Tolerance of combined submergence and salinity in the halophytic stem-succulent Tecticornia pergranulata

Background and Aims

Habitats occupied by many halophytes are not only saline, but are also prone to flooding. Few studies have evaluated submergence tolerance in halophytes.

Methods

Responses to submergence, at a range of salinity levels, were studied for the halophytic stem-succulent Tecticornia pergranulata subsp. pergranulata (syn. Halosarcia pergranulata subsp. pergranulata). Growth and total sugars in succulent stems were assessed as a function of time after submergence. Underwater net photosynthesis, dark respiration, total sugars, glycinebetaine, Na⁺, Cl⁻ and K⁺, in succulent stems, were assessed in a NaCl dose-response experiment.

Key Results

Submerged plants ceased to grow, and tissue sugars declined. Photosynthesis by succulent stems was reduced markedly when underwater, as compared with in air. Capacity for underwater net photosynthesis (P_N) was not affected by 10–400 mm NaCl, but it was reduced by 30 % at 800 mm. Dark respiration, underwater, increased in succulent stems at 200–800 mm NaCl, as compared with those at 10 mm NaCl. On an ethanol-insoluble dry mass basis, K⁺ concentration in succulent stems of submerged plants was equal to that in drained controls, across all NaCl treatments. Na⁺ and Cl⁻ concentrations, however, were elevated in stems of submerged plants, but so was glycinebetaine. Submerged stems increased in succulence, so solutes would have been ‘diluted’ on a tissue-water basis.

Conclusions

Tecticornia pergranulata tolerates complete submergence, even in waters of high salinity. A ‘quiescence response’, i.e. no shoot growth, would conserve carbohydrates, but tissue sugars still declined with time. A low K⁺ : Na⁺ ratio, typical for tissues of succulent halophytes, was tolerated even during prolonged submergence, as evidenced by maintenance of underwater P_N at up to 400 mm NaCl. Underwater P_N provides O₂ and sugars, and thus should enhance survival of submerged plants.Key words: Flooding, halophyte, Halosarcia pergranulata, inundation, inland salt marsh, respiration, Salicornioideae, salt lake, submergence–salinity interaction, tissue solutes, underwater net photosynthesis     

Separation of grassland litter and ecosite influences on seasonal soil moisture and plant growth dynamics

While plant litter is known to regulate soil moisture, little is known about the extent to which litter impacts moisture over and above the physical environment (i.e., ecosite) throughout the growing season, particularly in cool-temperate grasslands where moisture is considered less limiting for plant growth. In this study, we examined the relative impact of litter and ecosite on growing season soil moisture in a northern rough fescue (Festuca hallii) grassland. We also examined the relationship between litter and plant biomass throughout the growing season, including linkages between litter, plant growth, and the effects of litter on microclimate. During May, only ecosite was found to be associated with soil moisture, with a similar finding for plant biomass. Litter became important in maintaining greater soil moisture in June and July, however, likely through its corresponding negative impact on soil temperature and associated evaporation. In general, litter had a stronger and more consistent influence on soil moisture than ecosite. Finally, litter had a positive relationship with above-ground biomass, but only during June and July, the same months when litter exhibited the strongest relationship with soil moisture. Litter therefore appears to promote mid-season plant growth in these temperate grasslands, presumably through its ability to reduce evaporation and maintain greater soil water during seasonal moisture limitations.     

Modelling of continuous microbial cultivation taking into account the memory effects

The problem of chemostat dynamics modelling for the purpose of control is considered. The "memory" of the culture is explicitly taken into account. Two possibilities for improving the quality of the proposed modelling approaches are discussed. A general model that accounts for the culture `memory' by means of different `memory' functions in the expressions of the specific growth rate and of the specific consumption rate and a polynomial function of the substrate concentration for the yield factor is proposed. The case where the maintenance energy is taken into account is also discussed. Two modifications of the general model (w-type and S-type) are presented. A zero-order `memory' function and a i-function with delay are applied in order to describe the `memory' effects. Continuous growth of the strain Saccharomyces cerevisiae on a glucose limited medium is considered as a case study. Detailed investigations of the variety of models, derived from the general model by applying different `memory' functions and different assumptions are carried out. The results are compared with those previously reported for the same process. It is shown that a significant improvement in predicting the substrate dynamics (not accompanied by any decrease in the quality of the model with respect to the biomass concentration) could be achieved, involving a first- or second-order polynomial function for the yield factor. It is also shown that the quality of the model mainly depends on the way that `memory' function is incorporated. The detailed investigations give priority to the w-type models. In this case past values of both biomass and substrate variables are considered. The time delay models with pure (constant) delay and those which account for the culture `memory' by zero-order `memory' function (adaptability parameter) are compared with respect to their utilization for the purpose of model-based control.     

A Reed-Frost model taking into account uncertainties in the diagnostic of the infection

In this paper, we model the epidemic course of a pathogen infection within a semi-closed group which generates clinical signals which do not necessarily permit its ready and certain identification. Typical examples of such a pathogen are influenza-type viruses. We allow for time-varying infectivity levels among individuals, and model the probability of infection per contact as a function of the clinical signals. In order to accomplish this, we introduce a modified chain-binomial Reed-Frost model. We obtain an expression for the basic reproduction ratio and determine conditions which guarantee that the epidemic does not survive in the long-term. These conditions being functions of the signal’s distribution, they can be used to design and evaluate interventions, such as treatment protocols.     

Herbivore impact on moss depth, soil temperature and arctic plant growth

We provide evidence for a mechanism by which herbivores may influence plant abundance in arctic ecosystems. These systems are commonly dominated by mosses, the thickness of which influences the amount of heat reaching the soil surface. Herbivores can reduce the thickness of the moss layer by means of trampling and consumption. Exclusion of grazing by barnacle geese and reindeer over a period of 7?years at Ny-Ålesund, Spitsbergen, caused an increase in the thickness of the moss layer, and a reduction in soil temperature of 0.9?°C. Soil temperature was negatively correlated with moss-layer thickness across sites, with highest soil temperatures where moss layers were shallow. We found that moss growth did not respond to experimental manipulation of soil temperature, but the grass Poa arctica (arctic meadow-grass) and the dicot Cardamine nymanii (polar cress) suffered a 50% reduction in biomass when growing in chilled soils.     

Effect of soil and water salinity on tomato growth

The yield of tomatoes for processing (Lycopersicon esculentum var. VF145 B. 7879) grown in artificially salinized plots, was reduced by 10% for every 1.5 mmhos/cm increase in EC_e above 2.0 mmhos/cm. Yield reduction was the same for equal mean soil salinities regardless of leaching and the rate of salt accumulation in the soil. Total soluble solids content increased with increasing salinity to offset, to a large extent, the yield reduction. Reduction in water uptake, as a result of an increase in soil salinity was directly related to fruit yield reduction, but not to stover yield which was not affected by salinity. The salt tolerance during germination was similar to subsequent growth in the salinity range of this experiment.Contribution from the Agricultural Research Organization. The Volcani Center, Bet Dagan, Israel 1972. Series, No. 2225-E.Contribution from the Agricultural Research Organization. The Volcani Center, Bet Dagan, Israel 1972. Series, No. 2225-E.     

Effects of temperature and salinity on Vibrio cholerae growth

Laboratory microecosystems (microcosms) prepared with a chemically defined sea salt solution were used to study effects of selected environmental parameters on growth and activity of Vibrio cholerae. Growth responses under simulated estuarine conditions of 10 strains of V. cholerae, including clinical and environmental isolates as well as serovars O1 and non-O1, were compared, and all strains yielded populations of approximately the same final size. Effects of salinity and temperature on extended survival of V. cholerae demonstrated that, at an estuarine salinity (25%) and a temperature of 10 degrees C, V. cholerae survived (i.e., was culturable) for less than 4 days. Salinity was also found to influence activity, as measured by uptake of 14C-amino acids. Studies on the effect of selected ions on growth and activity of V. cholerae demonstrated that Na+ was required for growth. The results of this study further support the status of V. cholerae as an estuarine bacterium.     

Use of the systems approach in modeling the growth dynamics of a microbial biomass taking into account the cell division process]

The possibility of using systemic approach in the construction of the mathematical model allowing for changes in the biomass and the number of cells is shown. Definite rules were followed in the process of construction, calculations were made with the use of a computer. The satisfactory coincidence of rated and experimental data was achieved (in this instance, E. coli M17 were used).     

Effectiveness of selection taking into account differences in parental couples for histocompatibility antigens

The connection of the histoincompatibility antigens, determined by the reaction in a mixed culture of lymphocytes of the pair of parents, with the litter of linear mice and live weight of cattle was studied. It was ascertained that the degree of the difference between mates for histocompatibility locus correlated with fruitfulness and productive qualities of the descendants. As a result, a greater quantity of descendants of animals, being more viable, are born. The descendants of the parents, having the high indexes of the reaction in the mixed culture of lymphocytes, are born larger and stronger and retain this advantage during succeeding life periods. The reaction in monozygotic twins has a minimum index. The index of the reaction increases when the relationship between individuals decreases. The method of mixed culture of lymphocytes can be used for prognosis of pairs' combination, for maintenance of the heterogeneity and for determination of the degree of relationship between animals.     

Improving tetanus prevention in the Krasnodar area taking the current epidemic situation into account]

An increase of percentage of elderly persons among those who fell ill with tetanus (70%) was noted against a sharp reduction of tetanus incidence under the effect of mass active immunization against this disease. A study of immunity in older and elderly individuals showed the percentage of immune persons among them to be rather low (48.8--55.6%). Due to difficulty of elderly individuals embracement by vaccination the authors suggest a single immunization scheme with a double toxoid dose (20 BU) followed by revaccination with 10 BU in one year. A total of 21 472 persons were placed under observation. The suggested immunization scheme was harmless, promoted stimulation of antitetanus immunity in persons vaccinated earlier; as to unvaccinated persons--it created a favourable immunological preparedness for revaccination, permitting to do without any antitetanus serum in case of trauma.     

The mathematical modelling of population dynamics taking into account the adaptive behavior of individuals

The general approach for modelling of abundance dynamic of biological populations and communities is offered. The mechanisms of individual adaptation in changing environment are considered. The approach is detailed for population models without structure and with age structure. The property of solutions are investigated. As examples the author studies the concrete definitions of general models by analogy with models of Ricker and May. Theoretical analysis and calculations shows that survival of model population in extreme situation increases if adaptive behaviour is taking into account.     

Effects of seasonal changes of soil salinity and soil nitrogen on the N-metabolism of the halophyteArthrocnemum fruticosum (L.) Moq.

Summary The N-metabolism ofArthrocnemum fruticosum (L.) Moq., growing in a saline area north-east of the Dead Sea in Jordan, was studied over its vegetative growth period from March to September 1981. Plant and soil samples were taken at monthly intervals. Water content, Na⁺, K⁺, Cl⁻, NH ₄ ⁺ , NO ₂ ⁻ and NO ₃ ⁻ concentrations were determined in the soil extracts, and the same determinations plus ash weight, soluble carbohydrates, proline, proteins andin vivo nitrate reductase in the plant roots and shoots. Soil humidity decreased and salinity increased from March to August, with re-wetting occurring in late July. K⁺ and Cl⁻ were much lower in the soils than Na⁺. Plant relative dry weight increased during summer due to the absorption of Na⁺ in addition to increased organic dry weight. The uptake of Na⁺ was not balanced by a similar uptake of Cl⁻. Ammonium and nitrate decreased in soil and plants in parallel with increasing salinity. Nitrite was only found in the roots and always in very low quantities. Proline was found only in March. The total soluble carbohydrates in the roots showed a short increase in June when the sodium in the plants also increased. It was concluded that carbohydrates may be used to balance osmotic shocks, but that another compatible compounds is necessary to maintatin long-term osmotic equilibrium. The nitrate reductase activity, measuredin vivo, and the soluble protein changed roughly in parallel with the internal nitrate from May to August, suggesting that nitrogen uptake and reduction in the plant is inhibited during summer when the soil is dry and very saline. This could be a direct effect of drought and/or salinity on the plants, or an indirect onevia an inhibition of nitrifying bacteria.     

Assessment of the human immunological status by taking into account the correlations among individual indices

The problem of correlation of the parameters of the immune system in the normal subjects and in patients with immunological diseases has been considered. The most informative relations have been determined and an attempt has been made to reveal common and specific signs of various immunological diseases.