Showing papers on "Allelopathy published in 1972"
TL;DR: Toxins such as p-hydroxybenzoic, p-coumaric, ferulic, syringic and o-cOUmaric acids are found in the soils beneath Arctostaphylos shrubs, and toxins can inhibit the germination and suppress the radicle growth of herbaceous plants at concentrations below 400 ppm.
Abstract: Arctostaphylos glandulosa var. zacaensis is a strong dominant of chaparral vegetation on Zaca Ridge in the San Rafael Mountains, California. It occurs in pure stands, sometimes openly spaced with the canopies covering 50 to 75% of the soil surface, or it may form completely closed cover. A barren soil surface, without seed- lings of any species in spite of sufficient light and soil moisture, char- acterizes the stands. Fire or artificial removal of shrubs results in growth of herbs and shrub seedlings until shrub dominance is again established. Detrimental biochemical interference (allelopathy) between Arcto- staphylos and associated plants is involved in this phenomenon. Aqueous leachate from Arctostaphylos foliar branches and from leaf litter is toxic to the growth of annual grasses. The allelopathic constituents leachable from Arctostaphylos plant organs have been identified as arbutin, hydro- quinone, and gallic, protocatechuic, tannic, vanillic, chlorogenic and p-hydroxybenzoic acids. Toxins such as p-hydroxybenzoic, p-coumaric, ferulic, syringic and o-coumaric acids are found in the soils beneath Arctostaphylos shrubs. These toxins can inhibit the germination and suppress the radicle growth of herbaceous plants at concentrations below 400 ppm; e.g., hydroquinone significantly inhibits radicle growth of Avena fatua and Bromus rigidus at a concentration of 50 ppm. Chem- ical constituents present in leaf litter appear to be more leachable after subjection to temperatures up to 160 C-resulting in increases of toxic- ity to herb growth-but are denatured at temperatures above 180 C, with complete loss of toxicity at temperatures above 200 C. Allelopathy
127 citations
TL;DR: It is conielude that the phytotoxins are leached from the straw by the first rains of the growing season and are carried from the Straw to the soil where they inhibit species with susceptible seeds or seedlinigs, e.g., Centaqtrea melitensis anid Silybunt marianum.
Abstract: TINNIN, R. O., anid C. H. MULLER (Uniiv. of Calif., Santa Barbara). The allelopathic inifluenee of Avena fatua: The allelopathic mechanism. Bull. Torrey Bot. Club 99: 287292. 1972.-The allelopathic mechanism associated with the straw of Avena fatua was inivestigated by bioassay and greenihouse experiments. Water leachates from the straw contained a group of phytotoxic pheniolic compounds. These compounids were inihibitory to germinationi anid seedlinig growth of other plant species in soil and are thought to be part of the toxic complex which is active in the field. We conielude that the phytotoxins are leached from the straw by the first rains of the growing season and are carried from the straw to the soil where they inhibit species with susceptible seeds or seedlinigs, e.g., Centaqtrea melitensis anid Silybunt marianum.
47 citations
01 Jan 1972
Abstract: Franseria dumosa Gray and Hilaria rigida (Thurb.) Benth. ex Scribn. seedlings were grown in a glasshouse in potted soil which was collected from the Mojave Desert near Mercury, Nevada. The soil represented areas under living shrubs and also areas between shrubs. Soil was either steam sterilized or not steam sterilized. The sterilization resulted in greatly decreased yields of plants possibly because of induced P deficiency. It was suggested that symbiotic mycorrhizae necessary for P absorption for the species involved might have been eliminated by the sterilization. The effect did not hold for a noncalcareous soil well supplied with available P. Soil sterilization increased both Mn and Zn in plants. There was an interaction in that plants did not grow well in soil from under shrubs regardless of steaming indicating possible allelopathic effects. re]19720711