PHOTOSYNTHETIC ACCLIMATION AND DECREASED CHLOROPHYLL(A + B) CONCENTRATIONS OCCUR IN NITROGEN-SUFFICIENT TOBACCO LEAVES IN RESPONSE TO CARBON DIOXIDE ENRICHMENT

Effects of carbon dioxide (CO₂) enrichment on plant growth and on nitrogen partitioning were examined in tobacco (Nicotiana tabacum L. cv. ‘Samsun’). Dry matter, leaf area and specific leaf weight were unchanged (P > 0.05) by CO₂ enrichment. Total soluble protein, soluble amino acids and inorganic nitrate also were unaffected by CO₂ enrichment (P > 0.05). Leaf chlorophyll (a + b) levels decreased 13% (P ≤ 0.05) in response to CO₂ enrichment. The diurnal accumulation of soluble amino acids was delayed and the initial slope of the A/C _i response curve was decreased 14% in the elevated compared to the ambient CO₂ treatment. The above findings showed that CO₂ enrichment affected leaf chlorophyll levels, diurnal soluble amino acid metabolism and photosynthetic responses to low intercellular CO₂ concentrations even though the plants were nitrogen sufficient. Inadequate nitrogen fertility cannot explain all of the effects of CO₂ enrichment on photosynthesis by tobacco leaves.     

Iron chlorosis development and growth response of peach rootstocks to bicarbonate 1

For dicots, bicarbonate (HCO₃‐) is regarded as a main factor in the induction of iron (Fe) chlorosis in calcareous soils, and sand and solution culture. In sand culture experiments, peach [Prunus persica (Batsch) L.] rootstock developed chlorosis only when HCO₃‐ levels were equal to or higher than 6 mM. Above this level, chlorosis increaeed as HCO3‐ level was increased. In spite of the lack of chlorosis at to or below 6 mM of HCO₃‐, large growth reductions (40–60% reduction in fresh shoot weight) were seen in all rootstocks, although the tolerant rootstock had less reduction than the more susceptible rootstocks. Shoot growth was affected by HCO₃‐ more than was root growth.     

Reduction of ferric iron by tumorous crown gall tissue is associated with cells modified by agro‐bacterium tumefaciens

Iron (Fe) uptake and use in plants is genetically controlled and physiological mechanisms such as Fe reduction are induced during Fe‐deficiency stress to make it available. Transfer of DNA into the cell genome by Agrobacterium tumefaciens alters physiological processes and causes undifferentiated growth. Tumor cells in sunflower (Helianthus annus L. cv. Mammoth Russian) show enhanced Fe reduction compared to normal stem tissue in a manner similar to root cells in plants that are genetically switched on or off to manage Fe acquisition. This study addresses whether alterations caused by the DNA transfer from A. tumefaciens result in Fe reduction or whether A. tumefaciens inoculum alone reduces Fe. Reduction of Fe was quantified from A. tumefaciens inoculum and from uninoculated or inoculated sunflower stem tissues daily over a 14‐day period. Neither A. tumefaciens inoculum nor uninoculated stem tissue alone activated massive Fe reduction. High rates of Fe reduction were associated with the proliferation of cells modified by A. tumefaciens. The mechanisms that transformed normal tissue to uncontrolled tumor growth appeared to be linked to active Fe reduction. These modified cells may provide a key to locating and understanding the genetic control of the Fe reduction process in plant cells. Our results suggest a critical role for Fe in development of tumorous tissues and raises the question of whether other tumor cells induce similar mechanisms for Fe acquisition.     

Analysis of iron‐deficiency induced hydrogen release by plant roots using chemical equilibrium and pH‐stat methods

Iron (Fe) is an essential nutrient for plants. When Fe‐deficient, most dicotyledonous and non‐graminaceous monocotyledonous plants exhibit Fe‐deficiency stress responses, which may include proton (H⁺) release from roots. Proton release is considered to be one of the factors contributing to plant Fe‐deficiency resistance. Several methods, including the pH‐stat, back‐titration, and pH‐drift procedures, have been used to evaluate the Fe‐deficiency induced acidification process. These methods actually determine total net acidity release, not H⁺ release. A method, based on the principles of chemical equilibrium, for the analysis of net free H⁺ release is introduced in this paper. By comparing results of the chemical equilibrium method with those of a method measuring total net acidity release, such as the back‐titration method, it is possible to determine the relative role of free H⁺ and organic acid to total acidity release. The pH‐stat method for analysis of total net acidity release, in which the pH of the incubation solution is held constant, eliminates the influence of pH decrease during plant incubation and thus results in a more accurate measurement of Fe‐deficiency induced acidity release. The advantages and disadvantages of each individual method are discussed.     

