摘要:

ABA‐dcficient (aba‐1) and ABA‐insensitive (abi3–1) double mutant seeds ofArabidopsis thalianaare desiccation‐intolerant. Carbohydrates are supposed to fulfill a role in membrane protection during dehydration. Desiccation tolerance can be induced in douhle mutant seeds in vivo by supplying the ABA‐analog LAB 173 711 to the plant root system. However. this does not lead to significant changes in the carbohydrate composition, in contrast, in vitro incubation of dissected immature seeds with ABA induced desiccation tolerance concomitant with an increase in the seed raffinose content. Thus, different desiccation tolerance‐inducing treatments show contradictory effects on seed carbohydrate composition and accumulation. It is concluded that. although carbohydrates might be invohed in membrane protection or glass formation during dehydration, it is unlikely that they are the sole factor determining desiccation tolerance inAr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08798.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Carbohydrate utilization inIris pseudacorusrhizomes was investigated under natural conditions in the field for a period of one year. The area of study was under flood from mid‐December to end of May and wet for the rest of the period of study. Rhizome samples were collected in the wild twice monthly. in order to determine glucose content and amount of reducing and non‐reducing sugars in the rhizome core material. For comparison with experimental anoxia, rhizomes were washed and kept under strict anoxia in the dark at +20°C. Carbohydrates were measured in groups as above. The amount of ethanol and the levels, of ATP. ADP and AMP were also measured and adenylate energy charge computed.Glucose content of the rhizomes was 10 mg g−1fresh weight in the autumn and decreased during winter to reach ca 5 mg g−1fresh weight in the spring. Total reducing sugars increased in w inter while the amount of non‐reducing sugars increased during early autumn and decreased during winter and spring. Not all non‐reducing sugar stores had been used up in the spring when growth was resumed. Under experimental anoxia adenylate energy charge remained relatively high for 30 days (near 0.6 or over) and then dropped quickly to bekm 0.3. indicating death of the tissues. After 30 days under anoxia the amount of ethanol still increased and that of total reducing sugars decreased. The level of non‐reducing sugars decreased from 0 to 15 days of anoxia before an increase took place durine th

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08799.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Clastogenic agents, i.e. agents that can induce chromosome or DNA breakage, have been shown to enhance the rale of direct gene transfer to protoplasts. The effect was analysed at the enzymatic level using protoplast homogenates as well as intact protoplasts. For that purpose existing procedures were modified to enable measurement of DNA polymerase in vivo. In the system used, external DNA was able to enter the cells without the addition of membrane‐permeabilizing compounds. When comparing total DNA polymerase activity of protoplasts irradiated with X‐rays or UV‐light with that of untreated cells we did not observe significant differences. Incubation of protoplasts with high doses of bleomycin affected total DNA polymerase activity negatively. but dideoxythymidine triphosphate‐sensitive activity was not influenced. We conclude that the DNA strand‐breaks induced by low doses of X‐rays. UV‐light or bleomycin do not increase the total or the repair‐DNA polymerase activity and. therefore. that the increase in the transformation rates after DNA strand‐breaking is not preceded by enhanced DNA po

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08800.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Seedlings and coppice shoots ofBetula pubescensEhrh. were grown under controlled conditions designed to simulate the annual growth cycle, and a water stress was introduced during the short day (SD). Alleviation of hud dormancy after increasing periods at chilling temperatures was tested under long day (LD) conditions. Abscisic acid (ABA) was analysed in leaf and bud samples by gas chromatography‐mass spectrometry using [2H4]ABA as the internal standard. Elongation growth of coppice shoots was faster than that of seedlings under both LD and SD conditions, while the final growth cessation occurred in a similar manner and was not affected by water stress, which significantly reduced growth rate in both plant types. Bud dormancy gradually decreased with increasing length of chilling, starting from the basal parts of the plant axis. Water stress did not retard hudhurst. but rather improved it in the chilled coppice shoots and in the non‐chilled and partially chilled seedlings. Water content of buds was higher in coppice shoots than in seedlings, but after exposure to SD. it gradually decreased to 45% in both plant types and was not affected by water stress or chilling. The ABA level in both leaves and buds increased during SD treatment and was” enhanced by water stress. No clear differences in bud ABA level were found between the seedlings and coppice shoots under SD conditions, although coppice shoots had less ABA during the preceding LD conditions. There was, in general, no clear effect of chilling on bud ABA level. Budbursl in chilled, single‐node cuttings was inhibited by external ABA treatment, which raised the internal ABA levels 10 to 150 times above normal. The observed correlation between ABA level and water content in buds during induction of dormancy under SD and water stress conditions indicates a possible role for ABA in the regulation of d

