THE MICROBIOLOGICAL BALANCE OF STRAWBERRY ROOT ROT SOIL AS RELATED TO THE RHIZOSPHERE AND DECOMPOSITION EFFECTS OF CERTAIN COVER CROPS

1941 ◽  
Vol 19c (6) ◽  
pp. 199-210 ◽  
Author(s):  
P. M. West ◽  
A. A. Hildebrand
Keyword(s):  
Cover Crops ◽  
Root Rot ◽  
Red Clover ◽  
Root Systems ◽  
The Other ◽  
Leguminous Plants ◽  
Other Hand ◽  
Living State ◽  
Rhizosphere Effects ◽  
Severity Of The Disease

Soybean and red clover, grown as cover crops and incorporated into strawberry root rot soil, showed a marked difference in ability to control the disease on variety Premier. Soybean caused a striking reduction in the incidence of root rot and a drastic shift in the bacterial equilibrium of the soil. Red clover had little effect on the severity of the disease or the general microflora of the soil.A study of "rhizosphere effects" reveals that the characteristic differences between the resultant bacterial equilibrium of the soils in which the two leguminous plants were grown, could not be attributed to influences exerted by the latter in the living state. However, the bacterial types favoured during decomposition in experimental cultures of tissues of red clover and of soybean, each inoculated with root rot soil, were identical with those isolated from root rot soil with which red clover and soybean, respectively, had been incorporated. In contrast to the putrefactive decomposition of red clover, soybeans apparently underwent a carbohydrate breakdown that could be reproduced essentially in culture by the substitution of glucose for soybean tissues. Beneficial changes in the bacteriology of actual root rot soils could be induced by the decomposition of pure carbohydrate in place of soybean. The favourable alteration in the bacterial equilibrium was accompanied by a corresponding modification of the fungous flora such that potentially pathogenic forms were replaced by presumably innocuous ones. These carbohydrate treated soils were capable of producing strawberry plants with well developed healthy root systems. The ability of soybean to control strawberry root rot therefore seems to depend primarily on a carbohydrate type of breakdown in diseased soil, causing a highly favourable shift in the microbiological equilibrium. The decomposition of red clover, on the other hand, did not under the same conditions induce these salutary effects.

STRAWBERRY ROOT ROT IN RELATION TO MICROBIOLOGICAL CHANGES INDUCED IN ROOT ROT SOIL BY THE INCORPORATION OF CERTAIN COVER CROPS

1941 ◽  
Vol 19c (6) ◽  
pp. 183-198 ◽  
Author(s):  
A. A. Hildebrand ◽  
P. M. West
Keyword(s):  
Cover Crops ◽  
Root Rot ◽  
Mycorrhizal Fungus ◽  
Red Clover ◽  
Soil Series ◽  
Infected Root ◽  
Agricultural Plants ◽  
Severity Of The Disease ◽  
Disease Attack ◽  
Balance Index

Strawberry plants, variety Premier, were grown in naturally-infected root rot soil in which consecutive "crops" of several agricultural plants had been turned under, and in other lots of the same soil that had been steam sterilized or fertilized with barnyard manure. On examination of their roots it was found that the incidence and severity of root rot were closely correlated with soil treatment. Plants grown in sterilized soil remained free from disease as did those of the soybean series until the third season when they were slightly affected. Plants in the manure, corn, red clover, timothy, and untreated soil series all became diseased, the severity of attack increasing in the respective series in the order named.Although roots of the various cover crops were found to contain representatives of several different genera of fungi, a specific fungus was dominant in each as was the nematode, Pratylenchus pratensis, in timothy and clover. This build-up of specific organisms appeared to be correlated with the incidence and severity of the disease in the roots of the strawberry plants that followed in the respective series.However, in strawberry plants grown in the variously treated soils, fungal infection was negligible and, on the whole, not related to that of the preceding cover crop. An exception to this was the heavy infection by the mycorrhizal fungus (Rhizophagus sp.?), following timothy and corn, but a lack of correlation, in many cases, between the presence of the fungus and discoloured and necrotic tissue indicated that other agencies might be responsible for the injury. In timothy and red clover treated soils, nematodes, particularly Pratylenchus pratensis, might have been an important factor.Fewer bacteria were found adjacent to roots of healthy plants than to those of diseased ones. Qualitative differentiation on the basis of nutritional requirements indicated a striking relationship between the incidence of certain groups of bacterial isolates and the severity of disease attack. The equilibrium between presumably "harmful" bacteria and the innocuous, normally occurring rhizosphere types is designated the Bacterial Balance Index. There are marked differences in the microbiological equilibria of the different soil series; increased severity of root rot is associated with a fall in the Bacterial Balance Index.

