Seed bioassay

Oryza sativa decomposing straw phenolics toxic in lettuce rice seed bioassays mungbean root assay 119... 

Fraction NA (dried vacuo) maintained the previous level of phytotoxicity observed for fraction EA in a lettuce seed bioassay. 

Aliotta, G. and Cafiero, G. 2001. Seed bioassay and microscope in the study of allelopathy radish and purslane responses. In Reigosa Roger, M. J. (Ed.), Handbook of Plant Ecophysiology Techniques. Kluwer Academic Publishers, 1-20... 

In our efforts to detect and isolate the allelcpathic agents from tall fescue and several other grass species, we extracted the detached plant material with water and/or organic solvents. Either solvent extraction method yielded extracts that were inhibitory to the seed germination and seedling growth in our bioassay systems. 

Root elongation bloassay of root exudates. Five ml aliquots of the root exudates were pipetted onto three layers of Anchor1 germination paper In a 10 by 10 by 1.5 cm plastic petri dish. Twenty five radish or tomato seeds were placed in a 5x5 array in each petri dish. Radish seeds were incubated at 20C for 96 hours tomato seeds were incubated at 20C for 168 hours, before the root length was measured. Experimental design was a completely randomized design with three replications (dishes) per treatment per bioassay seed species. The bioassay was repeated each week for 23 weeks. 

Comparison of the results of these two bioassays reported in table II illustrates the importance of the choice of the bloassay species, as well as the variability of results to be expected when "phytotoxins" are released into the environment. Treatments applied to the radish and tomato seeds were identical, but most treatments tended to inhibit radish growth and stimulate tomato growth. 

Seed germination bioassay of root exudates. Bioassay results are presented as a 23 week mean for each germination count time (Table III, IV, V, VI). Means were separated by LSD after data normalization by the inverse sine transformation. 

Bioassays. Biological activity of various isolated compounds was determined using Chenopodium album L. seed collected in North... 

The following chemicals were obtained commercially (Sigma Chemical Co.) and bioassayed with C. album and Amaranthus retroflexus L. (seeds collected in North Carolina in 1980) following identification DL-3-hydroxybutyric acid (DL-3-hydroxy-butyric acid as a Na salt) and L-3-phenyllactic acid (L-2-hydroxy-3-phenyl-propanoic acid). 

Some Palmer amaranth samples prepared at SRRC were first extracted with hexane (HX), rather than PE. The organic solvent extracts were supplied for bioassay in the form of oils or solids remaining after solvent removal in vacuo. After each extraction step aliquots of the crude extracts from the roots, stems, or leaves (and thyrses) were evaluated for seed germination regulatory activity. 

The germination bioassay consisted of germinating the seeds of a number of crop and weed species (Table I) for 72 h in the dark at... 

The fourth isolated and identified compound from Palmer amaranth is chondri 11 asterol (5a-stigmasta-7,22-dien-30-ol), a sterol closely related structurally to the major plant sterols, stigmasterol and sitosterol. This compound, isolated as the free sterol, is not soluble in water or 0.1% DMS0, and germination bioassays required pretreatment of the test seed with a 0.1 mM solution of the sterol in DCM. 

Bioassay on Solid Medium. A-9, a medium previously shown to be favorable for antibiotic production by actinomycetes in shake flasks (36), was modified for bioassays on solid medium. We halved the concentration of components in A-9 and adjusted the pH to 6.9-7.1 with KOH to reduce the possibility of osmotic or toxic effects of medium components themselves on seed germination and seedling growth. The medium was amended with 15 g agar per liter and poured into 10 x 10 x 1.5 cm square plastic petri dishes, about 60 ml per plate. 

Bioassay of Extracts. Extracts tested for the presence of cyclohexi-mide were also bioassayed for phytotoxicity. The extracts were redis-sOlved in acetone, and 0.2 mg in 2 pi was applied to 6-cm-dia disks of filter paper. The extract was distributed on the paper with 0.2 ml of methanol. The disks were dried with warm air, placed in 1.5 x 6 cm petri dishes, and moistened with 1.5 ml distilled water. Ten cress seeds were placed on the paper, and after incubation for 3 d at 28 C radicle length of the seedlings was measured. 

Seeds of lettuce and other species have frequently been used to bioassay for the allelopathic activity of plant exudates (17.18.19). As with the use of cell suspensions, there are certain advantages and disadvantages to this methodology. The experimental simplicity, small amounts of material required and short time frame are certainly attractive qualities. However, species used in such bioassays quite often do not represent the actual target species under consideration. This is especially true when terrestrial crop species are substituted for weeds of aquatic systems. Nevertheless, information obtained from such experiments are often valuable when used in conjunction with results of other assays. 

Most of the work on correlation of molecular structure with bioactivity in witchweed seed germination has been produced by two groups (7-10). Johnson, et al. (7-9) prepared and evaluated a large number of strigol analogs and many approached the activity of strigol. In many studies by others, the results of the bioassays are presented, but the compounds from Johnson are described only by GR-number. GR-7 and -24, probably the more promising of these compounds, have been used in extensive field studies, and their structures are known. 

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