Application of 31P NMR to Monitor Phosphorus Compounds and their Changes During Germination of Legume Seeds

Extracts of embryonic axes and cotyledons of 19 species of legumeswere analysed by ³¹P nuclear magnetic resonance; the effectof different extraction procedures on the solubilization ofthe several phosphocompounds was investigated. The contentsof phytic acid, inorganic phosphate, phosphomonoesters and phosphodiesterswere determined. The relative contents of these phosphocompoundswere very different when embryonic axes and cotyledons werecompared, and were greatly influenced by the taxonomic affiliationof the corresponding species. Phytic acid and inorganic phosphatewere by far the major phosphocompounds found in cotyledon extracts;an unusual phosphodiester component was detected only in embryonicaxes and was particularly abundant in species belonging to theLotoideae sub-family. The changes in the amount of the phosphodiestercompound were followed during germination and the results suggestthat it is not a phosphorus reserve. Furthermore, this componentwas preferentially present in the roots of the new plants. Itwas partially hydrolysed by RNAse and to a smaller extent byproteases, but not affected by DNAse. The hypothesis that thisunusual component might be a ribonucleoprotein is discussed. Key words: ³¹P NMR, legumes, seed components, phosphorus compounds, solubilization     

Weed performance in crop rotations with and without leys and at different nitrogen levels

Weed populations were studied from a 26-year-old field experiment in southern Sweden with three different 6-year crop rotations, each with four rates of nitrogen application. The rotations differed in that one had a two-year legume-grass ley, another had a two-year grass ley, and that the third had spring wheat followed by a repeatedly harrowed fallow. The leys and the fallow were followed by turnip rape, winter wheat, oats and barley which was undersown in the two ley rotations. Data on weed biomass, collected in one season, were subjected to multivariate analysis.
Winter turnip rape had the highest weed biomass. However, of the several weed species, only Matricaria perforata Merat was important in wheat (the crop following turnip rape in the rotation). The weed flora did not differ consistently between rotations. We conclude that none of the three rotations had developed any major weed problems under the past weed management regime (herbicides applied to cereal crops).
There was no consistent effect of nitrogen fertilisation on total weed biomass in any of the three rotations. However, when comparing the weed floras in winter wheat, turnip rape and oats, the unfertilised plots differed from the plots receiving nitrogen. In the two latter crops, the abundant, low-growing annual Stellaria media (L.) Vil. performed best in fertilised plots with dense stands. Equisetum arvense L., the most abundant perennial weed, was important only in unfertilised plots.     

Plastic resource polymorphism: effects of resource availability on Arctic char (Salvelinus alpinus) morphology

Resource polymorphism has been suggested to be a platform for speciation. In some cases resource polymorphism depends on phenotypic plasticity but in other cases on genetic differences between morphotypes, which in turn has been suggested to be the ongoing development of a species pair. Here we study environmentally induced morphological differences in two age classes of Arctic char ( Salvelinus alpinus ) influencing char performance and diet in relation to resource availability. We found that structurally complex habitats with relatively lower zooplankton densities gave rise to individuals with a deeper body, and a downward positioned tip of the snout compared with individuals from structurally simple habitats with relatively higher zooplankton densities for both age classes. Environment also had an effect on foraging efficiency on zooplankton, with fish from structurally simple habitats had a higher foraging rate than fish from structurally complex habitats. Diet analyses showed that resource use in char mainly depends on the relative abundance of different resources. Therefore, to gain further understanding of resource polymorphism we suggest that future studies must include population dynamic feedbacks by the resources on the consumers.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 341–351.     

The effects of temperature and photoperiod on life history parameters of Daphnia magna (Crustacea: Cladocera)

SUMMARY. 1. The life history responses of two common and three rare Daphnia magna clones to constant conditions of temperature and photoperiod were investigated, and intraspecific variation in the genes controlling growth, survivorship and reproduction was observed.
2. Rearing temperature had a significant effect on growth, survivorship and on all reproductive parameters measured (generation time, intrinsic rate of increase and male production), while photoperiod influenced significantly only survivorship and male production.
3. The maximum proportion of male offspring was produced at a low temperature (14°C) and at a mid-range photoperiod (L:D16:8).
4. The likely mechanism whereby clones with different life histories are maintained in the population is discussed.     

Seasonal changes in primary and secondary inoculum during epidemics of leaf blotch (Rhynchosporium secalis) on winter barley

Seasonal changes in numbers of conidia of Rhynchosporium secalis on debris from previous barley crops infected with leaf blotch (primary inoculum) were monitored in 1985–86 and 1986–87. In 1986–87, changes in numbers of conidia on leaves of plants in the new winter barley crop (secondary inoculum) were also recorded. The greatest increases in production of primary inoculum were in early spring after rain, when temperatures were increasing after periods of sub-zero temperatures when there was little conidial production. Subsequently, more conidia were recovered from this debris after cycles of drying and rewetting than when it remained wet. After January 1987, amounts of secondary inoculum produced on the crop were much greater than amounts of primary inoculum on debris. Most spores were produced on the basal leaves and more spores were present on the September-sown than on the November-sown crop. Thus, while primary inoculum was a source of disease when plants were emerging, secondary inoculum on basal leaves was the main source of disease at stem extension, especially on early-sown crops.     

Restriction fragment length polymorphism of DQ and DR class II genes of the bovine major histocompatibility complex

DQ alpha, DQ beta, DR alpha and DR beta class II genes of the bovine major histocompatibility complex (MHC) were investigated by Southern blot hybridizations using human probes. Hybridizations of these probes to genomic DNA, digested with PvuII or TaqI, revealed extensive restriction fragment length polymorphisms (RFLPs). The polymorphisms were interpreted genetically by analysing a family material, comprising five sires, 48 dams and 50 offspring, and a population sample comprising 197 breeding bulls. The analysis resolved 20 DQ alpha, 17 DQ beta, 5 DR alpha and 25 DR beta RFLP types. The segregation data were consistent with simple Mendelian inheritance of the RFLPs. The analysis of the bull sample showed that it is possible to apply the RFLP method for routine typing of class II polymorphism in population samples. The linkage disequilibrium in the DQ-DR region was found to be extremely strong as only about 20 DQ and about 30 DQ-DR haplotypes were observed despite the large number of possible haplotypes. Close linkage to the blood group locus M was also found; the M' allele occurred in strong linkage disequilibrium with the class II haplotype DQ1BDR alpha 4DR beta 1B. A population genetic analysis of the DQ data in the sample of breeding bulls revealed that the frequency of homozygotes was significantly lower than Hardy-Weinberg expectation and that the allele frequency distribution deviated significantly from the one expected for selectively neutral alleles.     

Labile sex expression in plants

The range of environmental sex determination and sex changes throughout plant taxa from bryophytes and pteridophytes to spermatophytes is reviewed. Lability in sex expression occurs in many plant taxa but only in homosporous pteridophytes is labile sex the rule. Among angiosperms, labile sex appears to be more common among dioecious and monoecious plants than among hermaphrodites. However, hermaphrodites can control allocation to male and female functions by varying the relative emphasis on pollen and ovules. A majority of plants with labile sex expression are perennials, which indicates that flexibility in sex is more important for species with long life cycles. Environmental stress, caused by less-than-optimal light, nutrition, weather or water conditions, often favours maleness. The extreme lability in the sex expression of homosporous pteridophytes is suggested to be related primarily to the mating systems.     

DNA fingerprinting in horses using a simple (TG)n probe and its application to population comparisons

A synthetic polynucleotide (TG)n was hybridized to equine DNA digested with HinfI and hypervariable hybridization patterns were obtained. Mendelian inheritance of these DNA fingerprinting patterns was confirmed by pedigree analysis. Estimates of the probabilities of identical band patterns in unrelated individuals of different breeds (Swedish Trotters, North Swedish Trotters, Thoroughbreds and Arabians) were in the range 1 x 10(-4) - 7 x 10(-6). The variability derived with the (TG)n probe in horses was higher than what we obtained with several other commonly used probes for DNA fingerprinting. Individuals within breeds tended to be more similar to each other with regard to DNA fingerprint pattern than to individuals of other breeds. Moreover, a parsimony analysis made on the basis of the hybridization patterns gave clustering of individuals within breeds. The possibility of using hypervariable probes for the identification of breed-specific characters is discussed.     

Sex-related adaptive responses of Populus cathayana to photoperiod transitions

Populus cathayana Rehd., a dioecious tree species, occupies a wide range of habitats in southwest China. Both males and females were grown under two regimes of photoperiod, from mid-length to short-day photoperiod (SD shift), or to long-day photoperiod (LD shift). SD shift triggered leaf senescence in both males and females by decreasing net photosynthesis rate ( A ), transpiration ( E ), and chlorophyll pigment ( Chl ), non-structural carbohydrate (NSC) and indoleacetic acid (IAA) contents, while increasing abscisic acid (ABA), malonaldehyde (MDA) and free proline (Pro) contents. The antioxidant enzyme (e.g. POD, CAT and SOD) activities and capability to maintain ultrastructural integrity also decreased under SD shift. Males exhibited faster leaf senescence than did females, as shown by greater decreases in A , E , Chl and IAA. However, males maintained a less senescent stage than did females, as indicated by higher values of A , Chl , NSC, IAA and antioxidant enzyme activities. Conversely, A , E , NSC and IAA contents and antioxidant enzyme activities were enhanced by lower O₂^•− in females, whereas reduced by higher O₂^•− in males under LD shift. Such sex-dependent responses of P. cathayana to photoperiod transitions showed that males and females possess different adaptabilities, which may relate to sex-specific leaf senescence speed under changing environments.