We have identified propiololdehyde as a product of the action of an electric discharge on mixtures of methane and water or methane, nitrogen, and water. The aldehyde reacts with cyanoacetaldehyde and ammonia (other "prebiological molecules") to yield nicotinonitrile. This substance can be hydrolyzed to nicotinamide and nicotinic acid.
Several cell wall-bound glycosidases present in Avena satira coleoptiles were assayed by following the hydrolysis of p-nitrophenyl-glycosides. Particular emphasis was placed on characterizing some parameters affecting the activity of ,-galactosidase. The pH optimum of this enzyme is 4.5 to 5.5; it is sensitive to copper ions and p-chloromercuribenzoate treatment and apparently has an exceptionally low turnover rate. Indoleacetic acid treatment enhanced in vivo P-galactosidase activity of coleoptile segments by 36% over control after 60 minutes. This enhancement was prevented by abscisic acid and cycloheximide. High buffer strengths and low pH reduced the indoleacetic acidenhanced increase in enzyme activity. These data lend support to the following proposed model of indoleacetic acid action. Indoleacetic acid enhances the release of hydrogen ions into the cell wall which promote the activities of cell wall glycosidases, some of which may participate in the cell extension process.It is well established that both indoleacetic acid and hydrogen ions can elicit rapid growth responses in a number of excised plant tissues (7-9, and references cited therein). In many respects, the H+-induced extension of Avena coleoptiles is similar to that evoked by IAA (7,9, 23) polysaccharides (9, 11), a condition which may lead to cell wall loosening. We have conducted some tests with this hypothesis in mind, and this paper relates substantial correlative evidence that at least the activity of one cell wall-bound glycosidase (a ,8-galactosidase) behaves as if it were involved in IAA-induced cell elongation. MATERIALS AND METHODSPreparation or Seedlings, Segments, and Celi Wails. Seeds of A vena sativa L. cv. Victory were surface-sterilized in 1 % NaOCI, rinsed, soaked in tap water for 2 hr, and then sown in moist vermiculite in the dark at 20 C. After 5 days, coleoptiles were excised under normal laboratory lighting conditions and placed on ice-cold moist toweling until enough were prepared for the experiment. Nonpeeled segments were prepared by cutting 10-mm sections beginning 3 mm below the apex. Peeled segments consisted of similar 10-mm sections from which the cuticle and epidermis had been physically removed. Cell walls were isolated at 4 C by grinding 15-to 20-mm coleoptile segments in distilled H,O in a mortar and pestle, then further homogenizing in a glass tissue grinder. Recovery of cell wall-bound glycosidase activity using such a method was no different than that obtained when an 80% (v/v) glycerol extraction technique (12) was employed (Cohen and Johnson, unpublished data). The homogenate was centrifuged at 5OOg for 5 min, and the resulting cell wall pellet was washed three times in 15 volumes of H20 by resuspension and recentrifugation at 5OOg for 10 min. Further HDO washes removed only about 3 % of the remaining pelletable enzyme activity with each wash and were therefore omitted.Enzyme Assays. For assays using nonpeeled or peeled segments, 20 nonpeeled or 5 peeled segments were rinsed thoroughly with distill...
It is hypothesized that there is a close relationship between the geologic evolution of the global plates of the Earth's crust and the chemical evolution of life on the Earth. Characteristics of the axes of plate spreading are discussed in relation to postulated environments conductive to the synthesis of chemical compounds thought to be important biological precursors. Likely locations for in situ measurements to test the hypothesis are identified.
The possibility of an auxin effect on the permeability of pea (Pisurt sativu"n L. cv. Alaska) segments to tritium-labeled water has been investigated by three separate laboratories, and the combined results are presented. We were unable to obtain any indication of a rapid effect of indoleacetic acid on the efflux of 'HHO when pea segments previously "loaded" for 90 minutes with 3HHO were transferred to unlabeled aqueous medium with indoleacetic acid. We were able to confirm that segments pretreated with 3HHO plus indoleacetic acid for 60 to 90 minutes can show an enhanced 3HHO release as compared with minus indoleacetic acid controls. However, this phenomenon appears to be due to an increased uptake of 'HHO during the prolonged indoleacetic acid pretreatment, and therefore we conclude that auxin does not alter the permeability of pea segments to 3HHO in either short term or long term tests. We confirm previous reports that the uptake of 'HHO in pea segments proceeds largely through the cut surfaces, and that the cuticle is a potent barrier to 'HHO flux.
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