Liberation of organic substances from higher plants and their role in the soil sickness problem

Imazapyr root exudation from eucalypt seedlings cultivated in nutritive solution

“…The presence of root exudation containing the imazapyr molecule caused root death (characterized by its darkening), height and total biomass reduction, due to the action of the herbicide in the plant growing points (meristems) causing inhibition of ALS (acetolactate synthase) activity, which involves inhibition of the branched-chain amino acid biosynthesis (leucine, isoleucine and valine) (CHIPMAN et al, 1998). Consequently, protein production and enzyme biosynthesis which are dependent on these amino acids are stopped, affecting DNA synthesis and cellular growth, besides reducing assimilate translocation (LIEBL and BRIDGES, 2000).…”

“…Several organic substances can be released by means of root exudates from herbaceous and woody species, in soil or in solution, such as: carbohydrates, amino acids, nucleotides, flavonoids, enzymes, and organic acids (BÖNER, 1960;SILVA et al, 2001). It has been reported that some herbicides can also be exuded through the root systems of weeds and agricultural crops.…”

Estudos sobre a vegetação das campinas amazônicas. VI - Aspectos ecológicos de Glycoxylon inophyllum (Mart. ex Miq.) Ducke (Sapotaceae)()

“…As espé(;1es americanas, Julg/ans nigra e J. cinera, são ri· cas em juglone, nas cascas das raízes. Este hormônio, quando liberado pelo órgão, oxida-se em contato com o ar, adquirindo caráter tóxico , para germinação e crescimento de outras plantas na área onde ocorrem (Borner, 1960 Fclhas frescas cortadas , mostraram conter material tóxico capaz de restringir a germinação e o crescimento, entretanto, "in natura ", não ocorre algo semelhante a corte de folhas, sendo portanto um experimento duvidoso, para interpretações ecológicas. Gráfico 4: Comprimento médio do hipocótilo de L. sativa L. em água destilada e extrato aquoso de folhas de G. inop hyllum (lOg: lOOml), após 3 dias.…”

Comparison of the Uptake of P32 and K42 by Intact Alfalfa and Oat Roots

“…In similar tests, however, alfalfa root segments took up (4,5,6,7) and Barber et al (1,2,14) reported that excision of the cotyledons from very young seedlings of certain varieties has significant effects on the number of nodes preceding the first flower.…”

“…Explanations for this growth reduction of the legume include competition for light (5,6), soil moisture (11,15), nutrients (1,4,7,9,10,13), excretion of toxic materials (2,12,14), and effects of the microflora (12).…”