Factors influencing infection of the tomato by Verticillium albo-atrum

Infection of tomato plants by Verticillium albo-atrum was encouraged by application of nitrogenous manures. Application of phosphate had no significant effect on the progress of the disease, but a deficiency of potash tended to encourage it. Steam-sterilized soil inoculated with Verticillium immediately after treatment produced a very high total of infected plants. When inoculation of the steamed soil by Verticillium was delayed for 17 days or longer after steaming, the steamed soil was no more favourable for development of the disease than untreated soil. Spread of Verticillium from the roots of an infected plant to those of neighbouring healthy plants was hastened by killing the infected plant.     

Organic acid production in vitro and plant growth promotion in maize under controlled environment by phosphate-solubilizing fluorescent Pseudomonas

Background  

Phosphorus deficiency is a major constraint to crop production due to rapid binding of the applied phosphorus into fixed forms not available to the plants. Microbial solubilization of inorganic phosphates has been attributed mainly to the production of organic acids. Phosphate-solubilizing microorganisms enhance plant growth under conditions of poor phosphorus availability by solubilizing insoluble phosphates in the soil. This paper describes the production of organic acids during inorganic phosphate solubilization and influence on plant growth as a function of phosphate solubilization by fluorescent Pseudomonas.     

Alterations in growth and metabolism of potato plants by calcium deficiency

Summary Experiment in water culture was conducted to evaluate the calcium deficiency symptoms and their cause inSolanum tuberosum L. var. Chandramukhi. Meristematic regions at stem and roots were severely affected and ultimately ceased to grow. Plants remained stunted with few and smaller tubers. Reducing sugar, non-reducing sugar and starch accumulated more in the leaves and stems and less in roots and tubers of calcium deficient plants. Deficiency caused decrease in protein nitrogen, RNA, DNA and increase in soluble nitrogen in all the plant parts. Potassium, phosphorus, calcium and sodium contents were lower and magnesium content higher in the deficient plant, than that of the healthy ones. Morphological symptoms of calcium deficiency can be established by ionic balance and accumulation of oxalic acid in potato plants.     

Soil potassium deficiency affects soybean phloem nitrogen and soybean aphid populations

The soybean aphid is an invasive pest in the midwest United States, with frequent population outbreaks. Previous work has shown that aphid population densities are higher on potassium-deficient soybean than on healthy soybean. The experiments reported here test the hypotheses that the potassium nutrition of the host plant affects the forms of phloem nitrogen available to soybean aphids, and subsequently, their abundance. In field surveys and an exclusion cage study when aphid populations were high, soybean plants with potassium deficiency symptoms had a higher density of soybean aphids than plants without deficiency symptoms. In clip cage experiments, this effect was caused by earlier aphid reproduction and higher numbers of aphid nymphs per mother on plants growing in lower-potassium soil. In phloem exudation samples, the percentage of asparagine, an important amino acid for aphid nutrition, increased with decreasing soil potassium, perhaps because of potassium's role in the nitrogen use of the plant. Taken together, these results show that soybean potassium deficiency can lead to higher populations of soybean aphid through a bottom-up effect. A possible mechanism for this relationship is that soybean potassium deficiency improves the nitrogen nutrition of these N-limited insects. By releasing these herbivores from N limitation, host plant potassium deficiency may allow soybean aphid populations to reach higher levels more rapidly in the field.     

The nutrition of the carrot

In sand-culture experiments with carrots, it was shown that a moderate quantity only of nitrogen was necessary for optimum growth compared with, for example, the turnip root. A moderate amount of (available) phosphorus was also sufficient for this purpose, as with the turnip, but contrary to experience with lettuce roots and tops. The greatest concentration of potassium applied, however, was probably the best for root development. Deficiency of phosphorus caused bronzing of the leaves, and absence of potassium, serious scorch; absence of boron resulted in a small, immature plant. Initial field trials on an old river gravel during experiments throughout the last 7 years indicated that dung gave no advantage over artificials, that artificials were possibly not needed on dunged land or land in good heart, and that land out of good heart, undunged and unfertilized throughout the 7 years, responded well to artificials, particularly phosphate and potash. The incidence of carrot fly, according to preliminary experiments, seemed to depend greatly on the nutrition of the carrots.     

Assessment of residues of phosphate application in some soils of northern Nigeria

Summary Phosphate residues in the soils of some manurial trials at Samaru, northern Nigeria were assessed as L and E values and by the isotopic-dilution factor. They gave significant correlations with yield and P uptake in a pot experiment. The E values, which were useful only when measured in the presence of carrier phosphate, and the I.D.F. values were both better in assessing the availability of residual phosphates than were L values on similar soils. re]19701124     

Production and prevention of frenching of tobacco grown in the greenhouse

Summary The induction and elimination of frenching capacity in soils was studied in the greenhouse. It was found possible to induce this physiological disease in tobacco plants grown in normal soils following partial steam sterilization. High counts ofBacillus cereus Frankland and Frankland, the assumed causal agent, also resulted. Lime was added to soil neutrality, together with high dicalcium phosphate and a moderate quantity of cellulose. Growing plants with bottom heat (35°C) was of great aid in shortening duration of tests. Use of a method of successive plantings progressively depleted the soil of nitrogen and was necessary to obtain uniform and reproduceable results. Results with fertilizer ingredients were inconclusive except that low soil nitrogen, low acidity and high phosphate tended to increase frenching. Nitrogen deficiency and frenching symptoms were distinctly different and appeared independently of each other.The converse experiments at three levels of soil acidity and four of potassium nitrate gave coordinating results. Acidity and abundant nitrate diminished or prevented frenching of the plants, without however eliminating frenching capacity of the soil.     

Dry mass partitioning and nitrogen uptake by Eucalyptus grandis plants in response to localized or mixed application of phosphorus

Plants respond to nutrient rich patches by changing root morphology and physiology. The aim of this paper was to analyze shoot and root growth of Eucalyptus grandis plants fertilized with the same amount of phosphorus applied in two different ways: thoroughly mixed in the soil or localized in a single hole near the plant. Localized fertilization increased root mass in the zone where fertilizer was applied, but total root mass was not altered by the type of fertilization application. With mixed fertilization plant growth was less than with localized fertilization, and plants showed nitrogen deficiency. Nitrogen uptake was measured in a split-root hydroponics system where phosphate was applied to the whole root system or in part of it. Growth of plants receiving phosphorus in the whole root system was limited by nitrogen uptake, as was revealed by low leaf N and low nitrate uptake. In conclusion, the positive effect of localized application of phosphorus must be ascribed not only to higher phosphorus but also to sustained nitrogen assimilation.     

The supply of soluble phosphorus to the wheat plant from inorganic soil phosphorus

Summary Pots containing a slightly acid, red-brown soil were maintained at three moisture levels, in half the pots wheat was grown and in the remainder there was no plant growth. Fractionation of the soil phosphorus showed the aluminium phosphates fraction to be the main source of plant-available phosphorus, but at the same time the growth of the plants reduced the significant increase in iron phosphates which occurred during the period in the no-wheat pots. The plant roots compete with the iron phosphates for the soluble phosphate released from the aluminium phosphates fraction.     

Influence of nitrogen on the production of hypericins by St. John’s wort

The effect of nitrogen supply on the production of ‘hypericins’ (hypericin and pseudohypericin) in leaves of St. John’s wort (Hypericum perforatum L.) was examined with plants grown in sand culture and soil. In sand culture, 56-d growth of St. John’s wort plants with decreased nitrogen levels resulted in increased production of hypericins in leaves. A short-term low nitrogen stress in sand culture also resulted in increased production of leaf hypericins. While growth in a low nitrogen-containing soil resulted in elevated levels of hypericins, their production was decreased by supplementation of the soil with additional nitrogen. Increased production of hypericins in St. John’s wort leaves did not require the nitrogen supply to be decreased to levels that resulted in nitrogen deficiency symptoms. Moreover, alteration in the production of leaf hypericins occurring with changes in nitrogen supply did not alter the concentration ratio of pseudohypericin and hypericin. Increased production of leaf hypericins was not associated with any significant changes in the number of dark glands on the leaves and only a weak correlation was observed between leaf dark gland number and levels of leaf hypericins. These results are discussed in terms of the biochemistry of naphthodianthrone production by St. John’s wort plants and implications for growth environment effects during cultivated growth of this medicinal plant.     

Colorado potato beetle control by application of the entomopathogenic nematode Heterorhabditis marelata and potato plant alkaloid manipulation

Control of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), with the entomopathogenic nematode Heterorhabditis marelata Liu and Berry (Nematoda: Heterorhabditidae) was examined in the laboratory and in potato fields in north central Oregon. This research tested the hypothesis that varying nitrogen fertilizer levels would affect foliar alkaloid levels, which would stress the host, and allow increased nematode reproduction and long‐term control of the CPB. Laboratory results indicated that nematodes tended to reproduce more readily in CPB fed on potato plants with high levels of fertilizer. Field trials tested CPB population responses to four treatments: application of nematodes vs. no nematodes, with application of low vs. high rates of nitrogen fertilizer. The higher nitrogen application rate increased field foliar levels of the alkaloids solanine by 35%, and chaconine by 41% over the season. Nematodes were applied twice during the season, causing a 50% reduction in adult CPB populations, and producing six times as many dead prepupae in nematode‐treated soil samples as in the untreated samples. However, no reproducing nematodes were found in the 303 dead prepupae and pupae collected from nematode‐treated plots. Nitrogen fertilizer levels, and their related alkaloid levels, did not affect nematode infection rates or reproduction in the field. Foliar alkaloid levels of plants from the growth chamber were 3–6‐fold as high as those in the field, which may explain the variation in nematode response to nitrogen applications to host plants of the CPB. Heterorhabditis marelata is effective for controlling CPB in the field, and does not have negative non‐target effects on one of the most common endemic CPB control agents, Myiopharus doryphorae (Riley) (Diptera: Tachinidae), but the low rate of nematode reproduction cannot be manipulated through alkaloid stress to the beetle. Until H. marelata can be mass‐produced in an inexpensive manner, it will not be a commercially viable control for CPB.     

Phosphorus and phosphate solubilizing bacteria: Keys for sustainable agriculture

Abstract

Phosphorus (P) is one of the most important minerals required for plant growth occupying a strong position among soil macro nutrients. Soil P deficiency is often fulfilled by phosphate fertilizers. P deficiency in soils is due to less total P contents in the soil and fixation of added P from chemical fertilizers as well as other organic sources like manures. The response of plant under P stress or even when it is present in adequate amount is very mild. The basic constraint in the availability of P is its solubilization as it gets fixed both in acidic and alkaline soil. Soil fixed P can only be solubilized by phosphate solubilizing microorganisms (PSMs).These bacteria released different types of organic acids in the soil which make P soluble and available to plants. The potential of these PSMs to solubilize P varies and mainly depends upon mechanism adopted for solubilization, their molecular genetics as well as their ability to release P in soil. The PSMs, having all the characteristics of phytohormone production, nitrogen fixation, as well as, heavy metal decontamination and creating salt stress tolerance in plants, are quite rare for sustainable agriculture. Application of this environment friendly approach for increasing crop productivity as well as its impact on soil and plant health is discussed in this review which will not only open new avenues of research but also provide fruitful information about phosphate solubilizing microbes for sustainable agriculture development.     

SOME EFFECTS OF HOST-PLANT NUTRITION ON THE MULTIPLICATION OF VIRUSES

The amounts of tobacco mosaic virus present in systemically infected tobacco plants varied greatly with the mineral nutrition of the plants and were related to the effects on plant growth. With plants in soil, supplements of phosphorus produced the greatest increases in plant size, in virus concentration of expressed sap, and in total virus per plant; nitrogen increased plant size only when phosphorus was also added, and only then increased virus concentration and total virus per plant. Combined supplements of phosphorus and nitrogen doubled the virus concentration of sap and increased the total virus per plant by factors up to forty. Potassium slightly reduced the virus concentration of sap, though it usually increased plant size and total virus per plant. From all plants, only about one-third of the virus contained in leaves was present in sap. Virus production seemed to occur at the expense of normal plant proteins, and the ratio of virus to other nitrogenous materials was highest in plants receiving a supplement of phosphorus but not of nitrogen.
The effects of host nutrition on the production of virus in inoculated leaves resembled those in systemically infected leaves, but were more variable.
No evidence was obtained, with plants grown in soil or sand, that host nutrition had any consistent effect on the intrinsic infectivity of tobacco mosaic virus.
The concentration of virus in sap from potato plants systemically infected with two strains of potato virus X was not consistently affected by fertilizers; the chief effect of host nutrition on virus production was indirect by altering plant size.     

Utilization of phosphate from different sources by six plant species

Summary Six plant species, wheat, paspalum grass (Paspalum plicatulum), maize, molasses grass (Melinis minutiflora), soybean and buckwheat (Fagopyrum esculentum) were compared for their abilities to utilize phosphate from superphosphate, a calcined aluminum phosphate and four rock phosphates.Buckwheat showed an exceptional behaviour in that it could utilize all phosphates. For the other plants, only the calcined aluminum phosphate and one rock phosphate (hyperphosphate) had significant fertilizing values. Their efficiencies, relative to superphosphate, were 0.45 and 0.11 for wheat, 0.73 and 0.43 for paspalum grass, 0.50 and 0.37 for maize, 0.46 and 0.42 for molasses grass, 0.28 and 0.38 for soybean, and 0.72 and 1.08 for buckwheat, respectively.For three P sources, superphosphate, calcined aluminum phosphate and hyperphosphate, a relationship between soil acidity and P uptake was found. Soil pH in its turn was negatively related to the ratio of total equivalents of cations and those of anions absorbed. Consequenly, P uptake was positively related to the ratio of total equivalents of cations to those of anions absorbed. The same effect of plant species on soil pH could also explain the difference in uptake of P from sparingly soluble phosphates. The relative efficiencies of calcined aluminum phosphate and hyperphosphate for the various plant species were closely related to the ratio of total cations and total anions absorbed by these plants.on leave at the Agricultural University during 1977.     

VERTICILLIUM WILT OF BRUSSELS SPROUT

A wilt disease of Brussels-sprout plants caused by Verticillium dahliae Kleb, is described. Field observations indicate that the disease is more severe in a wet than in a dry season, the various stages of the pathological symptoms appearing earlier and developing more rapidly. This was corroborated by experiment; under dry conditions the onset of wilt symptoms was delayed and the severity of attack diminished. Since nine different strains and/or species of Verticillium wound-inoculated into Brussels sprouts failed to induce wilt, and since the isolate from this host proved to be non-pathogenic to a wide range of plants usually susceptible to attack by Verticillium spp., it is suggested that the V. dahliae from Brussels sprouts is a distinct physiological strain. Variations in the amounts of the different chemical constituents of the soil (calcium, nitrogen from two different sources, phosphate and potassium) have no apparent effect upon the incidence of disease. The pathogen is not seed-borne but it may be spread by the dissemination of infected plant tissues. Some control measures are suggested and farmers are advised to grow in the infected soil runner beans, cauliflower and broccoli which are resistant to attack by this fungus.     

Mineral Nutrient Limitations of Calcifuge Plants in Phosphate Sufficient Limestone Soil

Twelve species of calcifuge plants were grown in an Ordovician-limestone soil with and without phosphate amendment, as well as in an acid silicate soil of their natural habitat. Phosphate treatment of the limestone soil raised the P concentrations of the plant biomasses to levels within sufficiency ranges reported for cultivated plants and productivity usually increased two- to five-fold. Out of twelve species studied,Scleranthus perenniswas unable to survive in the limestone soil unless treated with phosphate, whereas growth and general performance ofGalium saxatilewas impaired by phosphate additions. Biomass dilution effects on micro-nutrients, but usually not on macronutrients, were recorded as a result of the phosphate treatment. Dilution of Mn was most distinct and Fe was least distinct. However, no foliar symptoms clearly assignable to Mn deficiency were observed. Symptoms of foliar chlorosis, reminiscent of Fe deficiency, developed inGalium saxatile, Carex piluliferaandVeronica officinalis. InC.pilulifera, but not inV.officinalis, chlorosis was accompanied by decreasing foliar Fe concentrations.     

Some causes of chlorosis and necrosis of sugar-beet foliage

The symptoms and characteristics of two virus and one fungus disease and four nutritional disorders of sugar beet which cause chlorosis and necrosis of the foliage are described. The causes of the diseases and methods of distinguishing between them have been investigated by analytical, pathological and field experimental methods.
Experiments in which diagnosis was confirmed by serological and spectrochemical methods show that the two often easily confused diseases, sugar-beet yellows virus and magnesium deficiency, can be visually distinguished.
Sugar-beet yellows virus reduces the potassium, but slightly increases the magnesium content of the leaves.
Magnesium deficiency symptoms are associated with a low magnesium content of the foliage, but may be induced by salt applications without greatly affecting the magnesium analysis.
'Potash' deficiency symptoms are often, but not necessarily, associated with a low potassium analysis and may actually be caused solely by a deficiency of sodium. In the field, symptoms are induced by sulphate of ammonia and phosphate applications and may be prevented in some cases by the application of either salt or muriate of potash, in others by salt only. Some interchangeability of the functions of potassium and sodium in the plant is suggested.
Manganese deficiency symptoms are associated with a low manganese content of the leaves, which can be readily increased by spraying or injection with manganese sulphate solution, but a high concentration of manganese in the foliage, such as sometimes occurs naturally on acid soils, has a toxic effect.     

长期施肥黄土旱塬农田土壤-微生物-植物系统碳氮磷生态化学计量特征

探讨长期不同施肥制度对农田土壤、植物生态系统的碳(C)、氮(N)、磷(P)含量及其生态化学计量比的影响,可为揭示该系统能量平衡和养分循环,实现农业生态系统元素平衡及可持续发展提供参考意义。以位于黄土高原半干旱地区的长武国家黄土高原农业生态实验站长期施肥试验为研究对象,选取不施肥(CK)、单施氮肥(N)、单施磷肥(P)、施氮磷肥(NP)、单施有机肥(M)、氮肥配施有机肥(NM)、磷肥配施有机肥(PM)、氮磷肥配施有机肥(NPM)8个处理,分析了黄土旱塬典型农田土壤-微生物-植物生态系统中C、N、P含量及其生态化学计量变化规律。研究结果表明:1)长期单施有机肥和化肥配施有机肥处理可显著提高土壤和有机质C、N、P含量。2)氮、磷肥的输入显著降低了土壤和小麦C∶N、N∶P,施P显著降低了有机态C∶P和小麦C∶P;有机肥配施对微生物生物量和小麦C∶N∶P的影响更为明显。3)长期有机肥配施条件下土壤养分和小麦化学计量比存在较强的相关关系。微生物生物量碳与有机C、N、P呈显著正相关,土壤微生物生物量氮与土壤N、P总量呈显著正相关,微生物生物量磷与土壤C、N、P总量含量呈显著负相关;植株碳含量与微生物...     

Correction to: The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment

Northern forest ecosystems are projected to experience warmer growing seasons and increased soil freeze–thaw cycles in winter over the next century. Past studies show that warmer soils in the growing season enhance nitrogen uptake by plants, while soil freezing in winter reduces plant uptake and ecosystem retention of nitrogen, yet the combined effects of these changes on plant root capacity to take up nitrogen are unknown. We conducted a 2-year (2014–2015) experiment at Hubbard Brook Experimental Forest in New Hampshire, USA to characterize the response of root damage, nitrogen uptake capacity, and soil solution nitrogen to growing season warming combined with soil freeze–thaw cycles in winter. Winter freeze–thaw cycles damaged roots, reduced nitrogen uptake capacity by 42%, and increased soil solution ammonium in the early growing season (May–June). During the peak growing season (July), root nitrogen uptake capacity was reduced 40% by warming alone and 49% by warming combined with freeze–thaw cycles. These results indicate the projected combination of colder soils in winter and warmer soils in the snow-free season will alter root function by reducing root nitrogen uptake capacity and lead to transient increases of nitrogen in soil solution during the early growing season, with the potential to alter root competition for soil nitrogen and seasonal patterns of soil nitrogen availability. We conclude that considering interactive effects of changes in climate during winter and the snow-free season is essential for accurate determination of the response of nitrogen cycling in the northern hardwood forest to climate change.     

SOME EFFECTS OF HOST NUTRITION ON THE SUSCEPTIBILITY OF PLANTS TO INFECTION BY CERTAIN VIRUSES

Fertilizer treatments that greatly influenced the growth of tobacco and potato plants in pots had little effect on the number that became infected with potato virus Y when the plants were colonized by equal numbers of infective aphids, though the number was slightly decreased by nitrogen and increased by phosphorus.
The number of local lesions produced on leaves of tobacco and Nicotiana glutinosa by tomato aucuba mosaic and tobacco mosaic viruses was increased by additions of both nitrogen and phosphorus, provided that these also increased growth. The predominant effect of both nutrients in increasing susceptibility was indirect by increasing plant size, but over certain critical ranges both elements also increased the numbers of lesions produced per unit leaf area. Conditions of maximum susceptibility approximated closely to those producing optimal growth, and susceptibility, whether measured by lesions per half-leaf or per unit area, was decreased by a deficiency or excess of either element. Sometimes the addition of nitrogen reduced susceptibility when still increasing plant growth.