ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04345.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY

摘要:

Summary1The effect of nitrogen and potassium on the fruiting of the tomato under glass is studied by observations on plants grown on completely manured plots and plots from which nitrogen and potassium respectively have been omitted from the scheme of manuring over a period of years.2Nitrogen starvation reduces the number of blossom‐buds formed, the percentage of buds that open and the mean numbers of fruits per flower‐truss. Potassium starvation does not affect the number of blossom‐buds formed or the percentage of buds that open but reduces the mean numbers of fruits per flower‐truss.3An outstanding feature of nitrogen starvation is retardation of the rate of development of successive flower‐trusses. With potassium starvation the rate of development is accelerated. Growth, estimated from increase in height of plants trimmed to a single axis by continuous removal of incipient axillary shoots, is retarded by both nitrogen and potassium starvation.4The “maturation period” (between opening of the blossom and ripening of the fruit) is lengthened by potassium starvation, shortened by moderate nitrogen starvation and lengthened by severe nitrogen starvation. From the present results, in conjunction with data published previously, it is concluded that the “maturation period” is shortened by a high carbohydrate‐nitrogen balance and lengthened by a low carbohydrate‐nitrogen balance.5In mid‐season all plants suffer a check to growth and development demonstrated by (a) retardation of the rate of differentiation of leaves and flower‐trusses, (b) cessation of growth in height, and (c) the occurrence of a high proportion of fruit with arrested development. This “mid‐seasonal check” is accentuated by nitrogen and potassium starvation, especially the former, corresponds with the period of maximal weight of developing fruit, and is attributed to competition for nutrient supply between the fruits and vegetative parts of the plants, leading to apparent antagonism between these processes.6The fruiting and foliage symptoms of the potassium‐starved plants are attributed to the following effects:(a) The potassium in starved plants is undergoing a continuous cycle, being translocated from older parts of the plant to the growing point, incorporated in young leaves and flower trusses and subsequently re‐translocated as these organs are approaching maturity.(b) The level of potassium supply regulates nitrogen metabolism, a moderately low potassium supply being associated with high protein level and a greater degree of seventy of potassium starvation with low protein level.7The results are discussed in relation to the problems of overbearing and potassium manuring. The observed effects of potassium deficiency on fruiting (acceleration of development of flower trusses, failure of pollination and prolongation of the “maturation period” of the fruit) are those also associated with carbohydrate

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04346.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY

摘要:

Summary1Manurial treatment exercises a strong influence on the growth of apple trees, their time of blossoming, the amount of bloom, the foliage colour and the fruit colour. The effect is mainly due to nitrogen which induces increased growth, earlier flowering, more bloom, greener foliage and softer and greener fruit. Potash and phosphate have little effect on the growth of the trees, or on blossoming or foliage, but favour the production of more highly colonred fruit.2Nitrogenous manuring increases the nitrogen content of the fruit. Thus in 1930 the mean nitrogen content for the samples from plots receiving and not receiving nitrogen, was 0.0229 and 0.0550 respectively. In the following year the results for similarly treated pots were 0.0430 and 0.0745 respectively. Considering the results obtained in the years in question the mean nitrogen content for 1930 when there was a good yield was 0.0372 in contrast with 0.0587 for 1931 when the yield was poor. The control plot alone gave values of 0.0218 and 0.0343.3In 1930 the rates of radial advance (in mm. per day) ofCytosporina ludibundafor samples from plots receiving different treatments were K, 0.082; K+P, 0.118; X, 0.130; P, 0.150; C, 0.259; N+K+P, 0.456; N+P, 0.678; N, 1.213; and N+K, 1.249. The rate for the ample from the plot treated with N+K is fifteen times that calculated for the apples from the plot treated with K. The effect of nitrogenous as compared with non‐nitrogenous or no manuring has been studied in each of three years. The mean values for radial advance obtained for samples from plots receiving no nitrogen were 1930, 0.153; 1931, 0.33; 1932, 0.54, while for samples from plots receiving nitrogenous manuring the values were 1930, 0.889; 1931, 1.08; and 1932, 0.89. The values obtained in 1930 receive confirmation from observations on the radial spread of the fungus on the sterilized tissue from apples produced on trees in the various plots. The value γrm=+0.9112 was obtained for the correlation between radial advance (R) and radial spread (M). In 1930 the rate of growth of the fungus in the sample from the plot treated with K was one‐third of that in the sample from the control plot.4Radial advance is correlated with nitrogen content (N) of the fruit and this relationship is shown by the following values for the correlation coefficient: 1930, γRN+=0.8571; 1931, γrm=+0.7277.5Nitrogenous manuring increases the intensity of the attack ofVenturia inaequalison the fruit in the orchard. Evidence is produced in support of the suggestion that fruit resistant to attack byV. inaequalismay also be resistant to invasion by a rot producing fungus in storage. The value of the correlation between radial advance (R) and the percentage weight of scabbed fruit (S) was γRS+=0.6395. The percentage weight of scabbed fruit was shown to be correlated with the nitrogen content of the fruit and the value of the coefficient obtained was γSN;

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04347.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY

摘要:

Summary1Tubers stored for 10–12 days at 18°C. lost considerably less weight during subsequent storage than those pre‐stored at 7°C. previous to permanent storage. This emphasizes the importance of pre‐storing potatoes for a brief duration at a higher temperature preparatory to permanent cold storage.2In the adolescent tubers the loss in weight during storage is high and decreases with increasing maturity of the tubers, the value for the total loss being about the same in mature and ripe tubers.3Although the magnitude of shrinkage during storage of mature and ripe potatoes is practically the same, the former are superior to the latter in that they keep longer in storage without sprouting.4During storage the loss in weight of potatoes due to respiration is very small in comparison with that caused by evaporation o

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04348.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY

摘要:

Summary1Adolescent, mature and ripe potatoes continue to be distinguished by their respiratory behaviour throughout the period of storage.2When potatoes are placed in storage there is a progressive increase in the concentration of internal carbon dioxide until the termination of the period of dormancy, the percentage of this gas falling rapidly with the commencement of sprouting.3Data concerning the composition of the atmosphere surrounding the tubers show that, in general, there is an accumulation of carbon dioxide in the surrounding air with increasing periods in storage.4There is a negative correlation between R.Q. and the percentage internal carbon dioxide during the stages of dormancy and sprouting.5Records concerning the composition of samples of air withdrawn from top, middle and bottom layers of potatoes show a slightly higher percentage of carbon dioxide in the bottom layer than in the middle and top ones.6Data concerning the permeability of the periderm of the potato to gas during storage indicate that the permeability of the superficial tissues decreases considerably during the dormancy of tubers.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04349.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04350.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY

摘要:

Summary1Poor stands of peas due to fungal rotting were observed in field experimental plots in widely separated pea‐growing districts.2The rotting was not due to seed‐borneAscochyta pisiorMycosphaerella pinodeswhich were apparently absent from the seed.3Isolations from surface sterilized cotyledons of several varieties of peas grown in sterilized and unsterilized soil showed an abundance of common moulds and several pathogenic fungi, namely: aFusariumof the sectionRoseum, Fusarium culmorumandBotrytis cinerea.4Isolations from surface sterilized rotting stems from five experimental centres at harvest time indicated the presence of a great variety of fungi including a number of species ofFusarium. Many of these, including all the common moulds such asPenicillium, were non‐pathogenic to the cotyledons.Fusarium avenaceumwas found to be highly pathogenic to the cotyledons;F. solanivar.Martiishowed some signs of causing rotting;Botrytis cinereawas highly pathogenic. Several non‐pathogenic species ofFusariumwere obtained.5Tests with numerous stock cultures show high pathogenicity of the following fungi to pea cotyledons:Botrytis cinereafromLactuca, Rosaand elsewhere.Fusarium avenaceumfromTriticum.Fusarium culmorumfromTriticum, DianthusandCallistephus.Fusariumspecies fromVicia fabaandTulipa.Helminthosporium sativumfromTriticum.Ophiobolus heterostrophusfromOryza.Sclerotiniaspecies fromLactuca.Fusarium GraminearumfromTriticum.6It is suggested that loss of stand in pea crops due to rotting of the cotyledons by these and other fungi is probably more important than diseases caused byAscochytaandMycosphaerellaand foot‐rots in the l

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04351.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY

摘要:

Summary1Viola plants, of the variety Kate Blyth, which were badly infected with the fungusRamularia deflecens, were received from Coventry in the early spring.2Sclerotium‐like bodies were found on the leaves.3Pycnidia containing pycnospores were obtained in culture.4By comparison it is seen that these sclerotium‐like bodies are really pycnidia which have not developed fully.5The formation of pycnidia in culture depends on nutrition.6Perithecia are found neither on the plant nor in cdture.7In the early spring positive results from infection experiments are obtai

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04352.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY

摘要:

Summary1The investigations were planned to ascertain the extent of the migrations of Winged aphides, their ability to detect individual plants, the development of aphis population following colonization, and the extent to which Virus diseases may be transmitted to isolated plants by winged aphides.2Plants were isolated in root crops on seven farms and at varying distances from probable sources of virus infection. Four farms were located in districts where aphis population is usually high and viruses spread very rapidly; two in districts where both aphides and spread of viruses are minimal, whilst one farm could be regarded as intermediate in both respects.3Evidence is submitted to show that winged aphides have no difficulty in detecting and colonizing isolated plants. Their numbers were large at the four eastern centres and very small at the three western centres. In all cases the aphis population on isolated plants was less than that of the nearest general crop and suffered more from predators and parasites.4It is shown that isolated plants can be reached by migrants from a distance of at least a quarter of a mile, and probably much further. Additional evidence is given that these initial migrants introduce little virus infection to potato crops from extraneous sources. The importance, however, of the later movements of winged aphides, whether initial migrants or those subsequently produced on potatoes, in spreading Viruses from crop to crop, is emphasized.5The practical aspects of protecting potato stocks is discussed under conditions of (a) heavy infestation by winged aphides and proximity of partially diseased crops; (b) minimal winged aphis infeatation where numerous sources of virus infection occur in neighbouring crops; and (c) where both aphis infestation and sources of infection are minimal. It is considered that regulations for the improvement of health in seed‐potato stocks should take cognisance of these various possibilitie

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04353.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY

摘要:

Summary1TheCitrusaphis reproduces parthenogenetically continuously throughout the year; sexual reproduction has not been observed.2The most favourable temperature for development and reproduction of the aphis is between 22 and 25° C. Between 18 and 22° C. the rate of reproduction and development is also suflicient to bring about heavy infestation.3The temperature below 18° C. is unfavourable for considerable increase of the population of this hisect. At 7° C. reproduction is barely taking place.4At 30–32° C. the mortality of the nymphs is almost 100%. At 34–35° C. reproduction ceases, and at 36° C. adult insects die within a short period.5The annual fluctuations of the population of the insect based on field observations are described.6Food as a factor in the increase of the population of the aphis is discussed.7The effect of the annual fluctuations of the temperature in Palestine upon the population of the aphis is pointed out.8The economic status of the insect is

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1938.tb04354.x

出版商:Blackwell Publishing Ltd    

年代:1938

数据来源: WILEY