摘要:

ATP inactivated plant pyruvate dehydrogenase complex (PDC) from broccoli (Brassica oleracea) mitochondria. ATP inactivation of the complex was time-dependent and proportional to the ATP concentration. Time-dependent incorporation of32P from [γ32P]ATP into trichloroacetic acid-precipitable protein corresponded to the inactivation of the PDC. It is concluded that plant PDC is phosphorylated and inactivated by a PDC kinase

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB

摘要:

The hormonal control of DNA and protein syntheses in cortical explants taken at 10 to 11 mm from the tip of 3-day-old seedling roots (Pisum sativumcv. Little Marvel) was examined. On the auxin medium, S2M, the cortical cells began to enlarge at day 4 in culture, with no DNA synthesis or cell division throughout the 7-day culture period. With the addition of kinetin to this medium, S2M + K, the DNA content of the explants increased about three times by day 3, with further increases thereafter. This DNA increase was followed by cell division activity and subsequent tracheary element differentiation initiated at day 5. At least two divisions per parent cortical cell were required prior to this cytodifferentiation. The absolute hormonal requirements for the DNA synthesis and cell division responses were substantiated by the lack of either response in explants cultured on basal (S2M medium minus auxins) or basal + K medium for 7 days. On the auxin medium, there was no protein accumulation in the cortical explants over the 7-day period. On S2M + K medium, protein accumulation beganafterday 2 with a steady rate of increase until day 4, and some fluctuation thereafter. The pattern of increasing uptake of14C-leucine was similar for days 0 to 4 in explants on either medium. After day 4 on S2M, the uptake continued to increase coincident with cell enlargement initiation, whereas on S2M + K there was a decline. Incorporation of14C-leucine into trichloroacetic acid-precipitates of the total buffered homogenate from explants on both media exhibited a similar pattern,i.e.an increase during days 0 to 3 and then a decline to a level about three times higher than day 0. Incorporation into the homogenate soluble fraction also showed a similar pattern in explants cultured with or without kinetin. From the differences in net protein accumulation and the incorporation data, speculation on a cytokinin effect on protein synthesis and degradation rates is presented.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB

摘要:

Despite continuing efforts to correlate unit area rates of photosynthesis of crop varieties with growth rates, there has been little or no success. It is reasonable to assume that partitioning of photosynthate into new leaf area is an important component of growth. Accordingly, an expression was developed to measure leaf area partitioning. Using growth analysis techniques, relative growth rates were compared to net assimilation rates, partitioning of daily weight gain into new leaf area, and partitioning of daily weight gain into new leaf weight of nine species grown in growth chambers under three temperature regimes. Day/night temperatures of 21/10, 32/21, and 38/27 C caused large differences in relative growth rates. Relative growth rates were closely correlated with leaf area partitioning in seven of the nine species, but were inversely correlated with leaf weight partitioning for six of the nine species. Relative growth rates were poorly correlated with net assimilation rates for five of the nine species. The product of net assimilation rate times leaf area partitioning is shown to be equal to the relative leaf area expansion rate.These results indicate that growth responses due to temperature shifts were more sensitive to changes in leaf area partitioning or relative leaf area expansion rates than to net assimilation rates. Because changes in leaf area partitioning or relative leaf area expansion rates can have an effect on relative growth rates that overshadow changes in net assimilation rates, and because net assimilation rates are largely a function of unit area rates of photosynthesis, the correlation of unit area rates of photosynthesis with growth should include consideration of leaf area partitioning or relative leaf area expansion rates.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB

摘要:

An enzyme catalyzing the phosphorylation of dihydroxyacetone has been identified in the halophilic alga,Dunaliella parva.Since glycerol and glyceraldehyde are not substrates, the enzyme is referred to as dihydroxyacetone kinase. Dihydroxyacetone kinase was purified 9-fold by ammonium sulfate fractionation followed by DEAE-cellulose chromatography.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB

摘要:

