摘要:

AbstractThis paper seeks to calarify conflicting reports on the nitrogen requirements forin vitroembryogenesis inDaucus carota.Tissue derived from petiole explants of the wild strain of this species were tested with a variety of sources of cellular nitrogen under conditions otherwise favorable forin vitroembryogenesis. The use of very small, sieved and well‐washed inocula reduced thecarry‐overof soluble materials with the inoculum. Embryo yield was quantified by direct counting of samples.Nitrate at concentrations ranging from 5 to 95 mMKNO3supportes only weak growth and very low embryogenesis under the exacting conditions of these experiments. As little as 0.1 mMNH4Cl added to a nitrate medium allows some embryogenesis and 10 mMNH4Cl is near optimal when KNO3is in the range of 12 to 40 mMconcentration. Glutamine, glutamic acid, urea and alanine can individually partially replace NH4Cl as a supplement to KNO3. Glutamine, alanine, and possibly glutamic acid can serve as sole sources of nitrogen supporting both good growth and embryogenesis. It was concluded that a reduced nitrogen source is required, at least as a supplement to nitrate, for rapid growth and forin vitroembryogenesis of cultured wild carrot tissue. The relationship of pH of the culture medium to growth and embryogenesis was explored and optima observed at approximately pH 5.4 for both proces

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03939.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe effect of different levels of both exogenous abscisic acid (ABA) and soil water potential on transpiration from intact maize leaves was studied in growth chamber experiments. The transpiration rate showed a more consistent decrease with decreasing soil water potential than with increasing concentration of applied ABA. The effect of exogenous ABA on the transpiration rate was markedly lower at low than at high levels of soil water potential.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03940.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractInfluence of light and dark aerobic conditions and of various metabolic poisons [3‐(3,4‐dichlorophenyl)1,1‐dimethylurea (DCMU), 2,4‐dinitrophenol (2,4‐DNP), carbonyl cyanide‐m‐chlorophenylhydrazone (m‐CCCP), α,α′bis(hexafluoroacetonyl) acetone (1799), N,N′‐dicyclohexylcarbodiimide (DCCD), sodium azide, fatty acids] on the active phosphate uptake and on the ATP level has been investigated. Cells in the dark have the same level of ATP as in the light though the phosphate transport is decreased. Similar findings are observed with DCMU. Other poisons used inhibit phosphate uptake and decrease ATP level. However their effect is more drastic on phosphate transport than on the ATP level. There is no good correlation between the ATP level

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03941.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractFactorial experiments using the three variables nitrate, ammonium, and kinetin at six different concentrations each (nitrate 4.64 to 215 mM; ammonium 2.15 to 100 mM; and kinetin 0.1 to 4.64 mg/l) were set up to measure the effects of each of these factors, and their interactions, on the fresh weight, protein, and enzyme activities of callus of Paul's Scarlet Rose. Optimum fresh weight values were obtained with nitrate at 46.4 mM. Ammonium inhibited growth at concentrations above 2.15 mM, and kinetin had no significant effect. Significant interaction between nitrate and ammonium effects on growth was found. Kinetin did not interact significantly with either nitrate or ammonium to influence the fresh weight. The specific activity of glutamate dehydrogenase (NAD) in the aminating reaction increased with increasing ammonium concentrations to 21.5; at higher concentrations the activity remained high. Glutamine synthetase specific activity was constant over a large range of nitrate and ammonium concentrations, increasing only when nitrate went from 46.4 to 100 mM. Glutamine synthetase was sensitive to the nitrate: ammonium interaction. Specific activity decreased at progressively higher ammonium levels when nitrate concentration increased. No glutamate synthase activity was detected at optimal nitrate concentrations.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03942.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractRespiration was measured under anaerobiosis in the roots of twoSeneciospecies:S. aquaticusHill, which is flood‐tolerant, andS. jacobaeaL., which is flood‐intolerant. NADH‐oxidation under anaerobiosis was measured in roots ofS. aquaticus, S. jacobaeaandS. vulgarisL., which is also flood‐intolerant.Protein content ofS. aquaticuswas about 15% higher under anaerobiosis. At 20°C respiration of the roots ofS. aquaticuswas 50% inhibited under anaerobiosis, while an almost complete inhibition occurred in the roots ofS. jacobaea. The activities of nitrate reductase, glutamate dehydrogenase and lactate dehydrogenase were considerably higher in the roots ofS. aquaticusgrown under anaerobic conditions than in roots grown under aerobic conditions. InS. jacobaeaglutamate dehydrogenase activity was lower and inS. vulgarisnitrate reductase was lower and glutamate dehydrogenase activity was higher in roots grown under anaerobic conditions. The possible role of these enzymes for metabolism under anaerobic conditions by oxidizing a surplus of NADH is discussed.Since oxidative phosphorylation is 50% inhibited under anaerobiosis, ATP has to be generated in a different way. It is argued that maintenance of the ATP‐level may be compensated by way of the enzymes mentioned above, in combination with a modified glucose u

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03943.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe role of ethylene and 2,4‐D in the abscission process, and the induction of cellulase isoenzymes in the abscission zones ofCitrusfruit at two physiological stages of fruit development, were studied using a new staining technique for the detection of cellulase isoenzymes in polyacrylamide gels following electrophoretic separation. Four to seven isoenzymes were detected in the shoot‐peduncle (zone A) and peduncle‐fruit (zone C) abscission zones; at least two of them could be detected at excision time, and of these at least one could not be connected with abscission. In the young fruit, ethylene enhanced and 2,4‐D delayed both abscission and the formation of several isoenzymes. In the older fruit, ethylene enhanced and 2,4‐D delayed the formation of isoenzymes at a time where no abscission occurred any more in zone A. A slower but significant increase in most of the isoenzyme activity detected was also observed in abscission zone A of untreated older fruit explants after excision. These results fully agree with those reported earlier in relation to total cellulase and polygalacturonase activity (Greenberget al., Physiol. Plant. 34: 1, 1975) tested at the same stages of fruit development. It is suggested, that the generality of the concept that a rise in hydrolytic enzymes in the abscission zone is necessarily followed by separation of the organ should be re

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03944.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe initial heat induced increase in permeability of beet (Beta vulgarisL.) root cell membranes, as measured by betacyanin efflux, is reversible. The leakage of betacyanin stopped when tissue held for 90 min at 45°C was transferred to 27°C.Stronger heat treatments, 10 min at 60°C or 150 min at 45°C, resulted in a continuous release of betacyanin indicating an irreversible change in membrane structure.Calcium ions inhibited the heat induced betacyanin efflux only if this was due to a reversible increase in permeabil

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03945.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractPhenylalanyl‐tRNA synthetase and phenylalanine ammonia‐lyase activities were demonstrated in partially purified extracts of pine (Pinus elliottii) suspension cultures. The optimum pH for the phenylalanyl‐tRNA synthetase reaction was 7.5 and the optimum ATP and Mg2+concentrations were 1.0 and 15 mMrespectively. Pine, calf liver and yeast tRNA were inadequate substitutes for pea tRNA in the synthetase reaction mixtures. The optimum pH for the phenylalanine ammonia‐lyase reaction was 9.0. TheKmfor phenylalanine was approximately 6.6 × 10−5M. The activity of both enzymes in the partially purified extracts was unstable

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03946.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractFunctioning of nitrate reductase and nitrite reductase was measured in intact cotyledons from radish seedlings (Raphanus sativusL.) grown in the dark in a nitrate medium. Reduction of nitrate to nitrate did proceed during the whole period of 45 h, whereas the reduction of nitrite in the intact cotyledons dropped abruptly between 20 and 23 h after exposing the roots to nitrate.The activity of the enzymes glucose‐6‐P dehydrogenase (G6PDH) and 6‐P‐gluconate dehydrogenase (6PGDH), measured in cotyledon extracts, showed a sharp decline simultaneously with the drop in nitrite reductase activity of the intact cotyledons. It was concluded that the amount of NADPH generated by the enzymes G6PDH and 6PGDH is not sufficient to allow continuous functioning of nitrite reductase after 20 h in cotyledons of seedlings grown in the dark. Therefore, the results from our experiments point to the functioning of nitrite reductase as the rate limiting step in the reduction pathway of nitrate in t

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03947.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe interaction between hormones and salinity on seed germination of three halophytic taxa in the genusSuaeda: S. maritima(L.) Dum. var.flexilisFocke and var.macrocarpaMoq., and S.depressa(Pursh) Wats, was studied. Exogenous applications of kinetin and gibberellic acid (GA3) were applied in order to determine if either of these growth‐promoting hormones would promote germination in the two dormant taxa,Suaeda depressaandS. maritimavar.flexilisand to see if osmotically induced dormancy by NaCl could be alleviated. Our results indicate that gibberellic acid is capable of breaking dormancy in these species with dormant seeds, but kinetin proved to be ineffective. A seed dormancy that was induced by osmotic stress could also be alleviated by treatments with gibberellic acid. Endogenous concentrations of both cytokinins and gibberellins were measured in seeds exposed to osmotic stress (0.85MNaCl), and we found a reduction in cytokinin activity in these three taxa. Gibberellin‐like activity was reduced inS. depressawhen seeds were soaked in 0.85MN

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03948.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY