Influence of Potassium and Nitrogen Fertilization on Parasitism by the Root-knot Nematode Meloidogyne javanica

The influence of various c oncentrations of K⁺, nitrogen sources, and inoculation with root-knot nematode Meloidogyne javanica were evaluated in tomato plants. Increased potassium concentration increased top and root fresh weights of intact plants and fresh weights of excised roots. Nitrate-fertilized plants weighed more than plants receiving ammonium independent of the K level in the medium. Nematode counts on roots were not affected by nutritional differences in intact or excised roots. In intact roots a high percentage of males was recorded at low K⁺ levels, whereas in excised roots the proportion of males in the population rose as the K⁺ levels increased. Inoculated intact roots accumulated K⁺ when the level of potassium supply was low; infected excised roots contained less K⁺ than did nematode-free roots.     

THE INORGANIC CARBON REQUIREMENTS OF CHLAMYDOMONAS SEGNIS (CHLOROPHYCEAE) FOR CELL DEVELOPMENT IN SYNCHRONOUS CULTURES1

The time in the cell cycle when CO₂ provision was required for cell development and division was determined in synchronous cultures of Chlamydomonas segnis Ettl bubbled with air (0.03% CO₂) or air enriched with 5% CO₂ under continuous light at 25°C and pH 7. Provision of CO₂ (% in air v/v) during the G₁-phase was found to be essential for the completion of the cell cycle. There was no demand for CO₂ supply throughout the S-phase and mitosis. Using cultures adapted to CO₂ concentrations ranging from 0.03 to 5% in air, the apparent CO₂ concentration (K_m) required for the cells to develop during the G_-1-phase and to attain one half the maximal rates of photo-synthetic O₂ evolution was calculated as 0.05%. This value increased to 0.1 and 0.5% during the S-phase. For total protein and carbohydrate accumulation, which would reflect inorganic carbon (CO₂+ HCO₃^?) assimilation, the K_m (% CO₂) were ca. 0.1 and 0.14 throughout the cell cycle, respectively. The CO₂ concentration at which the cells exhibited the shortest generation time (6.7 h) was 0.1%. These results showed that during development, cells photosynthesizing (evolving O₂) at maximal rates but accumulating protein and carbohydrate at one half the maximal rates or less would complete their vegetative life cycle in the shortest time.     

Responses of alfalfa and Barley to foliar application of N and P on a coal mine spoil

Summary To ensure adequate growth of plants on the highly impoverished and erodable surface mined lands, the application of N and P fertilizers by suitable methods is essential. In the present study, five growth chamber experiments were conducted to evaluate the relative efficacy of foliar and spoil application of N and P using alfalfa (Medicago sativa L. var. Erand) and barley (Hordeum vulgare L. var. Manker) as test crops on a freshly exposed coal mine spoil collected from western North Dakota. In general, barley responded to both N and P, but alfalfa mainly to P. Growth responses of barley to foliar or spoil-applied N+P were substantial and similar in magnitude. However, the yields were much higher when the plants received 3–4 sprays of 1.5–2.2% urea, with P supplied through the spoil. Increasing the number of 2.2% urea sprays from 1 to 3 increased the growth response from 40 to 243%. In another study, increasing the concentration of foliar-applied urea from 0 through 1% resulted in further increases in the dry weights of barley at all the levels of spoil-applied (0, 25, 75, 225 g/g) N.Foliar sprays of 0.5–1.0% NaH₂PO₄ increased the dry weights of alfalfa and barley by an average of 366% and 86%, respectively. However, the yield response of alfalfa to spoil-applied P (100 g/g) was as high as 782% compared to only 117% for barley. Alfalfa responded significantly to increasing concentrations of H₃PO₄ (0–0.3%) in foliar sprays only in the absence of spoil-applied P. With increasing rates of spoil-applied P, alfalfa yields increased steadily, but additional supply of P sprays caused leaf burning which intensified as the P concentration in sprays increased.The results of chemical analyses indicated that foliar applications were more effective than soil applications in increasing the concentration of N or P in the plants. Moreover, urea sprays increased the uptake of K, Zn, and Fe in barley, whereas spraying alfalfa with P compounds caused increases in its K and Fe content and decreases in those of Zn and Na. The results of these experiments indicated that the nutritional requirements of plants grown on coal mine spoils can be met through foliar fertilization as effectively as, or better than, through conventional soil fertilization methods.Presented at the Annual Meeting, American Society of Agronomy, Chicago, Illinois, Dec. 3–8, 1978.     

The effects of nitrogen and phosphorus on seed yield and composition in peas

Summary The effects of nitrogen and phosphorus on seed yield and seed nutrient content inPisum sativum L. cv Sprite were studied. In the first experiment (spring-sown) seed yield was increased by 55% due to the combined effect of high nitrogen and phosphorus, although in subsequent experiments (during the summer) nitrogen had no effect on seed yield, and a response to phosphorus was obtained in only one of two experiments. In all experiments, increased plant nitrogen and phosphorus supply resulted in increased concentration of the respective element in the seed.     

