Showing papers by "Kerstin Huss-Danell published in 1994"
TL;DR: The sampling of forest soils at a site in northern Sweden during the snow-free period in June and September 1991 suggests that the nodulating ability of Frankia is controlled largely by the physiological status ofFrankia, as indicated by infectivity, rather than total population size, as indicating by GU.
Abstract: Little is known about the seasonal dynamics of Frankia populations in soils. For this purpose, we sampled forest soils at a site in northern Sweden (66°31'N) twice during the snow-free period: in June and September 1991. Several treatments were established at this site during 1977–1980, including planting lupine ( Lupinus nootkatensis Donn), alder ( Alnus incana (L.) Moench)—an actinorhizal host, liming and NPK fertilization. We collected soil samples from control, lupine, alder, alder limed, alder plus NPK, and alder limed plus NPK. Populations of Alnus -infective Frankia were measured in two ways: (i) a plant bioassay MPN to determine nodulation units (NU) of Frankia , and (ii) the polymerase chain reaction with oligonucleotide primers specific to Alnus -infective Frankia to quantify the number of Frankia genomic units (GU). Numbers of NU ranged from 25 to 182 g −1 soil and GU from 1700 to 3400 g −1 soil. There were statistically-significant treatment and seasonal effects on NU. The control and alder limed treatments had about 2.5 times higher NU than the lupine and alder limed plus NPK treatments. Frankia NU decreased almost 3-fold from June to September. There were no significant treatment or seasonal effects on Frankia GU. These data suggest that the nodulating ability of Frankia is controlled largely by the physiological status of Frankia , as indicated by infectivity, rather than total population size, as indicated by GU.
65 citations
TL;DR: The bioassay seems appropriate for comparisons between soils when the same plant genotypes are used under the same conditions, but otherwise comparisons should be made with caution.
Abstract: Methods based on amplification and recognition of Frankia -specific DNA have recently been developed to quantify Frankia in soil. But measuring numbers of infective Frankia in soil still requires bioassays involving nodulation of appropriate host plants. We compared three alder species, Alnus glutinosa (L.) Gaertn., A. incana (L.) Moench and A. rubra Bong, grown in two nutrient solutions under controlled conditions in a climate chamber. Plants were either kept in the same cultivation tube or, to remove most of the inoculum, they were moved into a new tube 2 weeks after inoculation. Soil dilution series prepared from a forest soil served as inocula. Roots were inspected for nodules weekly for 8 weeks and the number of nodulation units (NU) g −1 soil was calculated according to the most probable number (MPN) method and according to a nodulation capacity method. Alnus glutinosa required the longest time to nodulate. The number of NU detected was in the order A. rubra > A. incana > A. glutinosa in each of the nutrient solutions used. Eight weeks after inoculation, number of NU ranged from 5 to 400 as determined by the MPN-method, and from 10 to 380 as determined by the nodulation capacity method in the different species, solution and tube combinations used. The bioassay seems appropriate for comparisons between soils when the same plant genotypes are used under the same conditions, but otherwise comparisons should be made with caution. The MPN method and the nodulation capacity method essentially gave the same results. The MPN method is somewhat less labour intensive.
32 citations
TL;DR: The role of vesicle envelope lipids in regulating oxygen diffusion of symbiotic nitrogen fixation in Alnus incana was examined in this article, showing that adaptation to different ambient oxygen tensions occurs at least partly by increasing the thickness of the vesicles and by changing its lipid composition.
Abstract: The role ofFrankia vesicle envelope lipids in regulating oxygen diffusion of symbiotic nitrogen fixation inAlnus incana was examined. Total lipids of symbioticFrankia (vesicle clusters) that had been adapted to oxygen tensions of 5,21, or 40 kPa were analyzed with a normal phase HPLC system. During the oxygen treatment, nitrogenase activity was measured as hydrogen evolution in an open flow-through system. When plants were transferred to low oxygen (5 kPa) or high oxygen (40 kPa), nitrogenase activity dropped initially. Activity recovered in both treatments with a rate comparable to the controls (21 kPa O2). Both lipid content and lipid composition of vesicle clusters were affected by the oxygen treatments. With increasing oxygen tension, the vesicle cluster lipid content increased. This correlated with structural data (fluorescence microscopy and TEM) which showed a thicker vesicle envelope at higher oxygen tension. Three hopanoid lipids, bacteriohopanetetrol (bht) and two isomers of phenylacetyl monoester of bht, made up approximately 80% of the vesicle cluster lipids. With changing oxygen concentrations, the ratio of the two bht esters changed whereas the relative proportion of bht remained fairly constant. Therefore, in theFrankia-Alnus incana symbiosis, adaptation to different ambient oxygen tensions occurs at least partly by increasing the thickness of theFrankia vesicle envelope and by changing its lipid composition.
31 citations
TL;DR: In this article, a modelling system is described that indicates the extent to which day-to-day variations in nitrogenase activity in young Alnus incana (L.) Moench, grown in defined conditions in the field, may be affected by weather conditions both during and prior to the day of measurement.
Abstract: A modelling system is described that indicates the extent to which day-to-day variations in nitrogenase activity in young Alnus incana (L.) Moench, grown in defined conditions in the field, may be affected by weather conditions both during and prior to the day of measurement. Nitrogenase activity (acetylene reduction activity, ARA) was measured weekly on intact field-grown grey alder (A. incana) plants, 0.15–0.42 m tall at planting, nodulated with Frankia. The measurements were done at noon on two groups of plants in 1987 and on two other groups in 1988. Each group was made up of five or six plants. Seven weather variables: daily sunshine hours, daily mean, maximum and minimum air temperature, daily mean and 1300 h relative humidity, and daily rainfall were used. The relation between log(ARA/leaf area) and the weather variables were analysed using a PLS model (partial least squares projection to latent structures). The advantage of PLS is that it can handle x-variables that are correlated. Data from 1987 were chosen as a training set. Multivariate PLS time series analysis was made by adding, in a stepwise manner, the weather data up to 5 d before the day of measurement. This procedure gave six models with n * 7 x-variables (n= 1–6). With the models from the time series analysis of 1987 data, true predictions of ARA per leaf area were made from weather data 1988 (test set 1) and from ‘early-season’ weather data from 1987 and 1988 (test set 2). The variation in ARA/leaf area could be predicted from the weather conditions. The predictions of the two test sets improved when the weather conditions one and two days before the day of measurements were added to the model. The further addition of weather data from 3 to 5 d before the day of measurement did not improve the model. The good predictions of ARA/leaf area show that the alders responded to the variable weather conditions in the same way in 1988 as in 1987, despite the ten-fold difference in size (leaf area) at the end of the growing season. Among the weather variables, air temperature and the daily sunshine hours were positively correlated to ARA, while relative air humidity and rainfall were negatively correlated to ARA. The daily minimum temperature and rainfall appeared to have least impact on ARA. By use of PLS, we could extract information out of a data set containing highly correlated x-variables, information that is non-accessible with conventional statistical tools such as multiple regression. When making measurements of nitrogenase activities under field conditions, we propose that attention should be paid to the weather conditions on the days preceding the day of measurement. The day-to-day variation in nitrogenase activity is discussed with reference to known effects of stress factors under controlled conditions.
9 citations