摘要:

Positive root pressure inVitis rotundifoliaMichx. cv. Noble was employed to quantify diurnal and temporal changes in the chemical profile of xylem exudate. Xylem fluid osmolarity (7.2 to 16.8 mM), water flux (8.2 to 18.5 ml h−1) and solute flux (0.7 to 2.2 mmol h−1) from a cut spur exhibited a diurnal pattern with maxima during midday and minima at night. Total osmolarity was similar to the sum of all organic and inorganic entitites quantified, indicating that the major solutes have been identified. Total amino acid and organic acid concentration were about equal (2 to 7 mM), and sugars accounted for a minor fraction of the total profile (<0.2 mM). Glutamine represented ca 80% of the organic N and 70% of the total N transported in the xylem fluid. A circadian rhythm in water flux and net flux of most organic and inorganic entities was observed with maxima during midday and minima at night. The increase in xylem fluid osmolarity occurring during midday was primarily a consequence of increased organic acid (oxalic, citric, tartaric, malic and succinic acids) and ion (NH4+, No3−, P and Ca) concentration. A diurnal cycle in amino acid concentration was less clear. The concentration of individual organic and inorganic entities varied asynchronously with time. Xylem solute was comprised of 80% organic and 20% inorganic components when collected 5 min to 2 h after the commencement of bleeding, but the ratio of organic to inorganic components fell to about 50% after 7

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02064.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A procedure for the determination of metabolites of the biochemical pathway ornithine to N‐methyl‐δ1‐pyrrolinium salt (N‐methylpyrroline) is described. Plant tissue was extracted with 0.5MHCl and the extract purified on C18‐cartridges. Ornithine was reacted witho‐phthaldialdehyde, putrescine and N‐methylputrescine with dansyl chloride and the products were separated by reversed‐phase high‐performance liquid chromatography (HPLC). N‐methylpyrroline was determined by cation‐exchange HPLC without derivatization. The metabolites in the roots of tobacco (Nicotiana) species with different nicotine‐producing capacities were determined. Furthermore, the specific activities of the enzymes ornithine decarboxylase (EC 4.1.1.17), putrescine N‐methyltransferase (EC 2.1.1.53) and N‐methylputrescine oxidase were determined. Both the metabolite pools and the enzyme activities were correlated with the different nicotine‐producing capacities of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02065.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Triacontanol (TRIA) treatment of plasma membrane‐enriched vesicles from barley (Hordeum vulgareL., cv. Conquest) roots resulted in stimulation of membrane‐associated, divalent cation‐dependent ATPase activity (EC 3.6.1.3). The stimulation at physiologically active concentrations of TRIA (10−11–10−9M) occurred only when the vesicles were treated with TRIA in the presence of calmodulin. Octacosanol, the C28‐analogue of TRIA, had no effect on divalent cation‐dependent ATPase activity. Consistent with in vivo studies, simultaneous treatment of vesicles with weight equivalents of TRIA and octacosanol reduced the stimulation of ATPase activity. The effect of calmodulin on the stimulation of ATPase activity was diminished by calmidazolium, a specific inhibitor of calmodulin. Circular dichroism studies did not show a change in the α‐helix content of calmodulin in the presence of TRIA. TRIA also had no apparent effect on soluble calcium‐calmodulin 3′,5′‐cyclic nucleotide phosphodiesterase activity. Removal of excess TRIA from the medium after treatment still resulted in stimulation of divalent cation‐dependent ATPase activity in the presence of calmodulin was comparable to treated vesicles from which excess TRIA had not been removed. These data further support the contention that TRIA affects mem

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02066.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Two further internode length genes are identified inPisum sativumL. and namedlka(identified from line NGB5865) andlkb(from NGB5862). These genes result in a similar phenotype, which includes reduced stem elongation, peduncle length and basal branching, and ‘banding’ of the stem. These effects are similar to, but less severe than, those of genelk. Geneslkaandlkbinfluence gibberellin (GA) sensitivity, since mutants NGB5865 and NGB5862 possess similar levels of endogenous GA‐like substances to the wild‐type parental cultivar Torsdag and respond less to applied GA1than do wild‐type plants or GA‐synthesis mutants of a similar stature. The action of geneslkaandlkbis localised in the young apical tissue but is not thought to involve GA‐perception, since plants possessing geneslkaandlkbare not true phenocopies of GA‐deficient plants. The genetic interaction of geneslkaandlkbis examined and the action of genelkbon alegene backgr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02067.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

When indole‐3‐acetic acid (IAA) is applied through the basal cut surface of greenwood cuttings fromPopulus tremulaL. with the aim to induce adventitious roots, it is observed that a positive correlation between the number of new roots and the duration of the application exists only for the first 5 to 6 hours. This is most likely due to the induction, during this time, of a metabolic system that transforms IAA to compounds unable to provoke new roots. The most important of these compounds was identified as 2‐indolone‐3‐acetylaspartic acid (OxlAasp). The metabolic pathway from IAA to OxIAasp via indole‐3‐acetylaspartic acid was demonstrated by thin layer c

