Pot Technique Research Articles

SITE OF UPTAKE OF SOIL‐APPLIED HERBICIDES*

Summary. We conducted studies to determine the effects on corn (Zea mays L, var. Indiana 654) and pea (Pisum sativum L. var. Alaska) of localizing various herbicides in the soil, using a double plastic pot technique which ensured separate exposure of the root and shoot zones of the plants to treated soil. Effects on corn and pea were similar in relation to site of uptake. 2,4‐D‐amine, naptalam, simazine, diuron and dalapon‐sodium entered primarily through the roots. Some shoot entry and also severe inhibition of roots occurred in soil treated with 2,4‐D and naptalam; these were noticed only to a slight extent with the other three herbicides.EPTC, chlorpropham and trifluraiin were most effective when applied to the shoot zone. Little effect on foliage growth was evident when the root zone alone was treated. However, roots in treated soil were severely inhibited by these three herbicides. Dinoseb displayed a contact type of action, injuring both shoots and roots. Treatment of both zones had an additive effect.Entry of chlorthal‐methyl which was tested on a susceptible species, sorghum (Sorghum vulgare Pers.) was mainly through the shoot, with only a slight effect on top growth when roots alone were treated. Roots in treated soil were slightly inhibited.Localisation de l'absorption des herbicides appliqués sur le sol

Testing for resistance to Polyspora lini Laff. in flax breeding

A pot technique by which the resistance of flax plants to stem-break can be determined within one growing season is described. Since all the inoculated plants develop the seedling phase of the disease, irrespective of whether they later show resistance or susceptibility to stem-break, it is ensured that they are all exposed to similar chances of developing stem-break. The technique is unsuitable for testing resistance to the browning phase, which can be satisfactorily determined in field experiments. The pot technique provides a more exacting test of resistance to stem-break than can be applied under field conditions; varieties showing resistance in the pot test are resistant in the field. Incidence of stem-break in a susceptible flax variety was unaffected when seedlings were inoculated at different stages of development. Wide variations in the air temperature at which plants were incubated after inoculation also brought about no effects. Development of stem-break was, however, greatly influenced by conditions during growth of the plants, the highest levels of attack being associated with high air humidity.

A fixação do nitrogênio do ar pelas bactérias que vivem associadas com as leguminosas crotalária e mucuna

Com a finalidade de conhecer a quantidade de nitrogênio fixado simbiòticamente por crotalária (Crotalaria juncea, L.) e mucuna anã (Stizolobium deeringianum, Bart.) e a influência de alguns fatôres sôbre o fenômeno, instalou-se uma experiência em vasos de Mitscherlich contendo solo tipo terra roxa misturada. Os tratamentos empregados foram os seguintes : 1) testemunha ; 2) NPK ; 3) NPK + calcário ; 4) NPK + inoculante ; 5) NPK + calcário + inoculante; 6) PK + calcário; 7) PK + calcário + inoculante. Dois meses após a germinação das sementes colheu-se o material para análise, dosando-se o N nas raízes e nas partes vegetativas das plantas. Nessa ocasião foram tiradas diversas fotografias, para documentação comparativa da nodulação das raízes nos diversos tratamentos.

Disponibilidade de nitrogênio em diversos fertilizantes nitrogenados

Neste trabalho são apresentados os resultados preliminares obtidos com a aplicação de diferentes fertilizantes nitrogenados, a fim de se determinar a forma de nitrogênio preferida pelo arroz durante os dois primeiros meses do ciclo vegetativo. Para isso instalou-se uma experiência em vasos contendo terra-roxa misturada e empregando-se os seguintes materiais nitrogenados : salitre do Chile, sulfato de amónio, calciocianamida, uréia, torta de algodão, farinha de chifre e casco, e solução de amoníaco. Os resultados apontaram a uréia como o fertilizante que propiciou maior produção de matéria sêca. Seguiram-se-lhe o sulfato de amônio, solução de amoníaco, farinha de chifre e casco, calciocianamida, torta de algodão e, finalmente, o salitre.

The behaviour of mercury compounds in soil*

The uses of inorganic compounds of mercury for the control of plant pests is reviewed, and a summary of the relevant chemical and physical properties of the compounds concerned is given. On chemical evidence a working hypothesis is propounded showing that all compounds may be expected to decompose into metallic mercury.A pot technique is described by means of which a correlation can be obtained between the effective mercury content of a given soil sample and the rate of growth of wheat seedlings. The mathematical treatment of the results is described, and the validity of the pot technique is verified by statistical analysis of results. Using the pot technique it is shown that volatilization losses are insignificant but that mercury is slowly rendered ineffective by the formation of mercuric sulphide. The effect of sulphur‐reducing bacteria is considered and the influence of Vibrio desulpkuricans on mercury is studied in detail.Experimental evidence obtained by the pot technique is produced to show that mercurous chloride slowly decomposes in the soil giving mercury and mercuric chloride, mercuric chloride rapidly decomposes into mercury and mercurous chloride, and other inorganic compounds decompose directly into mercury. The working hypothesis is substantiated in all major aspects.The uses and properties of the organo‐mercury compounds are then discussed. Type compounds selected are ethyl mercury phosphate, phenyl mercury acetate and methoxyethyl mercury acetate.Using the pot technique it is shown that the formation of organo‐mercury clays takes place and that these clays decompose giving metallic mercury. A mechanism is suggested.