摘要:

Experiments were carried out to determine what degree of intervarietal cross‐pollination occurs when two radish varieties are grown at varying distances apart. The varieties chosen were Icicle and Scarlet Globe. Hybrids are distinctive; thus crossing is readily determined.In closely planted experiments, where one half of the plot was Icicle and the other half Scarlet Globe, the amount of intercrossing ranged from 30 to 40 % at a distance of 9 in. to an average of about 1 % at 15 ft. Intercrossing decreased fairly regularly and rapidly with distance.Single plants of Icicle were run out from plots of Scarlet Globe; in 1941 at distances from 9 in. to 95 ft. and in 1942 from 9 in. to 408 ft. In the plants near the red plots crossing was approximately 100 %. In 1941 there was a regular and rapid fall with distance and intervarietal crossing stopped at 95 ft. In 1942 the plots were closer to beehives; intercrossing was less regular and extended farther than in 1941, but beyond 240 ft. it was only 0.1%, and in an all‐white plot 360 ft. from a red plot with no intervening stringer plants it was nil.Given a mass of plants and a profusion of flowers, bees confine their flower visiting to a small area. When radishes are grown in quantity 300 ft. guards against contamination of stock due to intervarietal crossing. If only small numbers are grown intercrossing is likely to occur over a greater dista

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06705.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY

摘要:

This paper completes the survey of the effects of five factors on flowering behaviour, bulbing, and ripening of onions grown from sets (Heath, 1943) and deals with the factors day length and temperature in the second season. The results from both papers are discussed and the main conclusions are as follows: Flowering is greatly reduced or completely inhibited by submitting the plants to high temperature whether (1) during the whole period of growth from seed to set, (2) during the first part or whole of the storage period (Oct.‐Mar.), or (3) throughout the second season of growth from set to mature onion bulb. Unless very high temperature (35d̀; C.) is reached, heat storage restricted to the last part of the dormant period may only delay but not reduce flowering. Cold storage (od̀; C.) throughout or for the first part of the storage period reduces flowering; when restricted to the last part it tends to increase bolting, but at any other period in the life history of the onion plant bolting is apparently favoured by medium temperature (10–15d̀ C). Long days (16 hr.) throughout the second season inhibit inflorescence emergence irrespective of temperature within the range investigated. Conditions of day length and temperature in the second season favourable to bulbing are inimical to flowering: thus both long days and high temperature tend to encourage bulbing and prevent bolting, while short days inhibit bulbing but allow of bolting if the temperature is not too high. Late planting of sets in the field therefore reduces bolting. Leaf emergence ceases abruptly when bulbing begins at high temperature, and even at low temperature few if any more leaves expand. The relation of this fact to optimal time of planting and the use of American varieties capable of bulbing in short photoperiods is discussed. Seedlings apparently need a longer photoperiod for bulbing than plants grown from sets. A day length just adequate for bulbing at high temperature will not allow of bulbing at low temperature, with the result that seedlings sown very late produce good bulbs at high temperature but may fail to bulb at low temperatures. High‐temperature storage, especially during the last part of dormancy, tends to the production of distorted leaves, especially when followed by growth of the sets at high temperature. Such plants show a high mortality. Heat storage also delays and restricts bulbing, which is reflected in the increased number of expanded leaves. Ripening is similarly delayed; this effect is not directly due to water loss during

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06706.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY

摘要:

Sand‐culture experiments with the radish demonstrated that the optimum concentrations of nitrogen for root development were the highest employed, 32.96 and 65.92 p.p.m. Deficiency of nitrogen led to poor growth and to a characteristic outlining of the cotyledons in red, with red petioles. As with the carrot and turnip, a low concentration of available phosphorus, here 2.05‐4.09 p.p.m., gave the best root growth; and a marketable radish was obtained with so little as 0.10 p.p.m., suggesting that the relatively large radish seed contains a considerable quantity of phosphorus. The highest concentration of potassium used, 22.44 p.p.m., yielded the largest roots, and a diminution in this amount led to loss of yield and eventually to serious scorch of the foliage. There is possibly some boron in the radish seed; for though absence of this from an otherwise satisfactory solution resulted in diminished yields, the foliage was normal in appearance, and the radish of eatable size; the radishes apparently lacked ability to sw

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06707.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY

摘要:

Control of basal rot of narcissus following hot‐water treatment against eelworm was equally good when 0.5% formalin was included in the bath or was used as a cold or warm steep immediately afterwards. When the formalin steep was delayed control was less good. All methods of applying formalin in connexion with hot‐water treatments used in these experiments were equally harmless to growth and flowering of the bu

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06708.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY

摘要:

Inoculations in situ of roots of narcissus plants with cultures ofFusarium bulbigenumin early summer gave positive results, as shown by the presence of rotted bulbs at the time of lifting or by subsequent rotting of bulbs in storage. These results were obtained only if the soil was wet at and after the date of inoculation. Cool weather delayed infection. Bulbs planted in the autumn in soil artificially or naturally contaminated withF. bulbigenumgave a complete stand in spring but later showed considerable losses from basal rot.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06709.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY

摘要:

Infection of tomato plants byVerticillium albo‐atrumwas 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 withVerticilliumimmediately 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 ofVerticilliumfrom the roots of an infected plant to those of neighbouring healthy plants was hastened by killing the infected pl

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06710.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY

摘要:

Appearance and spread of infection with mosaic‐inducing viruses were studied for three seasons in tomato crops under glass. Comparison was made between the reactions of plants raised from virus‐free seed and those of plants raised from virus‐infected seed, on plots distributed at random in a house in which no precautions against entry and spread of virus were taken. Freedom from mosaic infection was maintained longest in plants raised from virus‐free seed. An experiment was carried out after steam sterilization of the soil and under exceptionally favourable weather conditions. Appearance of mosaic symptoms occurred later in the life of the plants in this season and plants raised from virus‐free seed did not react differently from other plants.The location of plants first showing mosaic symptoms was related to the depth and texture of soil beneath those plants.Tests were made of the apparent virus content of infected tomato seed during germination and differences were found in the persistence of virus during germination in seeds of differing origin.Apparent, ‘delayed’ seed transmission of mosaic‐inducing viruses occurs in the tomato crop, but as yet, this condition can only be interpreted in terms of differences in the resistance of plants raised from seed of differing origin to the multiplication and systemic spread of those viruses. The use of virus‐free seed taken from well‐nourished vigorous plants is essential to the production of a virus‐free tomato crop under

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06711.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY

摘要:

The reactions of 146 potato varieties to graft infection with viruses X, A, B and C are recorded, on the basis of their top‐necrotic or non‐necrotic symptoms. Evidence is given that the viruses B and C used in this work were uncontaminated with other viruses. Reference is made to the effects of varietal reaction on virus distribut

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06712.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY

摘要:

Studies on the spread of potato viruses X and Y and cucumber mosaic virus in the field are described: tobacco was used as the experimental plant. The plants were set out in the form of a cross, one series with the leaves in contact and one with the leaves not touching. No spread of potato virus X was observed, but there was extremely rapid permeation of virus Y throughout the plots. The spread of cucumber mosaic virus was much slower than that of virus Y.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06713.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY

摘要:

Records were obtained for the emergence of the first and second generation flies at Chatteris and Cambridge. There is a correlation between the age of the carrot crop and the commencement of the emergence of the second generation from it. The first generation was successfully controlled by killing the flies with a poison bait sprayed on the dikesides of the carrot fields. This treatment reduced the popúlation of second generation flies and also their attack. Spraying the dikesides and/or the headlands of eight maincrop carrot fields in August and September greatly reduced the second generation damage. Very high kills of carrot fly were obtained on the headlands of treated fields. Poor results were given by the treatment on three very weedy fields which were incompletely treated. A marked increase in attack occurred in three untreated areas in 1942 as compared with the previous year.Application of the poison bait spray in the field is discussed. Creosote‐treated string gave promising results in small‐scale experiments for the control of the second generation. Calomel dust (4°) with and without grass cuttings caused no reduction in attack.In hot sunny weather the flies shelter in the vegetation around carrot fields from about 10 a.m. until about 5 p.m. In the cooler conditions of early morning and evening there is a movement of flies into the field. This rhythm is not maintained in dull warm weatherSeedling carrots may be attacked in the field any time after the cotyledon stage. This enables the first generation of flies to propagate on main crop carrots. Soil sections about carrot rows showed that pupae of the overwintering generation are closely congregated around the carrots. Various insecticides were tested for the destruction of pupae in the soil. A creosote‐sawdust mixture gave the best results.Storage experiments showed that clamped carrots deteriorate much less than those unlifted. The population of flies is greatly increased by allowing attacked carrots to remain unlifted throughout the winter or by ploug

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1943.tb06714.x

出版商:Blackwell Publishing Ltd    

年代:1943

数据来源: WILEY