Transpiration measurements on apple trees with an improved stem heat balance method

Since the late eighties a handy and user-friendly sap flow meter (Dynagage®) is on the market which can quantify 0205 the sap flow through intact plant stems, based on the stem heat balance method. The documentation about its accuracy and reliability, however, is still too limited to use it as a standard method in field experiments with apple trees. We therefore tested this commercial system on potted apple trees (Malus domestica L.; cv. Red Elstar and Jonagold; on rootstock M9 vf) with stem diameters of 1.8 to 4 cm. The measured sap flow was compared with mass loss measured by an automated balance, supposing the total mass loss of the trees was equal to the water loss by transpiration. The results revealed three major problems:

The impact of NO inf3 sup− loading on the freshwater macrophyte Littorella uniflora: N utilization strategy in a slow-growing species from oligotrophic habitats

The decline and disappearance of Littorella uniflora from oligotrophic waters which have become eutrophic has been associated with shading or reduced CO₂ supply. However NO _inf3 ^sup– concentrations can reach very high levels (100–2000 mmol m^–3 compared with <1–3 in oligotrophic habitats). To investigate the impact of NO _inf3 ^sup– loading alone, plants were grown under three NO _inf3 ^sup– regimes (very low, near-natural and high). The interactive effects of NO _inf3 ^sup– and photon flux density (low and high regimes) on N assimilation and accumulation, CO₂ concentrating mechanisms, C₃ photosynthesis and growth were also examined. The results were unexpected. Increased NO _inf3 ^sup– supply had very little effect on photosynthetic capacity, crassulacean acid metabolism (CAM) or lacunal CO₂ concentrations ([CO₂]_i), although there was considerable plasticity with respect to light regime. In contrast, increased NO _inf3 ^sup– supply resulted in a marked accumulation of NO _inf3 ^sup– , free amino acids and soluble protein in shoots and roots (up to 25 mol m^–3, 30 mol m^–3 and 9 mg g^–1 fresh weight respectively in roots), while fresh weight and relative growth rate were reduced. Total N content even under the very low NO _inf3 ^sup– regime (1.6–2.3%) was mid-range for aquatic and terrestrial species (and 3.1–4.3% under the high NO _inf3 ^sup– regime). These findings, together with field data, suggest that L. uniflora is not growth limited by low NO _inf3 ^sup– supply in natural oligotophic habitats, due not to an efficient photosynthetic nitrogen use but to a slow growth rate, a low N requirement and to the use of storage to avoid N stress. However the increased NO _inf3 ^sup– concentrations in eutrophic environments seem likely have detrimental effects on the long-term survival of L. uniflora, possibly as a consequence of N accumulation.     

Lipofection of Synthetic Oligodeoxyribonucleotide Having a Palindromic Sequence of AACGTT to Murine Splenocytes Enhances Interferon Production and Natural Killer Activity

A synthetic 22-mer oligodeoxyribonucleotide having an AACGTT palindrome, AAC-22, induced interferon (IFN) production and augmented the natural killer (NK) activity in murine splenocytes, whereas its analogue, ACC-22, having an ACCGGT palindrome, did not. The binding of AAC-22 to splenocytes was not different from that of ACC-22. Lipofection of AAC-22 to splenocytes remarkably enhanced IFN production and NK cell activity, whereas that of ACC-22 caused little enhancement. These results strongly suggest that the prerequisite for IFN production is not the binding of AAC-22 to the cell surface receptors, but its penetration into the spleen cells.     

Effects of short-term salinity on leaf gas exchange of the fig (Ficus carica L.)

The influence of short-term salinity (day 1–day 2: 50 mol m^–3 NaCl, day 3–day 7: 100 mol m^–3 NaCl in the nutrient solution) on leaf gas exchange characteristics were studied in two fig clones (Ficus carica L.), whose root mass had been varied in relation to the leaf area. The stomatal conductance was diminished by NaCl in the first week of treatment. NaCl slightly reduced the calculated intercellular partial pressure of CO₂. The net photosynthetic rate of plants with many roots was stimulated by NaCl on some days of the first week of treatment, whereas the net assimilation rate of the plants with few roots remained unaltered or decreased by NaCl. Only the assimilation of the salt-treated plants of one clone for some days during the first week of treatment seemed to be influenced by stomatal conductance. Nonstomatal factors were primarily responsible for the changes in CO₂ uptake in response to salt and/or root treatment. The water use efficiency increased during several days of the first week of NaCl treatment. Decreased stomatal conductance, increased water use efficiency and stimualtion of the net CO₂ assimilation rate appear to enhance salt tolerance during the first few days of salinity. ei]H Lambers     

City refuse compost as a phosphorus source to overcome the P-fixation capacity of sesquioxide-rich soils

In sesquioxide-rich soils of tropical and subtropical areas and volcanic-ash soils with high levels of active Al(Fe), large amounts of phosphate fertilizers are needed to overcome their high P-fixation capacity (quenching strategy). A greenhouse pot experiment has been used to evaluate the effectiveness of city refuse compost (CRC) as a P-source for these variable-charge soils, compared to inorganic P. Mature CRC and K₂HPO₄ were applied at rates equivalent to 125, 250, 375, 500 and 625 kg P ha^–1 to a ferrallitic soils from Tenerife Island (Andeptic Paleudult) with a high content in active Al+Fe (4.82%) and a high P-fixation capacity (87%). Perennial ryegrass (Lolium perenne L.) was grown in pots and plants were harvested at regular intervals after seedling emergence. CRC increases plant P concentration and soil labile-P proportional to the applied rate. The best results were obtained from a compost application of 30 t ha^–1 equivalent-rate, after a residence time of at least three months. An important residual effect in the supply capacity of P in relation to the phosphate fertilizer was also observed. The relative agronomic effectiveness (RAE) in comparison to K₂HPO₄ was 66% after 6 months, considering P uptake + soil labile-P. The soil P-fixation capacity was significantly reduced from a compost application of 40 t ha^–1 equivalent-rate. Competition in adsorption between organic ligands and phosphate, in combination with net mineralization of organic P in compost, might account for the high RAE value obtained. The main conclusion is that the city refuse compost could be a suitable P-amendment for resquioxic soils due to its high RAE, and the residual effect on P-supply. ei]H. Lambers     

Minimizing the effect of mineral nitrogen on biological nitrogen fixation in common bean by increasing nutrient levels

Although common bean (Phaseolus vulgaris L.) has good potential for N₂ fixation, some additional N provided through fertilizer usually is required for a maximum yield. In this study the suppressive effect of N on nodulation and N₂ fixation was evaluated in an unfertile soil under greenhouse conditions with different levels of soil fertility (low=no P, K and S additions; medium = 50, 63 and 10 mg kg^–1 soil and high = 200, 256 and 40 mg kg^–1 soil, respectively) and combined with 5, 15, 60 and 120 mg N kg^–1 soil of ¹⁵N-labelled urea. The overall average nodule number and weight increased under high fertility levels. At low N applications, nitrogen had a synergistic effect on N₂ fixation, by stimulating nodule formation, nitrogenase activity and plant growth. At high fertility and at the highest N rate (120 mg kg^–1 soil), the stimulatory effect of N fertilizer on N₂ fixation was still observed, increasing the amounts of N₂ fixed from 88 up to 375 mg N plant^–1. These results indicate that a suitable balance of soil nutrients is essential to obtain high N₂ fixation rates and yield in common beans.     

The natural history of de Brazza's monkey in Kenya

Polygynous groups of de Brazzas monkeys (Cercopithecus neglectus) were observed in the Kisere Forest Reserve between December 1987 and March 1989. Total number of contact hours was 528. Three troops numbered 11, 13, and 16 monkeys. Three solitary adult males were seen. All troops had a single adult male, at least three adult females, and juveniles. Five births occurred in the course of the study. Home range varied from 4.1 to 6 ha, and flooded areas of the forest were heavily used. This species was only found near rivers and spent more than 50% of the time below 5 m. Daily path length ranged from 330 to 1001 m. The de Brazza's monkeys were mainly frugivorous, but leave and invertebrates also formed a substantial part of the diet. Other guenons avoided de Brazza's, which did not join polyspecific interactions.     

Metabolic engineering of Clostridium acetobutylicum ATCC 824 for increased solvent production by enhancement of acetone formation enzyme activities using a synthetic acetone operon

The ability to genetically alter the product-formation capabilities of Clostridium acetobutylicum is necessary for continued progress toward industrial production of the solvents butanol and acetone by fermentation. Batch fermentations at pH 4.5, 5.5, or 6.5 were conducted using C. acetobutylicum ATCC 824 (pFNK6). Plasmid pFNK6 contains a synthetic operon (the "ace operon") in which the three homologous acetone-formation genas (adc, ctfA, and ctfB) are transcribed from the adc promoter. The corresponding enzymes (acetoacetate decarboxylase and CoA-transferase) were best expressed in pH 4.5 fermentations. However, the highest levels of solvents were attained at pH 5.5. Relative to the plasmid-free control strain at pH 5.5, ATCC 824 (pFNK6) produced 95%, 37%, and 90% higher final concentrations of acetone, butanol, and ethanol, respectively; a 50% higher yield (g/g) of solvents on glucose; and a 22-fold lower mass of residual carboxylic acids. At all pH values, the acetone-formation enzymes were expressed earlier with ATCC 824 (pFNK6) than in control fermentations, leading to earlier induction of acetone formation. Furthermore, strain ATCC 824 (pFNK6) produced butanol significantly earlier in the fermentation and produced significant levels of solvents at pH 6.5. Only trace levels of solvents were produced by strain ATCC 824 at pH 6.5. Compared with ATCC 824, a plasmid-control strain containing a vector without the ace operon also produced higher levels of solvents [although lower than those of strain ATCC 824 (pFNK6)] and lower levels of acids. Strains containing plasmid-borne derivatives of the ace operon, in which either the acetoacetate decarboxylase or CoA-transferase alone were expressed at elevated levels, produced acids and solvents at levels similar to those of the plasmid-control strain. (c) 1993 John Wiley & Sons, Inc.     

Complete ammonia oxidization in agricultural soils: High ammonia fertilizer loss but low N2O production

The contribution of agriculture to the sustainable development goals requires climate-smart and profitable farm innovations. Increasing the ammonia fertilizer applications to meet the global food demands results in high agricultural costs, environmental quality deterioration, and global warming, without a significant increase in crop yield. Here, we reported that a third microbial ammonia oxidation process, complete ammonia oxidation (comammox), is contributing to a significant ammonia fertilizer loss (41.9 ± 4.8%) at the rate of 3.53 ± 0.55 mg N kg⁻¹ day⁻¹ in agricultural soils around the world. The contribution of comammox to ammonia fertilizer loss, occurring mainly in surface agricultural soil profiles (0–0.2 m), was equivalent to that of bacterial ammonia oxidation (48.6 ± 4.5%); both processes were significantly more important than archaeal ammonia oxidation (9.5 ± 3.6%). In contrast, comammox produced less N₂O (0.98 ± 0.44 μg N kg⁻¹ day⁻¹, 11.7 ± 3.1%), comparable to that produced by archaeal ammonia oxidation (16.4 ± 4.4%) but significantly lower than that of bacterial ammonia oxidation (72.0 ± 5.1%). The efficiency of ammonia conversion to N₂O by comammox (0.02 ± 0.01%) was evidently lower than that of bacterial (0.24 ± 0.06%) and archaeal (0.16 ± 0.04%) ammonia oxidation. The comammox rate increased with increasing soil pH values, which is the only physicochemical characteristic that significantly influenced both comammox bacterial abundance and rates. Ammonia fertilizer loss, dominated by comammox and bacterial ammonia oxidation, was more intense in soils with pH >6.5 than in soils with pH <6.5. Our results revealed that comammox plays a vital role in ammonia fertilizer loss and sustainable development in agroecosystems that have been previously overlooked for a long term.