Germination measurement

Various assay methods have been used to detect the presence of inhibitory substances. These include some of the classical tests used by investigators of growth-promoting substances—i.e., the various Avena coleoptile assays which utilize intact, decapitated, or isolated cylinders and the split pea stem test. Effects on seed germination and seedling shoot or root growth and development have also been measured in addition to other visible expressions of inhibition. Details of many of these tests have been compiled by Mitchell et al. (99). Tests have been carried out in Petri dishes, with various solution culture techniques, and by sand and soil culture. Effects so measured may or may not be similar to those obtained under field situations— i.e., the establishment of inhibition under controlled conditions pro-... 

Five ml aliquots of leachate or extract were pipetted onto 3 sheets of germination paper in a petri dish. Twenty five tomato or radish seeds were placed in each dish. Each treatment/seed combination was replicated five times. The assays were incubated at 20°C radish roots length was measured at 96 hrs and tomato at 168 hrs. 

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. 

During the tests the inner characteristics of the raw slurry, the purified liquid and solid phases were determined and the performance intake of the technological equipment was measured. The biological effect of the purified substance has been controlled by germinating trials. 

The germination experiments (in quadmplicate) were carried out on filter paper in peril dishes. The corresponding water extracts (5 mL) (1/10) from the sewage sludge or soils were introduced into the dishes, with distilled water as the control in other dishes. Twenty-five radish seeds Raphanus sativus) were then placed on the filter paper and the dishes placed in a germination chamber maintained at 20°C. The root lengths were measured after three days. 

Light absorption is usually quite fast (time scale = 1-10 femtoseconds), and various physical measurements can be used to characterize the properties of intermediates that are formed along the reaction coordinate. This strategy was introduced by Porter who later shared the Nobel Prize in Chemistry with Eigen and Norrish for their germinal contributions to fast reaction kinetics. See Chemical Kinetics... 

Lengths of roots and stems were measured and the percent of germination was calculated. All results were statistically analyzed with an F test. 

The last inhibitor from rose seeds was identified as 2,5-dihydro-furan-2-carboxylic acid (2 ). The specific activity of this compound is not very high, but rose seeds contain enough of it to exert measurable inhibition of seed germination. The bioactivity seems to depend on this particular structure because a number of similar compounds (29 - 37) have no activity or much lower activity than 2 . 

Barley seeds (cv F. Union) were germinated at 25°C and after 6 days were subjected to water stress. Four days later, plants were analyzed for proline and betaine content and the water potential of the leaves was measured. At this time, plants were infested with aphids and the insects were counted six days later. 

Extracts (12 mL each) were added to Petri dishes 10 cm in diameter containing 50 g of 30-mesh washed sand covered with filter paper circle (7-cm diameter, Whatman 1). Controls were moistened with doubly distilled water. Ten indicator seeds were placed on the filter paper in each dish with the embryo down and the hypocotyl pointed to the center of the Petri dish. Each indicator/extract combination had 3 replicates. The Petri dishes were kept in a dark growth chamber for approximately 72 hr at 25°C. The radicle length of each germinated seedling was measured at 72 hr. 

Bioassav of Organic Compounds from the Soil. Bioassay experiments measured the germination and early growth (generally the most sensitive time of any plant s life) of wheat. The methods are similar to those of McPherson and Muller (151 and others in the field, and are summarized below. 

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