Extracts Of Seedlings Research Articles

STUDIES ON SWEET CLOVER FAILURES IN SOUTHWESTERN ONTARIO

The etiology of sweet clover failures that have occurred in recent years in southwestern Ontario was investigated further through studies of the possible role of adverse environmental factors, of insects, and of pathogenic bacteria and fungi. A number of soil-borne parasites were found. They exhibited unusual parasitism at the point of initial infection and as the disease occurred in the field. Phytophthora cactorum was found to cause the disease, and its parasitism of sweet clover was investigated. The susceptibility of the host varied sharply with its stage of development and was at a minimum in the seedling stage and greatest early in the second season's growth. Numerous lenticels on the tap roots provided natural breaks in the periderm through which the fungus probably entered. Invasion of the tissue by the fungus was intracellular in the relatively small number of instances when first season plants were attacked and was always intercellular when second season plants were attacked. The fungus sporulated when seedlings were infected and when extracts of seedlings were added to common artificial media. Mycelium of the fungus was found abundant in cortical parenchyma considerably in advance of lesions. Secondary organisms quickly followed the initial infection. Epidemiological studies of sweet clover failures indicated that outbreaks were characterized by relatively short periods of high disease incidence in the early part of the second growing season in individual clover stands. An analysis of weather data for the period during which recent epidemics occurred suggested that sustained high soil moisture in the early part of the growing season was prerequisite to epidemic outbreaks of the disease, with higher than average soil temperatures favorable as well. No phonological condition, however, seemed responsible for confining the outbreaks to the beginning of the second season of growth, which appeared to be incidental to some physiological change correlated with the developmental rhythm of the host.

The oxidation of amines by extracts of pea seedlings.

The oxidation of amines by extracts of pea seedlings.

PHYSIOLOGICAL AND BIOCHEMICAL STUDIES IN PLANT METABOLISM: II. RESPIRATORY ENZYMES IN WHEAT

The kinetics of the malic dehydrogenase in cell-free extracts of wheat seedlings have been studied by the Warburg technique, using methylene blue. The enzyme behaves analogously to the animal enzyme in that it is coenzyme I-linked and its oxidation product, oxalacetic acid, is inhibitory to the reaction. Oxalacetic acid is removed by either a ketone fixative or l(+) glutamic acid, the latter by being involved in a transamination. Cell-free extracts also contain peroxidase and ascorbic acid oxidase, but no phenolases. In embryonic tissue the succinoxidase system, including cytochrome oxidase, is present. Using l(+) glutamic acid to remove oxalacetic acid, ascorbic acid can replace methylene blue and function as a respiratory carrier mobilizing the hydrogen from dihydrocoenzyme I indirectly via a pigment of unknown chemical nature. A proposed carrier system for the wheat plant includes coenzyme I, flavin, pigment, and ascorbic acid. In vitro, the entry of oxygen to the system is catalyzed by ascorbic acid oxidase supported by a thermostable copper-catalyzed reaction. Alcohol, hexosediphosphate, and fumarate can donate hydrogen to this carrier system.

Antibacterial Activity of Seedling Extracts of Cultivated Plants

Antibacterial Activity of Seedling Extracts of Cultivated Plants

ADAPTATION OF THE METHOD OF LOWRY AND LOPEZ TO THE ESTIMATION OF INORGANIC AND ORGANIC PHOSPHATE IN PLANT EXTRACTS

The method of Lowry and Lopez using ascorbic acid as the reducing agent with the Fiske–Subbarow reagents at pH 4.0 is proposed for the estimation of phosphate in plant extracts. The method has been reinvestigated with respect to its adaptation to the Coleman Universal spectrophotometer, Model 14, to suitability of wave length, pH range, reagent concentration, rate of reaction, color stability, and the effect of silicate. The experiments, in general, confirm those of Lowry and Lopez. A wave length of 650 mμ has been employed. No blue color is formed in the reagent blank between a pH of 3.1 and 4.2; accordingly a pH of 4.0, maintained by a sodium acetate – acetic acid buffer, has been used. A concentration of 0.25% ammonium molybdate and 0.1% ascorbic acid has been shown to be optimum for maximum color development in concentrations of phosphate up to about 25 μgm. P in the final volume. The reduction of phosphomolybdic acid is complete in about five minutes, and the method is characterized by a high degree of color stability. Silicate interferes with the reaction. Where the plant has a liberal silicate economy the cell wall material, with which the silicon is associated, must be removed from the extract. The method has been applied to the estimation of phosphate liberated from organic combination by hydrolysis for specified times in 1 N hydrochloric acid. Total phosphate is estimated by wet ashing with 60% perchloric acid. Recovery tests of known amounts of inorganic phosphate and glucose-1-phosphate added to wheat leaf and seedling extracts give an absolute error within 2%, which is considered permissible. A balance sheet of phosphate fractions in the supernatant, residue, and whole juice of wheat leaves is discussed.