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08801.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In batch cultures ofPetunia hybridacv. Rosy Morn Fertile. one respiratory peak is usually observed shortly after subculturing. However, two types of peak respiration could be distinguished, one connected with the dilution process and one with sugar addition at low biomass concentrations. The dilution peak was observed when cells were diluted in medium without sugar, in the presence or absence of mannitol. The sugar peak occurred only after previous dilution of the cells and not when sugar is added at high biomass concentrations Apparently the existence of a dilute suspension is a prerequisite for the induction of the peak. The presence of sugar is not a prerequisite for the increased respiratory activity but it is necessary lor growth: however, growth is possible without the increase in respiration, as was shown by the addition of sugar to a culture with a high biomass concentration. The peak caused by dilution either in the presence or absence of sugar showed no significant differences in height. The height of the peak caused by sugar addition to a previously diluted cell suspension was correlated with the sugar concentration. The respiratory peak disappeared long before the end of the growth period; this decline of the respiratory rates was not connected to sugar or oxygen limitation. In a continuous culture ofPetunia hybridagrowing at low biomass concentration, the respiration was always at the high level as observed during the peak of batch culture. Growing at lower biomass concentrations might be more expensive for plant cell suspensions.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08802.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The relationship between availability of external nitrate and N translocation between root and shoot was studied in N‐limited barley (Hordeum vulgareL. cv. Golf). Nitrate‐N was added at a relative rate (i.e. N added per unit time and unit N in plant biomass) of (1.09 da‐1, and distributed between the subroots at ratios of 50:50 or 80:20. The plants were grown for 13 days under these conditions of nitrate nutrition, and for another three days with the nitrate distribution reversed from 80:20 to 20:80. The nitrale‐N doses thus experienced by individual subroots ranged from 2 to 11 mg N g‐1root dry weight day‐1.15N‐Nitrate labellings were performed after 2 to 3 and 12 to 13 days of nitrate nutrition. and 2 to 3 days after reversal of nitrate additions. For all treatments, between 60 and 82% of the absorbed label initially left the root, and between 25 and 55% of the label recovered in roots had been supplied (cycled) via the shoot. Labelling of xylem N at the end of the 24‐h labelling period ranged from to 36 to 46% indicating that a substantial fraction of the N in the xylem had been absorbed by the plant prior to labelling. It is concluded that cycling of N to roots, and cycling of N in the plant as a whole, is substantial also during N‐limited growth. N allocation to roots increased with external nitrate dose. An increased utilization of non‐translocated N as well as an increased translocation of N from the shoot contributed to this effect. Thus, the results indicate that increased external availability of N also increased the sink strength of the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08803.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Endogenous gibberellins (GAs) were extracted and purified from apical buds ofEucalyptus nitens(Deane and Maid.) Maid. and the cambial region ofE. globulus(Labill.). then analysed by capillary gas chromatography‐mass spectrometry. GA1GA19GA20and GA29were identified by full scan mass spectra. Kovats retention indices and high resolution selected ion monitoring. Using deuterated internal standards. GA1. GA19. GA20and putative GA29and GA53were quantified in the apical buds, while GA4. GA8. GA9and GA44were shown to be either absent or present at very low levels. From the cambial region. GA1and GA20were quantified at levels of 0.30 ng (g fresh weight)‐1and 8.8 ng (g fresh weight)‐1respectively. These data suggest that the early 13‐hydroxylation pathway is the dominant pathway for GA biosynthesis inEuc

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08804.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08805.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The mutant C‐2A’of the unicellular green algaScenedesmus obliquusaccumulates the chlorophyll‐precursors protocbloropbyllide and the already eslerified protochlorophyll when grown heterotrophically in the dark. Two derivatives of protochlorophyll. monovinyl protochlorophyll (MV‐PChl) and divinyl protochlorophyll (DV‐PChl), were isolated from dark‐grown cells of mutani C‐2A’and characterized by absorption and fluorescence spectroscopy. Their molecular masses were determined by plasma desorption mass spectrometry. Both MV‐ and DV‐PChl were mainly esterified with geranylgeraniol. However, some esterification with the more saturated alcohols dihydrogeranylgeraniol. tetrahydrogeranylgeraniol and phytol cou

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08806.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Transformation of plants with exogenous proteinase inhibitor genes represents an attractive strategy for the biological control of insect pests. However, such a strategy necessitates a thorough characterization of endogenous proteinases. which represent potential target enzymes for the exogenous inhibitors produced. In the present study. changes in general endoproteolytic activity were monitored during sprouting of potato (Solanum tuberosumL. cv. Kennebec) tuber. Quantitative data obtained using standard procedures showed that an increase in cysteine proteinase (EC 3.4.22) activity occurs during sprouting. This increased activity results from the gradual appearance of new cysteine proteinase forms, as demonstrated by the use of class‐specific proteinase activity gels. While only one cysteine proteinase form was present during early sprouting, at least six new active forms of the same class were shown to appear gradually after the mature tuber was sown, suggesting the involvement of a complex cysteine proteolytic system in the last stages of tuber protein breakdown. Interestingly, oryzacystatins I and II. two cysteine proleinase inhibitors potentially useful for insect control, had no effect on any tuber proteinase delected. Similar results were obtained with leaf, stem and stolon proteinases. This apparent absence of direct interference supports the potential of oryzacystatin genes for production of insect‐tolerant transgenie potato pla

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb08807.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY