Inhibition of Respiration, Germination, and Growth by Substances Arising During the Decomposition of Certain Plant Residues in the Soil

Abstract

Substances capable of markedly inhibiting the respiration, germination, and growth of tobacco seedlings were obtained after residues from timothy, corn, rye, or tobacco plants had been allowed to decompose under appropriate conditions in the soil. Bio-assay tests, based on manometric methods, made it possible to determine some of the conditions under which the decomposition gave rise to phytotoxic by-products and to obtain rapidly an accurate measure of the degree of their toxicity. Among the factors influencing the production of the toxic products, the species and stage of maturity of plant material added, the water content and pH of the soil, and length of decomposition period seemed most important. Substances capable of reducing the respiration of tobacco seedlings by 50 to 90% were consistently obtained when any of the abovementioned plant residues had been decomposing for 15 to 25 days under conditions of high soil moisture and when the pH of the soil solution was below 5.5 throughout this period. Timothy gave rise to substances possessing the highest toxic activity, followed by corn, then rye, and finally tobacco. Aqueous extracts of unamended soil or of macerated plant tissues prepared either before decomposition had taken place or when decomposition was inhibited by autoclaving the soil were not toxic.The toxic substances, obtained by water extraction, exhibited an inhibiting effect on respiration of tobacco seedlings after an exposure of less than one hour and also induced darkening and necrosis of root cells. Some extracts affected the cells of the apical meristem most severely while others affected only the cells of the elongation region.While the toxic substances have not been identified, they were relatively nonspecific in their action, affecting tobacco, timothy, and barley in approximately the same manner and in many instances possessed also antifungal activity. They were soluble in water, insoluble in petroleum ether, stable in acid, and most active in the pH range 4.5 to 5.8. They were precipitated by alkali and the activity was markedly reduced when readjusted to the acid range. They were also heat stable and did not lose their activity in storage at 1°–3 °C. provided they were covered by a layer of toluene.Because of their rapid production and the marked injurious effects exerted on various plants it is believed that these toxins may perform a significant role in the field as the primary cause of some root rots and in predisposing plants to attack by organisms not normally regarded as pathogenic.

The Influence of the Extract of Some Crops and Soil Residues on Germination and Growth

“…More evide.ce has accumulatecl recer-rtly to show ma'y plants co'tain germinatio'and growth inhibitors (1,2,3,4,6, 10, 12, 13, t-S) and also to show that toxic compounds are producecl in the decomposition of crop residues in the soil (1,4,15). The effects of crop residues on the development of soil pathogens have also been investigated (7,I0, 12, lS,17, 6).…”

Wheat straw placement effects on total phenolic compounds in soil and corn seedling growth

“…Water extracts of certain plant species caused darkening of apical meristerms and cells in elongation regions (Patrick and Koch 1958). The inhibitory effect of phenolic compounds on germination and radicle length in petri-dishes suggests that such an effect could take place early in the germination process and affect the entire phase of seedling growth.…”

Efeitos da interação de ácido ferúlico e glifosate em soja

“…0 aumento da precipitação anual, que favorece aumentos de restos de culturas imediatamente anteriores e sua posterior lixiviação, tem mostrado correlação E. Voll com a redução de produção de culturas subseqüentes (Papendick & Miller, 1977). A toxicidade do solo, devida a estes constituintes orgânicos, mostra-se mais freqüentemente associada a solos pesados, mal arejados, ou inundados (Patrick & Koch, 1958). Métodos de preparo do solo podem influir na produção destas substâncias fitotóxicas (Liebl & Worsham, 1983).…”