Der einfluss Klimatischer Faktoren auf die Ertragsbildung im ISDV‐Standort vergleich Grüppenbühren‐Rauischholzhausen‐Puch

Im Standortvergleich zwischen den Standorten Grüppenbühren bei Oldenburg, Rauischholzhausen bei Gießen und Puch bei München werden in der 1. Mitteilung Zusammenhänge zwischen mittleren Trockenmasseerträgen bei Winterweizen einerseits und den Klima‐Elementen Temperatur, Niederschlag und Strahlungsbilanz andererseits aufgezeigt. Die der Auswertung zugrundeliegenden Daten wurden innerhalb der "Internationalen Stickstoff‐Dauerdüngungs‐ Versuche ISDV”; ermittelt. Die Versuchsreihe ISDV wurde auf insgesamt 24 Standorten in Europa als Stickstoffsteigerungsversuch (6 N‐Stufen ohne und 3 N‐Stufen mit organischer Düngung) mit einer dreigliedrigen Fruchtfolge in den Jahren 1972–1983 von der Internationalen Arbeitsgemeinschaft für Bodenfruchtbarkeit innerhalb der Internationalen Bodenkundlichen Union konzipiert und betreut. Die Ergebnisse lassen sich wie folgt zusammenfassen:

Die Ergebnisse lassen sich wie folgt zusammenfassen:

? Der Einfluss der Klima‐Elemente auf die untersuchten Ertragskomponenten differiert deutlich zwischen den Standorten.

? Eine unterschiedliche Wirksamkeit in den N‐Düngungsvarianten konnte am Standort Grüppenbühren und Rauischholzhausen in der Tendenz aufgezeigt werden.

? Für den Standort Puch war kein gesicherter Einfluss festzustellen.

? Weitere Auswertungsschritte auf der Ebene der Monatsdaten und Pentadenwerte sind vorgesehen.     

Diurnal patterns of nitrate assimilation in Kentucky bluegrass

Kentucky bluegrass (Poapratensis L.) is a major C₃‐type forage and turfgrass, but it is less efficient than many grasses in utilizing nitrogen(N). To determine how this grass can accommodate its greater N need, diurnal patterns of nitrate reductase activity (NRA) and nitrite reductase activity (NiRA) in its leaves and roots were examined and compared with those in barley (Hordeum vulgare L.). Plants were grown under greenhouse or growth room conditions and assayed for NRA and NiRA by optimized in vivo methods. The diurnal patterns of NRA and NiRA indicated that Kentucky bluegrass could assimilate nitrate during the night at rates greater than or similar to those during the day. Leaf NRA of Kentucky bluegrass was minimal approximately 4 and 10 h after illumination commenced and increased at night. The diurnal pattern of leaf NRA among Kentucky bluegrass cultivars did not differ significantly. In roots, NRA of Kentucky bluegrass was high in the morning and decreased sharply during the afternoon and evening, but increased again late at night. Unlike Kentucky bluegrass, barley exhibited greater leaf NRA during the day than during the night and exhibited the greatest activity 6 or 10 h after illumination commenced. In both species, the equilibrium leaf nitrate pool was 20 to 30 times larger than the ammonium pool and 3, 000 to 13, 000 times larger than the nitrite pool. Leaf nitrate pool size showed a diurnal pattern complementary to that of leaf NRA. Our results suggest that a nighttime N use strategy might exist in Kentucky bluegrass.     

Chemical Amendments and Process Controls To Reduce Ammonia Volatilization During In-House Composting

Composting inside high-rise, caged layer facilities can produce atmospheric ammonia (NH₃) concentrations exceeding standards for human and poultry health. Control measures that reduce NH₃ volatilization are necessary for in-house composting to be sustainable. Due to differences specific to in-house composting — low carbon to nitrogen ratios of composting material, continuous manure addition, and frequent turning — it is not known whether NH₃ control measures used previously for poultry manure will work. The objectives of this study were to evaluate various amendment and process controls on NH₃ produced during simulated in-house composting in the lab, and to evaluate select chemical control measures during composting inside a high-rise layer facility. Ten amendments (aluminum sulfate; chloride salts of aluminum, calcium, magnesium, and potassium; gypsum; sodium bisulfate; zeolite (clinoptilolite); straw; and cellulose) and four process controls (moisture; temperature; turning frequency; and particle size) were evaluated in lab incubations in 1 L vessels wherein samples of poultry manure compost were incubated to simulate composting. Vials of boric acid solution were used to capture NH₃ evolved during incubations. With the exception of zeolite and cellulose, all amendments reduced NH₃ capture. Low moisture and temperature also reduced NH₃ capture, although managing temperature and moisture to achieve low NH_g would adversely impact microbial activity and other desired benefits of composting. When evaluated inhouse, aluminum sulfate, calcium chloride and magnesium chloride did not reduce NH evolution from compost measured on three different dates with a gas sensor. Spatial variability along treated segments of windrow apparently masked amendment effects. At the end of a six-week composting cycle, total nitrogen content was higher in compost treated with aluminum sulfate than control or chloride salt treatments. Aluminum sulfate and process controls such as moisture content, carbon source and particle size have potential to reduce NH₃ loss from poultry manure composted inside high-rise layer structures. In-house compost management to reduce NH₃ volatilization must consider the cost of amendments, effectiveness, and impacts on the composting process.