摘要:

AbstractThe rate of light saturated photosynthesis ofNitzschia paleawas reduced by crude oil, naphthalene and benzene. A decrease in the rate of photosynthesis at weak irradiance was also found with crude oil and naphthalene and high concentrations of benzene. On a mg/1 basis naphthalene decreased photosynthesis to a greater extent than did crude oil and crude oil to a greater extent than did benzene. A linear proportionality was found between the decrease in light saturated photosynthesis and the concentrations of aromatic hydrocarbons. The effects on photosynthesis were generally reversible, but a concentration of 700 mg benzene/1 stopped photosynthesis completely and irreversibly.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01558.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractLiposomal dispersions in water were used as a tool to study photo‐oxidation of chlorophyll‐aand photo‐oxidation of unsaturated lipids at 1 or 4°C. The presence of monogalactosyl diglyceride stimulated chlorophyll‐adegradation. In addition the level of linolenic acid was decreased in liposomal dispersions containing chlorophyll‐a, dipalmitoyl phosphatidyl choline, and monogalactosyl diglyceride, indicating that monogalactosyl diglyceride and chlorophyll‐awere coupled in the preparations. In liposomal dispersions containing equal (molar) quantities ofa‐tocopherol, monogalactosyl diglyceride, and chlorophyll‐a,a‐tocopherol fully protected linolenic acid against photo‐oxidative degradation, while chlorophyll‐adegradation was only slightly reduced. In liposomal preparations containinga‐tocopherol, chlorophyll‐aand phosphatidyl choline,a‐tocopherol catalyzed degradation of chlorophyll‐a. Absorption spectra of the liposomal dispersions showed that the presence ofa‐tocopherol caused increased absorption in red light, which was attributed to structural changes in the liposomal preparations and thus could explain the noted effects. Tocopherol itself was rapidly degraded in chlorophyll‐acontaining liposomal preparations. Complex formation between chlorophyll‐aand monogalactosyl diglyceride in chloroplasts is suggested and protection bya‐tocopherol against photo‐oxidation in chilling‐sensitive plants; a suggestion which is founded on the similarities that exist between chloroplast preparations and liposomal preparations containing chlorophyll‐aand monogalactosyl diglyceride as regards photo‐oxidative degradation of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01559.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractCuttings obtained from seedlings ofPisum sativumL. were rooted in water solution. Shoot growth continued after excision and shoot length increased considerably before roots emerged. Increase in dry weight was strongly dependent on light supply. Continued growth was dependent on supply of mineral nutrients to the rooting solution.Mineral nutrients had no or slight influence on the number of roots formed on cuttings from stock plants grown in fertilized soil, but the growth in length of the roots was dependent on the presence of calcium in the solution. Root formation was dependent on photosynthetic products formed after excision. No roots were formed on cuttings kept in the dark. The number of roots increased with increasing irradiance given to the leafy part of the cutting. At a low level of irradiance sucrose supply through the rooting medium increased the number of roots. Light given to the basal part of the cuttings had a strongly inhibitory effect on the number of roots formed. It is concluded that the carbohydrate level easily becomes a limiting factor for root formation in growing pea cuttings. Availability of mineral nutrients influences in the first place the growth of the shoots.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01560.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractDiurnal and seasonal changes in plant water potential, leaf diffusion resistance, and stem radial changes ofAcer saccharumandBetula papyriferatrees were studied in northern Wisconsin during the 1974 and 1975 growing seasons. Water potential decreased during the day, following relatively high values in the morning, and increased in the late afternoon and evening. Diurnal patterns and actual values of water potential varied with species, soil water availability, and factors influencing transpiration(e.g., solar radiation, vapor pressure deficit, and transpiration flux density). When plant water deficits were not severe, leaf resistance of both species was rather stable during the day. During severe droughts, however, leaf resistance increased (stomata closed) during the day when light intensity was high. Leaf resistance at high light intensity was higher inAcerthan inBetula. Stomatal closure with decreasing light intensity varied between species and amongAcertrees. Tree stems of both species shrank during the day, as internal water deficits developed, and they expanded as trees rehydrated during the night. Stems ofAcershrank more than those ofBetula. The amount of daily stem shrinkage increased as the season progressed if the trees were not under severe water deficits. During severe droughts the amount of diurnal stem shrinkage decreased. Shrinkage of stems lagged behind water potential changes by 1 to 2 h inAcerand less than 1 h inBetula. The relationship between stem radius and leaf water potential was not constant throughout the growing season.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01561.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe effect on nitrogen fixation of excising leaves or pods in pea (Pisum sativumL. cv. Alaska) was determined over a 60‐day period. Flower buds or their subtending leaves were removed, and C2H2reduction, H2evolution and N accumulation were measured at weekly intervals. Highest percentage nitrogen content in all treatments coincided with time of maximal C2H2‐reduction rates. Nitrogen fixation, calculated from C2H2reduction and H2‐ evolution data, was significantly lower in the partially defoliated and generally higher in the depodded plants than in the controls. Total N accumulation was greatest in the depodded plants and least in the defoliated ones. Percentage nitrogen content and N2‐fixation rates in the depodded plants were maximized approximately 10 days later than in the defoliated or control plants. The absolute rates of C2H2reduction and H2evolution were significantly altered by plant organ removal, but the relative rates were proportional. As a result the ratios of H2/C2H4production and the related relative efficiency of N2fixation in the treatments were not significantly different from the c

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01562.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractHomocontinuous cultures of the unicellular green algaScenedesmus obliquuswere grown under strong (28 W/m2∼28,000 lux) and weak (5 W/m2∼5000 lux) light conditions to simulate the conditions of ‘sun’ and ‘shade’ plants. As in higher plants the cells adapted to strong light had less chlorophyll but demonstrated a higher photosynthetic capacity and a higher respiration rate, so that their compensation point was reached at three times higher energy than in the cells grown under low light intensities. The CO2fixation rate and the RuDP carboxylase activity under saturating light intensities were both higher in the cells grown in strong light. In spite of the differences in the pigment content and in the light saturated photosynthetic capacities for both cultures, the quantum yields of photosynthetic oxygen evolution were equal. As documented for some species of higher plantsScenedesmusis not genetically determined to be either a ‘sun’ or ‘shade’ organism but can adapt its photosynthetic apparatus to the differen

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01563.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractSimulating ‘sun’ and ‘shade’ conditions of higher plants, homocontinuous cultures ofScenedesmus obliquuswere grown under 28 W/m2(∼28,000 lux) or 5 W/m2(∼5000 lux). In the high light intensity grown culture the photosynthetic capacity per chlorophyll was three times higher than in the low light intensity grown cells. The activity of photosystem II changed parallel to the photosynthetic capacity, whereas photosystem I activity was influenced to a lesser amount by the light intensity under whichScenedesmuswas grown. The molar concentration of all cytochromes and reactive plastoquinone were higher in cells grown under high light intensities. Since only plastoquinone activity represented changes equivalent to photosynthetic capacity, its activity is regarded as the rate limiting step. In spite of the changes in the photosystems and the electron transport chains, the size of the photosynthetic units is independent of the light intensity under which the cells are grown. The results reported forScenedesmusrepresent a striking similarity to those published for higher plants grown under different light

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01564.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractProtoplasts have been isolated from leaves of shoot cultures of six dihaploid clones ofSolanum tuberosumL. (2n = 2x = 24). In the KM medium (Kao and Michayluk 1975), sustained cell divisions were obtained in up to 50% of the plated protoplasts of four clones, whereas only a few divisions occurred in the other two clones. The first mitosis appeared 2–8 days after plating, dependent on the clones. In the clones showing sustained cell divisions, a protoplast titre of about 5 × 103per ml turned out to be optimal. The culture conditions for protoplasts of one of the poorly growing clones, clone H2140, have been improved using modified KM media, plating at a concentration of as high as 5 × 104cells per ml, and subsequent diluting at intervals 5 days. The dilutions were carried out with media containing 0.25% agar. Up to 60% of the plated protoplasts underwent divisions within 10 days under these conditions. After about 15 days, the regenerants were transferred onto media inducing organogenesis. Shoots and roots were formed on modified media MS (Murashige and Skoog 1962) and B5 (Gamborget al.1968). Plants have been regenerated in four of the investigated clones. Countings of chromosomes revealed a satisfactory stability of the karyotype in shoot culture and protoplast regenerat

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01565.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractInvestigations using steady‐state culture conditions indicate that carbonic anhydrase activity is correlated to the photosynthetic rate inEuglenain some but not all circumstances. When cultures grown with 5% CO2were changed to air growth, the photosynthetic rate was independent of the carbonic anhydrase activity.While experiments using the inhibitor acetazolamide indicated a close correlation between photosynthetic capacity and carbonic anhydrase activity, the inhibitor was found to be nonspecific. Acetazolamide altered photosystem activities directly as measured by the photoreduction of DCPIP in chloroplast preparations, whole‐cell fluorescence transients of chlorophylla, and by whole chain photoelectron flow. Ethoxzolamide, another inhibitor of carbonic anhydrase, was also found to inhibit photosystem activities,i.e., the photoreduction of DCPIP, andin vivophotoelectron flow, at high concentrations.Cells grown in 5% CO2were less sensitive to the effects of acetazolamide than cells exposed to air. The rate of electron flow in chloroplasts from cells grown with 5% CO2and exposed to 10 mMacetazolamide was 2.5‐fold faster than that of chloroplasts from air‐grown cells exposed to the same concentration of inhibitor. The whole cell chlorophyllafluorescence transients of cultures grown with high CO2were completely different from those of air‐grown cells and also showed fewer effects on exposure to acetazolamide.These results suggest a reevaluation of the hypothesis that carbonic anhydrase activity regulates photosynthesis. It is also apparent that results from air‐grown and 5% CO2‐grown cultures cannot be directly compared in

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01566.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe method of indolo‐α‐pyrone fluorescence‐determination of indoleacetic acid was investigated to study possible interference from 4‐chloro‐indoleacetic acid and 5‐hydroxyindoleacetic acid, which occur naturally. Both compounds show about 40% of the fluorescence of indoleacetic acid after conversion into theira‐pyrones. Other halogenated indoleacetic acids show between zero and 60% of the fluorescence of indoleacetic acid.It is concluded that the concentration of indoleacetic acid cannot be determined in crude extracts in the presence of 4‐chloro‐ or 5‐hydroxy‐indoleacetic acid, because separate determinations of each of these compounds are not possible by changing the excitation or fluorescence wave‐lengths

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01567.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY