MOVEMENT OF EELWORMS

Experiments on vertical migration through saturated soil fractions, horizontal migration through soil fractions at different pressure deficiencies and migration in single layers of particles showed that the beet eelworm, Heterodera schachtii Schmidt, attained maximum speed when the pore diameters were between 30–60 μ. Speed of the eelworms increased as lateral displacement of the body was restricted by external resistances acting perpendicularly to the body axis; at the maximum speed there was no lateral movement, each part of the body following the part immediately in front of it. The speed of beet eelworm larvae in water films of various thickness was measured; maximum speed occurred in a film 2–5 μ thick. Four arbitrarily classified types of progression were observed in the pore spaces. It is suggested that the 'moisture characteristic' supplies most of the information required about the physical properties of the soil in relation to eelworm movement. By examining such a curve the pore size distribution can be ascertained and the probable behaviour of beet eelworm larvae in the medium predicted.     

MOVEMENT OF EELWORMS

The optimum crumb sizes for movement of potato-root eelworm larvae in a sandy loam, a heavy clay and a peat soil were 150–250 and 250–400 μ. Mobility was very similar in clay and sandy loam, in both of which there was an optimum suction for movement. In the peat, however, mobility increased with suction and no optimum suction was established. Larvae may be able to move in peat at high suctions because friction between the larvae and the peat crumbs is less than between clay or sand crumbs. Larvae moved to the wet end of a moisture gradient in sand, the number increasing with the steepness of the gradient. The rate of spread of larvae in sand 150–250 μ diameter varied between 2 and 3 cm. a day, depending on suction. As pore size increases, any upward movement in a moisture gradient is opposed by falling under gravity. Larvae do not respond to a moisture gradient or fall under gravity in sand where the width of the pore approximates to the diameter of the larva. The presence of host roots also counteracted the response to a moisture gradient; the degree of orientation to the roots increased with the time the roots were in the sand. Direct observation on larvae, newly emerged from cysts, in the presence of host plant roots, suggests that larvae orientate themselves at a distance from the root and do not reach the root by random movement. Many of the movements of eelworms are explicable by considering the relationship between pore size, eelworm diameter and water distribution, and a diagram relates movement and various soil factors.     

MOVEMENT OF EELWORMS

Tracks were plotted of about 300 individual eelworms comprising six species among water droplets on a glass surface. Measurements of the tracks indicated that the product of length and activity of an eelworm divided by its speed was a constant. This supports the hypothesis that the speed of an eelworm among water droplets is a function of its length and activity. This principle can only be applied to movement in soil where the length of the eelworm is less than about three times the particle diameter. Under such conditions the eelworms move in thin films or water droplets over particles. Among smaller-sized particles the speed of the eelworms is influenced by particle size. With increasing eelworm length there is an increase in soil particle size for maximum mobility.     

AMPHOTERIC COLLOIDS : IV. THE INFLUENCE OF THE VALENCY OF CATIONS UPON THE PHYSICAL PROPERTIES OF GELATIN.

1. A method is given by which the amount of equivalents of metal in combination with 1 gm. of a 1 per cent gelatin solution previously treated with an alkali can be ascertained when the excess of alkali is washed away and the pH is determined. The curves of metal equivalent in combination with 1 gm. of gelatin previously treated with different concentrations of LiOH, NaOH, KOH, NH₄OH, Ca(OH)₂, and Ba(OH)₂ were ascertained and plotted as ordinates, with the pH of the solution as abscissæ, and were found to be identical. This proves that twice as many univalent as bivalent cations combine with the same mass of gelatin, as was to be expected. 2. The osmotic pressure of 1 per cent solutions of metal gelatinates with univalent and bivalent cation was measured. The curves for the osmotic pressure of 1 per cent solution of gelatin salts of Li, Na, K, and NH₄ were found to be identical when plotted for pH as abscissæ, tending towards the same maximum of a pressure of about 325 mm. of the gelatin solution (for pH about 7.9). The corresponding curves for Ca and Ba gelatinate were also found to be identical but different from the preceding ones, tending towards a maximum pressure of about 125 mm. for pH about 7.0 or above. The ratio of maxi mal osmotic pressure for the two groups of gelatin salts is therefore about as 1:3 after the necessary corrections have been made. 3. When the conductivities of these solutions are plotted as ordinates against the pH as abscissæ, the curves for the conductivities of Li, Na, Ca, and Ba gelatinate are almost identical (for the same pH), while the curves for the conductivities of K and NH₄ gelatinate are only little higher. 4. The curves for the viscosity and swelling of Ba (or Ca) and Na gelatinate are approximately parallel to those for osmotic pressure. 5. The practical identity or close proximity of the conductivities of metal gelatinates with univalent and bivalent metal excludes the possibility that the differences observed in the osmotic pressure, viscosity, and swelling between metal gelatinates with univalent and bivalent metal are determined by differences in the degree of ionization (and a possible hydratation of the protein ions). 6. Another, as yet tentative, explanation is suggested.     

造纸废水对离体鱼头呼吸运动的影响

本文采用离体鱼头灌注法,以两个造纸厂的制浆造纸废水对147个鲤鱼头进行了人工灌流。结果表明:废水在低浓度(如4%以下)体积稀释液时,鱼头呼吸速率基本未产生影响,而以较高浓度的废水(如5%以上)稀释液灌流与不含废水的鸭绿江水源地水灌流的对照组鱼头比较,几乎均发生了显著性变化,即对鱼鳃盖运动产生了抑制作用,出现了Biot氏呼吸。以往学者们认为,造纸废水主要是由于水中溶解氧(DO)减少而使鱼类致死的,但本工作灌注液中已人工给予足够的DO,提示:有毒物质本身似已直接危及延髓呼吸中枢。 实验同时表明,离体鱼头灌注法可供环境保护部门应用于含多种有机毒性物质的制浆造纸废水的现场监测。     

STUDIES IN THE PHYSIOLOGY OF FOREST TREES. IV. MOISTURE MOVEMENT IN DECAPITATED STEMS

Greenidge , K. N. H. (Dalhousie U., Halifax, Nova Scotia.) Studies in the physiology of forest trees. IV. Moisture movement in decapitated stems. Amer. Jour. Bot. 47(10) : 816–819. Illus. 1960.—The rates and patterns of moisture movement in large, decapitated ring-porous stems have been investigated with the aid of water-soluble dyes injected into the lower boles of standing trees. A few observations have been made also in diffuse-porous trees treated in the same manner. Movement has been found to continue to the very apices of the stubs of oak and elm stems in the complete absence of foliar surfaces. Similar results were obtained in untouched stubs, and in stubs, the sawn surfaces of which were shellacked following decapitation and prior to injection. In oak and elm thus treated, maximum rates of movement approached 1/2 the velocities characteristic of entire stems. In shellacked and unshellacked stubs injected 20–24 hr. after decapitation, rates of movement, although commensurable, were further decreased. The relative distance moved by the stain varied on occasion in ash, and rates of movement dropped markedly in this species following decapitation. Similarly, speeds of travel were much reduced in diffuse-porous species following detopping.     

ON THE CAUSE OF THE INFLUENCE OF IONS ON THE RATE OF DIFFUSION OF WATER THROUGH COLLODION MEMBRANES. II

1. It had been shown in previous publications that when pure water is separated from a solution of an electrolyte by a collodion membrane the ion with the same sign of charge as the membrane increases and the ion with the opposite sign of charge as the membrane diminishes the rate of diffusion of water into the solution; but that the relative influence of the oppositely charged ions upon the rate of diffusion of water through the membrane is not the same for different concentrations. Beginning with the lowest concentrations of electrolytes the attractive influence of that ion which has the same sign of charge as the collodion membrane upon the oppositely charged water increases more rapidly with increasing concentration of the electrolyte than the repelling effect of the ion possessing the opposite sign of charge as the membrane. When the concentration exceeds a certain critical value the repelling influence of the latter ion upon the water increases more rapidly with a further increase in the concentration of the electrolyte than the attractive influence of the ion having the same sign of charge as the membrane. 2. It is shown in this paper that the influence of the concentration of electrolytes on the rate of transport of water through collodion membranes in electrical endosmose is similar to that in the case of free osmosis. 3. On the basis of the Helmholtz theory of electrical double layers this seems to indicate that the influence of an electrolyte on the rate of diffusion of water through a collodion membrane in the case of free osmosis is due to the fact that the ion possessing the same sign of charge as the membrane increases the density of charge of the latter while the ion with the opposite sign diminishes the density of charge of the membrane. The relative influence of the oppositely charged ions on the density of charge of the membrane is not the same in all concentrations. The influence of the ion with the same sign of charge increases in the lowest concentrations more rapidly with increasing concentration than the influence of the ion with the opposite sign of charge, while for somewhat higher concentrations the reverse is true.     

