Showing papers on "Allelopathy published in 1981"

The microbial origin of the allelopathic potential of Adenostoma fasciculatum H & A.

Abstract: The release of phytotoxic compounds has been proposed to be involved in the inhibition of seed germination under the canopy of Adenostoma fasciculatum (McPherson and Muller 1969). McPherson et al. (1971) tentatively identified the phytotoxins as phenolic compounds; however, the soil extraction data presented in this study indicate that insufficient quantities of available phenolics are present in the soil to account for the lack of growth observed in the field. Soil from burned and unburned Adenostoma—dominated sites were exchanged and planted with herb seeds. While toxicity developed in soil from the unburned site, the resulting pattern of germination suggested that the toxicity originated from the soil and not from the shrub canopy. Treatments to disrupt the metabolism of soil microbes, and to isolate selectively the microbial fraction from the soil, as well as other experiments, lead to the conclusion that the soil toxicity was the result of phytotoxins of microbial origin. It is suggested that the role of Adenostoma in the suppression of herb growth may lie in its association with soil microbes that produce and release substances capable of inhibiting the germination and growth of plants.

Herbicides and Plant Growth Regulators

Abstract: Herbicides and plant growth regulators , Herbicides and plant growth regulators , کتابخانه دیجیتالی دانشگاه علوم پزشکی و خدمات درمانی شهید بهشتی

Allelopathic effects of Sorghum vulgare Pers.

Abstract: Sorghum vulgare Pers. a tropical fodder crop significantly reduced the vertical growth and drymass of Sorghum vulgare, Pennisetum americanum, Zea mays and Setaria italica. Aqueous extracts of various plant parts, field soils and decaying mulch significantly reduced germination, radicle growth and water contents of all test species. The toxicity levels were depending upon the plant parts used in the biossay experiments and the sensitivity of the test species. It is suggested that the Sorghum fields be rotated with other crops to maximize the crop productivity.

Allelopathic effects of Artemisia tridentata leaves on germination and growth of two grass species.

Abstract: Volatile substances and aqueous extracts from Artemisia tridentata leaves were tested for their effects on germination, shoot growth and radicle growth o? Elymus cinereus and Agropyron cristatum. Germination of E. cinereus and A. cristatum seeds was significantly inhibited by both uncrushed and crushed A. tridentata leaves, as well as by aqueous extracts from the latter. Crushed A. tridentata leaves significantly reduced shoot and radicle growth of A. cristatum seedlings and radicle growth of E. cinereus seedlings. Introduction The role of chemical inhibition (allelopathy) in patterning of vegetation has been extensively studied in shrub communities of the western United States (Rice, 1974, 1979). Numerous studies have presented evidence that Artemisia sp. have allelopathic effects against neighboring species. Artemisia tridentata, big sagebrush, is the most widespread and common shrub of western North America, and it is particularly abundant in the Great Basin (McArthur et ai, 1979). The success of A. tridentata may partly depend on its production of allelopathic substances which inhibit the germination and growth of potential competitors (Weaver and Klarich, 1977). Hoffman and Hazlett (1977) and M?ller (1966) have implied that allelopathy may be a predominant influence in A. tridentata-dominated vegetation of the Great Basin, although the latter presented no data. Phytotoxins may be either volatile or water-transported. Aqueous extracts of litter and leaves (Schlatterer and Tisdale, 1969; Hoffman and Hazlett, 1977), as well as volatile substances (M?ller, 1966; Klarich and Weaver, 1973; McCahon et ai, 1973) from Artemisia tridentata have been shown to inhibit germination, shoot growth and radicle growth of several grass and herbaceous species. Klarich and Weaver (1973) stated that smaller amounts of volatile materials were released from uncrushed A. tridentata leaves than from crushed leaves. Their results indicated that growth of plants exposed to vapors from crushed leaves was always significantly less than that of plants exposed to uncrushed leaves. Additionally, Muller et al. (1964) indicated that root growth inhibition of test species was directly proportional (logarithmically) to increasing amounts of crushed A. californica leaves. Klarich and Weaver (1973) reported a similar finding with increasing amounts of crushed A. tridentata leaves, but presented no data. The purpose of the present investigation was to test the hypothesis that allelopathic substances from Artemisia tridentata inhibit germination, shoot growth and root growth of two test species, Agropyron cristatum (crested wheat grass) and Elymus cinereus (giant wild rye). The investigation was designed to overcome the problems of insufficient sample sizes, inadequate controls, improper test species and lack of statistical treatment of data which have occurred in previous allelopathic studies of Artemisia tridentata. Agropyron cristatum and E. cinereus were chosen as test species because they are grasses often found in close association with Artemisia tridentata in the Great Basin. Although Agropyron cristatum is an introduced species, it has been widely planted in sagebrush regions where invasion of such seeded areas by Artemisia tridentata is common. Materials and Methods Sagebrush plants {Artemisia tridentata ssp. tridentata), each approximately 15-20 cm in height, were transplanted during January 1980, from the Gibson Jack Creek Watershed (Pocatello, Idaho) to growth chambers at Idaho State University. Each plant was potted in a 15-cm clay pot with Bacto^ soil and acclimated for 3 weeks from a winter photoperiod and temperatures (12L/12D, 15 C day/8 C night) to a summer

Mechanisms for Differential Interference among Cucumber (Cucumis sativus L.) Accessions

Abstract: Competitive and allelopathic characteristics of a cucumber cultivar `Pioneer' were compared with those of a wild accession PI 169391, which demonstrated respective weak and strong interference abilities. Leachates collected 0-9 days after imbibition from PI 169391 suppressed 10-day seedling dry weight by 40% and percentage of germination by 46% in proso millet (Panicum miliaceum L). Leachates collected from PI 169391 10 days after imbibition to fruiting, as well as all Pioneer leachates, were nontoxic. Growth analyses conducted during the growth period associated with biochemical interactions indicated that the allelopathic PI 169391 did not exceed the net assimilation rate or relative growth rate of Pioneer. Leaf area ratios indicated that PI 169391 may have a greater competitive shading advantage than Pioneer. Although competitive parameters are always present, there was no indication that strong interspecific competition was present during seedling emergence. Allelopathy appears to be more important th...

Allelopathy in spring wheat mixtures

Abstract: In a study with binary mixtures of 3 spring wheat cultivars harmful effects due to allelopathy were observed on root number, root growth and fresh weight of the seedlings.

Cucumis sativus l.) accessions

Abstract: Competitive and allelopathic characteristics of a cucumber cultivar 'Pioneer' were compared with those of a wild accession PI 169391, which demonstrated respective weak and strong interference abilities. Leachates collected 0-9 days after imbibition from PI 169391 suppressed 10-day seedling dry weight by 40% and percentage of germination by 46% in proso millet (Panicum miliaceum L.). Leachates collected from PI 169391 10 days after imbibition to fruiting, as well as all Pioneer leachates, were nontoxic. Growth analyses conducted during the growth period associated with biochemical interactions indicated that the allelopathic PI 169391 did not exceed the net assimilation rate or relative growth rate of Pioneer. Leaf area ratios indicated that PI 169391 may have a greater competitive shading advantage than Pioneer. Although competitive parameters are always present, there was no indication that strong interspecific competition was present during seedling emergence. Allelopathy appears to be more important than competition during the early seedling growth stages of PI 169391.