scholarly journals 576 Strawberry Yields of Normal vs. “J” Root Plants

HortScience ◽  
1999 ◽  
Vol 34 (3) ◽  
pp. 546A-546
Author(s):  
Warren E. Bendixen
Keyword(s):  
Ground Surface ◽  
Soil Surface ◽  
Root Systems ◽  
Fruit Yield ◽  
Fresh Fruit ◽  
The Other ◽  
Yield Reduction ◽  
Field Surveys ◽  
Plant Vigor ◽  
Other Hand

Many factors contribute to the reduction of strawberry yields. Field surveys in previous years have shown that the lack of plant vigor associated with poor crown and root systems was the result of “J” root plants. A 1998 strawberry trial was established on 7 Nov. 1997 to evaluate the fruit yield of “J” root plants in comparison with normal roots. A “J” root plant occurs when the workers place the crown at the soil surface, while the other hand then pushes the center of the root into the slotted area, leaving the lower roots near or above the ground surface. The workers used a trowel to plant the normal root plants, place the roots straight down. The variety Camarosa was planted on 64-inch-wide beds. Each plot was one bed wide and 30 feet long and replicated four times. The strawberry plants were spaced 14 inches apart within the rows and the rows 10 inches apart. Strawberry yields of normal vs. “J” root plants showed the “J” roots reduced yields more early in the season. The March, April, and May yields were harvested as fresh fruit. The normal plants yielded 33,653 lb/acre, compared to 28,411 lb/acre for the “J” roots. The June and July yields were harvested as freezer fruit. The yields for normal plants were 36,421 lb compared to 32,941 for “J” root plants. The season total yields were 70,074 lb/acre for the normal roots compared to 61,352 lb for the “J” roots, or a 14.2% yield reduction. In 1998, 10 commercial strawberry fields were surveyed to evaluate the number of “J” root plants. The results showed an average of 54% of the plants were “J” root plants, with the fields ranging from 25% to 77.5%.

STUDIES ON ROOT ROT OF CORN IN ONTARIO

1942 ◽  
Vol 20c (4) ◽  
pp. 241-256 ◽  
Author(s):  
J. K. Richardson
Keyword(s):  
Cover Crops ◽  
Root Rot ◽  
Severe Damage ◽  
Corn Root ◽  
Field Crops ◽  
Soil Temperatures ◽  
Severity Of The Disease ◽  
Corn Root Rot ◽  
Micro Organisms ◽  
Intermediate Effect

Root rot of corn in Ontario is caused primarily by parasitic soil micro-organisms, the most important of which are species of Pythium, Helminthosporium, and Fusarium in that order. The disease causes a decrease in the stand by pre-emergence killing and a dwarfing of the plants by the parasitic invasion and destruction of their roots by the organisms. The pathogens have different optimum soil temperatures but the lower ranges favour those that cause the most severe damage. The roots of other field crops can be parasitized by the organisms found associated with corn root rot, but their effect on the development of the crop varies greatly. It has been proved under greenhouse conditions that the severity of the disease is greatly reduced if the corn is preceded by cover crops of soybeans and materially increased when preceded by timothy. Other crops tested have an intermediate effect.

ON CHLOROPHYLL TURNOVER IN MONOCOTYLEDONS AND DICOTYLEDONS

1963 ◽  
Vol 41 (2) ◽  
pp. 221-226 ◽  
Author(s):  
Harold J. Perkins ◽  
D. W. A. Roberts
Keyword(s):  
Sodium Acetate ◽  
Red Clover ◽  
Chlorophyll Synthesis ◽  
The Other ◽  
Mature Leaves ◽  
Other Hand

Sodium acetate-1-C14 or (in one case) succinic-2,3-C14 acid was fed to both immature and mature leaves of four monocotyledons (lily, oats, philodendron, and tradescantia), three dicotyledons (red clover, petunia, geranium), a gymnosperm (spruce), and a pteridophyte (Boston fern). These experiments have indicated that chlorophyll synthesis and thus chlorophyll turnover in the mature leaves of the monocotyledons is very slow or non-existent. On the other hand, considerable amounts of C14 were incorporated into the dihydroporphyrins isolated from the mature leaves of the dicotyledons, the gymnosperm, and the pteridophyte.

RECENT OBSERVATIONS ON STRAWBERRY ROOT ROT IN THE NIAGARA PENINSULA

1934 ◽  
Vol 11 (1) ◽  
pp. 18-31 ◽  
Author(s):  
A. A. Hildebrand
Keyword(s):  
Root Rot ◽  
Mycorrhizal Fungi ◽  
Lateral Roots ◽  
Root Systems ◽  
The Other ◽  
Cultivated Plants ◽  
Frequency Of Occurrence ◽  
The Moment ◽  
Apparently Healthy

The investigations reported here have centred largely around isolations from, and critical microscopic examination of, the roots of affected plants. Isolations from 684 young, adventitious and lateral roots showing definite lesions bordered by turgid, healthy tissue, yielded representatives of approximately 20 different genera of fungi, ranging in frequency of occurrence from 0.4% in the case of Gliocladium to 32.7% in the case of Fusarium. Next to Fusarium, isolates of Ramularia and Pythium appeared most frequently and consistently in culture, the former in 28.5%, and the latter in 10.8%, of the plantings. Results of infection experiments involving these as well as other genera, including Penicillium, Rhizoctonia, Hainesia, Cylindrocladium, Coniothyrium and Helminthosporium, are not yet available and it is impossible at the moment to evaluate the significance of their association with the diseased condition of the roots from which they were isolated. Isolations from 125 apparently healthy rootlets occurring on root systems, other parts of which were more or less severely diseased, yielded representatives of nine different genera of fungi, ranging in frequency of occurrence from 1.6% in the case of Alternaria to 5.6% in the case of Ramularia. Isolates of Fusarium appeared in 4.0% of the plantings.Microscopic examination of 550 adventitious and lateral roots of wild and cultivated plants has revealed the almost universal occurrence in their tissues of two of the so-called "endotrophic mycorrhizal fungi." One of these is of the characteristic phycomycetoid type, producing arbuscules and vesicles, the other, of the Rhizoctonia type familiar in orchids. The former type has been observed much more consistently than the latter. In a number of instances both types have been found in the tissues of the same rootlet. At least three strains of the Rhizoctonia type have been isolated but so far all efforts to culture the other organism have been unsuccessful. Resting spores of Olpidiaster (Asterocystis) and the spherical, smooth-walled spores of some member of the Plasmodiophoraceae were observed in diseased rootlets in the early part of the growing season. Pythium was noted in abundance occurring on diseased roots obtained in the field during September and November.Nematodes have been encountered in association with diseased roots in numbers and frequency sufficient to suggest a possible causal relationship to strawberry root rot.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

Stories and the Self

2020 ◽  
Vol 32 (2) ◽  
pp. 47-58 ◽  
Author(s):  
Stefan Krause ◽  
Markus Appel
Keyword(s):  
Meta Analysis ◽  
The Self ◽  
The Other ◽  
Lower Degree ◽  
Contrast Effects ◽  
Self Perception ◽  
Self Perceptions ◽  
Other Hand ◽  
The One ◽  
Implicit And Explicit

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.

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