The Effect of Cultivar and Cultural Factors on Embryo-sac Volume and Seed Weight in Carrot (Daucus carota L.)

The influence on carrot seed weight of cultivar, plant density,position of the seed on the plant, and of shading and removingumbels at different stages of growth was examined. CultivarDanvers produced seeds of approx. 2.5 mg, nearly twice as heavyas those of cv. Amsterdam with cv. Chantenay having an intermediateweight. Seeds from plants grown at 80 plants m^–2 were,on average, approx. 20 per cent lighter than those from plantsgrown at 10 plants m^–2 as were those from secondary thanprimary umbels. There were few differences in seed RGR betweencultivars, plant densities or seed positions and the differencesin seed weight produced by the treatments were largely associatedwith the duration of seed growth and with the volumes of theovary, ovule and embryo-sac at the time of fertilization. Shading(66 per cent reduction in irradiance) for the period of twoweeks before or two weeks after fertilization reduced seed weightcompared with unshaded plants. Removing the secondary and higherorder umbels from plants at these stages compared with no removalor removal at a later stage of growth increased seed weightof the remaining primary-umbel seed. Carrot, Daucus carota, seed weight, growth duration, RGR, embryo-sac, ovule, shading, pruning     

The responses of Lucilia cuprina to odours from sheep, offal and bacterial cultures

Abstract. The responses of gravid female Lucilia cuprina to odours from sheep urine, faeces and gut mucus, and to odours from liver/sodium sulphide mixtures was tested using a bioassay which measured the movement and probing response of walking flies. The same bioassay was used to test the response to odours from cultures of bacteria isolated from liver/sodium sulphide and liver/water mixtures. A significant movement towards odours from faeces, gut mucus and urine was observed. Odours from cultures of the bacteria Proteus mirabilis, Dermatophilus congolensis and Serratia marcescens also elicited significant movement. A probing response was elicited by odours from gut mucus, fresh urine, liver/sodium sulphide mixtures and cultures of P.mirabilis, D.congolensis and gram-positive species. Odours from cultures of Pseudomonas aeruginosa, Entero-bacter aerogenes and Citrobacterfreundii did not elicit significant movement or probing. The movement and probing responses are discussed with reference to the possible uses of the substances tested as a bait for attracting L.cuprina.     

A comparison of methods for evaluating seed quality in carrots (Daucus carota)

Comparisons of embryo length, ISTA (International Seed Testing Association), cold (10 ^oC), controlled-deterioration, and slope tests for estimating seedling size variability and percentage seedling emergence were made using eighteen stocks of carrot seeds. The coefficient of variation (C.V.) of seedling weight was closely correlated with the C.V. of embryo length (r = 0–87 D.F., 16) and also with the C.V. of root length from the slope test (r = 0–63 D.F., 16). Poorer estimates of percentage seedling emergence were obtained from the cold test in all three sowings (correlation coefficients were between 0–65 and 0–70 D.F., 16) compared with the ISTA, controlled deterioration, and slope tests. For these three tests the correlation coefficients varied between 0–80 and 0–87 (D.F., 16) for all sowings. The embryo test is a rapid (1 man hour per seed lot) and accurate method of assessing potential variability between seed lots. The slope test could provide a less labour demanding method of assessing potential variability than the embryo length test though the results would not be available immediately. However, the slope test could also provide as good an estimate of seedling emergence in the field as the ISTA or controlled-deterioration tests.     

Plasmodium berghei NK65 in the Inbred A/J Mouse: Age Immunity in the Female Retired Breeder A/J Mouse*

SYNOPSIS. Death rates of A/J and CF₁ female mice 4 weeks and 6 months of age were compared after the mice were infected with Plasmodium berghei NK65C deme (population) and NK65RR deme. Death rates were compared also when female A/J retired breeder mice were infected with blood passages 18 and 40 of NK65C. NK65C was found to be less virulent than NK65RR. The 40th blood passage of NK65C was more virulent than the 18th passage, but still not as virulent at the NK65RR deme. A/J retired breeders were clearly more resistant to infection than 4 week old A/J mice, while little difference was found in the different age groups of the CF₁ mice.     

Induced Regeneration of Hindlimbs in the Newborn Opossum

The North American marsupial, Didelphys virginiana, has provedto be uniquely suited for studies of replacement of mammalianlimb. The newborn opossum provides the rare opportunity to performchronic experiments on extremely young mammalian limbs. Sincethis marsupial is born without lymphocytes, xenoplastic as wellas homoplastic transplants are tolerated; supplementary nervetissue was transplanled to newborn hindlimbs and the limbs wereamputated immediately above the ankle. When the implant remainedin place, a regenerative response ensued. Results of controlexperiments indicate that neither the trauma of simple amputation,the trauma of implantation, nor the implantation of other tissuescan evoke the response which results after implanting nervetissue. These studies demonstrate that young opossum limbs arecapable of regenerating when additional nervous tissue is supplied.     

THE PRODUCTION OF ANTIBIOTICS IN SOIL V. BREAKDOWN OF GRISEOFULVIN IN SOIL

When griseofulvin (I; R = Cl, R '= OCH₃), a chlorine-containing antibiotic produced by Penicillium nigricans , was added to fresh garden loam, after an initial lag it disappeared rapidly. When further griseofulvin was added it was inactivated from the start and at rates which increased with each successive addition, suggesting that it was degraded biologically. The numbers of one organism, a Pseudomonas sp., increased in the soil steadily after adding griseofulvin.
When a little soil was added to a solution (pH 7·0) containing inorganic salts and griseofulvin as the sole carbon source, bioassays showed that the griseofulvin disappeared within 5 days. An organism isolated from the broth was identified as the Pseudomonas sp. thought to break down griseofulvin in soil. Griseofulvin also disappeared from a broth at pH 5·0 inoculated with soil, but at this lower pH value a dematiaceous fungus was responsible for its breakdown.
The Pseudomonas sp. also degraded two derivatives of griseofulvin, dechlorogriseofulvin (I; R = H, R'= OCH₃) and the amine (I; R = Cl, R '= NH₂). Cl^– was detected in the solutions after breakdown of griseofulvin by the Pseudomonas ; the amount present agreed well with that calculated on the assumption that all the chlorine in the griseofulvin supplied was liberated as Cl^–. Spectrophotometric examination of the solutions showed no metabolites with the aromatic ring intact, and confirmed the complete breakdown of griseofulvin suggested by the liberation of Cl-.     

An Examination of a Method of Auxin Assay using the Growth of Isolated Sections of Avena Coleoptiles in Test Solutions

1. Methods of auxin assay using the Avena coleoptile are discussed.
2. A review is given of experimental procedure and evaluationofresults in the straight-growth method using isolated sectionsof coleoptiles in test solutions.
3. Possible sources of variationin the straight-growth methodare investigated and discussed.
4. A revised experimental procedure for the straight-growth methodis described.

The author wishes to thank Professor E. Ashby for his adviceand encouragement during the course of the experiments. Thanks are also due to Mr. D. Payne, a technical assistant inthe Botany Department, for his assistance in some of the assays.