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     

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.     

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.     

Eutrophication and macroalgal blooms in temperate and tropical coastal waters: nutrient enrichment experiments with Ulva spp.

Receiving coastal waters and estuaries are among the most nutrient‐enriched environments on earth, and one of the symptoms of the resulting eutrophication is the proliferation of opportunistic, fast‐growing marine seaweeds. Here, we used a widespread macroalga often involved in blooms, Ulva spp., to investigate how supply of nitrogen (N) and phosphorus (P), the two main potential growth‐limiting nutrients, influence macroalgal growth in temperate and tropical coastal waters ranging from low‐ to high‐nutrient supplies. We carried out N and P enrichment field experiments on Ulva spp. in seven coastal systems, with one of these systems represented by three different subestuaries, for a total of nine sites. We showed that rate of growth of Ulva spp. was directly correlated to annual dissolved inorganic nitrogen (DIN) concentrations, where growth increased with increasing DIN concentration. Internal N pools of macroalgal fronds were also linked to increased DIN supply, and algal growth rates were tightly coupled to these internal N pools. The increases in DIN appeared to be related to greater inputs of wastewater to these coastal waters as indicated by high δ¹⁵N signatures of the algae as DIN increased. N and P enrichment experiments showed that rate of macroalgal growth was controlled by supply of DIN where ambient DIN concentrations were low, and by P where DIN concentrations were higher, regardless of latitude or geographic setting. These results suggest that understanding the basis for macroalgal blooms, and management of these harmful phenomena, will require information as to nutrient sources, and actions to reduce supply of N and P in coastal waters concerned.     

Single‐nucleotide Polymorphism of CD36 Locus and Obesity in European Adolescents

CD36 is a membrane receptor with a wide variety of functions, including the regulation of energy metabolism, fat storage, and adipocyte differentiation. To assess the relationship between CD36 gene single‐nucleotide polymorphisms (SNPs) and obesity in adolescents, we evaluated the relationship between CD36 SNPs and the risk of obesity in a case–control study composed of 307 obese (age = 15.0 ± 1.1 years) and 339 normal‐weight adolescents (age = 14.6 ± 1.1 years). To validate the results, we assessed the relation between the same SNPs and percentage of body fat (BF%) and BMI in 1,151 European adolescents (age = 14.8 ± 1.4 years). SNPs with a minor allele frequency >0.10 were selected to tag CD36. Genotyping was performed on an Illumina system. Four SNPs (rs3211867, rs3211883, rs3211908, and rs1527483) were associated with increased risk of obesity in the case–control study (odds ratio (OR) (95% confidence interval)): 1.96 (1.26–3.04], P = 0.003; 1.73 (1.16–2.59), P = 0.007; 2.42 (1.47–4.01), P = 0.0005 and 1.95 (1.25–3.05), P = 0.003, respectively). The same four SNPs were associated with higher BMI (P < 0.05) and BF% (P < 0.04) in the validation study. Further analyses identified a haplotype (frequency: 0.05) carrying the minor allele of these SNPs as being associated with obesity (OR: 2.28; P = 0.0008) in the case–control study and with excess adiposity (i.e., higher BF% (P = 0.03) and BMI (P = 0.04)) in the validation study. Our data suggest that genetic variability at the CD36 gene locus could be associated with body weight variability in European adolescents but these findings require replication.     

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.