initial damage in Norway spruce canopies using hyperspectral airborne data

Current broadband sensors are not capable of separating the initial stages of forest damage. The current investigation evaluates the potential of hyperspectral data for detecting the initial stages of forest damage at the canopy level in the Norway spruce (Picea abies (L.) Karst) forests of Czech Republic. Hyperspectral canopy reflectance imagery and foliar samples were acquired contemporaneously for 23 study sites in August 1998. The sites were selected along an air pollution gradient to represent the full range of damage conditions in even-aged spruce forests. The changes in canopy and foliar reflectance, chemistry and pigments associated with forest damage were established. The potential of a large number of spectral indices to identify initial forest damage was determined. Canopy hyperspectral data were able to separate healthy from initially damaged canopies, and therefore provided an improved capability for assessment of forest physiology as compared to broadband systems. The 673-724 nm region exhibited maximum sensitivity to initial damage. The nine spectral indices having the highest potential as indicators of the initial damage included: three simple band ratios, two derivative indices, two modelled red-edge parameters and two normalized bands. The sensitivity of these indices to damage was explained primarily by their relationship to foliar structural chemical compounds, which differed significantly by damage class.

Spectral characteristics of lignin and soluble phenolics in the near infrared- a comparative study

Prediction of canopy chemical compounds including lignin based on reflectance or absorbance in the near infrared has been demonstrated using hyperspectral data. Little attention has been paid to the fact that many types of plant phenolics have chemical structures similar to lignin and may have similar spectral responses in the near infrared. To address this problem we have analysed near infrared spectral signatures of dry powder standards of lignin and tannin, dissolved lignin, tannin and other soluble phenolics, lignin and soluble phenolics extracted from Norway spruce needles, as well as wooden blocks containing varying amounts of tannin. Our results provide solid evidence that the spectral signatures of lignin and tannin are very similar and that spectral features and wavelengths used previously for lignin determination are in fact likely to be due to tannin and lignin reflectance features. This similarity may greatly affect near infrared assessments of canopy lignin concentrations and impact analyses for which these predictions are used. Additionally, certain near infrared reflectance properties associated with increasing levels of foliar damage may be due to increased levels of tannins in affected mesophyll cells. We have also identified the existence of a threshold lignin concentration below which spectrometry cannot precisely detect lignin.

Ericaceous dwarf shrubs affect ectomycorrhizal fungal community of the invasive Pinus strobus and native Pinus sylvestris in a pot experiment

This study aimed to elucidate the relationship between ericaceous understorey shrubs and the diversity and abundance of ectomycorrhizal fungi (EcMF) associated with the invasive Pinus strobus and native Pinus sylvestris. Seedlings of both pines were grown in mesocosms and subjected to three treatments simulating different forest microhabitats: (a) grown in isolation and grown with (b) Vaccinium myrtillus or (c) Vaccinium vitis-idaea. Ericaceous plants did not act as a species pool of pine mycobionts and inhibited the ability of the potentially shared species Meliniomyces bicolor to form ectomycorrhizae. Similarly, Ericaceae significantly reduced the formation of Thelephora terrestris ectomycorrhizae in P. sylvestris. EcMF species composition in the mesocosms was strongly affected by both the host species and the presence of an ericaceous neighbour. When grown in isolation, P. strobus root tips were predominantly colonised by Wilcoxina mikolae, whereas those of P. sylvestris were more commonly colonised by Suillus and Rhizopogon spp. Interestingly, these differences were less evident (Suillus + Rhizopogon spp.) or absent (W. mikolae) when the pines were grown with Ericaceae. P. strobus exclusively associated with Rhizopogon salebrosus s.l., suggesting the presence of host specificity at the intrageneric level. Ericaceous plants had a positive effect on colonisation of P. strobus root tips by R. salebrosus s.l. This study demonstrates that the interaction of selective factors such as host species and presence of ericaceous plants may affect the realised niche of the ectomycorrhizal fungi.

