摘要:

To discriminate among possible mechanisms responsible for the differential response to cold temperatures among ecotypes of the C4grass weed speciesEchinochloa crus‐galli(L.) Beauv., the specific activities of five oxygen‐scavenging enzymes responsible for the elimination or reduction of free radicals and hydrogen peroxide during cold‐induced photoinhibition were determined in 5‐week‐old plants of two populations of the species collected from sites of contrasting climates, Québec (QUE) and Mississippi (MISS). Enzyme activities were measured at temperatures ranging from 5 to 30°C. The specific activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase were significantly higher in cold‐adapted QUE plants at low assay temperatures than in warm‐adapted MISS plants at the same temperature. The specific activities of superoxide dismutase assayed at 5 and 25°C were similar among plants of the twoE. crus‐gallipopulations. Ascorbate concentrations were not different among plants of the two populations, suggesting that the observed differences in the specific activities of ascorbate peroxidase assayed at 5°C, truly reflect a better capacity of the QUE enzyme to reduce H2O2to water at temperature conditions associated with the photoinhibitory process. The enhanced specific activity of four of the five oxygen‐scavenging enzymes measured in the cold‐adapted QUE population at low assay temperatures correlates with the syndrome of cold‐adapted features reported for plants of this popu

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970201.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The biostimulating action of seed treatment with the synthetic antioxidant, Ambiol (2‐methyl‐4‐Edimethylaminomethyl‐5‐hydroxybenzimidazole dihydrochloride) on subsequent growth and transpiration of seedlings was studied. To study growth and transpiration responses, seeds of four agricultural species, soybean (Glycine maxL.), rapeseed (Brassica napusL.), winter wheat (Trilicum aestivumL.) and corn (Zea maysL.), were soaked in Ambiol for 24 h, using the following concentrations: 0, 0.01, 0.1, 1, 10 and 100 mg 11. The subsequent seedlings were subject to simulated soil drought, using computer‐automated root misting chambers. The influence of Ambiot on transpiration rate under simulated air drought was studied by growing plants under low humidity in a controlled humidity chamber. Response to Ambiol varied, depending on its concentration, the species used and the environment. Compared to untreated plants, 10 mg 1‐−1Ambiol reduced the mid‐day transpiration rate and total daily water usage of soybean by approximately 25%. Under simulated soil drought in the root misting chamber, 10 and 100 mg 1‐−1Ambiol increased growth of rapeseed and soybean by 25–45%, relative to the 0 mg 1‐−1treatment, yielding plants comparable in size to the fully‐irrigated controls. However, Ambiol failed to promote growth of two drought‐stressed monocotyledons (corn and winter wheat). At 100 mg P. Ambiol inhibited growth of both well‐watered wheat and rapeseed, although this in

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970202.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Availability of assimilates in apple trees (Malus domesticacv. Jonagored) was affected by removing young fruits to obtain 3 ranges of fruit/leaf ratios with average values of 130, 268 and 381 fruits per kg leaf dry matter. Fruit analyses were carried out at fruit harvest and 4 times during a 3‐week ripening period. The analyses included detection of volatile aroma components from the juice by headspace gas chromatography. At a low fruit/leaf ratio, higher concentrations of total dry matter, soluble solid and titrateable acids were found. The flesh was also firmer, and ethylene development proceeded at a lower rate and reached a lower maximum value. Aroma compounds consisted of ca 20% esters, 73% alcohols and 6% C‐6 aldehydes. The production of butylacetate and hexylacetate, which were the dominating esters, peaked during the ripening period and was most pronounced at the lowest fruit/leaf ratios. At the last sampling date this was also the case for butanol, which was the dominating alcohol. Other esters and alcohols behaved similarly, while C‐6 aldehydes showed no significant differences in the fruit/leaf ratio. We suggest that the greater availability of assimilates when internal competition is relieved at a low fruit/leaf ratio causes increased accumulation of fatty acid aroma precursors and aroma compounds as well as of sugars, acids and other compounds in the f

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970203.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Respiration of 18‐month‐oldSolarium tuberosumL. tubers was about 53% greater than that of 6‐month‐old tubers during sprouting at 23°C; yet, a significant loss of sprout vigor in the older tubers was apparent. Involvement of alternative oxidase (AO) in the age‐induced difference in tuber respiration was assessed. AO was only detected in immunoblots if tissue disks from tubers were pre‐incubated for 24 h prior to isolation of submitochondrial membrane particles (SMPs). No AO1was detected in SMPs from nonincubated tuber tissue of either age, indicating that it was not contributing to tuber respiration during sprouting as previously thought. Respiratory control and ADP/O ratios indicated that oxidative phosphorylation was fully coupled to electron transport in mitochondria isolated from 6‐ and 18‐month‐old tubers. Cytochromecoxidase (EC 1.9.3.1) activities of intact mitochondria were also not affected by tuber age. The difference in respiration during sprouting was unique to whole tubers, as oxygen consumption by mitochondria from young and oid tubers was equal on a milligram protein basis. Sprouting 18‐month‐old tubers had 15% more mitochondrial protein per gram fresh weight than did 6‐month‐old tubers. Older tubers also produced more ATP than younger tubers prior to and during sprouting, through a fully coupled, Cyt‐mediated respiratory pathway, reduced sprout vigor notwithstanding. From 5 to 10 days of sprouting, coinciding with development of the age‐induced difference in whole‐tuber respiration, ATP concentration in 18‐month‐old tubers increased to become 52% higher than that in 6‐month‐old tubers. ATP synthase (EC 3.6.1.34), assessed by SDS‐PAGE and immunoblots of β‐ and oligomycin‐sensitivity conferring protein‐subunits, also increased as a proportion of SMP protein in older tubers during this period. Relative to 6‐month‐old tubers, the increased respiration and associated oxidative phosphorylation of 18‐rnonth‐old tubers during sprouting were probably in response to a lower adenylate energy charge (AEC) prior to sprouting (from 0 fo 5 days). From 5 to 10 days of sprouting, AEC of 18‐rnonth‐old tubers increased to equal that of 6‐month‐old tubers and the two tuber ages maintained the same AEC for the remainder of the 20‐day sprouting interval. Higher respiration and lower AEC of older tubers in storage at 4°C, along with the fact that older tubers respired at a higher rate to achieve the same AEC as younger tubers d

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970204.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Gravitropism was studied in roots of wild type (WT)Arabidopsis thaliana(L.) Heynh. (strain Wassilewskija) and three starch‐deficient mutants that were generated, by T‐DNA insertional mutagenesis. One of these mutants was starchless while the other two were intermediate mutants, which had 51% and 60%, respectively, of the WT amount of starch as. determined by light and electron microscopy. The four parameters used to assay gravitropism were: orientation during vertical growth, time course of curvature, induction, and intermittent stimulation experiments. WT roots were much more responsive to gravity than were roots of the slarchless mutant, and the intermediate starch mutants exhibited an intermediate graviresponse. Our data suggest that lowered starch content in the mutants primarily affects gravitropism rather than differential growth because both phototropic curvature and growth rates were approximately equal among all four genotypes. Since responses of intermediate‐starch mutants were closer to the WT response than to that of the starchless mutant, it appears that 51–60% of the WT level of starch is near the threshold amount needed for full gravitropic sensitivity. While other interpretations are possible, the data are consistent with the starch statolith hypothesis for gravity perception in that the degree of graviresponsiveness is proportional to the total mass of plastids p

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970205.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Aminoglycoside antibiotics are frequently used for the selection of transgenic plant cells. However, for a number of species aminoglycoside selection is inefficient. The objective of the present study was to elucidate factors affecting the phytoloxic effects of aminoglycoside antibiotics. Using non‐transgenic sugar beet cotyledonary explants the interaction between three aminoglycoside antibiotics, kanamycin, neomycin and hygromycin. and Ca2+was studied by monitoring the effects on growth and shoot formation. The phytotoxic effects of the aminoglycoside antibiotics were strongly dependent on the calcium concentration in the growth media. At comparable levels of the antibiotics (kanamycin 170 μM, neomycin 220 μM, hygromycin 9.5 μM, an elevation of the calcium concentration from 1 to 10 mMresulted in growth increases of approximately 3‐, 2.5‐ and 8‐fold, respectively, and shoot formation was enhanced 1.5‐, 2‐and 6‐fold, respectively. At lower concentrations of the antibiotics, the toxic effect was nearly abolished by increasing the calcium concentration. Additional magnesium, sodium and ammonium did not affect the phytotoxic effects of the aminoglycoside antibiotics. Moreover, the phytotoxic effects of the herbicides glyphosate and phosphinothricin were not decreased by additional calcium. These data suggest the existence of a specific interaction between calcium and aminoglycoside anfibiotics in plants. The implications of these results for the use of aminoglycosides as selective agents in plant transformati

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970206.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Water loss by cell suspensions during centrifugation is well defined by simple physical principles. The major factors affecting water release during centrifugation are: duration of centrifogation, depth of the cell mass, density of cells, relative centripetal acceleration and centripetal force. Water release during centrifugation was best described by an exponential decay process with a decay constant that increases with acceleration from 0.31 ± 0.01 to 0.66 ± 0.12 min−1(mean ± SE) between 4 825 and 19 300 m s−2, respectively. The cell mass relative water content (RWC) at equilibrium was not a function of rate of water loss and was constant for each acceleration. A centripetal force was generated by the mass of the cells being accelerated away from the axis of rotation. This force generated a pressure that removed some of the cell wall and symplast water, by compression at contact points between the cells and by compression of the cytoplasm. Pressure induced by centripetal forces ranging from −0.02 to −0.23 MPa gave a linear relationship (r2>0.99) between force and RWC. The slope (0.900 MPa) was proportional to the cell wall modulus of elasticity (±). and the intercept was interpreted to give the mass of the cells at full turgor without interstitial water (RWC=1). This interpretation is supported by the findings, of two independent experiments. Centrifuged cells suspended at 100% relative humidity for over 48 h reached the same water content as predicted by the intercept. Interstitial water was labelled with solutions of polyethylene glycol (PEG. Mr8 000), the diameter of which was too large to enter the pores of plant cell walls. Centripetal accelerations greater than 10 900 m s−2removed PEG‐labelled water to levels below 0.9% of cell water content. Removal of interstitial water and other loosely bound water provided a convenient method for determination of growth, RWC and ±. The centrifugal methods provide the foundation for new quantitative methods for cell culture water re

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970207.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The control of ion concentration in the cytosol and the accumulation of ions in vacuoles are thought to be key factors in salt tolerance. These processes depend on the establishment in vacuolar membranes of an electrochemical H+gradient generated by two distinct H+‐translocating enzymes: a H+‐PPase and a H+‐ATPase. H+‐lrans locating activities were characterized in tonoplast‐enriched membrane fractions isolated by sucrose gradient centrifugation from sunflower (Helianthus annuusL.) roots exposed for 3 days to different NaCl regimes. The 15/32% sucrose interface was enriched in membrane vesicles possessing a vacuolar‐type H+‐ATPase and a H+‐PPase, as indicated by inhibitor sensitivity, pH optimum, substrate specificity, ion effects kinetic data and immunolabelling with specific antibodies. Mild and severe stress did not alter the pH profile, ion dependence, apparent Kmnor the amount of antigenic protein of either enzyme. Saline treatments slightly increased K+‐stimulaied PPase activity with no change in ATPase activity, while both PPi‐dependent and NO3‐sensitive ATP‐dependent H+transport activities were strongly stimulated. These results are discussed in terms of an adaptative mechanism of the moderately tolerant sunflowe

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970208.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

To assess genotypic variability in nutrient supply of shoot branches, the distribution of32P and45Ca exported from a source nodal root (24‐h uptake period) was measured within a genotype of a large‐leaved (Kopu) and a small‐leaved (Tahora) cultivar ofTrifolium repens. Source‐sink relationships of plants were modified by root severance, defoliation, and shade treatments. In control plants of both genotypes distribution of32P and45Ca closely followed the pathways that could be predicted from the known phyllotactic constraints on the vascular system. As such there was little allocation of radioisotopes (3.1% and 2.5% of exported32P and45Ca, respectively) from the source root to branches on the apposite side of the parent axis (far‐side branches). However, genotypic differences in nutrient allocation were apparent, when treatments were imposed to alter intra‐plant source‐sink relationships. In the large‐leaved genotype, the imposed treatments had minor effects on the allocation to far‐side branches: whereas, in the small‐leaved genotype, root severance and defoliation treatments increased lateral transport to far‐side branches to 30% (32P) and 10% (45Ca) of exported radioisotopes. Genotypes with low (8–9) and high (12–13) numbers of vascular bundles were selected from within the large‐leaved cultivar. Distribution of32Pwas then measured after plants had been pre‐treated by removal of all far‐side roots two days prior to labelling. Genotypes with low vascular bundle number allocated 20% and those with high vascular bundle number 3.2% of exported32P to far‐side branches. It was concluded (1) that genotypic variation exists withinT. repensfor potential to alter intra‐plant allocation of mineral nutrients, in response to treatments that modify source‐sink relationships within plants; and (2) that this variation is correlated with differences among genotypes in the organisatio

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970209.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Sweet sorghum (Sorghum bicolorL. Moench) stems of different cultivars (NK 405. Keller and Tracy) reveal a different pattern of sucrose accumulation with respect to in‐ternodal sugar content and distribution. The onset of sucrose storage is not necessarily associated with the reproductive stage of the plant, as was hitherto assumed, but obviously occurs after cessation of internodai elongation as was postulated for the sugarcane stem. For at least two of the three cultivars, ripening is an internode to internode process beginning at the lowermost culm parts. Intensive growth of the internodes, combined with a high hexose content in stern parenchyma, shows a strong positive correlation (r |Mg 0.94) to the activity of sucrose synthase (SuSy; EC 2.4.13), but not to invertase (EC 3.2.1.26) which is not present as soluble (neutral and acid) or cell wall‐bound, salt‐extractable enzyme in the three culsivars investigated. Sucrose synthase measured in sucrose cleavage and synthesis direction reveals divergent activity rates and sensitivity towards exogenously applied Mg2+ions and pH. SuSy activity is connected to the increase of internodai sucrose content in so far as (1) its decline is a prerequisite for the onset of sucrose accumulation and (2) it remains at a constant low level during sucrose storage. Sucrose phosphate synthase (SPS; EC 2.4.1.14) activity in the sorghum stem is low compared to SuSy and uniformly distributed over all inter‐nodes. Only source leaves of sorghum show a considerable SPS activity, but neither stem nor leaf SPS reveal a positive correlation to the increase of internodai sucrose content. Sucrose phosphate phosphatase (SPP; EC 3.1.3.24) amounts lo only 24–30% of the respective SPS activity but follows the same distribution pattern. None of the enzymes under study proves to be responsible for the extent of sucrose storage in the stem, so other phenomena such as transport processes within the stern tissue require further inve

ISSN:0031-9317    

DOI:10.1034/j.1399-3054.1996.970210.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY