In Vitro Culture of Orobanche aegyptiaca

Calli derived from seedlings of the parasitic plant Orobancheaegyptiaca were grown on enriched nutrient agar. Growth wasenhanced by the addition of 0.1 mg 1^–1 NAA and 5 % coconutmilk. The calli developed two kinds of elongated protrusions:thin ones which resemble the young root radicle and thick oneswhich resemble the adventitious roots of Orobanche plants. Bothformed pad-like structures when touching the substrate. In liquidculture, some of the calli were observed to surround isolatedcultured tomato roots. Orobanche aegyptiaca Pers., in vitro culture, germination, coconut milk, root parasite     

Carbonic Anhydrase and the Regulation of Photosynthesis

THE role of CO₂ in the regulation of photosynthetic and respiratory metabolism in plants is little understood in the unicellular alga Chlorella pyrenoidosa; for example, after autotrophic growth in high CO₂ (5·5% by volume), transfer to a CO₂ concentration about ten times less than the concentration in air results initially in low rates of photosynthesis characterized by the virtual absence of the Calvin cycle¹ of CO₂ fixation². An induction period of about 2 h is necessary before normal photosynthetic rates are established. Cells grown in air (0.03% CO₂) do not show this effect and photosynthesize at comparatively high rates even in very low concentrations of CO₂.     

The control of Aphis fabae Scop, on spring-sown field beans (Vicia faba L.)

Disulfoton or phorate granules or demeton-S-methyl, menazon and vamidothion sprays, applied once in early June as preventive treatments before heavy aphid colonies developed, gave good control of Aphis fabae Scop, on field beans. Phosalone gave relatively poor results and DDT was ineffective. Applications in June to crops sown in February and early March were made with minimal wheel damage to the crop and are known to be less harmful to bees than sprays at flowering time. Eradicant treatments with demeton-S-methyl and dimethoate sprays or with disulfoton or phorate granules on heavily infested plants during flowering were also effective, but menazon was less satisfactory. These eradicant sprays are likely to be harmful to bees, and wheel damage in late June reduced yield by 1–2 cwt/acre (125–250 kg/ha). Peak populations of 3000 aphids/plant in early July reduced yield by 6 cwt/acre (750 kg/ha) in one trial.     

Ecological, Evolutionary, and Physical Factors Influencing Aquatic Animal Respiration

Compared to air-breathers, animals that respire aquaticallyhave limited access to O₂ and their habitats are more subjectto hypoxia. Because O₂ diffuses more slowly through water thanair, animals in water experience greater diffusion boundarylayer effects on respiratory gas diffusion. While ventilationand specialized exchange surfaces mitigate O₂ diffusion limitationson respiration, most animal phyla, particularly those confinedto aquatic habitats, lack these. Diffusion limitation influencesthe ontogeny of aquatic animals and may have also shaped Precambrianmetazoans. In spite of a more limited O₂ access, aquatic animalsdisplay a much greater spectrum of respiratory adaptation, rangingfrom the loss of Hb in icefishes to the independent evolution,invention, and acquisition of Hb in many invertebrates confinedto hypoxic habitats. Three features of aquatic respiratory systemsdistinguishing them from aerial systems are the widespread occurrenceof integumental respiration, the frequent presence of combinedrespiratory and feeding surfaces, and the profound effect ofhypoxia on shaping respiratory adaptation, both in shallow waterand in the deep sea.     

Interannual variability in phytoplankton biomass and species composition in a subtropical reservoir

• 1 The interannual variability of the dominant phytoplankton populations is described in a subtropical reservoir in Queensland using weekly data for a 16-year period between 1978 and 1994. North Pine Dam, Brisbane, is in an area characterized by strong interannual variability in rainfall. This variability is linked to El Nino Southern Oscillation (ENSO) events. Between 1978 and 1994 periods of drought (during strong ENSO events) were interspersed by periods of flooding rains. Rainfall on the catchment and temperature and oxygen within the dam showed strong 40-day periodicities which also varied in strength interannually in response to ENSO events. Similar patterns of fluctuations in the 40-day periodicity have been found elsewhere in SE Australia. Seasonal cycles of stratification in the dam were a function of both hydrographic and hydrological events. Intermittent rain storms caused partial turnovers and large outflows. As much as 90% of the dam volume was exchanged in a single flood event.
• 2 The dominant phytoplankton species were similar to those frequently found in tropical and subtropical lakes and reservoirs. The phytoplankton community switched between cyanobacterial blooms (Cylindrospermopsis, Microcystis) during drought and falling water levels and diatom blooms (Aulacoseira) in response to inflows and seasonal turnovers. There appeared to be a subtle interaction between inflows, water column stability, the periodic overturns and the occurrence of the dominant species. All the dominant species showed long periods (2–4 years) of exponential increase or decrease superimposed on top of the seasonal fluctuations in abundance. These patterns of abundance led to marked interannual variability in the phytoplankton biomass. Climate variability had a major impact on the seasonal and interannual changes of the dominant phytoplankton species.
• 3 Phytoplankton biomass tended to be depressed for about 3 months after individual storm events but the data also displayed long-term lag effects (2–4 years) which destroyed any significant correlation between water residence time and biomass. Summer maxima of biomass dominated by cyanobacteria disappeared between 1985 and 1990 and were replaced by smaller winter peaks. The data presented here are not capable of unequivocally identifying the precise reason for these longer-term effects. Because of the implications for water quality management in subtropical and tropical reservoirs they warrant further study.

     

Comparison of Suitability of Great Bay, New Jersey, and Parsonage Creek, New York, for Alexandrium tamarense

ABSTRACT. Alexandrium tamarense (Lebour) Balech (= Gonyaulax tamarensis Lebour) has been widely distributed and occasionally abundant in coastal waters of Long Island, New York in recent years. However, the distribution on the New Jersey coast has been sparse and this fact cannot be explained by this dinoflagellate's ability to migrate, or by its nutritional and physiological characteristics, or by the region's general suitability for phytoplankton. Therefore, the possibility that New Jersey coastal waters might be chemically exclusionary for A. tamarense seemed worth exploring. In a limited approach, we tested for water quality detrimental to the species in one New Jersey site (Great Bay) with a series of annual assays. Parsonage Creek, Long Island, New York, was assayed for comparison; this creek is assumed to have had at least marginal suitablity for A. tamarense , based on its reported long-term presence. Results provide tentative support for our working hypothesis, i.e. Great Bay chemical water quality is generally unfavorable for A. tamarense. Inhibition of A. tamarense growth, or culture decline, occurred in both assay series, but was substantially greater in Great Bay water. Inimical water quality was the most important factor distinguishing the two sites. Chelation with EDTA had greatest overall benefit in Great Bay assays, suggesting that lower availability of a natural chelator in the bay could be a secondary factor. Assay metal response is problematic, but we believe it permits speculation that essential metals could be partially limiting to A. tamarense in Great Bay, but would not be a critical regulator.     

Axenic Cultivation of Entamoeba dispar Brumpt 1925, Entamoeba insolita Geiman and Wichterman 1937 and Entamoeba ranarum Grassi 1879

ABSTRACT. Three species of Entamoeba have been grown in axenic culture for the first time. In two cases, novel methods for adapting the organisms to growth without bacteria were employed. While E. ranarum was axenized by the classic technique of Diamond, from a monoxenic culture with Trypanosoma cruzi as the associate, both E. dispar and E. insolita were first grown in axenic culture medium supplemented with lethally irradiated bacteria. From there, E. insolita was axenized directly, but E. dispar initially required the presence of fixed bacteria. After prolonged culture under this technically axenic but unwieldy culture system, E. dispar was eventually adapted to growth in the absence of added bacteria.     

YI-S, a Casein-free Medium for Axenic Cultivation of Entamoeba histolytica, Related Entamoeba, Giardia intestinalis and Trichomonas vaginalis

ABSTRACT. Pancreatic digests of casein are major ingredients of media used in the axenic cultivation of lumen-dwelling parasitic protozoa, especially Entamoeba, Giardia , and trichomonads. The digest used almost exclusively in the development of these media, Medo-Peptone (Trypticase® BBL), has not been available since 1981. Moreover, none of dozens of similar type digests tested since then in our laboratory has proved equal to Medo-Peptone, and in the last two years it has become increasingly difficult to obtain new batches which will support even modest growth of Entamoeba histolytica . In response to this problem we have developed a casein-free medium, YI-S, consisting of a nutrient broth, vitamin mixture and serum. We recommend it as a replacement for the casein-dependent medium TYI-S-33, currently the most widely used for axenic culture of Entamoeba histolytica and other lumen-dwellers.     

Growth responses of individual roots of Opuntia ficus-indica to salinity

Responses of individual roots of the widely cultivated cactus Opuntia ficus-indica to salinity stress were evaluated using a split-root system. Three roots from a plant with at least 20 roots were isolated from the remainder of the root system and exposed to 0, 30 or 100 mol m^-3 NaCl for up to 28 d. Cortical cells became shorter and lateral root development was substantially reduced as salinity increased. Compared with the control, the increase in dry weight for the isolated roots was reduced 40% by 30 mol m^-3 NaCl and 93% by 100mol m^-3 NaCl. The sodium content of roots increased only two-fold with increasing salinity. Respiration rates of roots exposed to 30 or 100 mol m^-3 NaCl were higher than those of the control. Carbon accumulation in roots measured 2 d after exposing shoots to ¹⁴CO₂ was not initially affected by 30 mol m^-3 NaCl but was substantially reduced at 100 mol m^-3 NaCl. Thus, roots exposed to short periods of moderate salinity stress maintained sufficient carbon sink strength for continued growth of the roots. Moreover, increased salinity led to decreased efficiency of carbon usage for the expansion of root surface area.