Discovery of transposable element activity among progeny of tissue culture--derived maize plants

Tissue culture-derived plants of many species have often been observed to possess both genetic and cytogenetic abnormalities. A high frequency of structurally altered chromosomes in maize (Zea mays L.) plants regenerated from tissue culture led to the prediction that newly activated transposable elements could be detected in regenerated plants. Testcrosses of 1200 progeny from 301 regenerated maize plants confirmed that ten regenerated plants from two independent embryo cell lines contained an active Actransposable element. No active Ac elements were present in the explant sources. Recovery of transposable element activity in regenerated plants indicates that some tissue culture-derived genetic variability may be the result of insertion or excision of transposable elements, or both.     

The nutrient and energy disposition of growing lambs. 2. Results of slaughter and animal carcass analysis

A total of 90 lambs (fattening hybrids of either sex of three different genetic constructions and male merino meat sheep) were butchered at the beginning (9...16 kg live weight) or at the end (29...33 kg live weight) of a growth experiment. Total body and the meat of carcass, cutlet and loin were analysed. Significant differences between the genotypes could only proved in the crude ash content. The female animals showed a significantly higher content of fat, dry matter and energy as well as a significantly lower content of crude ash--at the end of the experiment also of protein--in the total body than the male animals. The content of nutrients and energy in the total body could be much more precisely derived regressively from the corresponding content values in the meat of the carcass than from the values of cutlet and loin.     

Suitability of plant physiological methods to estimate the transpiration of agricultural crops

Transpiration is the main part of the water balance in the system soil-plant during the vegetation period. Its determination or calculation is essential for modeling of soil moisture content or solute transport. Transpiration is difficult to quantify because it is influenced by the atmosphere, the soil, and the plants. This paper describes the potential and limitations of plant physiological methods (sap flow, gas exchange, leaf water potential) to estimate the transpiration. A weighable lysimeter was used as reference method. Results are shown for corn [Zea mays L.] and rape [Brassica napus L.]) for the years 1998 and 1999. At days without rain the diurnal transpiration rates, determined by the plant physiological methods and by the lysimeter differ by less than 12%. The results demonstrate that the plant physiological methods applied are important for an understanding of the complex transpiration process. Limitations lie in the difficulties in up-scaling, and the impossibility of measurements of the absolute actual transpiration rates of agricultural crops for longer periods like months or years.     

Untersuchungen zur gezielten 15N-Substitution und -Akkumulation in der organischen Substanz ausgewählter Dauerversuchsböden

Investigation of specific ¹⁵N-substitution and accumulation in organic matter of soil from continuous fertilizer experiments Ray grass was grown in pots with upper layer substrates of longterm fertilizer experiments and fertilized with ¹⁵N labelled ammonium sulphate for three years. The ¹⁵N-labelled harvested mass was returned into the soil at the end of each year. Using the ¹⁵N tracer technique the accumulation of N in humic and nitrogen fractions was studied. After the first year, all fractions contained ¹⁵N. In sandy soil especially easily soluble compounds were formed and accumulated with ¹⁵N. On the contrary in loamy-soils more resistant fractions marked with the isotop were increased.     

Evolutionary studies on the Assulina-Valkanovia complex (Rhizopoda,Testaceafilosia) in Sphagnum and soil

Summary The taxonomy and evolution of the Assulina-Valkanovia complex were investigated in a spruce forest soil which included a Sphagnum plot (GDR, Thuringia). In both habitats Assulina muscorum occurred in two colour forms (brown and colourless) and four shapes. A quantified phenospectrum from Assulina muscorum was obtained. The four shapes were distributed differently between the brown and the colourless forms in Sphagnum and soil. The shell measurements showed statistically significant differences between the brown and the colourless forms. Even between the two brown populations there were some significant differences. Each of the four shape types of brown and of colourless Assulina can be kept in clonal cultures for some time. However, without selection, single cultures eventually revert to mixed types. The four shape types show different degrees of stability. These colour and shape forms are genotypes, which can also occur for short periods in the natural habitats. The brown populations in Sphagnum and in the soil were dominated by different shape types during the period of investigation. Valkanovia elegans cannot be distinguished from Assulina muscorum type 4, but Valkanovia can inhabit both upper and lower soil horizons, whereas Assulina and its forms lives exclusively in the upper horizon (litter). Valkanovia from the lower horizon is constant in clonal culture. The conclusion of the present investigation is that there are stable and unstable constellations within a changeable genome, which give asexual groups both a taxonomic structure and a continuum of forms. Selection can increase stability, by polygenic control of features.Dedicated to the late Prof. Dr. W. Kühnelt     

Die wirksamkeit des nitrifikationshemmers dimethylpyrazolphosphat zu winterroggen auf sandboden

Auf einem schluffigen Sandboden mit einem C_org‐Gehalt von 600 mg 100 g^?1 Boden wurde ein einjähriger Freilandmodellversuch mit Winterroggen durchgeführt. Die Kleinparzellen (50×50 cm) wurden mit umgerechnet 120 kg ha^?1 N als Ammonsulfatsalpeter einmalig bzw. in geteilter Gabe von 80+40 kg ha^?1 N gedüngt. Die Gesamt‐ und Teilgaben des Mineraldüngers waren wechselseitig mit dem Stabilisotop ¹⁵N markiert und mit dem Nitrifikationsinhibitor 3,4‐Dimethylpyrazolphosphat (DMPP, Handelsname ENTEC^®) formuliert.

Mit Beginn des Schossens setzte die Differenzierung des Biomassezuwachses gegenüber ungedüngt ein. Im Vergleich zum Standard 60 + 40 + 20 kg ha^?1 N (=100%) war der Kornund Strohertrag der 0‐Variante nur 33 bzw. 37%. Ein signifikanter Mehrertrag erzielte das Prüfglied einmalige Gabe von 120 kg ha^?1 N. Alle anderen Varianten haben sich biostatistisch nicht unterschieden.

Die Nitrifikationsverzögerung ist nach 6 Wochen beendet. Bei der 2. N‐Gabe wurde keine Wirkung durch DMPP erreicht. Der Inhibitor hat die apparente ¹⁵N‐Immobilisation erhöht, der DMPP‐Effekt betrug bis zu 24% der Dünger‐N‐Anwendung. In der Folge war zwischenzeitlich auch die Dünger‐N‐Ausnutzung bis 25% geringer. Schließlich war im N‐Entzug der DMPP‐Varianten der Anteil von Boden‐N relativ größer und in den DMPP‐freien Prüfgliedern der Anteil von Dünger‐N relativ höher.