Petri Dish Tests Research Articles

Nature of the Attractant in Sucrose Fed on by House Flies

The attractiveness to house flies ( Musca domestica L.) of traps containing other house flies feeding on sucrose is probably related to a relative-humidity gradient generated by the moisture excreted by the flies. In a group of tests run at 50 to 73% ambient relative humidity flies responded to traps in which the relative humidity was 18 to 38% higher than the ambient value. The addition of about 6% of water to sucrose increased its attractiveness in Petri-dish tests so that the mixture was usually more attractive than sucrose fed on by house flies. No evidence was found for a volatile chemical reaction product of sucrose having appreciable attractiveness. In the tests only 10 to 15% of the f1icswere attracted to fed-on sucrose, indicating that the fly factor is low- order attractant.

On the Germination of the Weed Seeds in the Soil Treated with 2, 4-D (Part 2)

1.Influence of the 2, 4-D treatment on germination was studied using verious weed species. The kinds of treatment were as follows, a) Petri's dish tests : The weed seeds were sown in the Petri's dishes containing each 0.1, 0.02, 0.01, 0.002, 0.001 and 0.0005% solutions of. 2, 4-D respectively.b) Pot tests:The weed seeds were sown in the pots treated with 2, 4-D. The amounts of 2, 4-D given to the pots were as follows -50, 100, 150, 200 and 300g per tan respectively.2. The weed species could be classified according to their resistance to 2, 4-D treat-ments as follows;a) Species affected by 0.01% solution of 2, 4-D:Mierostegium vimineum A. CAnsus, Poa annua L.b) —0.002%:Microlespedeza stricta MAKINO., Portulaca oleraeea L., Polygonum nepalence MEISN., Cyperus microiria STEUD., Digitaria ciliaris PERS., D. ichaemum MUHL., Agrostis Matsumurae HACK.c) —0.001%: Bidens dipinnata L., Plantago major L. var asiatica DECNE., Mollugo stricta L., Cyperus Iria L.d) —0.0005%:Erigeron linifolius WILLD.3) In Petri's dish tests, development of young root was inhibited by the treatment with 0.01- 0.002% solutions of 2, 1-D, and cotyledons (or first leaves) were damaged by 0.001-0.0005% solutions. When the seeds were covered with soil, the damage was severer than when not covered.4.In pot tests, germination was severely damaged when 50g of 2, 4-D per tan was given 3 or 4 days after sowing to the following weed species, i. e., Bidens dipinnata L., Micro-lespedeza stricta, MAKINO, Cyperus microiria SrEUD., Digitaria ciliaris PERS, and D. ichaemum MuaL., but when 2, 4-D was given about one month after sowing, the sign of damage could not be detected.