InAnkistrodesmus braunii, in the absence of CO2,i.e.in CO2-free air or N2, photosynthetic nitrate uptake and nitrate reduction were inhibited, especially at low pH. Under such conditions, glucose stimulated nitrate uptake and reduction to almost the same level in the pH range between 6 and 8.5. CO2at 0.03% effected an intermediate pH dependence of nitrate uptake; saturating CO2concentration (more than 1%) eliminated the pH dependence, as did glucose, but the rates were enhanced compared with glucose. Glucose and, even more, CO2, drastically reduced the release of nitrite and ammonia to the medium, the stoichiometry between alkalinization of the medium and nitrate uptake (OH−/NO3−) approached 1.Due to the lack of storage vacuoles inAnkistrodesmus, nitrate uptake and nitrate reduction were closely coupled processes whose experimental separation is difficult. The relieving effect of glucose and CO2suggests a carrier-mediated nitrate uptake which is more limiting than nitrate reduction and is sensitive to low pH, but which is stabilized by some intermediate originating from an active carbon metabol

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB

摘要:

The kaurene synthetase from immature seeds ofMarah macrocarpus(Greene) Greene was partially purified from cell-free homogenates of endosperm by a combination of QAE-Sephadex A-25 chromatography and hydroxyapatite chromatography and freed of contaminating phosphatase activity. The two catalytic activities associated with kaurene synthetase, the cyclization of geranylgeranyl-pyrophosphate to copalyl-pyrophosphate (activity A) and the cyclization of copalyl-pyrophosphate toent-kaurene (activity B), were not even partially resolved from one another during these procedures. Both activities had identical elution profiles from a calibrated Sepharose 4B column corresponding to a molecular weight less than that of ovalbumin (45,000).The A and B activities had pH optima of 7.3 and 6.9, respectively. Both activities required millimolar concentrations of the following divalent cations in the order: Mg2+>Mn2+>Co2+. Activities A and B were both sensitive to inhibition by Hg2+, Cu2+,p-hydroxymercuribenzoate, andN-ethylmaleimide, but activity B was much more sensitive than activity A. The average value of Km′(apparent Kmin the absence of substrate inhibition) for geranylgeranyl-pyrophosphate was 1.6μm. Values of 0.5 and 0.6μmwere obtained for Km′and Km, respectively, for copalyl-pyrophosphate. The Vm′values for the two activities were similar: 12 and 9 pmol/minute·μg protein for activities A and B, respectively.N,N-Dimethylaminoethyl-2,2-diphenylpentanoate (SKF-525A) andN,N-dimethylaminoethyl-2,2-diphenylphentyl ether (SKF-3301A), tributyl-2,4-dichlorobenzylphosphonium chloride (Phosfon D), tributyl-2,4-dichlorobenzylammonium chloride (Phosfon S), 2′-isopropyl-4′-(trimethylammonium chloride)-5′-methylphenyl piperidine-1-carboxylate (Amo-1618), 2-(N,N-dimethyl-N-heptylammonium bromide)-p-methan-1-ol (Q-58), and 2-(N,N-dimethyl-N-octylammonium bromide)-p-methan-1-ol (Q-64), at concentrations from 1 to 5μm, were effective inhibitors of kaurene synthetase activity A. Acetylcholine chloride and 2-chloroethyl-trimethylammonium chloride were effective inhibitors of activity A only at concentrations of 5 mmor greater. Abscisic acid, indole-3-acetate, gibberellin A1, gibberellin A3, a mixture of gibberellins A4and A7, gibberellin A13, andN,N-dimethylaminosuccinamic acid (B995) were not inhibitory at any of the levels tested. None of these compounds was an effective inhibitor of activity B at concentrations

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB

摘要:

Parasitism byCuscutaandOrobancheonPetunia hybridaresulted in decreased choline kinase activity and phospholipids in the host shoots. TheCuscuta-infected host roots suffered a decline in phospholipid concentration with no appreciable change in enzyme activity, whereas the roots of theOrobanche-infected plants exhibited a substantial increase in phospholipid concentration despite a marked lowering in enzymic activity. Superimposition of infection byCuscutaonOrobanche-infected plants resulted in an increase in both enzyme activity and phospholipid in host shoots; the host roots recorded a decline in phospholipid, although enzyme activity was increased. As compared to the filaments infecting singly,Cuscuta, in sequential infection, registered an increase in phospholipid concomitant with a fall in enzyme activity, whereas the root parasite revealed a lowered enzyme activity and a slight decrease in phospholipid. It is hypothesized that a physiological response to infection by root parasite was an accumulation of phospholipids at the region under infection, and to that by shoot parasite was an uptake of phospholipids by the parasite from the host; this was effected not byde novosynthesis but rather by mobilization from distal regions.

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB

摘要:

Incubation of spinach chloroplast membranes for 90 minutes in the presence of 50 mmKCN and 100μmHgCl2produces an inhibition of photosystem I activity which is stable to washing and to storage of the chloroplasts at−70 C. Subsequent exposure of these preparations to NH2OH and ethylenediaminetetraacetic acid destroys O2evolution and flow of electrons from water to oxidizedp-phenylenediamine, but two types of phosphorylating cyclic electron flow can still be observed. In the presence of 3-(3,4-dichlorophenyl)-1,1′-dimethylurea, phenazinemethosulfate catalyzes ATP synthesis at a rate 60% that observed in uninhibited chloroplasts. C-Substitutedp-phenylenediamines will also support low rates of photosystem I-catalyzed cyclic photophosphorylation, butp-phenylenediamine is completely inactive. When photosystem II is not inhibited,p-phenylenediamine will catalyze ATP synthesis at rates up to 90μmol/hr·mg chlorophyll. This reaction is unaffected by anaerobiosis, and an action spectrum for ATP synthesis shows a peak at 640 nm. These results are interpreted as evidence for the existence of photosystem II-dependent cyclic photophosphorylation in these chloroplast prepar

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB

摘要:

A decaploid tall fescue (Festuca arundinaceaSchreb) genotype has been found which exhibits net photosynthetic rates of 32 to 41 mg CO2/dm2·hour as opposed to a mean of 22 mg CO2/dm2·hour for 10 hexaploid genotypes. The decaploid genotype exhibited a ribulose 1,5-bisphosphate (RuBP) carboxylase specific activity 1.3- to 2-fold higher than typical tall fescue genotypes. Specific activities of photorespiratory enzymes and nitrate reduction enzymes were lower in the decaploid than the hexaploid genotypes. Results suggest that genetic expression of RuBP carboxylase activity may have been altered to increase the net photosynthesis rate in the decaploid genotyp

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB

摘要:

Panicum milioides, a naturally occurring species with reduced photorespiration,P. bisulcatum, a C3species, andP. miliaceum, a C4species, were grown for 4 weeks at altered pO2and pCO2and several vegetative growth parameters were determined at weekly intervals. Compared to a pO2of 10%, a greater O2inhibition of the relative growth rate and dry matter production was observed forP. bisulcatumthan forP. milioidesat both 21% and 40% O2, whereas little effect of O2was noted forP. miliaceum.Similarly, exposures to elevated pCO2of 500 and 1000μ1 CO2/liter resulted in a greater stimulation of vegetative growth forP. bisulcatumthan forP. milioides, with little effect onP. miliaceum.The CO2compensation concentration ofP. milioideswas less than that ofP. bisulcatumover a pO2range of 5 to 40%. At 5% O2, the compensation concentration was relatively O2-insensitive, whereas above 5% it increased with increasing pO2. It is concluded thatP. milioidesrepresents the first well documented example of a C3plant with reduced photorespiration, based onbothleaf CO2exchange parameters and growth analyses of dry matter production

ISSN:0032-0889    

出版商:American Society of Plant Biologists    

年代:1977

数据来源: ASPB