An effect of potassium on chiasma frequency and recombination

High and low concentrations of potassium and calcium were combined factorially and applied to the plant,Lolium temulentum. An effect on mean plant chiasma frequency was detected when such plants underwent meiosis at 30°C. Potassium rather than calcium was shown to be the mineral responsible for the observed effects. High concentration of potassium resulted in an increase in mean chiasma frequency. At 20°C little effect of either mineral could be demonstrated, although potassium again was responsible for most of the variation produced.Potassium has also an effect on stability. At 30°C high concentrations of potassium reduce plant variation, whereas at 20°C the converse occurs and an increase in plant variation results. It is suggested that such a difference between the two temperatures supports the conclusion that different genetic systems control the plant means and plant variation.The effect of potassium on chiasma frequency was confirmed inDrosophila melanogaster by studying its effects on recombination in the X chromosome. A striking influence on body size, possibly correlated with recombination, was also observed.The conflict of such results with previous work in which calcium has been shown to be the most important mineral is discussed. The difficulties of arguing a direct role at meiosis for external treatments is emphasised.     

Genetic differences in phosphorus absorption among white clover populations

Summary Eight semi-natural white clover populations and two cultivars were grown in culture solutions containing 10 ppm and 0.01 ppm phosphorus (P). The rate of P uptake by the intact plants was then measured in solutions containing 10 ppm P.Phosphorus uptake per unit root length was twice as great by plants previously grown at 0.01 ppm P than those grown at 10 ppm P. Large differences in total P uptake were found among populations regardless of the pretreatment; most of this variation was accounted for by differences in root length. Only small differences were found between populations for P uptake per unit root length, and then only after pretreatment with 10 ppm P; this variation was largely accounted for by relative growth rate and shoot %P.     

Effect of temperature on rice growth in nutrient solution and in acid sulphate soils from Vietnam

Climatic and soil factors are limiting rice growth in many countries. In Vietnam, a steep gradient of temperature is observed from the North to the South, and acid sulphate soils are frequently devoted to rice production. We have therefore attempted to understand how temperature affects rice growth in these problem soils, by comparison with rice grown in nutrient solution. Two varieties of rice, IR64 and X2, were cultivated in phytotrons at 19/21°C and 28/32°C (day/night) for 56 days, after 3 weeks preculture in optimal conditions. Two soils from the Mekong Delta were tested. Parallel with the growing experiments, these two soils were incubated in order to monitor redox potential (E _h ), pH, soluble Al and Fe, soluble, and available P. Tillering retardation at 20°C compared to 30°C was similar in nutrient solutions and in soils. The effect of temperature on increasing plant biomass was more marked in solutions than in soils. The P concentrations in roots and shoots were higher at 20°C than at 30°C, to such an extent that detrimental effect was suspected in plants grown in solution at the lowest temperature. The translocation of Fe from roots to shoots was stimulated upon rising temperature, both in solutions and in soils. This led to plant death on the most acid soil at 30°C. Indeed, the accumulation of Fe in plants grown on soils was enhanced by the release of Fe²⁺ due to reduction of Fe(III)-oxihydroxides. Severe reducing conditions were created at 30°C: redox potential (E _h ) dropped rapidly down to about 0 V. At 20°C, E _h did not drop below about 0.2 V, which is a value well in the range of Fe(III)/Fe(II) buffering. Parallel to E _h drop, pH increased up to about 6–6.5 at 30°C, which prevented plants from Al toxicity, even in the most acid soil. Phosphate behavior was obviously related to Fe-dynamics: more reducing conditions at 30°C have resulted in enhancement of available P, especially in the most acid soil.     

Determination of the phytotoxicity of barium in leach-field disposal of gas well brines

Summary A study was conducted to determine the effect of barium on yield and elemental composition of plants growing near natural gas wells. Brines containing potentially phytotoxic concentrations of barium are periodically released into leach-fields at these wells. Data on plant yield, soil and plant Ba, Ca, Mg, Na, and K concentrations, and soil pH were collected from high-barium well sites, and from greenhouse experiments using simulated brines. Barium had no detectable effect upon plant yield, and contributed only to variations in its own concentration in plants studied. Barium also exhibited biodiminution, in contrast to all other elements studied. Sodium was implicated at the major cause of phytotoxicity at gas well leach-fields. Due to interference of potassium uptake by soidum, the soil sodium/potassium ratio was found to be closely correlated with plant yield fluctuations.     

Improved growth,productivity and quality of tomato (Solanum lycopersicum L.) plants through application of shikimic acid

A field experiment was conducted to investigate the effect of seed presoaking of shikimic acid (30, 60 and 120 ppm) on growth parameters, fruit productivity and quality, transpiration rate, photosynthetic pigments and some mineral nutrition contents of tomato plants. Shikimic acid at all concentrations significantly increased fresh and dry weights, fruit number, average fresh and dry fruit yield, vitamin C, lycopene, carotenoid contents, total acidity and fruit total soluble sugars of tomato plants when compared to control plants. Seed pretreatment with shikimic acid at various doses induces a significant increase in total leaf conductivity, transpiration rate and photosynthetic pigments (Chl. a, chl. b and carotenoids) of tomato plants. Furthermore, shikimic acid at various doses applied significantly increased the concentration of nitrogen, phosphorus and potassium in tomato leaves as compared to control non-treated tomato plants. Among all doses of shikimic acid treatment, it was found that 60 ppm treatment caused a marked increase in growth, fruit productivity and quality and most studied parameters of tomato plants when compared to other treatments. On the other hand, no significant differences were observed in total photosynthetic pigments, concentrations of nitrogen and potassium in leaves of tomato plants treated with 30 ppm of shikimic acid and control plants. According to these results, it could be suggested that shikimic acid used for seed soaking could be used for increasing growth, fruit productivity and quality of tomato plants growing under field conditions.     

Nodulation and growth ofPhaseolus vulgaris in solution culture

Summary Conditions and techniques for achieving good nodulation ofPhaseolus vulgaris L. in continuously aerated solution were developed from greenhouse experiments.If nodules had been established, their growth and activity and the growth of the plant were at least as good in solution culture as in gravel culture. Nodule formation was observed within 10 days of inoculation in small volumes of solution culture (1 liter). In large volumes (19 liters), similarly prompt nodulation occurred only if the plants were inoculated before or immediately after the seedlings were transferred to the solution from gravel or vermiculite; and the nodules were restricted to the roots that had been present at the time of transfer. Delayed inoculation, 2 days after transfer to large volume solutions, led to sparse nodulation observed only after 3 weeks. Delay or inhibition of nodulation in large volumes of solution could not be explained by failute of bacteria to colonize roots or by sparsity of root hairs.Nodule initiation in solution culture was severely inhibited at pH below 5.4. An additional problem in growing N₂-dependent bean in solution culture was the buildup of Cl^– to toxic levels in the plant in nitrate-free media, even at solution concentrations as low as 0.4 mM Cl^–. Daily addition of 0.5 to 1.0 mg N per plant delayed nodule growth and activity slightly, but increased plant growth and alleviated the severe N-deficiency that otherwise developed before the onset of N₂-fixation.     

Variations in response to high temperature treatments in anther culture of Brussels sprouts

The level, time of application and duration of the high temperature treatment necessary for embryo production from Brussels sprouts anther culture were examined. The effects of 29, 32, 35, and 38°C given for 24 h immediately following removal of the anthers from the bud, were tested on different cultivars, on different plants within the cultivars and on different occasions for each plant. Most embryos were produced following 32 and 35°C, very few following 30°C and none following 38°C. Although there was a tendency for some cultivars to respond better to one or other of the two more favourable temperatures, this varied considerably between individual plants. Plant to plant variation was also seen in the overall level of the response, although responsiveness tended to decline with successive samplings of the same plant. Experiments with cultivars Hal and Gower suggested that high temperature was required for at least 12 h after anther removal, but beyond that time the optimum period varied from plant to plant. If the excised anthers were held at 25°C for 16 h or more with Hal or 24 h or more with Gower before being exposed to the high temperature treatment, embrogenesis tended to be reduced. It is suggested that apparent non-responsiveness in anther culture may result to a large extent from the specific conditions that are used during the anther culture process.     

