Capitalizing on multi-element interactions through balanced nutrition — A pathway to improve nitrogen use efficiency in China,India and North America

A viable option for increasing nitrogen (N) use efficiency and mitigation of negative impacts of N on the environment is to capitalize on multi-element interactions through implementation of nutrient management programs that provide balanced nutrition. Numerous studies have demonstrated the immediate efficacy of this approach in the developing regions like China and India as well as developed countries in North America. Based on 241 site-years of experiments in these countries, the first-year N recovery efficiency (RE) for the conventional or check treatments averaged 21% while the balanced treatments averaged 54% RE, for an average increase of 33% in RE due to balanced nutrition. Effective policies to promote adoption are most likely those that enable site-specific approaches to nutrient management decisions rather than sweeping, nation-wide incentives supporting one nutrient over another. Local farmers, advisers and officials need to be empowered with tools and information to help them define necessary changes in practices to create more balanced nutrient management.

     

ULTRASTRUCTURE AND ECOLOGY OF AUREOCOCCUS ANOPHAGEFERENS GEN. ET SP. NOV. (CHRYSOPHYCEAE): THE DOMINANT PICOPLANKTER DURING A BLOOM IN NARRAGANSETT BAY,RHODE ISLAND,SUMMER 19851

Observations of a marked cessation of feeding in filter feeding animals maintained in flowing Narragansett Bay seawater in June 1985 drew our attention to a bloom of a golden alga 2 μm in diameter at unprecedented populations of 10⁹ cells. L^?1. This picoplankter lacked morphological features useful in discriminating it from other similar sized forms with either phase contrast or epifluorescence light microscopy. Natural populations of picoplankton, obtained from the height of the bloom until its decline, were examined in thin section with transmission electron microscopy. A cell with a single chloroplast, nucleus, and mitochondrion and an unusual exocellular polysaccharide-like layer was apparently the bloom alga. The ultrastructure of this alga is consistent with that of the Chrysophyceae, and a new genus and species, Aureococcus anophagefferens is described. Attempts to grow this previously unrecognized picoplanktonic alga as an obligate phototroph failed and only yielded cultures of other previously described picoalgae. Facultative and obligate phagotrophic protists with ingested cells of Aureococcus were only observed as the bloom waned and minute diatoms became common. Cells of A. anophagefferens with virus particles typical for picoalgae occurred throughout the bloom. Populations of the usually dominant photosynthetic picoplankter, the cyanobacterium Synechococcus Nägeli, were depressed during the bloom. This could be due in part to selective grazing on Synechococcus rather than Aureococcus by elevated populations of Calycomonas ovalis Wulff which accompanied the algal bloom.     

SECRETORY VESICLE FORMATION IN GLANDULAR TRICHOMES OF CANNABIS SATIVA (CANNABACEAE)

Formation of secretory vesicles in the noncellular secretory cavity of glandular trichomes of Cannabis saliva L. was examined by transmission electron microscopy. Two patterns of vesicle formation occurred during gland morphogenesis. 1) During initial phases of cavity formation small hyaline areas arose in the wall near the plasma membrane of the disc cell. Hyaline areas of elongated shape and different sizes were distributed throughout the wall and adjacent to the secretory cavity. Hyaline areas increased in size, some possibly fusing with others. These hyaline areas, possessing a membrane, moved into the cavity where they formed vesicles. As membraned vesicles they developed a more or less round shape and their contents became electron-dense. 2) During development of the secretory cavity and when abundant secretions were present in the disc cells, these secretions passed through the wall to accumulate as membraned vesicles of different sizes in the cavity. As secretions emerged from the wall, a membrane of wall origin delimited the secretory material from cavity contents. Vesicles released from the wall migrated in the secretory cavity and contacted the sheath where their contents permeated into the subcuticular wall as large or diffused quantities of secretions. In the subcuticular wall these secretions migrated to the wall–cuticle interface where they contributed to structural thickening of the cuticle. This study demonstrates that the secretory process in glands of Cannabis involves not only secretion of materials from the disc cell, but that the disc cell somehow packages these secretions into membraned vesicles outside the cell wall prior to deposition into the secretory cavity for subsequent structural development of the sheath.     

EFFECTS OF SILICON DEFICIENCY ON LIPID COMPOSITION AND METABOLISM IN THE DIATOM CYCLOTELLA CRYPTICA1

The effects of silicon deficiency on the metabolism and composition of lipids in Cyclotella cryptica T13L Reimann, Lewin, and Guillard were examined. Silicon-deficient cells had higher levels of neutral lipids (primarily triacylglycerols) and higher proportions of saturated and monounsaturated fatty acids than silicon-replete cells. After 4 h of silicon deficiency, the percentage of newly assimilated NaH¹⁴CO₃ partitioned into lipids increased from 27.6% to 54.1%, whereas the percentage partitioned into chrysolaminarin decreased from 21.6% to 10.6%. In addition, pulse-chase experiments with NaH¹⁴CO₃ indicated that the amount of ¹⁴C in the total cellular lipid fraction increased by 32% after 12 h of silicon deficiency despite the absence of additional photoassimilable ¹⁴C. Therefore, the accumulation of lipids in response to silicon deficiency appears to be due to two distinct processes: (a) an increase in the proportion of newly assimilated carbon partioned into lipids, and (2) a slow conversion of previously assimilated carbon from non-lipid compounds into lipids     

The use of clip cages to restrain insects reduces leaf expansion systemically in Rumex obtusifolius

Abstract. 1. Clip cages have been used widely by experimental ecologists to contain insects on plants.
2. Under controlled conditions, the effect of applying clip cages alone and clip cages and the chrysomelid beetle Gastrophysa viridula on systemic leaf expansion of Rumex obtusifolius was investigated. Treatments were applied to the fully expanded fourth leaf and expansion of leaf 8 was measured over a period of 22 days.
3. The application of clip cages reduced the rate at which leaf area increased and led to reductions in final leaf areas.
4. Clip cages have systemic effects on plant development and these effects are sustained even after the clip cage is removed. Investigators should take this into account in designing experiments.     

Effect of gibberellic acid on pod set in soybean

Field-grown soybean plants (Glycine max (L.) Merr. cv. Evans) were treated with gibberellic acid (GA₃; 10gl^–1) and/or (2-chloroethyl)-trimethylammonium chloride (CCC; 0.8gl^–1) in 1983 and 1984, and subsequent anthesis, pod set, seed size, seed number, and seed yield were determined at one node. The treatments were applied to five leaves in the center of each plant (typically leaves 7–11) and reproductive development at the node in the center of those leaves was monitored. Gibberellin A₃ applied Early (about 3d before anthesis of the first flower at the monitored node) had no effect on the number of flowers produced, but decreased the fraction of flowers that set pods in both experimental years (by 32% in 1983 and 76% in 1984). Seed size was slightly decreased by the GA₃ treatment in 1983 but not in 1984. The Middle GA₃ treatment (applied about 3 days after the Early treatment) slightly decreased the number of pods set; and Late treatments (9 days after) had no effect. None of the monitored parameters were affected by CCC.The Early experiments were repeated with two additional genotypes, Lincoln and T210. Genotype T210 is a single-gene, dwarf mutant of Lincoln whose stem elongation and leaf expansion are insensitive to GA₃. Gibberellin A₃ affected the reproductive parameters in Lincoln very similarly to Evans but those in T210 were unaffected. This indicates that GA₃ exerts its effect by increasing the mass of vegetative tissue and thus diverting assimilates away from the pods. However, since the mutation in T210 might affect a receptor that is in flowers as well as shoots, it is possible that GA₃ exerted its effect on the normal genotypes directly on the developing pods, rather than indirectly by diverting photoassimilates.     

Denitrification with methanol in the presence of high salt concentrations and at high pH levels

Summary In the combined ion exchange/biological denitrification process for nitrate removal from ground water, in which nitrate is removed by ion exchange, the resins are regenerated in a closed circuit by a biological denitrification reactor. This denitrification reactor eliminates nitrate from the regenerant. Methanol is used as electron donor for biological denitrification. To obtain sufficient regeneration of the resins within a reasonable time, high NaCl or NaHCO₃ concentrations (10–30 g/l) in the regenerant are necessary. High NaHCO₃ concentrations affected the biological denitrification in three ways: a) a slight decrease in denitrification capacity (30%) was observed; b) the yield coefficient and CH₃OH/NO₃ ^-–N ratio decreased. When high NaHCO₃ concentrations (above 10g NaHCO₃/l) were used, the yield coefficient was 0.10–0.13 g VSS/g NO₃ ^-–N and the CH₃OH/NO₃ ^-–N ratio was 2.00–2.03 g/g; c) high NaHCO₃ concentrations influenced nitrite production. Nitrite is an intermediate product of biological denitrification and with rising NaHCO₃ concentrations nitrite accumulation was suppressed. This was explained by the effect of high NaHCO₃ concentrations on the pH in the microenvironment of the denitrifying organisms. High NaCl concentrations also resulted in a slight decrease in denitrification capacity, but the second and third effects were not observed in the presence of high NaCl concentrations.Although the pH in the regenerant will rise as a result of biological denitrification, the capacity of a denitrification reactor did not decrease significantly when a pH of 8.8–9.2 was reached.