Dark requirement for cell regeneration and colony formation by mesophyll protoplasts ofNicotiana plumbaginifolia Viv.

Summary The protoplasts ofNicotiana plumbaginifolia required darkness for cell regeneration and colony formation. Maximal plating efficiency of the protoplasts could be achieved by keeping the cultures in dark instead of light or dark/light sequence. Only two days of darkness prior to the illumination at 400 or 3,000 lux resulted in appreciable plating efficiency, than those of light from the beginning, but these values could not match the high plating efficiency in total darkness.     

The effect of silicon on the manganese nutrition of soybeans (Glycine max (L.) Merrill)

Summary Silicon during the early vegetative stage did not affect the oven dry weight of any of the various tissues of the soybean plant. Silicon did, however, decrease the Mn concentration in the youngest fully mature leaf at intermediate levels of Mn. This effect did not occur at the lowest or highest Mn levels. Deficiency and toxicity symptoms were moderated to a slight degree by Si except at the highest level of Mn.     

Nickel requirement for chemolithotrophic growth in hydrogen-oxidizing bacteria

In a comparative study the requirement of several strains of autotrophic hydrogen-oxidizing bacteria for nickel was examined. Autotrophic growth was studied both in liquid media, previously freed from trace metals; and on solidified media, using a plate diffusion assay. The latter assay was based on the observation that EDTA causes complete inhibition of autotrophic growth on agar medium as a result of nickel deficiency. Nickel was shown to be required as a trace element in five strains of Alcaligenes eutrophus, in two strains of Xanthobacter autotrophicus, in Pseudomonas flava, in Arthrobacter spec. 11X and in strain 12X. In these bacteria nickel was not replaceable by cobalt, copper, manganese or zinc ions. No significant nickel requirement was detected by these methods, however, for Paracoccus denitrificans and Nocardia opaca 1b.     

Growth factor requirement of Thiobacillus novellus

Thiobacillus novellus cannot be grown in mineral salts media unless supplied with yeast extract. The requirement is only for miniscule amounts of yeast extract and is not fully expressed unless cells grown in a complex medium are allowed to multiply in a mineral salts medium for four to five generations. Individual sulfur-containing organic compounds, namely biotin, coenzyme A, and lipoic acid, but not reduced inorganic sulfur compounds, can substitute for the yeast extract requirement. Biotin can fully satisfy this requirement at a concentration insufficient to fulfill the biosynthetic sulfur needs; further, the organisms continue to incorporate ³⁵SO₄ into cellular protein in the presence of yeast extract or biotin. It is concluded that biotin is required as a growth factor and not owing to an inability to obtain sulfur from sulfate; the reasons why coenzyme A and thiamine pyrophosphate can substitute for biotin are discussed.Non-standard Abbreviations MS Mineral Salts Base     

Relative addition rate and external concentration; Driving variables used in plant nutrition research

Abstract An increasing literature accounting for various types of experiments indicates that far lower external nutrient concentrations are required by plants than is usually thought to be the case. It is concluded that the ion uptake capacity of the roots, as described by the carrier concept, is high compared to that required for maintenance of the internal concentration. Serious errors in experimental conclusions are associated with insufficient and constant nutrient addition rates. The main errors are caused by non-steady states of the plants both with regard to the internal nutrient concentrations and the relative growth rate. A dynamic concept has been proposed for direct use as the treatment variable within the range of sub-optimum nutrition. The nutritional factor is expressed as a flow, the relative nutrient addition rate in laboratory studies and the nutrient flux density in the field. The experimental use of the relative addition rate has led to steady-state nutrient status and relative growth rate and the interpretation of plant responses which differ fundamentally from accepted views. Thus, for instance, deficiency symptoms disappear, as in natural conditions, when the internal nitrogen concentration is stable, independent of level. The nutrition/growth relationships are very different from those observed when external concentration is varied. The regression line of relative growth rate on relative addition rate passes near to the origin at an angle close to 45 to the axes, which implies that the obtained relative growth rate approximates closely the treatment variable. A striking example of observed differences is the positive effect on nitrogen fixation exerted by high relative nitrogen addition rates compared to the well-known negative effect of increasing external nitrogen concentration. The application of fertilizer on the basis of the nutrient flux density concept provides the possibility of supplying fertilizers corresponding to the consumption potential of the vegetation and to the natural flux density resulting from mineralization in the soil. Nitrogen utilization is high under such conditions and the resulting feedback of nutrition on the mineralization rate suggests that there will be a long-term increase in fertility.     

Growth and mineral nutrition of two Chlorococcalean algae

The effect of composition of the medium and pH on the growth of Pediastrum duplex Meyen and Dictyosphaerium pulchellum Wood was studied. Both species showed preference to alkaline conditions. The ammonium nitrate grown colonies of D. pulchellum lacked mucilage and showed a more compact form, resembling D. pulchellum var. minitum Deflandre. From this it appears that D. pulchellum var. minitum is a nutritional variant of the species and not a stable variety.