摘要:

AbstractIn water‐culture experiments with potato plants (Solanum tuberosumL. cv. Ostara), the influence of tuberization initiated by a 7‐day period of nitrogen withdrawal (discont. N) on the cytokinin activity in shoots, roots and exudate was studied. Plants with a constant supply of nitrogen (cont. N) were used as control. — Whereas no tuberization could be observed with cont. N, discont. N led to tuberization already 2 days after nitrogen withdrawal and all plants had been induced after another 4 days. In the roots of plants with discont. N, there was a temporary increase in cytokinin activity, whereas the activity decreased steadily with cont. N. In the exudate, cytokinin activity was greatly reduced during nitrogen withdrawal, whereas this activity in the exudate increased steadily with cont. N. — In the shoot with cont. N cytokinin activity decreased steadily, but with discont. N, after an initial decrease, the activity increased steeply. This increase is mainly or exclusively caused by a shift between the water‐soluble and butanol‐soluble fractions of the cytokinins in favour of the latter. The shift in cytokinin activity of the shoot is assumed to be in causal connection with an increased photosynthetic activity after the onset of tuber growth as ‘sink’

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01614.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractIn water‐culture experiments with potato plants (Solanum tuberosumL. cv. Ostara), changes in cytokinin activity in the stolon tips and newly formed tubers during tuberization were studied. Tuberization was induced by withdrawing nitrogen from the nutrient solution. — The cytokinin activity was low in the stolon tips prior to tuberization, but increased considerably in both stolon tips and young tubers during tuberization. At the same time qualitative changes in the cytokinin spectrum occurred. These qualitative changes are reversible if ‘regrowth’ of young tubers is brought about by a sudden high supply of nitrogen. — Despite the close correlation between tuberization and cytokinin activity, it is assumed that cytokinins are not directly responsible for the onset of tuberization, although they play an important role in tub

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01615.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe effect of 14 combinations of photoperiod, soil and air temperature, and growth substance applications on the cold hardiness ofChrysanthemum morifolium‘Astrid’ rhizomes was evaluated. Both triphenyl tetrazolium chloride and regrowth tests were used to determine the viability of the cold‐stressed rhizome tissues. The rhizomes exhibited different degrees of cold hardiness under these environmental conditions. A combination of short photoperiod and low air and soil temperatures induced maximum cold hardiness. Low soil temperature accompanied by long photoperiods and warm aerial temperatures did not induce rhizome hardening, while some hardening in cool soils was evident under either short photoperiods or low aerial temperatures. Warm soils reduced rhizome hardening under the normally inductive short photoperiod‐cool aerial conditions. Since the induction of rhizome hardening was dependent on the induction of the aerial organs, the involvement of translocatable hardiness promoters is indicated. Foliar applications of low levels of gibberllic acid (GA3) or abscisic acid only slightly influenced rhizome ha

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01616.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe activity levels of enzymes involved in photosynthesis, respiration and nitrogen metabolism were evaluated in a diploid and in the derived autotetraploidLycopersicon esculentum. The autotetraploid exhibited, compared to the diploid, higher protein and reduced dry matter content; reduced rate of protein synthesis; enhanced activity of malate dehydrogenase, acid invertase, glutamate dehydrogenase, and nitrate reductase; decreased peroxidase activity; unchanged polymorphism of the above‐listed enzymes as revealed by electrofocusing, namely reduced CO2fixation caused by lower ribulose‐1‐5‐diphosphate carboxylase and even lower phosphoenolpyruvate carboxylase activities in accordance with a smaller contribution of the C4carboxylating cycle; lower activities of the two “key” enzymes of photorespiration ribulose‐1‐5‐diphosphate oxygenase and glycolate oxydase. The results suggest that the gene expression of the double gene dosage is enhanced in some cases and depressed in others, resulting in more unfavourable balance of the met

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01617.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractIn a study of the adaptation ofPlantagospecies to their specific environment the lipid composition of the roots of several species:Plantago majorL. ssp.major, Plantago majorL. ssp.pleiospermaPilger,Plantago lanceolataL.,Plantago mediaL.,Plantago maritimaL.,Plantago coronopusL. was studied as well as the effect of the nutritional regime. Upon exposure to low‐salt conditionsPlantago majorL. ssp.majorL. andPlantago maritimaL. maintained the level of free sterols in the roots, despite a depressed level of total sterols, and the root lipids were more saturated than under high‐salt conditions. Both factors may reduce nutrient leakage from the roots to the low‐salt condition. Upon exposure to low‐salt conditions, allPlantagospecies showed a decreased level of galactolipid (exception:Plantago coronopus) and a decreased level of sitosterol (exception:Plantago maritima); the latter being compensated by an elevated level of cholesterol + tocopherol inPlantago majorssp.pleiosperma, Plantago lanceolataandPlantago media. Plantago coronopuswas the only species which under low‐salt conditions showed an increased level of free sterols, among which cholesterol was the most important; thus indicating a high degree of regulation of membrane permeability under alternating nutritional conditions. The level of sulfolipid was kept constant in allPlantagospecies, with the highest level observed inPlantago maritima. The role which various lipids may play in maintenance of membrane integrity under alternating nutritional conditions is

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01618.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe fate of the herbicide diphenamid was determined in cell suspensions of soybean [Glycine max(L.) Merr. ‘Wilkin’] at different stages of cell growth: early log phase (3 to 7 d), log phase (7 to 14 d), and stationary phase (14 to 18 d). [Carbonyl‐14C]‐diphenamid was added to the suspensions as an acetone solution. Neither diphenamid (2 to 3μM) nor acetone (0.5% v/v) was phytotoxic. The14C‐labeled products were identified tentatively by thin layer chromatographic comparison with reference compounds. The major metabolic products formed wereN‐hydroxymethyl‐N‐methyl‐2,2‐diphenylacetamide,N‐methyl‐2,2‐diphenylacetamide, 2,2‐diphenylacetamide, and two polar metabolites (0.9 to 25% of the applied14C activity) that appeared to be glucose conjugates; one an acidic glucoside. All metabolites were found in both the cell extract and the culture medium, except for the acidic glucoside, which was recovered in small amounts only from the cell extracts. These products were the same as those recovered from intact plants. Similar results were obtained from cell suspensions of different ages. The rate of metabolism by log phase cells was slightly less than the rate for either young or old cells. The results indicated that soybean cell suspensions can be used to obtain reliable information on the fate of agricu

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01619.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractAn improved method for polyethylene glycol‐induced fusion of protoplasts isolated from auxotrophic mutants ofNicotiana tabacumL. cv. Gatersleben was developed. By using Petri dishes coated with concanavalin A the attachment of protoplasts induced by polyethylene glycol was strengthened. As a consequence of the stronger attachment more fusion products remained after the dilution and washing procedure. It was also found that a shorter treatment combined with a more rapid dilution of the polyethylene glycol solution was superior to previous fusion methods used for plant protoplast

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01620.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractThe temperature dependence of net CO2exchange was determined at various soil water potentials for two sympatric desert species.Notholaena parryiD. C. Eat. (Pteridaceae) andEncelia farinosaGray (Compositae). As water stress increased, the temperature optimum of apparent (net) photosynthesis shifted 7 to 10°C downward and the maximum rate decreased for both species. The downward shift in temperature optimum with water stress was the result of a greater fractional stomatal closure with increasing temperature and a lowering of the temperature where maximal CO2residual conductance of the mesophyll cells occurred. This lowering of the temperature for maximal CO2residual conductance appears to reflect (1) a greater effect of water stress on gross photosynthesis than on respiration plus photorespiration and (2) the higher temperature optimum for respiration plus photorespiration than for gross photosynthesis. The downward shift in the temperature optimum of apparent photosynthesis can have a significant effect on the predicted carbon balance of plants as the soil water potential decreases

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01621.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractChloroplasts were isolated from primary needles of 1‐year‐old seedlings and from secondary needles of a 20‐year‐old pine tree in a natural stand. In autumn the electron transport capacities of PSII, PSI and PS (II + I) decreased and the electron transport between PSII and PSI became inhibited in October in the 20‐year‐old tree. This inhibition lasted until May the following year. The partial reactions of PSI and PSII still showed low but fairly constant rates during the whole winter seedlings. Seasonal changes in the electron transport properties of 1‐year‐old showed the same general trends as observed in the 20‐year‐old tree, but the changes were less pronounced. However, in snow‐covered seedlings the PSI‐mediated electron transport and the electron transport from H2O to NADP increased during the late winter when the seedlings were still covered by snow. The total chlorophyll content of the needles decreased in autumn and winter. Low temperature fluorescence ratios of F692/F680 and F726/F680 indicated more severe destruction of the chlorophyllaantennae closely associated with the two photosystems than of the light harvesting chlorophylla/bcomplex. In this case, too, the changes were more pronounced in the 20‐year‐old tree than in the 1‐year‐old seedlings. The chlorophyll/P700 ratios indicated a more marked reduction in the reaction centre molecules during autumn than in the antennae chlorophyll molecules. The changes in electron transport and low temperature fluorescence properties which occurred during autumn and winter wer

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01622.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

AbstractUptake of Rb+was investigated in 6–8‐day‐old intact barley plants (Hordeum vulgarecv. Kristina), which had been cultivated or pretreated in nutrient solutions with various K+concentrations. The relationship between Rb+influx and the K+concentration of roots appeared to be sigmoidal for plants grown in solutions containing K+, indicating regulation of Rb+uptake by allosteric inhibition of the uptake mechanism. Pretreatment of the roots in K+‐free solutions changed the pattern of uptake and caused the Rb+influx to become linearly related to the chemical Rb+potential of the uptake solution. Pretreatment in K+‐free solutions probably abolishes the allosteric inhibition of a carri

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1978.tb01623.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY