Showing papers in "Plant and Soil in 1983"

Rapid assay for determination of water soluble quaternary ammonium compounds

Abstract: The periodide method for quaternary ammonium compounds (QAC) analysis was modified to permit rapid screening of numerous replicate plant samples. This procedure provides a valuable tool for assessing salt tolerance. Aqueous plant extracts were used without further purification. Total QAC were precipitated as the periodide complexes at low pH. In neutral media, only choline periodide crystallized; other major QAC (e.g. glycinebetaine) were soluble at pH 6.8–7.0 QAC concentration was then determined spectrophotometrically.

Acidification and alkalinization of soils

Abstract: Acidification or alkalinization of soils occurs through H+ transfer processes involving vegetation, soil solution and soil minerals. A permanent change in the acid neutralizing capacity of the inorganic soil fraction (ANC(s)),i.e. soil acidification (ΔANC 0), results from an irreversible H+ flux. This irreversible H+ flux can be caused either by direct proton addition or depletion, by different mobility of components of the ANC(s) or by a permanent change in redox conditions. The contributions of (a) acidic atmospheric deposition, (b) nitrogen transformations, (c) deprotonation of CO2 and of organic acids and protonation of their conjugate bases, (d) assimilation of cations and anions by the vegetation, (e) weathering or reverse weathering of minerals and (f) stream output to changes in the ANC(s) are illustrated by means of H+ budgets for actual soils and watersheds.

Growth responses of several plant species to mycorrhizae in a soil of moderate P-fertility: I. Mycorrhizal dependency under field conditions

Abstract: The growth of twenty plant species was compared under field conditions in a methyl bromide fumigated and non-fumigated soil. The non-fumigated soil had a wild endomycorrhizal flora and contained 100 μg/g of available phosphorus. No phosphorus was added to the soil but both fumigated and non-fumigated plots received a basal fertilization of 100 kg/ha N−NH4NO3 and 100 kg/ha K−KCl. Based on plant growth responses, three groups of plants were distinguishable. Plants from group I were mycorrhizal and had better growth in non-fumigated than in the fumigated soil. This group was the most important, including sixteen plant species. Stunting of plants from group I following soil fumigation was mainly attribuable to the destruction of mycorrhizae. Plants from group II (oat and wheat) grew equally well in non-fumigated and fumigated soils. For these plants which were mycorrhizal in the non-fumigated plots, the P-content of the soil was sufficient for growth and therefore no stunting was observed in the absence of mycorrhizae. Plants from group III (cabbage and garden beet) grew better in fumigated than in non-fumigated soil. Their better growth in fumigated soil was tentatively attributed to the destruction of soil-borne pathogens. They did not form mycorrhizae in non-fumigated soil.

The acquisition of phosphorus byLupinus albus L.: III. The probable mechanism by which phosphorus movement in the soil/root interface is enhanced

Abstract: SummaryLarge quantities of citrate ions have been shown to be secreted by the roots ofLupinus albus. It is postulated that these react in the soil to form ferric hydroxy phosphate polymers which diffuse to the root surface where they are degraded by the action of reducing agents in the presence of an Fe II uptake mechanism balanced by hydrogen ion secretion. Some known chemical behaviour of Fe III and citrate which supports this postulate is reviewed. Evidence is also presented which suggests that much of the Fe absorbed circulates within the root system and is subsequently precipitated.

Root architecture and tree stability

Abstract: Root anchorage is discussed with a view to determining the optimum use of root material for enhanced stability Field observations were made on Sitka spruce root systems while lateral forces were applied to the stem with a winch to pull the tree over Measurements included the applied force, angles of inclination, soil and root movement, timing of the sound of root breakage using buried microphones, weight and shape of the root-soil plate and damage to the roots

The distribution and productivity of fine roots in boreal forests

Abstract: The important role of fine roots in the energy expenditure of boreal forests has only recently been illuminated in ecosystem research. As demonstrated in recent research, fine roots are in constant flux, with death and replacement taking place simultaneously. Closely related to the energy costs of development and maintenance of the different roots systems are their functional effectiveness as organs for the absorption of water and nutrients. In forests the dynamics of fine roots need to be considered further in order to make reliable comparisons of plant productivity on an ecosystemic level.

Influence of phosphate and nitrate supply on root hair formation of rape, spinach and tomato plants

Abstract: Experiments with tomato, rape and spinach in nutrient solutions have shown that the formation of root hairs is strongly influenced by phosphate and nitrate supply. Decreasing the phosphate concentration of the nutrient solution from 100 to 2 μM P resulted in an increase of root hair length from 0.1–0.2 to 0.7 mm of the three plant species. Root hair density also increased by a factor of 2–4 when the P concentration was lowered from 1000 to 2 μM. The variation of these two root properties raised the root surface area by a factor of 2 or 3 compared to plants well supplied with P. Root hair length was closely related to the phosphate content of the root and shoot material. On the other hand, spinach plants grown in a split-root experiment produced root hairs in solutions of high P concentration (1000μM P) if the major part of the total root system was exposed to low P concentration (2 μM P). It is therefore concluded that the formation of root hairs does not depend on directly the P concentration at the root surface but on the P content of the plant.

Sensitivity of simulated phosphorus uptake to parameters used by a mechanistic-mathematical model

Abstract: Chemical methods for determination of soil P available to plants do not take into account the effect of roots on P uptake by the plant. Moreover, the relative significance of root parameters, as compared to soil supply parameters in determining P uptake, is unknown. Simulation models have been verified for P uptake by corn (Zea mays L.) and soybeans (Glycine max L. Merr.). The objective of this paper was to use the Cushman simulation model, which has 11 plant and soil parameters, for a sensitivity analysis of the parameters involved in P uptake. Initial parameter values were those obtained from soybeans grown in Raub (Aquic Argiudoll) silt loam. Phosphorus uptake was simulated with each parameter changed independently, from 0.5 to 2.0 times initial value while all the other parameters remained constant. In addition, P uptake was simulated where interrelated parameters were changed according to their dependence. Root growth rate and root radius were the most sensitive parameters influencing P uptake. Soil P supply parameters were more sensitive than root physiological uptake parameters. Phosphorus concentration in soil solution affected P uptake more than the diffusion coefficient and buffer power. Reduction of root radius while root volume was maintained constant by increasing root length increased P uptake. Where both soil volume and root volume were kept constant, reduction of root radius to the size of root hairs or mycorrhizal hyphae gave the greatest P uptake.

The structure and function of mycelial systems of ectomycorrhizal roots with special reference to their role in forming inter-plant connections and providing pathways for assimilate and water transport

Abstract: In the past function of mycorrhizas has been examined at the level either of the isolated individual root or of the individual entire plant. It is shown here that ectomycorrhizal mycelial strands can extend from plant to plant, thus initiating infection in seedlings, and that the resulting fungal interconnections provide functional pathways for the transfer of labelled assimilate between individuals. Mycelial strands also provide a pathway for the transport of physiologically significant quantities of water. Strand functions are examined in relation to structure, and their role as morphological and physiological extensions of the root system is emphasized. The significance of the experimental observations is discussed in relation to nutrient cycling processes in natural ecosystems.

Plant injury and adaptation to oxygen deficiency in the root environment: A review

Abstract: Mise au point des connaissances sur les conditions d'apport insuffisant d'oxygene pour les racines des plantes et sur les mecanismes de degât sur la croissance vegetative des plantes non adaptes aux habitats humides et sur les mecanismes d'acclimatement des especes de zones humides ou non a un manque d'oxygene dans l'environnement racinaire

Root turnover and productivity of coniferous forests

Abstract: Fine roots and mycorrhizae have recently been shown to produce a major portion of the organic matter entering decomposition. Roots and mycorrhizae constitute 63 to 70% of total net primary production in Douglas-fir and Pacific silver fir stands. The importance of roots in primary production makes the method of root extraction from the soil important. Wet-sieving with small mesh screens is more effective than hand-sorting for fine roots and mycorrhizae. Screen size, the efficiency of recovery, the physiological status of the roots and conversion factors to derive biomass from the numbers of root tips should be stated. Published data is enhanced if the phenological status of the stand, its age, tree density, and soil texture are quoted.

The determination of soil chitinase activity: Conditions for assay and ecological studies

Abstract: Chitinase activity was determined by incubating a mixture of toluene-treated soil with 1% (w/w) colloidal chitin suspension for 18 h at 37°C and then, after dilution, assaying the amount of N-acetyl-glucosamine released. Maximal chitinase activity was observed at 45°C and optimal pH for enzymatic reaction was 5.0–5.5. Soil chitinase activity decreased with increasing soil depth and was significantly affected by crop cover and fertilization regime. Chitin added to soil stimulated chitinase activity. Enzyme activity was correlated with the soil fungal population but not with numbers of actinomycetes or bacteria. A specialized mycoflora was associated with chitin decomposition.

Vesicular arbuscular mycorrhizal mediation of grass response to acidic and heavy metal depositions

Abstract: The perennial bunchgrassEhrharta calycina was grown with and without V.A.M. fungal infection (Glomus fasciculatum) in a sandy loam exposed to a range of acidic and heavy metal depositions. Heavy metals (Cu, Ni, Pb, Zn, Fe, and Co) were applied in simulated rain (pH 3.0, 4.0, and 5.6) at deposition rates approximating those observed to result from smelter efluents. Metal concentrations in the roots and shoots of mycorrhizal plants were greater than those of non-mycorrhizal plants. Mycorrhizal enhancement of plant metal uptake increased with greater acidity and higher heavy metal content of treatment. The growth of mycorrhizal plants was reduced compared to non-mycorrhizal plants when metal depostion was combined with simulated acid rain. We propose that mycorrhizal enhancement of heavy metal uptake caused reduced growth in plants exposed to acidic and heavy metal depositions.

The physiology of vesicular-arbuscular mycorrhizal roots

Abstract: The fungi of vesicular-arbuscular mycorrhizae colonize considerable portions of the root system and in spite of the carbon drain they impose on the host plant, their presence within the root tissues can positively influence several aspects of the host plant’s physiology In the majority of cases, improved phosphate uptake is the primary cause of growth and yield enhancements in the mycorrhizal plants Mycorrhizal roots have different phosphate absorption kinetics and lower threshold values than nonmycorrhizal roots The external hyphae developing around mycorrhizae explore a large volume of soil and absorb available phosphate beyond the depletion zone at the root surface Phosphate accumulating in the external fungal hyphae is translocated to the internal mycelium by a well-developed transport system and transferred to the host tissues mainly across the intracellular arbuscules Certain specialized enzyme activities are specifically associated with this alternative pathway of phosphate nutrition in mycorrhizal plants Improved phosphate nutrition is not always sufficient to explain the observed effects of vesicular-arbuscular mycorrhizae on the host plant’s physiology

Nutrient reserves in roots of fruit trees, in particular carbohydrates and nitrogen

Abstract: In trees, nutrient reserves built up in the previous year are of primary importance for early spring growth. Despite the relatively great importance of roots for nutrient storage, the root system should not be regarded as a special storage organ. Quantitatively, carbohydrates predominate in these reserves, but qualitatively N and other minerals are of more than minor significance. In roots carbohydrates are usually stored in insoluble form, mainly as starch; sorbitol is the predominant soluble compound in apple and peach. For nitrogen reserves, the soluble form predominates in roots, especially arginine in apple and peach, followed by asparagine. The level of reserves usually becomes maximal early in the winter. During leafing-out the reserves are drawn on until, later in the season, the supply of newly produced or absorbed nutrients exceeds the demand and replenishment occurs. The initial carbohydrate reserves do not determine the amount of new growth, whereas reserve nitrogen is of decisive importance for shoot growth vigour. Environmental factors such as light intensity and temperature affect the level of carbohydrates in roots; the concentration can be reduced by defoliation and summer pruning and increased by ample supply of nitrogen fertilizer in the autumn. The main cultural factors that influence nitrogen reserves are the amount and the time of nitrogen fertilization.

Nitrogen nutrition, photosynthesis and carbon allocation in ectomycorrhizal pine

Abstract: Studies examined net photosynthesis (Pn) and dry matter production of mycorrhizal and nonmycorrhizal Pinus taeda at 6 intervals over a 10-month period. Pn rates of mycorrhizal plants were consistently greater than nonmycorrhizal plants, and at 10 months were 2.1-fold greater. Partitioning of current photosynthate was examined by pulse-labelling with 14CO2 at each of the six time intervals. Mycorrhizal plants assimilated more 14CO2, allocated a greater percentage of assimilated 14C to the root systems, and lost a greater percentage of 14C by root respiration than did nonmycorrhizal plants. At 10 months, the quantity of 14CO2 respired by roots per unit root weight was 3.6-fold greater by mycorrhizal than nonmycorrhizal plants. Although the stimulation of photosynthesis and translocation of current photosynthate to the root system by mycorrhiza formation was consistent with the source-sink concept of sink demand, foliar N and P concentrations were also greater in mycorrhizal plants.

Plant genotype differences in the uptake, translocation, accumulation, and use of mineral elements required for plant growth

Abstract: Plant genotypes differ in their uptake, translocation, accumulation, and use of mineral elements. Examples of genotype differences to iron, nitrogen, phosphorus, potassium, calcium, magnesium, manganese, boron, copper, zinc, and molybdenum are discussed. Current knowledge is sufficient to indicate that many crop plants can be improved for the efficient use of mineral elements and better adaptation to mineral stress conditions.

The concept of succession in relation to the spread of sheathing mycorrhizal fungi on inoculated tree seedlings growing in unsterile soils

Abstract: Repeated annual assessments of the toadstools (fruitbodies) of mycorrhizal fungi associated with a mixed stand of Betula spp. indicated that they were produced in a pattern ordered in time and space, suggesting a succession with identifiable early- and late-stage fungi. This concept is supported by below-ground observations of mycorrhizas which, however, need to be augmented.

Effects of N fertilisation on populations of fine roots and mycorrhizas in spruce humus

Abstract: Fertilisation with N alters the numbers, biomass and seasonal pattern of activity of fine roots and mycorrhizas in spruce humus. Production and mortality decrease, and longevity increases. Fertilisation reduces mycorrhizal infection, alters the relative proportions of mycorrhizal types and permits the appearance of new types.

Method of measuring invertase activity in soils

Abstract: Invertase (β-D-fructofuranoside fructohydrolase, EC [Enzyme Commission] 3.2.1.26) is the enzyme that catalyzes the hydrolysis of sucrose and yields glucose and fructose. The activity of this enzyme was monitored by systematically developing a sensitive and rapid method to detect reducing sugars with the precision of 1.4 to 6.1% C.V. The method involves the colorimetric determination of reducing sugars which react with 3,5-dinitrosalicylic acid when soil is incubated with buffered sucrose solution and toluene at 37°C for 24 h. The detection limit for the method described is 100 μg of reducing sugar per ml of soil extract. The color intensity remained constant up to 24 h. Comparative studies showed that the method described was in good agreement to other invertase assay procedures reported in the literature. Studies on the stability and distribution of invertase in soils by using the method described showed that air-drying of field-moist soil samples resulted in decreased activity ranging from 15.3 to 23.7% (avg.=19.8%). Statistical analyses indicated that invertase activity was significantly correlated with total N (r=0.78***) and organic C (r=0.70***) in the topsoil of 19 diverse samples. There was no significant correlation between invertase activity and soil pH, cation exchange capacity, percentage of clay and percentage of sand. The activity of this enzyme was concentrated in surface soils and decreased with profile depth. Regression analyses showed that invertase activity was significantly correlated with organic carbon content of three soil profiles examined.

The acquisition of phosphorus by Lupinus albus L., 4: the effect of interplanting wheat and white lupin on the growth and mineral composition of the two species

Abstract: The maintenance of soil fertility is of prime importance in any agricultural system and an important component of this is nitrogen availability. In advanced agricultural systems, nitrogen availability to crops is usually maintained either by the application of nitrogen fertilizers, or by a system of ley farming in which a legume-based phase and a non-legume phase of varying periods are alternated. In more primitive agricultural systems, crops often consist of mixtures of legumes and non-legumes and this is thought to have enabled continuous cultivation of the land to occur over long periods without an associated decline in soil fertility, albeit at a low level of productivity14. Similarly, under pastures, which commonly consist of mixtures of legumes and non-legumes, soil nitrogen usually remains constant or increases with time. There are two ways by which nitrogen can be transferred from legumes to nonlegumes. The first is by the breakdown of the nitrogen rich plant as it or parts of it die, thereby releasing nitrogen to plants growing after the death of the legume. The second is by the secretion of nitrogenous compounds from the roots of the legume. This latter mechanism was elucidated by research conducted prior to 1934, and has been reviewed by Nicol13 who concluded that these compounds can be utilized by associated non-legumes. Subsequent work has generally supported this conclusion2'8,16'20'22 although it is recognized that species of legumes differ in their ability to transfer nitrogen17'21.

Sequences and interactions of mycorrhizal fungi on birch

Abstract: Soil cores collected under a birch tree (Betula pubescens) on an experimental plot showed a progressive change in types of sheathing mycorrhiza with distance from the tree base. Seedlings grown in cores in a glasshouse also developed different mycorrhizal types depending on distance from the tree at which the cores were taken, but the types on seedlings were often different from those in the parent cores. When cores were taken directly beneath fruitbodies and sown to birch in a glasshouse, seedlings developed mycorrhizas of Laccaria, Inocybe and Hebeloma in cores from beneath these fruitbodies, but they seldom developed Lactarius mycorrhizas and never developed Leccinum mycorrhizas in cores taken beneath these fruitbodies. Similarly, when seedlings were grown in soils supplemented with vermiculite-peat inocula in a glasshouse, Laccaria and Hebeloma readily formed mycorrhizas, but Lactarius pubescens seldom did so and Leccinum and Amanita muscaria never dit so. Yet all these fungi form mycorrhizas on birch seedlings in aseptic conditions.

Effects of cadmium and lead on radish plants with particular reference to movement of metals through soil profile and plant

Abstract: Studies were made of the effects of insoluble and soluble compounds of Cd and Pb on the growth of radish plants. The effect of Cd toxicity was progressive chlorosis, particularly of the young leaves, followed by necrosis. The effect of Pb toxicity was stunted growth. Root growth was more inhibited than shoot growth in metal-contaminated soils. On a molarity basis Cd was twenty times more toxic than Pb.

Nature of oxidizing power of rice roots

Abstract: The oxidizing power of rice roots comprises two components,i. e., oxygen release and enzymatic oxidation as measured by α-naphthylamine oxidation. Microscopic examination of roots shows a columnar arrangement of cells having structural intercellular spaces that may serve as air passage pipes in the tip region of the root. Both oxygen release and α-naphthylamine oxidation were studied as function of atmospheric oxygen concentration, light, temperature of root environment, respiratory inhibitors, and nutritional status of the plant. The results led to the concept that α-naphthylamine oxidation is a part of the respiration, and that the oxygen which is not consumed by respiration is diffused into the surrounding environment. Both processes are governed by molecular oxygen supply from shoots. At 25°C, the oxygen release of 3-week-old seedlings of IR36 was about 9 times greater than the amount of oxygen needed to account for α-naphthylamine oxidation rate.

Interactive effects of salinity and nitrogen on growth and yield of tomato plants

Abstract: Tomato (Lycopersicon esculentum var. VF 145) plants were grown with Typic Xerofluvents soil in a greenhouse irrigated with recycled nutrient solutions having increasing levels of N and salinity. Positive response of plants to increasing levels of N was obtained at the lowest initial salinity level of 1 dS/m (dS/m=mmho/cm, referenced at 25°C). At the higher initial salinity levels of 5 and 9 dS/m, increasing N was ineffective in counteracting adverse effects on growth and yield caused by the presence of enhanced salt concentrations of the nutrient solution. Total N uptake was linearly correlated with the total water uptake and was severely suppressed by impaired growth associated with the two higher initial salinity levels, irrespective of N levels. The effect of salinity on leaf N concentrations changed over time. Leaf Cl and P concentrations indicated a possible suppressing effect of Cl on P uptake into plant tops.

Agronomical and physiological aspects of the role of nitrogen in yield formation of cereals

Abstract: Nitrogen exerts its influence on crop growth and grain yield in various ways. Early top dressings or a high level of soil nitrogen stimulate tiller formation and leaf growth, which results in an increase of shoot dry weight and leaf area index. Late top dressings promote the survival of ear-bearing tillers, grain set and leaf area duration.

A comparison of methods, including angled and vertical minirhizotrons, for studying root growth and distribution in a spring oat crop

Abstract: Four methods of measuring root distribution in a spring oat crop were compared: minirhizotrons installed vertically, minirhizotrons installed at an angle of 45°, core-break root counts and direct measurement of lengths of root washed from soil cores.

Growth and spatial distribution of nutrient-absorbing organs: selective exploitation of soil heterogeneity

Abstract: The soil is a heterogeneous medium with respect to decomposition activity and consequently with respect to nutrient availability. Roots of forest trees and hyphae of vesicular-arbuscular mycorrhizal (VAM) fungi, principal nutrient absorbing organs, have previously been observed to associate with decomposing organic matter and other localized sites of nutrient availability in the soil.

Growth responses of several plant species to mycorrhizae in a soil of moderate P-fertility: II. Soil fumigation induced stunting of plants corrected by reintroduction of the wild endomycorrhizal flora

Abstract: SummaryA greenhouse experiment was carried out comparing the growth of various plant species in non-fumigated, fumigated, and fumigated-inoculated soils. The soil used contained numerous pieces of root of Broom-Corn Millet (Panicum miliaceum L.) that were found intensely colonized by indigenous endomycorrhizal fungi. The soil was fumigated with methyl bromide and the inoculum used was a mixture of VA mycorrhizal root fragment from plants grown in the field from which the soil was collected. Plants used were cabbage (Brassica oleracea L. var Copenhagen Market), carrot (Daucus carota L. var. Nantaise), leek (Allium porrum L. var. American Flag), marigold (Tagetes patulus L. var. Golden Boy), tomato (Lycopersicum esculentum Mill. var. Michigan Ohio), sweet corn (Zea mays L. var. Span Cross) and wheat (Triticum aestivum L. var. Glenlea). No phosphorus was added to the soil which contained 93 μg/g of available P (bray II). All plants tested formed mycorrhizae except cabbage. Generally, values of the root endomycorrhizal colonization (REC) index were higher in fumigated-inoculated soil than in non-fumigated soil. Cabbage grew equally well in fumigated and fumigated-inoculated soil, but better than in non-fumigated soil. Cabbage did not form VA mycorrhizae and its better growth in fumigated soil was tentatively attributed to the destruction of soil-borne pathogens and the absence of competition. Wheat grew equally well in the three treatments, because 93 μg/g of available P is sufficient for wheat growth and thus the mycorrhizae were not efficient. The five other plant species used were severely stunted in fumigated soil and the inoculation permitted the reestablishment of normal growth as in non-fumigated soil. Growth stimulation is attributed to the efficiency of VA mycorrhizae since these plants were mycorrhizal in non-fumigated soil and in fumigated-inoculated soil. Stunting of these plants in fumigated soil was due to the destruction of VA mycorrhizae since results show that this stunting cannot be attributed to methylbromide residues in the soil. Moreover soil pH and nutrient content were not markedly changed after fumigation.

Phosphatase production by mycorrhizal fungi

Abstract: Sheathing mycorrhizal fungi have been shown to possess phosphatase enzymes which can hydrolyse inositol hexaphosphate. In a range of mycorrhizal fungi, this activity was often greater than in two common decomposer basidiomycetes. Mycorrhizal birch and pine roots both produce phosphatases. In birch production is inversely related to the inorganic phosphorus concentration in the growth medium. Mycorrhizas reduce phosphatase activity compared with non-mycorrhizal plants.