Early growth and final yield of autumn sownVicia faba L cultivars given different forms of fertiliser N over winter

Summary Between 3 Nov. 1983 and 9 Apr. 1984, six applications of fertiliser N (ammonium, nitrate or urea) were given to four autumn sown (26 Oct. 1983)Vicia faba L cultivars, Banner Winter (BW) and Maris Beagle (MBg), cold tolerant cultivars normally sown in the autumn, and Herz Freya (HF) and Maris Bead (MBd), cold sensitive cultivars more commonly sown in the spring. The effects of additional N were determined by comparison with plants given zero-N (controls). Application of N, regardless of form, had no effect on % emergence at the first sampling (15 Dec. 1983); >90% for BW, MBg and HF, but only 40–60% for MBd. At this time the dry weight, carbon content and nitrogen content of all cultivars was approximately 20% less than that of the seed on planting. No more plants emerged after 15 Dec. 1983. Between 15 Dec. 1983 and 20 Feb. 1984, all cultivars, regardless of N treatment, showed little change in dry weight, carbon content and nitrogen content but the proportion of total plant dry weight, carbon content and nitrogen content in the cotyledons decreased while the proportions in root, stem and leaf tissue increased. On 20 Feb. 1984 there were no N effects. All cultivars but especially BW and MBg, showed progressive increases in dry weight, carbon content and nitrogen content during the period 20 Feb. 1984 to 8 May 1984. Pooled results for all four cultivars indicated that on 8 May 1984, plants given ammonium and urea had a greater dry weight, carbon content and nitrogen content than controls. At harvest (1–3 Sep. 1984), BW and MBg outyielded (g dw seed m⁻²) HF and MBd. Pooled results for all cultivars indicated that application of N regardless of form gave increased yield and an increased N concentration (mg N g⁻¹ dw) in the seed.     

Spiders in mofette fields—Survival of the toughest in natural carbon dioxide springs?

In mofette fields, natural carbon dioxide springs, organisms have to stand extreme CO₂ concentrations up to 100%. These hostile conditions are spatially small-scaled and further influenced by earth tides, wind and temperature. The present project investigated the influence of increased atmospheric CO₂ concentration on spiders as representatives of above-ground organisms by means of pitfall traps in three mofette fields, differing in habitat conditions in the Plesná valley, eastern Cheb Basin, Czech Republic.Among the 71 recorded spider species four were rarely found in the Czech Republic. A canonical correspondence analysis revealed significant influences of environmental parameters on the spider assemblages. Two groups of spiders are clearly distinguishable, one being positively influenced by humidity and the second by temperature. A cluster analysis showed distinct and congruent results: spider assemblages of pitfall traps at spots with a mean CO₂ concentration above 7.6% grouped close together and this grouping was independent of site. At >7.6% CO₂ significantly fewer individuals and species were found in comparison to areas with lower CO₂ concentration. Between 2.5 and 10% CO₂, spiders indicated increased CO₂ concentrations much more sensitively than endogeic organisms (Nematoda, Collembola) in a nearby mofette field. Unlike in nematodes, collembolans and plants, no mofettovageous or mofettophilous spiders were detected. In contrast to humidity, CO₂ concentration and temperature, the vegetation cover was not among the factors, which significantly influenced spiders. This is explained by the fact that mofettophilous plants occurred at spots where almost no spiders could live. In a field experiment, most Pardosa pullata males tested passed a 30 cm long corridor with increased carbon dioxide concentration. These results and that of pitfall traps showed that relatively large and wandering specimens respectively were able to transit moderately hostile spots. Further experiments are necessary to find out if there is any active avoidance of high-CO₂ areas by spiders.     

Determination of field output correction factors of radiophotoluminescence glass dosimeter and CC01 ionization chamber and validation against IAEA-AAPM TRS-483 code of practice

PurposeTo determine the field output correction factors of the radiophotoluminescence glass dosimeter (RPLGD) in parallel and perpendicular orientations with reference to CC01, the ionization chamber.MethodsThe dose to a small water volume and the sensitive volume of the RPLGD and the IBA-CC01 were determined for 6-MV, 100-cm SAD, 10-cm depth using egs_chamber user-code. The RPLGD in perpendicular and parallel orientations to the beam axis were studied. The field output correction factors of each detector for 0.5 × 0.5 to 10 × 10 cm² field sizes were determined. These field output correction factors were validated by comparing field output factors against data determined from IAEA-AAPM TRS-483 code of practice.ResultsThe field output correction factors of all detectors were within 5% for field sizes down to 0.8 × 0.8 cm². For 0.5 × 0.5 cm², the field output correction factors of CC01, RPLGD in perpendicular and parallel orientations differed from unity by 14%, 19%, and 5%, respectively. The percentage difference between field output factors determined using RPLGD and CC01 data, corrected using the field output correction factors determined in this work and measurements with CC01 data corrected using TRS-483, was less than 3% for all field sizes, except for the smallest field size of RPLGD in perpendicular orientation and the CC01.ConclusionsThe field output correction factors of RPLGD and CC01 are reported. The validation proves that RPLGD in parallel orientation combined with the field output correction factors is the most suitable for determining the field output factors for the smallest field used in this study.     

A new precipitation technique provides evidence for the permeability of Casparian bands to ions in young roots of corn (Zea mays L.) and rice (Oryza sativa L.)

Using an insoluble inorganic salt precipitation technique, the permeability of cell walls and especially of endodermal Casparian bands (CBs) for ions was tested in young roots of corn (Zea mays) and rice (Oryza sativa). The test was based on suction of either 100 µm CuSO₄ or 200 µm K₄[Fe(CN)₆] into the root from its medium using a pump (excised roots) or transpirational stream (intact seedlings), and subsequent perfusion of xylem of those root segments with the opposite salt component, which resulted in precipitation of insoluble brown crystals of copper ferrocyanide. Under suction, Cu²⁺ could cross the endodermis apoplastically in both plant species (although at low rates) developing brown salt precipitates in cell walls of early metaxylem and in the region between CBs and functioning metaxylem vessels. Hence, at least Cu²⁺ did cross the endodermis dragged along with the water. The results suggested that CBs were not perfect barriers to apoplastic ion fluxes. In contrast, ferrocyanide ions failed to cross the mature endodermis of both corn and rice at detectable amounts. The concentration limit of apoplastic copper was 0.8 µm at a perfusion with 200 µm K₄[Fe(CN)₆]. Asymmetric development of precipitates suggested that the cation, Cu²⁺, moved faster than the anion, [Fe(CN)₆]^4–, through cell walls including CBs. Using Chara cell wall preparations (‘ghosts’) as a model system, it was observed that, different from Cu²⁺, ferrocyanide ions remained inside wall-tubes suggesting a substantially lower permeability of the latter which agreed with the finding of an asymmetric development of precipitates. In both corn and rice roots, there was a significant apoplastic flux of ions in regions where laterals penetrated the endodermis. Overall, the results show that the permeability of CBs to ions is not zero. CBs do not represent a perfect barrier for ions, as is usually thought. The permeability of CBs may vary depending on growth conditions which are known to affect the intensity of formation of bands.     

Sodium-induced calcium deficiency in salt-stressed corn

Abstract The effect of the Na⁺/Ca²⁺ ratio in the root media on salt-stressed corn (Zea mays L. cvs DeKalb XL-75 and Pioneer 3906) was determined in greenhouse experiments. Plants grown in a complete nutrient solution salinized with 86.5 mol m^?3 NaCl exhibited severe Ca²⁺ deficiency symptoms at the four-leaf stage. The symptoms disappeared when part of the NaCl was replaced with 10 mol m^?3 CaCl₂ (Na⁺/Ca²⁺ molar ratio = 5.7). Salt stress at an iso-osmotic potential of ?0.4 MPa substantially decreased shoot growth at all solution Na⁺/Ca²⁺ ratios from 34.6 to 0.26. However, the dry weights of blades at 26 d of age were much less when plants were salinized with NaCl alone, particularly that of DeKalb XL-75 which was more susceptible to Na-induced Ca²⁺ deficiency than was Pioneer 3906. The growth of sheaths was similarity reduced by sail stress at all Na⁺/Ca²⁺ ratios. The symptoms of Ca²⁺ deficiency were correlated with low Ca²⁺ concentrations in the leaf tissue. Ca²⁺ concentrations in the developing blades of NaCl-stressed plants were much lower than in control plants. As the Na⁺/Ca²⁺ ratio in the solution was decreased, Ca²⁺ levels increased in both the blades and sheaths while Na⁺ concentrations greatly decreased. DeKalb XL-75 was much less effective than Pioneer 3906 in restricting the uptake of Na⁺. The results clearly indicate that NaCl stress may cause lesions and unique plant responses that are not manifested on agronomic plants grown on saline soils.     

Photoinactivation of δ-aminolevulinic acid dehydratase from maize by flavin mononuclotide

The -aminolevulinic acid dehydratase activity was irreversibly inactivated by irradiation of the enzyme in presence of flavin mononucleotide. The loss of enzyme activity was dependent on time of irradiation, concentration of FMN and intensity of irradiance. It required oxygen and was markedly enhanced in heavy water. The presence of levulinic acid (a competitive inhibitor of -ALAD) during irradiation prevented the inactivation considerably indicating photooxidative damage at or near the active site. Superoxide dismutase, sodium benzoate and sodium formate offered no protection, but singlet oxygen quenchers like azide and tryptophan were effective. NADH, electron donor to excited flavins, also prevented the loss of enzyme activity. These results indicate that singlet oxygen produced by light absorption of FMN was responsible for the photooxidative inhibition of the enzyme.Abbreviations ALAD -aminolevulinic acid dehydratase - FMN flavin mononucleotide - O₂ ^- superoxide - H₂O₂ hydrogen peroxide - 10₂ singlet oxygen - LA levulinic acid - PBG porphobilinogen - BSA bovine serum albumin - BME 2-mercaptoethanol - SOD superoxide dismutase - pHMB para-hydroxymercuribenzoate - DTT dithiothreitol - FAD flavin adenine dinucleotide - NADH nicotinamide adenine dinucleotide     

The influence of earthworms (Lumbricidae) on the nitrogen dynamics in the soil litter system of a deciduous forest

Summary The influence of earthworms (Aporrectodea caliginosa (Savigny) and Lumbricus castaneus (Savigny)) on the rate of nitrogen net mineralization of the soil was studied in the laboratory and in the field. The additional mineralization of nitrogen cause by the burrowing activity of the substrat feeding earthworm A. caliginosa (N _L )was directly correlated to the biomass of the lumbricids independently of their number. A rise in temperature caused an exponential increase in N _L values. The Q ₁₀ value of this process (2.18) was found to be much higher than that of the nitrogen mineralization without earthworms (Q ₁₀=1.22). At 15°C the N _L value caused by A. caliginosa was calculated to be about 250 g N g^-1 fresh body wt d^-1. Using the experimentally determined exponential relationship between temperature and N _L values, the additional nitrogen mineralization caused by a population of A. caliginosa in a beechwood on limestone was calculated to be 4.23 kg ha^-1 a^-1.In contrast to A. caliginosa the litter dwelling species L. castaneus lost considerable amounts of biomass (56%) during the 4 week incubation period. Only 1/3 of the nitrogen equivalent to the weight loss of the animals was recovered in the mineral nitrogen pool.The addition of litter (old beech leaf litter, freshly fallen beech and ash leaf litter) had a pronounced effect on both nitrogen net mineralization and N _L values of the soil. Presence of old beech leaves caused an increase in both values, wheres the other litter types effected a decrease in nitrogen net mineralization. Fragmented ash litter was found to have the most distinct effect on N _L values (-69%) and nitrogen net mineralization (-74%).     

The effect of pretransplant inoculation with VA mycorrhizal fungi on the subsequent growth of leeks in the field

Summary Leek plants were preinoculated with a mixed inoculum ofGlomus caledonium, Glomus fasciculatum andGlomus sp., and transplanted to Dazomet disinfected and untreated field plots of moderate P deficiency. Successive harvests were made until 99 days after transplanting. Preinoculated leeks attained marketable weights 25 days earlier than uninoculated leeks from untreated soil and their final dry matter yields were 5.7 and 1.5 times as high as those of uninoculated leeks from disinfected and untreated soil, respectively. Phosphorus concentration in preinoculated leeks remained highest for at least 22 and 75 days after transplanting in untreated and disinfected soil, respectively. Preinoculation had a similar, although smaller, influence on Cu and Zn concentrations. Infection levels produced by introduced and indigenous VA endophytes in leeks reached plateaus of 90% and 40%, respectively, 47 days after transplanting. It is concluded that VAM is essential to leeks grown in moderately P deficient soils, and the potential for inoculating seedlings in commercial leek production is discussed.     

Field response of tomato (Lycopersicon esculentum Mill ‘Pusa Ruby’) to inoculation with a VA mycorrhizal fungusGlomus fasiculatum and withAzotobacter vinelandii

Summary The response of tomato (Lycopersicon esculentum Mill) to inoculation with the vasicular arbuscular mycorrhizal (VAM) fungusGlomus fasiculatum andAzotobacter vinelandii singly and in combination was tested in the field. It was found thatG. fasiculatum as well asA. vinelandii significantly increased leaf area, shoot dry weight, nitrogen content phosphorus content and yield in respect to uninoculated control. While, VAM fungal treatment alone could bring about substantial increase in growth, nitrogen content, phosphorus content and yield, its combination withA. vinelandii produced additional effects on leaf area, shoot dry weight, phosphorus content and yield. Contribution No. 304/83 of Indian Institute of Horticultural Research, Bangalore-89.     

Anaerobic metabolism enzymes as markers of flooding stress in maize seeds

Maize (Zea mays L.) seeds differ in their relative tolerance to the anaerobic environment caused by flooding. Seed tolerance to flooding stress depends on cellular and metabolic processes since gross anatomical responses have not developed at the pre-emergence stage. The study reported here characterizes the activities of four anaerobic respiratory enzymes: pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), and malic enzyme (ME) in the flood-tolerant A632 and floodsusceptible Mo 17 inbred maize seeds during flooding at 10 and 25°C. Each inbred consisted of two seed lots possessing 95% and 75% germination levels. Flooding increased the activities of all four enzymes. However, no consistent correlation between anaerobic enzyme activity and flood tolerance was observed across genotype, seed quality and flooding temperature. The results indicate that it may not be feasible to use whole-seed anaerobic enzyme activities to predict maize seed performance under flooding stress. Contribution from the Soil Drainage Research Unit, USDA-ARS, Columbus, OH, in cooperation with the Ohio Agricultural Research and Development Center, The Ohio State University. OARDC Journal Article No. 66–86.