摘要:

Previous papers have dealt with the effects of five factors on the external aspects of flowering, bulbing and ripening in onions grown from sets and also the production of sets from seed and their storage through the winter; the present communication is concerned with changes in the internal morphology of onion sets and plants from the same experiments. The previously recorded effects on flowering of high and low temperatures are confirmed and further elucidated by data from dissections, which show the changes occurring at the growing point. Thus high temperature throughout the first season's growth from seed to set exerted an after‐effect, completely preventing initiation of inflorescences in the following spring. This effect may, however, have been due to the smaller size of the sets produced at high temperature. High temperature for the first 8 of the 22 weeks' experimental storage period produced a similar after‐effect in delaying and greatly reducing inflorescence initiation; here there was no question of a size effect being involved. High temperature throughout the 22 weeks not only completely prevented such initiation during treatment, but also practically inhibited it subsequently; when given during the latter part of storage only, it at least delayed initiation of inflorescences. High temperature during the growth from set to mature onion showed a direct effect in suppressing the emergence of inflorescences already initiated in the sets, apart from the effect of bulbing. (Bulb development, which occurs under the stimulus of long days if the temperature is not too. low, also inhibits such emergence.) Inflorescences prevented from emerging, whether by high temperature or bulbing, were displaced by the axillary bud which carried on the further development of the plant. Low temperature for the first 8 weeks of storage exerted an after‐effect in reducing the incidence of inflorescence initiation. When cold storage was given for the whole 22 weeks or the last 8 weeks only, initiation was prevented during treatment, but whereas in the former case subsequent initiation was greatly reduced, in the latter a rapid flush of initiation occurred on return of the sets to normal temperature. The effects of high‐ and low‐storage temperatures on formation of new leaf initials were mainly direct; the only after‐effect was a tendency for sets from treatments preventing leaf initiation to produce initials more rapidly on return to normal temperatures. (In the case of late cold storage this resembled the effect just noted for inflorescence initiation.) Sets produced at low temperature were prevented from forming leaf initials by continuous high‐temperature storage and those produced at high temperature by continuous cold storage; this suggests some degree of acclimatization to low and high temperature respectively. It appears that the 1 to 2 leaf primordia formed at normal temperatures between mid‐October and mid‐March are initiated mainly during the latter part of that period. The number of swollen bulb scales in an onion set is nearly constant at 3, irrespective of set size. Even the unswollen leaf initials vary little in number over a considerable range of set size, and therefore the better yields given by large sets (if they do not bolt) must be due rather to large size of parts than to high number of leaf initials ready for emergence. The size effect on flowering is likewise not connected with number of leaf initials present in the sets; it may be a matter of the number of emerged leaves in the previous season. There appears to be a minimal total number (12‐14) of leaves which must be initiated before an inflores

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06724.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Assimilable nitrogen in various forms prolonged the life ofOphiobolus graminisin infected wheat straw, whether added directly to the straw or to the surrounding soil. When the infected straws were buried in washed quartz sand, 0.5 g. nitrogen per 100 g. air‐dry straw was the optimum dressing for longevity of Ophiobolus. Addition of sodium phosphate did not significantly increase longevity.Nitrogen is considered to prolong the life ofOphiobolusby enabling the mycelium to form new branch hyphae, which can explore unexhausted parts of the substrate; it is suggested that aged mycelium dies from carbohydrate starvation, through exhaustion of the zones of enzymic erosion around the hyphae. This hypothesis is supported by the extended life of the fungus in infected straws that were shaken twice weekly in 3 % dextrose solution.Ophioboluswas found to survive longer in infected straws buried in a fallow soil than in the same soil under oats, mustard or trefoil; this finding suggests the use of catch crops as competitors withOphiobolusfor soil nitroge

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06725.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Tomato plants receiving adequate supplies of mineral nutrient acquired great resistance to infection byVerticillium albo‐atrumif the leaf‐shoot ratio was reduced; this effect is attributed to reduction in carbohydrate content of the host. Wide variation in potash manuring did not affect susceptibility of tomatoes toVerticill

