摘要:

Two millimeter long secondary root tips of etiolated mung bean (Phaseolus aureus) plants were given 4 minute consecutive treatments of darkness, red light, far red light, and acetylcholine during darkness. We studied the effects of these treatments on exogenous (H+) changes, ATP utilization, O2uptake, P1levels, and ATPase activity. Red light and acetylcholine increased the level of P1, O2uptake, and exogenous H+, but decreased ATP concentrations. Darkness and far red light caused the amount of ATP to increase and decreased the O2uptake and P1level. O2uptake of both excised root tips and isolated mitochondria was promoted by acetylcholine levels of the same order of magnitude that promoted the other photomimetic phenomena. ADP-O ratios indicated that acetylcholine did not cause an appreciable decrease in ATP synthesis. The total ATPase activity remained constant throughout all treatments. Ouabain caused no adhesion to negatively charged glass in the dark, while the inhibitors valinomycin, atractyloside, digitoxin, gramicidin, and oligomycin caused immediate adhesion. All of the inhibitors prevented release from the glass. In red light ouabain increased adhesion, whereas the other inhibitors caused caused immediate and complete adhesion.These data seem to imply that one of the functions of the phytochrome-mediated response to red light in roots, regulated by acetylcholine, is to cause the rapid utilization of ATP pools; far red light appears to inhibit this utilization.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB

摘要:

The present report shows that the effect of red and far red light on the synthesis of phenylalanine ammonia-lyase can be ascribed to the action of phytochrome Pfr. This is true not only for short term irradiation but also for the action of continuous far red light. In the latter case, the model worked out by Hartmann implicating some excited species of phytochrome has to be taken into account.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB

摘要:

Cytokinin was released into the medium by cultures of bothRhizobium japonicumandR. leguminosarum. Calculations show that the amount of cytokinin released during the logarithmic phase of growth byR. japonicumwould be sufficient to initiate the cortical cell divisions necessary to form a root nodule. The substance released byR. japonicumwas identified as a zeatin-like compound on the basis of paper chromatography in four solvent systems. Two solvents clearly separated the rhizobial product from N6-Δ2-isopentenyladenine and its ribonucleoside. The predominant intracellular cytokinin found in both enzymatic hydrolysates of sRNA and alkaline hydrolysates of total RNA also was similar to zeatin

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB

摘要:

The release of potassium and sodium from excised roots ofZea mayshaving similar contents of potassium and sodium was studied. At low temperature (2 C) the efflux rates of both cations were very similar, but at higher temperature (20 C) the potassium release was reduced considerably, whereas the sodium release was hardly affected. Also, under anaerobic conditions the potassium efflux rate was nearly as high as the sodium efflux rate, but with normal O2supply the potassium release was reduced to about one-fifth. Since a changing efflux medium compared with a constant efflux medium had no great influence upon the sodium release but influenced the potassium release very much, it is assumed that the low potassium release under normal metabolic conditions is due to a reabsorption of effluxed potassium from free space. For sodium this reabsorption is of minor significance, as the uptake potential of maize roots for sodium is very poor. It is concluded that the release of potassium and sodium is a diffusion process and that the cell membranes have rather similar diffusivities for these two cations.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB

摘要:

Germinating wheat embryos (Triticum vulgarevar. Florence) synthesize proteins before the onset of DNA synthesis. The onset of DNA replication occurs at about 15 hours of germination and was shown to depend on proteins synthesized before 9 hours of germination with the use of blasticidin S, a specific inhibitor of protein synthesis. A 10-fold increase in the activity of DNA-dependent DNA polymerase was found in extracts derived from germinated embryos, as compared to the activity found in extracts from ungerminated embryos.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB

摘要:

Pretreatment of pea (Pisum sativumvar. Alaska) sections with any active auxin induces an enzyme which forms aspartate conjugates of exogenously supplied indoleacetic acid, naphthaleneacetic acid, or benzoic acid. Whereas induction of this system is an absolutely auxin-specific process, another enzyme, which forms benzoylmalic acid, is induced both by auxins and by physiologically inactive aromatic carboxylic acids. Induction of both enzymes is abolished by low levels of RNA and protein synthesis inhibitors. The induction specificities and other characteristics of the two systems are compared.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB

摘要:

Catalase, glycolate oxidase, and hydroxypyruvate reductase, enzymes which are located in the microbodies of leaves, show different developmental patterns in the shoots of wheat seedlings. Catalase and hydroxypyruvate reductase are already present in the shoots of ungerminated seeds. Glycolate oxidase appears later. All three enzymes develop in the dark, but glycolate oxidase and hydroxypyruvate reductase have only low activities. On exposure of the seedlings to continuous white light (14.8×103ergs cm−2sec−1), the activity of catalase is doubled, and glycolate oxidase and hydroxypyruvate reductase activities increase by 4- to 7-fold. Under a higher light intensity, the activities of all three enzymes are considerably further increased. The activities of other enzymes (cytochrome oxidase, fumarase, glucose-6-phosphate dehydrogenase) are unchanged or only slightly influenced by light. After transfer of etiolated seedlings to white light, the induced increase of total catalase activity shows a much longer lag-phase than that of glycolate oxidase and hydroxypyruvate reductase. It is concluded that the light-induced increases of the microbody enzymes are due to enzyme synthesis. The light effect on the microbody enzymes is independent of chlorophyll formation or the concomitant development of functional chloroplasts. Short repeated light exposures which do not lead to greening are very effective. High activities of glycolate oxidase and hydroxypyruvate reductase develop in the presence of 3-amino-1,2,4-triazole which blocks chloroplast development. The effect of light is not exerted through induced glycolate formation and appears instead to be photomorphogenetic in character.In senescing leaves excised from the plants decreases in activity of glycolate oxidase, and hydroxypyruvate reductase follow with some delay the decrease in chlorophyll content. The activity of catalase, however, is maintained at high levels, especially when the detached shoots are kept in l

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB

摘要:

Crude particulate fractions from wheat leaves (Triticum vulgareL.) were separated on continuous sucrose density gradients, resulting in: broken chloroplasts, a mitochondrial fraction (indicated by cytochromecoxidase), and microbodies. The visible band of the microbody fraction from adult leaves appears at a buoyant density of 1.25 grams per cm3and contains most of the activities of catalase, glycolate oxidase, and hydroxypyruvate reductase on the gradient. In the shoots of freshly soaked seeds, catalase is already highly particulate. During further development in light or in darkness, 40 to 60% of the total activities of catalase and glycolate oxidase and 25 to 40% of the total activity of hydroxypyruvate reductase are always found in the particulate fractions of the leaves. In young developmental stages, the peaks of the activity profiles of the microbody enzymes appear on sucrose gradients at relatively low densities, first between 1.17 to 1.20 grams per cm3. During development in light, the buoyant density of the microbody fraction shifts to the final value of 1.25 grams per cm3. However, even after 1 week of growth in the dark, the microbody fraction from etiolated leaves was observed at buoyant densitites 1.17 to 1.24 grams per cm3and did not appear as a defined visible band. A characteristic visible microbody band at a buoyant density 1.24 grams per cm3was found when the dark-grown seedlings received only three separate 5-minute exposures to white light. A similar peak was also obtained from light-grown leaves in which chloroplast development had been blocked by 3-amino-1,2,4-triazole.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB

摘要:

Attempts to measure the rates of synthesis and degradation of protein in plant tissues with isotopes are complicated by the presence of at least two pools of amino acids, only one of which contributes to the synthesis of protein. Direct measurement of the protein precursor pool is thus difficult. This paper shows that one solution to this problem is to assume that the amino-acyl transfer RNA is the strict precursor of protein amino acid. By using labeled methionine, the variation with time of the specific radioactivities of methionine bound to RNA and protein have been examined under two different growth conditions inLemna minor.From these data rates of flux of methionine into and out of protein may be easily determined.A second method of determining the rates of protein synthesis and degradation assumes that the specific radioactivity of the methionyl transfer RNA in label chase conditions is effectively zero. Evidence is presented to support this contention, and the rates determined by this method agree with those calculated by the first method.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB

摘要:

The control of protein turnover inLemna minorhas been examined using a method described in the previous paper for determining the rate constants of synthesis and degradation of protein. IfLemnais placed on water, there is a reduction in the rate constants of synthesis of protein and an increase (3- to 6-fold) in the rate constant of degradation. The net effect is a loss of protein from the tissue. Omission of nitrate, phosphate, sulfate, magnesium, or calcium results in increases in the rate constant of degradation of protein.An unusual dual effect of benzyladenine on the turnover constants has been observed. Treatment ofLemnagrown on sucrose-mineral salts with benzyladenine results in alterations only in the rate constant of synthesis. Treatment ofLemnagrown on water with benzyladenine alters only the rate constant of degradation. Abscisic acid on the other hand alters both rate constants of synthesis and degradation of protein together. Inclusion of growth-inhibiting amino acids in the medium results in a reduction in the rate constants of synthesis and increases in the rate constant of degradation of protein. It is concluded that the rate of turnover of protein inLemnais very dependent on the composition of the growth medium. Conditions which reduce growth rates also reduce the rates of synthesis of protein and increase those of degradation.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1972

数据来源: ASPB