ON THE CAUSE OF THE INFLUENCE OF IONS ON THE RATE OF DIFFUSION OF WATER THROUGH COLLODION MEMBRANES. I

1. In three previous publications it had been shown that electrolytes influence the rate of diffusion of pure water through a collodion membrane into a solution in three different ways, which can be understood on the assumption of an electrification of the water or the watery phase at the boundary of the membrane; namely, (a) While the watery phase in contact with collodion is generally positively electrified, it happens that, when the membrane has received a treatment with a protein, the presence of hydrogen ions and of simple cations with a valency of three or above (beyond a certain concentration) causes the watery phase of the double layer at the boundary of membrane and solution to be negatively charged. (b) When pure water is separated from a solution by a collodion membrane, the initial rate of diffusion of water into a solution is accelerated by the ion with the opposite sign of charge and retarded by the ion with the same sign of charge as that of the water, both effects increasing with the valency of the ion and a second constitutional quantity of the ion which is still to be defined. (c) The relative influence of the oppositely charged ions, mentioned in (b), is not the same for all concentrations of electrolytes. For lower concentrations the influence of that ion usually prevails which has the opposite sign of charge from that of the watery phase of the double layer; while in higher concentrations the influence of that ion begins to prevail which has the same sign of charge as that of the watery phase of the double layer. For a number of solutions the turning point lies at a molecular concentration of about M/256 or M/512. In concentrations of M/8 or above the influence of the electrical charges of ions mentioned in (b) or (c) seems to become less noticeable or to disappear entirely. 2. It is shown in this paper that in electrical endosmose through a collodion membrane the influence of electrolytes on the rate of transport of liquids is the same as in free osmosis. Since the influence of electrolytes on the rate of transport in electrical endosmose must be ascribed to their influence on the quantity of electrical charge on the unit area of the membrane, we must conclude that the same explanation holds for the influence of electrolytes on the rate of transport of water into a solution through a collodion membrane in the case of free osmosis. 3. We may, therefore, conclude, that when pure water is separated from a solution of an electrolyte by a collodion membrane, the rate of diffusion of water into the solution by free osmosis is accelerated by the ion with the opposite sign of charge as that of the watery phase of the double layer, because this ion increases the quantity of charge on the unit area on the solution side of the membrane; and that the rate of diffusion of water is retarded by the ion with the same sign of charge as that of the watery phase for the reason that this ion diminishes the charge on the solution side of the membrane. When, therefore, the ions of an electrolyte raise the charge on the unit area of the membrane on the solution side above that on the side of pure water, a flow of the oppositely charged liquid must occur through the interstices of the membrane from the side of the water to the side of the solution (positive osmosis). When, however, the ions of an electrolyte lower the charge on the unit area of the solution side of the membrane below that on the pure water side of the membrane, liquid will diffuse from the solution into the pure water (negative osmosis). 4. We must, furthermore, conclude that in lower concentrations of many electrolytes the density of electrification of the double layer increases with an increase in concentration, while in higher concentrations of the same electrolytes it decreases with an increase in concentration. The turning point lies for a number of electrolytes at a molecular concentration of about M/512 or M/256. This explains why in lower concentrations of electrolytes the rate of diffusion of water through a collodion membrane from pure water into solution rises at first rapidly with an increase in concentration while beyond a certain concentration (which in a number of electrolytes is M/512 or M/256) the rate of diffusion of water diminishes with a further increase in concentration.     

MOVEMENT OF EELWORMS: V. OBSERVATIONS ON APHELENCHOIDES RITZEMA-BOSI (SCHWARTZ, 1912) STEINER, 1932 ON FLORISTS' CHRYSANTHEMUMS

Adults of Aphelenchoides ritzema-bosi tend to migrate up the stems of chrysanthemum plants in stationary water films possibly by a negatively geotropic response. A current of water down the stem opposes such an upward movement. Greatest mobility occurred in thick films of water in places with a high concentration of epidermal hairs as at the top of the stem and on the undersurface of leaves. Ciné films of movement in thick and thin films showed that there were fundamental differences in the type of locomotion in these two environments. Invasion of leaves via stomata was observed and the method of movement is described. The presence of A. ritzema-bosi in leaves appears to render the epidermis permeable to water. During dry weather there is little movement inside the leaf, but after rainfall activity increases as water enters the leaf. Spread of eelworm infestation in the leaf occurs in the mesophyll and across veins although initially these act as barriers. Emergence occurs via the stomata, chiefly on the undersurface. When the leaf is wet, about 50% of the eelworms emerge in the first hour. During wet weather many eelworms were recovered from the surfaces of leaves and it is suggested that eelworms spread mostly under these conditions.     

INFLUENCE OF A SLIGHT MODIFICATION OF THE COLLODION MEMBRANE ON THE SIGN OF THE ELECTRIFICATION OF WATER

1. It is shown that collodion membranes which have received one treatment with a 1 per cent gelatin solution show for a long time (if not permanently) afterwards a different osmotic behavior from collodion membranes not treated with gelatin. This difference shows itself only towards solutions of those electrolytes which have a tendency to induce a negative electrification of the water particles diffusing through the membrane, namely solutions of acids, acid salts, and of salts with trivalent and tetravalent cations; while the osmotic behavior of the two types of membranes towards solutions of salts and alkalies, which induce a positive electrification of the water particles diffusing through the membrane, is the same. 2. When we separate solutions of salts with trivalent cation, e.g. LaCl₃ or AlCl₃, from pure water by a collodion membrane treated with gelatin, water diffuses rapidly into the solution; while no water diffuses into the solution when the collodion membrane has received no gelatin treatment. 3. When we separate solutions of acid from pure water by a membrane previously treated with gelatin, negative osmosis occurs; i.e., practically no water can diffuse into the solution, while the molecules of solution and some water diffuse out. When we separate solutions of acid from pure water by collodion membranes not treated with gelatin, positive osmosis will occur; i.e., water will diffuse rapidly into the solution and the more rapidly the higher the valency of the anion. 4. These differences occur only in that range of concentrations of electrolytes inside of which the forces determining the rate of diffusion of water through the membrane are predominantly electrical; i.e., in concentrations from 0 to about M/16. For higher concentrations of the same electrolytes, where the forces determining the rate of diffusion are molecular, the osmotic behavior of the two types of membranes is essentially the same. 5. The differences in the osmotic behavior of the two types of membranes are not due to differences in the permeability of the membranes for solutes since it is shown that acids diffuse with the same rate through both kinds of membranes. 6. It is shown that the differences in the osmotic behavior of the two types of collodion membranes towards solutions of acids and of salts with trivalent cation are due to the fact that in the presence of these electrolytes water diffuses in the form of negatively charged particles through the membranes previously treated with gelatin, and in the form of positively charged particles through collodion membranes not treated with gelatin. 7. A treatment of the collodion membranes with casein, egg albumin, blood albumin, or edestin affects the behavior of the membrane towards salts with trivalent or tetravalent cations and towards acids in the same way as does a treatment with gelatin; while a treatment of the membranes with peptone prepared from egg albumin, with alanine, or with starch has no such effect.     

MOVEMENT IN THE CYANOPHYCEAE : THE EFFECT OF pH UPON MOVEMENT IN OSCILLATORIA

The effect of pH upon the velocity of translatory movement of Oscillatoria formosa Bory in inorganic culture solutions was determined. Unhindered movement occurred in the range of about pH 6.4 to 9.5. Above and below these limits inhibition was marked. In the unfavorable acid and alkaline ranges inhibition was progressive with exposure time; in the favorable range continuous movement was maintained for 24 hours.     

THE INFLUENCE OF P-RETENTION BY SOILS AND SEDIMENTS ON THE WATER QUALITY OF THE LIONS RIVER

SUMMARY

The soils of Midmar dam catchment and the sediments of the Lions river are shown to have high P-retention properties. Present conditions result in little leaching of PO₄ ^?4 from the soils and favour a net transport of P from overlying water to the sediments. P levels in the water are likely to remain low even if the loading rate of P were increased substantially. It is postulated however that other factors may induce a release of P from the sediments and adversely affect the load carried by the water.