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06726.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

The observations and experiments reported in the present paper were carried out in Suinin, Szechuan Province, West China, through the period 1938‐41. Under local conditions, the incidence of most cotton diseases was observed to be influenced chiefly by air humidity. No matter whether it attacks the seedlings, mature plants, or bolls, such a disease requires a humid condition preceding the occurrence of an epidemic. For sore shin disease, soil moisture and soil temperature, however, have a more profound influence. Cyrtosis, which is a disorder caused by leafhopper injury, responds to the climatic factors in a different way. During the period of rapid reproduction of the leafhopper, higher temperatures result in the earlier appearance of the disease, while heavy rainfalls reduce the intensity.Modification of the environmental conditions by varying the time of sowing influences the incidence of diseases occurring in both the seedling and mature stages of the cotton plant. Among seedling diseases, anthracnose is further proved to be influenced chiefly by air humidity in its prevalence. Sore shin disease, on the other hand, requires a moist soil condition for its spread and development. In the mature plant, late sowing increases the intensity of cyrtosis but reduces that of bacterial blight and anthracnose.Modification of several cultural practices was also tested. Nitrogenous fertilizers generally increase the incidence of most diseases. Denser stand and closer spacing bring about a heavier infection in stem and leaf diseases but not in boll diseases. A mixed cropping system appears to have no effect on the fungal and bacterial diseases but reduces the intensity of cyrtosis when the crop interplanted with cotton is not susceptible to the infestation of leafhoppe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06727.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Losses from hard rot, measured by an arbitrary disease index, were reduced by treating the dehusked corms before planting with mercuric chloride (with or without the addition of 10% hydrochloric acid), mercurous chloride (calomel), three proprietary mercury compounds (Aretan, Uspulun and Ceresan) and one proprietary non‐mercury compound (Folosan). Calomel was the least effective. All the treatments were relatively less effective when corms with definite lesions were treated.The weight of clean corms produced per old corm planted (weight index) was usually increased by all the fungicides tried, but calomel and Ceresan were less satisfactory than the others.Mercuric chloride (3 hr. steep in a 0.1% solution) was not rendered more effective by the addition of hydrochloric acid nor by a preliminary dip in methylated spirits to facilitate wetting, while the addition of a proprietary wetting compound (Agral) was definitely harmful to the corms and usually less effective than mercuric chloride alone. Increase in time of steeping or concentration of mercuric chloride was not beneficial and was sometimes harmful. Reduction in time of steeping to 1 hr. gave promising results.Treatment in November had some advantages over treatment in March.All the mercury compounds tended to delay flowering, this being most marked in the presence of the wetting compound. Stunted foliage and poor quality flowers resulted from the use of Ceresa

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06728.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Inoculation experiments show that (1) young corms are more susceptible than old and become less susceptible as they develop, (2) infection of unwounded corms readily takes place, (3) inoculation of the top of an old corm is more effective than that of the side or base.The percentage diseased new corms produced from infected parent corms varies from o to 100 according to soil conditions. Disease is favoured by wet soil.Removal of ‘husks’ (leaf bases) increases the susceptibility of corms planted in contaminated soil, but the presence of husks is not an effective control. Dehusking did not increase the number of diseased young corms in an infected stock planted in new soil.No variety was strikingly more resistant than the rest.Good control was obtained when, corms of a diseased stock were treated with mercuric chloride, mercurous chloride (calomel) or the proprietary mercury fungicide Aretan. Calomel gave the most consistent results. Various other treatments were tested in small‐scale trials with some success. Red copper oxide, formalin and the proprietary mercury compound, Ceresan, were harmful.Sterilization of contaminated soil with formalin, mercuric chloride, Aretan or Uspulun gave good but not complete control. Formalin was the least effe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06729.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

An account is given of the use of the short wet method of seed disinfection for the prevention of Helminthosporium disease of oats. Equally good results were obtained by its use as those given by the dusting method. A soluble organo‐mercury preparation (Ceresan, U. 564) was employed as the disinfectant. Suitable machinery is necessary for carrying out the short wet method of treatment, and two of the machines manufactured for this purpose are described. They are the ‘Primus’, a hand‐operated machine for dealing with small quantities (3/4 cwt. lots) of seed, and the ‘Kontramix’, a power‐driven machine designed for carrying out continuous seed treatment at rates varying from 5

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06730.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

The toxicity of a number of dyestuffs to the spores ofFusarium culmorumandCercosporella herpotrichoideswas determined by the slide‐germination technique. No attempt was made to distinguish between fungistatic and fungicidal activity.The toxicity of basic dyestuffs was unaffected by the acid radicle associated with the dye base.The high toxicity toFusarium culmorumof malachite green dye base was reduced weight for weight and mole for mole by substitution of ethyl, propyl or butyl groups for methyl groups.The reduction of malachite green to malachite greenleucobase removed toxicity.The substitution of amino groups and alkylated amino groups in benzene nuclei of triphenyl methane increased toxicity, whereas acid groups reduced toxicity. Sulphonation and carboxylation reduced toxicity to vanishing point.Alkylation of amino groups increased, but alkylation of benzene nuclei did not affect toxicity appreciably.When the central carbon atom of the triphenyl methane dyestuffs was replaced by nitrogen (e.g. Bindschedler's green) the diphenyl ammonium compounds were less toxic than the corresponding triphenyl‐methane compounds.The prevention of rotation of the aminated benzene rings by bridging, in theo‐position to central atom, with O or N, and so obtaining a planar molecule only slightly affected toxicity.Certain acid dyes stimulated fungal growth.The toxicity of the basic dyestuffs seems to depend not on one specific part but on the molecule as a whole, and within certain limits the structure may be varied without pronounced changes in tox

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06731.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

The date of wheat blossom midge emergence in an insectary some distance away from the growing wheat can give as reliable an estimate of the forwardness of the crop as field observation of the date of ear emergence. The percentage grain attacked by the wheat blossom midges, which can be assessed by routine workers without any special experience of wheat, can give in early July a useful first estimate of the crop yield.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06732.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY

摘要:

Detailed studies of the growth of wireworms kept at a constant temperature of 15d̀ C. for 3 years and at natural soil temperatures for 2 years are presented. It is shown that small wireworms grow rapidly and moult frequently, but large wireworms grow slowly or remain constant in weight and moult infrequently. A basic pattern to account for the decreasing frequency of moulting during the life cycle is presented.The feeding activity and moulting frequency of a population of wireworms has been studied in detail throughout the season. Definite peaks in feeding activity and moulting frequency occur during the season. A suitable method for the analysis of such activity in a population has been found by dividing the population into groups on a basis of the number of annual moults.It is shown that increase in dry weight is a more valid estimate of growth than increase in fresh weight. The rate of growth of wireworms is strongly influenced by the food on which they feed: some plants (wheat and carrots) permit rapid growth; other plants (grass and clover) permit slower growth; while certain other plants (mustard and potatoes) allow the wireworm to maintain its weight. Wireworms reared on flax actually decrease in dry weight.In a field experiment it was found that the type of crop grown after breaking up old pasture had a distinct effect on the wireworm damage done to the following cereal crop. Beans had the effect of reducing the population to a level at which a very successful crop was grown. Better yields were obtained after wheat and grass than after the other crops, excepting beans, at similar levels of population.The cuticle of wireworms is permeable to water, and it is shown that in its relations to soil moisture the wireworm may be regarded as an osmotic system. ThepFscale of soil moisture is shown to be of value in expressing the soil‐moisture relations of wireworms. Wireworms feed more actively in moist soil than in dry or wet so

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1944.tb06733.x

出版商:Blackwell Publishing Ltd    

年代:1944

数据来源: WILEY