Sperm-related phenotypes implicated in both maintenance and breakdown of a natural species barrier in the house mouse

The house mouse hybrid zone (HMHZ) is a species barrier thought to be maintained by a balance between dispersal and natural selection against hybrids. While the HMHZ is characterized by frequency discontinuities for some sex chromosome markers, there is an unexpected large-scale regional introgression of a Y chromosome across the barrier, in defiance of Haldanes rule. Recent work suggests that a major force maintaining the species barrier acts through sperm traits. Here, we test whether the Y chromosome penetration of the species barrier acts through sperm traits by assessing sperm characteristics of wild-caught males directly in a field laboratory set up in a Y introgression region of the HMHZ, later calculating the hybrid index of each male using 1401 diagnostic single nucleotide polymorphisms (SNPs). We found that both sperm count (SC) and sperm velocity were significantly reduced across the natural spectrum of hybrids. However, SC was more than rescued in the presence of the invading Y. Our results imply an asymmetric advantage for Y chromosome introgression consistent with the observed large-scale introgression. We suggest that selection on sperm-related traits probably explains a large component of patterns observed in the natural hybrid zone, including the Y chromosome penetration.

The Co-occurrence and Morphological Continuum Between Ericoid Mycorrhiza and Dark Septate Endophytes in Roots of Six European Rhododendron Species

Ericaceae associate with a wide spectrum of root mycobionts, but the most common are ascomycetous ericoid mycorrhizal fungi and dark septate endophytes (DSE), followed by basidiomycetous fungi and glomeracean arbuscular mycorrhizal fungi. We investigated distribution and morphological diversity of ericoid mycorrhizae (ErM), DSE associations, ectomycorrhizae (EcM) and arbuscular mycorrhizae (AM) in hair roots of six European native Rhododendron species and found that i) while EcM and AM were absent, ErM and DSE associations were simultaneously present in all screened plants; ii) their levels were negatively correlated, suggesting Ericaceae preference for certain root-fungus association in certain habitats; iii) the highest ErM colonization occurred at sites in southern and central Europe, while the highest DSE colonization was found in a subarctic site in northern Finland and in a subalpine site in the Carpathians, suggesting a latitudinal/altitudinal shift in Ericaceae root-fungus associations; iv) some mycelia could simultaneously form structures corresponding to ErM and DSE association, which occasionally resulted in a unique ectendomycorrhizal colonization comprising an intercellular parenchymatous net and intracellular hyphal coils. These results indicate frequent interactions between ErM fungi and DSE in roots of European rhododendrons and a morphological continuum between ErM and DSE associations. The new ectendomycorrhizal type deserves further investigation.

Intracellular colonization ofRhododendron andVaccinium roots byCenococcum geophilum, Geomyces pannorum andMeliniomyces variabilis

Fourin vitro experiments were set up to verify the colonization potential of ectomycorrhizal (EcM)Cenococcum geophilumFr. (strain CGE-4), saprotrophicGeomyces pannorum (Link)Sigler & Carmichael (GPA-1) and a frequent root-associated, potentially ericoid mycorrhiza (ErM)-formingMeliniomyces variabilisHambleton & Sigler (MVA-1) in roots ofRhododendron andVaccinium. A typical ErM fungus,Rhizoscyphus ericae (Read)Zhuang & Korf (RER-1), was included for comparison. All fungal strains intracellularly colonized rootedVaccinium microcuttings: GPA-1 occasionally produced hyphal loops similar to ErM, MVA-1 and RER-1 exhibited a typical ErM colonization pattern. CGE-4 hyphae grew vigorously on and around newly formed roots and rarely penetrated turgescent rhizodermal cells forming intracellular loose loops. Rooting ofRhododendron sp. microcuttings was not promoted by any fungal strain except CGE-4, which also promoted the most vigorous growth ofRhododendron ponticum L. seedlings. The widespread EcM fungusC. geophilum has a potential to colonize non-EcM roots and support their development which may influence overall growth of ericaceous plants. As shown forG. pannorum, structures resembling ErM may be formed by fungi that are to date not regarded as ericoid mycorrhizal.

Carbohydrate status during somatic embryo maturation in Norway spruce.

SummaryThe development of Norway spruce (Picea abies (L.) Karst.) somatic embryos on a maturation medium was accompanied by changes in nonstructural carbohydrate status. During embryo maturation, the content of total soluble sugars in the embryonal suspensor mass decreased and the partitioning between sucrose and hexoses changed considerably in favor of sucrose. Developing somatic embryos were mainly responsible for these changes. Osmotic stress caused by the presence of 3.75% polyethylene glycol (PEG) in the maturation medium (decrease in osmotic potential by 52.5 kPa) resulted in dramatic changes in the content of endogenous saccharides. There was a lower total carbohydrate content in the embryonal suspensor mass grown on the medium containing PEG in comparison with the untreated control. Isolated embryos from later stages of embryo development contained mainly sucrose with a small amount (20%) of fructose and nearly no glucose. A further increase in PEG concentration in the medium (7.5%; decrease in osmotic potential by 112.5 kPa compared to the maturation medium) led to a large increase in the total endogenous sugar content. This increase in sugars was a result of the enhanced content of sucrose, fructose, and glucose. The increased glucose content was in contrast to embryos grown on the medium with lower or no PEG content.

Annual dynamics of the content of non-structural saccharides in the context of structural development of vegetative buds of Norway spruce.

Summary Apical buds are very important organs as they determine further growth and development of tree species. Bud physiological state, including saccharide metabolism, determines their growth activity, and thus the development of the whole crown architecture. The present study focused on annual dynamics of the contents of non-structural saccharides (NSS) related to structural development in terminal vegetative buds of Norway spruce ( Picea abies L. Karst.) during 1995. Two types of material were analysed: 1) four-year-old nursery-planted trees; and, 2) adult individuals from two mountain sites in the Czech Republic. Sugar and starch contents were determined, and starch was localised histochemically. Generally, the dynamics of the NSS content reflects the major morphogenetic and developmental changes occurring during the annual cycle. The highest content of sugars corresponds with a bud dormant state. Bud break is accompanied by the lowering of sugar content, reflecting the transition of buds to metabolically active sinks. During bud cold hardening in autumn, a massive gradual sugar accumulation takes place. The most pronounced change during the annual cycle is found in the content of raffinose, with the highest values observed during autumn and winter. The possible role of raffinose in bud frost tolerance is discussed. The results obtained from the buds sampled at the mountain sites are both qualitatively and quantitatively similar to the more detailed NSS-dynamics of young trees, thus, giving the justification to generalisation of the above described pattern for vegetative buds of Norway spruce.

Development of arbuscular mycorrhizal biotechnology and industry: current achievements and bottlenecks

Advanced scientific knowledge on arbuscular mycorrhizal symbioses recently enhanced potential for implementation of mycorrhizal biotechnology in horticulture and agriculture plant production, landscaping, phytoremediation and other segments of the plant market. The advances consist in significant findings regarding:—new molecular detection tools for tracing inoculated fungi in the field;—the coexistence mechanisms of various fungi in the single root system;—new knowledge on in vitro physiology of the AM fungi grown in root organ cultures;—mechanisms of synergistic interactions with other microbes like PGPR or saprotrophic fungi; discovery of mycorrhiza supportive compounds such as strigolactones. Scientific knowledge has been followed by technological developments like novel formulations for liquid applications or seed coating, mycorrhiza stimulating compounds or new application modes. Still the missing components of biotechnology are appropriate, cheap, highly reproducible and effective methods for inocula purity testing and quality control. Also there is a weak traceability of the origin of the mycorrhizal fungi strains used in commercial inocula. Numerous poor quality products can still be found on the markets claiming effective formation mycorrhiza which have very low capacity to do so. These products usually rely in their effects on plant growth not on support of host plants via formation of effective mycorrhizal symbiosis but on fertilizing compounds added to products. There is growing number of enterprises producing mycorrhiza based inocula recently not only in developed world but increasingly in emerging markets. Also collaboration between private sector and scientific community has an improving trend as the development of private sector can fuel further research activities. Last but not least there is apparent growing pull of the market and increasing tendency of reduction of agrochemical inputs and employment of alternative strategies in planting and plant production. These circumstances support further developments of mycorrhizal inocula production and applications and maturation of the industry.