Growth performance of an inland population of Plantago maritima in response to nitrogen and salinity

The inland distribution of Plantago maritima in Ireland and Britain is strongly western and generally associated with base-rich soils or with flushes in more acidic upland soils. Plants from an eastern Irish salt marsh and from an inland population growing on shallow calcareous soils in east County Clare, Ireland, were grown in culture solutions with a range of seawater dilutions (10–100%) and nitrogen (2.8–140 ppm N) concentrations added as ammonium nitrate. A low nitrogen supply (2.8 ppm N) resulted in very low dry matter production but with increased nitrogen, plant growth increased, even of inland population plants in 50% seawater. Some inland plants survived 100% seawater, but growth was much reduced. The relatively high salinity tolerance of this inland population is discussed.Nomenclature follows Flora Europaea (Tutin et al., 1964–80) for angiosperms, Watson (1968) for bryophytes and Hawksworth et al. (1980) for lichens.Thanks are due to the Central Marine Services Unit and Michael Coughlan, Microbiology Department at University College Galway for Mullaghmore soil nitrogen analyses.     

Growth and physiological responses of trembling aspen (Populus tremuloides), white spruce (Picea glauca) and tamarack (Larix laricina) seedlings to root zone pH

Background and aims

Soil pH is among the major environmental factors affecting plant growth. Although the optimum range of soil pH for growth and the tolerance of pH extremes widely vary among plant species, the pH tolerance mechanisms in plants are still poorly understood. In this study, possible mechanisms were examined to explain the differences in tolerance of boreal plants to root zone pH.

Methods

In the controlled-environment solution culture experiments, we compared growth, physiological parameters and tissue nutrient concentrations in aspen, white spruce and tamarack seedlings that were subjected to 8 weeks of root zone pH treatments ranging from 5.0 to 9.0.

Results

The pH treatments had little effect on dry weights and net photosynthesis in white spruce seedlings despite reductions in transpiration rates at higher pH levels. In aspen and tamarack, both the growth and physiological parameters significantly decreased at pH higher than 6.0. The chlorosis of young tissues in aspen and tamarack was associated with the reductions in foliar concentrations of several of the examined essential nutrients including Fe and Mn. Although the plants varied in their ability to deliver essential nutrients to growing leaves, there was no direct correlation between tissue nutrient concentrations, chlorophyll concentrations and plant growth. The results also demonstrated strong inhibition of transpiration rates by high pH.

Conclusions

The results suggest that high root zone pH can upset water balance in pH sensitive species including aspen. Although the uptake and assimilation of essential elements such as Fe and Mn contribute to plant tolerance of high soil pH, we did not observe a direct relationship between growth and foliar nutrient concentrations to account for the observed differences in growth.     

Spent medium analysis for liquid culture micropropagation of <Emphasis Type="Italic">Hemerocallis</Emphasis> on Murashige and Skoog medium

Residual nutrients from Murashige and Skoog medium were analyzed following a 5-wk multifactor experiment. Plant density, sugar concentration, and plant growth regulators (benzyladenine and ancymidol) were examined using four genotypes of daylily (Hemerocallis) to determine which factors most influenced nutrient use. Active nutrient uptake was observed for 11 nutrients (potassium, sodium, copper, phosphorus, iron, calcium, magnesium, manganese, boron, sulfur, and zinc) with lower concentrations in spent medium than in the tissue water volume (fresh-dry mass expressed as mL H₂O). Two patterns of nutrient use were visualized by correlative analysis of nutrient uptake. Greatest growth lowered plant nutrient concentrations of potassium, sodium, phosphorus, iron, and copper in all genotypes, and luxuriant uptake was indicated with least growth. Potassium, sodium, iron, and copper concentrations in plant dry matter were equal to or exceeded what is observed in vigorously growing nursery plants. However, phosphorus concentration in plant dry matter was low enough to be considered deficient when compared to Hemerocallis plants in nursery production. With a second group of nutrients (calcium, magnesium, manganese, and boron), the genotype, “Barbara Mitchell” lacked active uptake and was deficient. Calcium concentration was low in all plants compared to Hemerocallis grown under nursery conditions (“Barbara Mitchell” was the lowest concentration) despite active uptake by the other three genotypes—“Brocaded Gown,” “Mary’s Gold,” and “Heart of a Missionary.” Magnesium concentration in these three genotypes was low enough in vessels with greatest growth to question its adequacy at high densities. Increased sucrose in medium reduced the dry matter concentrations of all tested nutrients. Plant growth regulators had less impact on nutrient use than genotype and plant density. Nutrient uptake may be an important physiological component of genotypic variation.     

Modelling frost resistance of Scots pine seedlings using temperature,daylength and pH of cell effusate

The annual course of frost resistance (LT₅₀) and the pH of the cell effusate in needles of two-year-old Scots pine seedlings were monitored in a field experiment in Oulu, Northern Finland (65° N, 25° E) during 1995. The aim of the work was to to develop model to predict the annual variation in frost resistance by pH of the cell effusate and meteorological data. The seedlings were covered with a fibre cloth shelter which transmitted sufficient light for them to experience the photoperiod, but prevented the accumulation of snow over them. The shelter above the seedlings was removed at the beginning of May and erected again at the end of September. The seedlings were watered only for the time when the shelter was removed, and received fertilizer only during the previous summer (1994).Frost resistance was only -5° C during the growing season but more than -100° C during the winter rest period. It was about -10° C at the end of August, increased to -55° C in the next three weeks, and reached -100° C at the beginning of October. The pH of the cell effusate was lowest during the growing season and highest in winter, the difference being about one and half pH unit. Needles exposed to -196° C showed pH from 4.0 in summer to 5.5 in winter, while pH of the non-frozen needles varied from 5.0 to 6.5, respectively. Seasonal variation in frost resistance was explained by a regression model well (R² = 0.9) when day length, minimum air temperature and pH were entered as variables.     

The influence of various physical parameters on anther culture of broccoli (Brassica oleracea var. italica)

Embryo formation by cultured broccoli (Brassica oleracea L. var. italica) anthers was best in the pH range of 5.5 to 5.8. Manipulation of the initial medium pH showed, however, that embryos could be recovered throughout the entire pH range tested. Experiments designed to test the influence of anther density on embryo production exhibited an apparent population effect. Comparison of anthers cultured with and without filaments showed a significantly lower level of embryo formation with filaments attached. The importance of anther orientation with the adaxial surface up was also demonstrated. Detailed studies of the effect of temperature on anther response showed the importance of 35°C treatments. Other temperatures and a variety of temperature manipulations were either comparatively ineffective or inhibitory. The duration of 35°C exposure required for optimal response varied widely between 18 and 48 h. Wide variation in plant to plant response was observed despite attempts to optimize the manipulation of physical parameters. Individual plants were identified that reliably formed many thousands of embryos, whereas other plants failed to form embryos under all tested conditions.     

Factors affecting chromate reduction in Enterobacter cloacae strain HO1

Summary Factors affecting chromate reduction by cultures of Enterobacter cloacae HO1 were investigated. The reduction was sensitive to oxygen stress and E. cloacae strain HO1 could reduce chromate only under anaerobic conditions. Rates of reduction of chromate were proportional to cell number. The optimal pH was between 7.0 and 7.8, and the optimal temperature was 30°–37°C. High rates of reduction were observed at levels of 1–2 mM potassium chromate, but concentrations above 5 mM were lethal to growing cells and prevented the reduction. Acetate, ethanol, malate, succinate and glycerol were effective electron donors for chromate reduction. Glucose, citrate, pyruvate and lactate supported anaerobic growth, but only limited amounts of reduction were observed with these organic compounds. Chromate reduction by strain HO1 was inhibited by molybdate, vanadate, tellurate and manganese oxide at concentrations where the cell viability was not significantly affected. Metabolic poisons including carbonylcyanide-m-chlorophenyl hydrazone, sodium cyanide, formaldehyde and zinc sulphate also inhibited chromate reduction.     

The seasonal pattern of CO2 exchange of Festuca rubra L. in a montane meadow community in Northern Germany

Summary Completely climatized cuvettes were used to follow the CO₂ gas exchange of red fescue (Festuca rubra L.), growing on a fertilized and an unfertilized plot, during a growing season from May through October. Objective of the study was to determine the effect of environmental factors on the seasonal CO₂ gas exchange.Gas exchange rates were calculated on the basis of leaf dry weight, surface area and chlorophyll content. Photosynthetic rates differed between the fertilized and unfertilized plants when based on leaf dry weight or leaf surface area but were similar when based on chlorophyll.Multiple regression analysis was used to related photosynthetic rates to radiation, temperature, water vapor concentration difference, chlorophyll content and time. A cubic regression equation based on daily radiation alone explained 85% of the variation for the fertilized plants and 87% of the variation for the unfertilized plants.During the growing season the unfertilized plants had a continual decline in their photosynthetic rates. The fertilized plants had high photosynthetic rates in the spring and in the fall.Light response curves indicated greater photosynthetic rates at light saturation as well as in the light limited portion of the light response curve for the fertilized plants. Photosynthetic rates of the fertilized plants were generally depressed during periods of warm temperature and high light intensity in June and July.Photosynthetic rates declined at temperatures above 24°C. The decline was greater for the more mesomorphic fertilized plants. A similar response was noted to increasing water vapor difference, although it was difficult to separate from the temperature effect. Maximum photosynthetic rates were found between 14°C and 22°C, although there was considerable variation in the maximum rates.The effects of cutting (mowing) on the gas exchange were difficult to determine due to the interaction of the environmental factors.Chlorophyll content showed significant correlation with photosynthetic rates.     

Short Note: Production and properties of pectinolytic enzymes from the thermophilic fungus, Thermomyces lanuginosus

Maximal pectinolytic activity was detected in the culture filtrates of Thermomyces lanuginosus when grown in medium containing pectin and sucrose. The pectinolytic enzyme system was optimally active at pH 5.5 and at 70°C with potassium pectate and at pH 4.5 at 50°C with pectin as substrates. Zymogram analyses showed two activity bands with pectin and three with potassium pectate.     

Recovery of photosynthetic reactions after high-temperature treatments of a heat-tolerant cactus

Inhibition and recovery of net CO₂ uptake and three photosynthetic electron transport reactions as well as plant survival following high-temperature treatments were investigated for Opuntia ficus-indica. For plants maintained at 30°C/20°C day/night air temperatures, treatment at 60°C for 1 h irreversibly inhibited net CO₂ uptake and photosynthetic electron transport, resulting in plant death in about 60 days. When a plant maintained at 30°C/20°C was treated at 55°C for 1 h, net CO₂ uptake was completely inhibited 1 d after the treatment but fully recovered in 60 d. Differential inactivation of photosystem (PS) I, PSII, and whole chain electron transport activities occurred; PSI was the most tolerant of 55°C and took the least time (45 d) for total recovery. All 30°C/20°C plants survived a 1-h treatment at 55°C, although some pale green areas were observed on the cladode surfaces. In contrast to growing at 30°C/20°C, plants acclimated to 45°C/35°C survived 60°C for 1 h without showing any necrotic or pale green areas on the cladode surfaces. When such a plant was transferred to 30°C/20°C following the high-temperature treatment, recovery in net CO₂ uptake began in 1 d and progressed to complete recovery by 30 d. Growth temperatures thus influence the possibility for recovery of photosynthetic reactions and ultimately the survival of O. ficus-indica following a high-temperature exposure.Abbreviations DCPIP 2,6-dichlorophenol indophenol - MV methyl viologen - PAR photosynthetically active radiation - PSI or PSII photosystem I or II - WC whole chain     

Cadmium effects on growth and physiology ofUlva lactuca

The chlorophyceanUlva lactuca L. was grown in the laboratory in unialgal culture to sufficient size so that up to 70 discs, 24 mm in diameter, could be punched out of a single plant. Using such discs,U. lactuca was then tested with various concentrations of Cd under continuous-flow conditions. A concentration of 4.5 ppm Cd was lethal toU. lactuca within 6 days. Control discs in unpolluted water increased in diameter at a rate of 8 to 13 % day⁻¹ over a 6-day period. At sublethal concentrations of Cd a sharp reduction in growth rate was observed at increasing concentrations up to approximately 0.3 ppm Cd, whereas from 0.3 ppm Cd to the lethal concentration the reduction of the growth rate was significantly less. Reduction in photosynthetic performance corresponded closely to the reduction in growth rate. At ambient concentrations of 0.8 ppm Cd, the plants concentrated Cd by a factor of approximately 50 in 6 days. Much higher concentration factors were attained in lower ambient concentrations. After removal from Cd-polluted water into flow-through culture in unpolluted water, a subsequent loss of Cd was indicated and the plants recovered rapidly. Plants exposed up to 3 d to 0.7 ppm Cd recovered sufficiently to produce viable gametes 7 days after removal from Cd. Because it has a relatively short life span and apparently loses Cd subsequent to exposure to Cd-polluted water,Ulva lactuca is not recommended as an alga for monitoring in-situ environmental pollution.     

Effect of soil temperature and drought on peanut pod and stem temperatures relative to Aspergillus flavus invasion and aflatoxin contamination

Peanut stem and pod temperatures of plants growing in irrigated, drought, drought-heated soil, and drought-cooled soil treatments were determined near the end of the growing season. Mean soil temperatures of the treatments during this period were 21.5°, 25.5°, 30° and 20 °C, respectively. Peanut stem temperatures in all drought treatments reached a maximum of ca. 40 °C and for 6–7 h each day were as much as 10 °C warmer than irrigated peanut stems. Pod temperatures in drought-heated soil and drought treatments were ca. 34 °C and 30 °C, respectively, for several hours each day. As pod temperatures approached the optimum for A. flavus growth (ca. 35 °C), the proportion of kernels colonized and aflatoxin concentrations increased. Increased plant temperature without accompanying pod temperature increases (drought-cooled soil) resulted in colonization percentages and aflatoxin concentrations only slightly higher than those of the irrigated peanuts.     

Arsenic in the rhizosphere soil solution of ferns

The aim of this study was to explore the evidence of arsenic hyperaccumulation in plant rhizosphere solutions. Six common fern plants were selected and grown in three types of substrate: arsenic (As) -tailings, As-spiked soil, and soil-As-tailing composites. A rhizobox was designed with an in-situ collection of soil solutions to analyze changes in the As concentration and valence as well as the pH, dissolved organic carbon (DOC) and total nitrogen (TN). Arsenite composed less than 20% of the total As, and As depletion was consistent with N depletion in the rhizosphere solutions of the various treatments. The As concentrations in the rhizosphere and non-rhizosphere solutions in the presence of plants were lower than in the respective controls without plants, except for in the As-spiked soils. The DOC concentrations were invariably higher in the rhizosphere versus non-rhizosphere solutions from the various plants; however, no significant increase in the DOC content was observed in Pteris vittata, in which only a slight decrease in pH appeared in the rhizosphere compared to non-rhizosphere solutions. The results showed that As reduction by plant roots was limited, acidification-induced solubilization was not the mechanism for As hyperaccumulation.     

The effect of temperature on salt uptake by tomato plants with diurnal and noctural waterlogging of salinized rootzones

Summary Tomato plants were grown at three constant temperatures (10, 20 and 28°C) with drained or waterlogged rootzones and were irrigated with saline solution (0.09M NaCl).Each increase in temperature resulted in an increase in leaf Na-ion and Cl-ion concentrations in plants grown with drained rootzones. However, with plants grown with waterlogged rootzones, maximum leaf concentrations of Na-ions and Cl-ions occurred at 20°C.At 10°C there were no differences between Na-ion and Cl-ion concentrations for drained or waterlogged treatments. At 20 and 28°C, waterlogging of the rootzone resulted in significantly higher concentrations of Na-ions and Cl-ions in leaf and stem tissues than occurred with drained rootzones.There were no differences in Na-ions and Cl-ions and Cl-ions in plant tops if plants were waterlogged with saline solution during the day or night.Transpiration increased significantly with each increase in temperature but showed no other treatment dependent responses.