Doris Krabel

Callase-(1,3-β-d-glucanase) activity during spring reactivation in deciduous trees

Abstract The activity of callose-degrading enzyme endo-1,3-β- d -glucanase (EC 3.2.1.39) was studied in tissue composed of cambium- and secondary phloem cells of goat willow (Salix caprea), sycamore maple (Acer pseudoplatanus), and european ash (Fraxinus excelsior) from January to May in 1989 and 1990, in relation to bud development in spring. Extracts were assayed colorimetrically for 1,3-β- d -glucanase activity by using a dye-substituted pachyman derivative as substrate. The pH optimum of glucanase activity in maple and ash was almost identical (6.0–6.5), whereas that of willow appeared to be in the acidic range (3.5–4.0). In general three seems to be a trend that glucanase activity rises in early spring consistent with it playing a role in dissolution of callose before bud break. An atypical early rise of glucanase activity in ash and maple in 1989 is probably explained by unusually high temperatures in January.

Rhabdocline needle cast—investigations on various Douglas fir tissue types

Douglas fir (Pseudotsuga menziesii) is one of the most important non-indigenous tree species in Germany. The species is characterized by a wide amplitude of growing conditions, and is of increasing interest, in particular from the perspective of climate change. Douglas fir is nevertheless particularly susceptible to fungal pathogens, such as Rhabdocline pseudotsugae. The aim of the present study was therefore to develop an early detection method for R. pseudotsugae based on the polymerase chain reaction (PCR). Existing molecular techniques were adapted and optimized to detect the pathogen in small sample volumes. Both healthy and infected Douglas firs were examined, with various tissue types (buds, cambial tissue, needles) and seeds tested for the presence of R. pseudotsugae. Non-infected Douglas firs did not give positive responses in the molecular analyses, but the pathogen was clearly detected in buds, cambial tissues, needles and seeds of infected trees. To date, the fungus has been considered an obligate biotrophic needle parasite. The present results provide clear evidence, however, for the existence of an endophytic stage in the life cycle of R. pseudotsugae. In contrast with previous studies, this paper investigates the dispersal of the fungus via seeds.

Acquisition of carbon in Elodea canadensis Michx.

Summary Mature shoots of Elodea canadensis Michx., grown in artificial pond water, were exposed to 14 CO 2 orsubmersed in solution containing H 14 CO 3 − for 30 min under PAR. The macroautoradiographs indicated that bicarbonate was used for photosynthesis, while gaseous 14 CO 2 was not incorporated. Accordingly, gas exchange measurements showed no reduction of CO 2 -content in the cuvette. Microautoradiographs indicated that 14 C was taken up by penetrating the epidermis of the stem and that of the lower side of the leaves. In the symplast, label was accumulated in the chloroplasts of both epidermal layers and in the plastid envelope of the chloroplasts of cortex cells. In the stem no label occurred inside the central cylinder. Among sieve tubes, only those of the leaf traces were labeled. Thin layer chromatograms of extracts of labeled plants were autoradiographed. The main spots were identified by co-chromatography as malic acid, glucose, asparagine, proline and hexose phosphates, while sucrose appeared only slightly labeled. By SEM, strands of stretched cells with inflated ends were observed and named ≪canal cells≫. In the light microscope, canal cells were found among cells of the lower leaf epidermis. Upon illumination with PAR they increasingly were filled with gas, but in the dark no gas collected in the canal cells. They probably are used for collecting and transferring photosynthetically produced oxygen. Accordingly, acquisition of carbon and release of oxygen seem to follow different pathways in Elodea canadensis .

Chloroplast Movement as Response to Wounding in Elodea canadensis

Summary Chloroplast movement was studied in intact, detached or cut leaves of Elodea canadensis Michx. The influence of external factors (light, temperature, water supply) and of leaf age on activity and pattern of chloroplast movement was observed. Chloroplast movement does not occur in unsevered leaves; in leaves severed either by detachment or by a lateral incision, chloroplast movement occurs at room temperature in similar patterns. In midrib cells axial chloroplast movement starts within 10 min after setting the wound, almost independently from external conditions. In epidermis cells, lateral chloroplast movement is time-limited depending on the pretreatment of the plant (light, dark, cold). Lateral chloroplast movement is minimal in young leaves and maximal in mature leaves. In the morning hours chloroplast movement is restricted to midrib cells, but in the afternoon additional lateral movement occurs. Predarkening of plants reduced lateral chloroplast movement, but continuous illumination activated the movement. Cooling of plants to the temperature of melting ice (+5 °C) inhibited chloroplast movement in detached and incised leaves. However, after transfer to room temperature, axial chloroplast movement started within 20 min, and lateral chloroplast movement started within 40 min. The velocity of movement was highest after several warm-cold-warm changes following detachment or incision (maximum 36.8 µm s -1 ). The time course of chloroplast movement coincides with rapid changes of the membrane potential with low amplitudes (humming, 4 to 7 mV), which was recorded with microelectrodes impaled into the midrib of the attached leaf. Cutting a leaf of the third, last-formed generation initiated a sudden depolarization (from -200 mV to -140 mV) and a subsequent hyperpolarization to -240 mV, which slowly increased, but after 10 min suddenly changed to the humming period in the range of -200 mV ± 1.5 mV. It is concluded that chloroplast movement is initiated and enhanced by wound reactions transmitted from cell to cell via plasmodesmata.

Sycamore Maple (Acer pseudoplatanus L.)

Sycamore maple (Acer pseudoplatanus L.) is native mainly to the mountainous regions of southern, southwestern, western, central and eastern Europe with the extreme easterly limit at the Casparian Sea. In several European countries, the species was firstly introduced in a period from the Roman Empire to the Middle Ages as an ornamental tree, later on also as a tree for reforestation purposes. In the present, sycamore maple is a minor forest species compared to beech and oak. However, in few regions the species has already gained a negative status as an invasive species. Sycamore maple is characterized by its highly valuable timber, fast growth and moderate site requirements.

Xylem cell length under drought and its value for predicting radial growth of SRF poplar cultivars (Populus spp.)

Xylem cell length of juvenile tree rings was investigated in poplars in order to check the hypotheses that fiber length or vessel element length are indicative of drought tolerance and have predictive value for final stem base diameter at the end of rotation. The radial increment in the drought year 2003 served as the reference indicator for quantifying drought tolerance. All nine investigated cultivars suffered severely. In terms of their moderately decreased radial increment in 2003, the two aspen cultivars were clearly less drought susceptible than the seven hybrid poplar cultivars. The variance components of xylem cell length data explained by the two genetic factors ‘cultivar’ and ‘botanic section’ as well as the ‘tree ring’ (of the years 2002 and 2003) were compared by means of ANOVAs. The cultivar effects were superior to the effects of the critical precipitation status in 2003 and the botanic section. Fiber and vessel element length were found to be less sensitive to the drought compared with radial increment. They did neither correlate with radial increment in the drought year 2003 nor in 2002. Therefore, higher xylem cell length cannot indicate drought tolerance in poplars. However, a linear relationship between fiber length of both juvenile tree rings and the stem base diameter proved to be highly significant to a linear mixed effect model. Higher fiber length of a juvenile tree ring was considered to be predictive of larger stem base diameter at the end of rotation.

Seasonal changes in sucrose concentration in trees

Summary Sucrose concentration was determined monthly in cambial and phloem tissue of Fagus sylvatica L. from February until October. We found three different stages of sucrose concentration in spring and a relatively high level of sucrose during summer (from June until end of September). The results are interpreted with respect to the developmental stages of a tree during a year and to the dynamics of starch concentration in the bark.

Influence of phloem transport on flower abscission in Hibiscus rosa-sinensis.

SummaryFlowering cultivars of Hibiscus rosa-sinensis L. were either cross-pollinated or self-pollinated. Fruit set was observed on 52% of the cross-fertilized flowers, while only 4.6% of the self-fertilized flowers were not abscised. Once during fruit and seed growth, the subtending leaf was exposed to 14CO2, and translocation of labelled photoassimilate was recorded by macro- and microautoradiography. Phloem transport into the raphe occurred in both fruits with fertilized and fruits with non-fertilized ovules. Since empty ovules showed some sink strength, it is assumed that growth of vegetative seed-tissue signalizes the retardation of completion of the abscission process. During fruit growth a considerable amount of starch is deposited in the distal layer of the abscission zone. Part of this starch is consumed during growth of cross-fertilized fruits.

PCR-based detection of single sequence variants from a natural collection of the non-model tree species European Aspen Populus tremula (L.)

Abstract In the present study we present and discuss the identification of species-specific SNPs to rule out any experimental influence of species-specific primer design (Populus tremula vs. the closely related model-species Populus trichocarpa) on the detectability of SNPs. Applying a species-optimized method, partial sequences of 14 genes involved in xylem cell development, xylogenesis, pectin formation, and drought stress reaction were analyzed at the genomic level. About 3 Mb of sequence information were generated by Sanger sequencing technology and 258 sequence variants were identified. 15 out of these represent insertions /deletions located exclusively in non-coding regions and the remaining 243 are SNPs found in coding and non-coding regions of candidate genes. The introduction of a species-specific SNP detection pipeline will help to detect nucleotide variants in P. tremula and to conduct association mapping in natural P. tremula populations.

Haemoglobin variants within the genus Cervus

Abstract Haemoglobins from a total of 168 red deer (Cervus elaphus), five Japanese Sika deer (Cervus nippon nippon), 49 hybrids between red deer and Sika deer (Cervus elaphus × Cervus nippon) as well as 32 fallow deer (Cervus dama) have been studied by isoelectric focusing in polyacrylamide gels. One single band showing no variation was found in all animals. All fallow deer exhibited an additional band. With respect to previous investigations on haemoglobin polymorphism, we must assume a high degree of genetic differentiation between European red deer populations at least for one haemoglobin gene locus. Gene duplication in the distant past or persistence of foetal haemoglobin are alternative hypotheses explaining the haemoglobin pattern of fallow deer.