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02068.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The hydroxynitrile lyase (HNL, EC 4.2.1.‐) ofHevea brasiliensis(Muell.‐Arg.) catalyzes the dissociation of acetone cyanohydrin and mandelonitrile, but shows higher activity towards the natural substrate acetone cyanohydrin. The ratio between the activities of linamarase (β‐glycosidase, EC 3.2.1.21) to HNL was screened for more than 30Heveaplants. In mixed‐enzyme incubations various ratios of HNL to β‐glucosidase were analyzed for the rapidity of HCN liberation. Addition of HNL increased the rate of HCN liberation up to 20‐fold, thus demonstrating the significance of the HNL for rapid cyanogenesis. Its physiological importance is shown by the fact that only plants possessing high HNL activity are able to liberate HCN efficiently. Cyanogenic plants have been described as being weakly or strongly cyanogenic depending on the total amount of HCN which is potentially liberated. The data presented in this paper suggest that cyanogenic plants should also be differentiated as fast or slow cyanogenic according to the observed velocity of HCN liberation. Thus, for evaluating the repellent action of cyanogenic plants not only the final level of the HCN liberated is important but rather the rate with which this lev

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02069.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The electrical currents associated with developing primary root tips ofTriticum aestivumL. cv. Slejpner,Avena sativaL. cv. Victory I,Lolium perenneL. cv. Melle,Vigna radiata(L.) Wilczek,Arachis hypogaeaL.,Pisum sativumL. cv. Keluedon Wonder,Lonchocarpus leucanthusBurk,Dalbergia nigraFr. Allen andPicea abies(L.) Karst. (U. K. Forestry Commission Number: 85/498/B). and that of the adventitious root tips ofFragaria vescaL.,Solanum tuberosumL. cv. Maris Piper andNeptunia plenaLindl. were examined with a vibrating electrode. Current was found consistently to enter the meristematic and elongating tissues of all the intact growing roots examined. Mature non‐growing root regions were responsible for generating the outword limb of the current loop. Peak inward current densities ranged between 2 mA m−2(Lolium) and 28 mA m−2(Arachis). The point at which the inward current reversed to outward current also varied between species. These results, which are derived from 5 taxonomically diverse families (Graminae, Leguminosae, Rosaceae, Solanaceae and Pinaceae) extend the range of different species that have been shown to generate ion currents that transverse, in a highly polar manner, the growing regions of their root systems. This supports the correlations between endogenous current generation and root develo

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02070.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

During starch degradation in intact isolated chloroplasts fromChlamydomonas reinhardtiigas exchange was studied with a mass spectrometer. Oxygen uptake by intact chloroplasts in the dark never exceeded 1.5% of the starch degradation rate [maximum 15 nmol O2(mg Chl)−1h−1consumed. 1 000 nmol glucose (mg Chl)−1h−1degraded]. Evolution of CO2under aerobic conditions [9.8–28 nmol (mg Chl)−1h−1] was stimulated by addition of 0.1–0.5 mMoxaloacetate [393–425 nmol CO2(mg Chl)−1h−1]. Pyridoxal phosphate (5 mM) inhibited starch degradation by more than 80%, but had no effect on O2uptake. Starch degradation rates and CO2evolution did not differ under acrobic and anaerobic conditions. Increasing Piin the reaction medium from 0.5 mMto 5.0 mMstimulated starch degradation by 230 and 260% under aerobic and anaerobic conditions, respectively. A rapid autooxidation of reduced ferredoxin was observed in a reconstituted system consisting of purifiedChlamydomonasferredoxin, purifiedChlamydomonasNADP‐ferredoxin oxidoreductase (EC 1.6.7.1) and NADPH. Addition of isolated thylakoids fromC. reinhardtiidid not affect the rate of O2uptake. Our results clearly indicate the absence of any oxygen requirement during starch degradation i

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02071.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Influx of Rb+(86Rb+) and Ca2+(45Ca2+) was determined in roots of winter wheat (Triticum aestivumL. cv. Weibulls Starke II) after 14 days at 16°C/16 h light, after 1 and 8 weeks of cold acclimation (2°C/8 h light) and at intervals after deacclimation (16°C/16 h light) for up to 14 days. The plants were cultivated at 3 ionic strengths: 100, 10 and 1% of a full strength nutrient solution, containing 3.0 mMK+and 1.0 mMCa2+.K+concentrations in roots and shoots increased during cold treatment, while Ca2+in the roots decreased. In the shoots Ca2+concentrations remained the same. Influx of Rb+as a function of average K+concentration in the roots of 14‐day‐old, non‐cold‐treated plants was high at a certain K+level in the root and decreased at higher root K+levels (negative feedback). The pattern for Ca2+influx versus average concentration of Ca2+in the root was the reverse. Independent of duration of treatment (1–8 weeks), cold acclimation partly changed the regulation of Rb+influx, so that it became less dependent upon negative feedback and more dependent on the ionic strength of the cultivation solution. After exposure to 2°C, Ca2+influx increased at high Ca2+concentrations in the root as compared with influx in roots of 14‐day‐old non‐cold‐treated plants. Under deacclimation, Ca2+influx gradually decreased again, and reached the level observed before cold treatment within 7–14 days at 16°C; the number of days depending on the exposure time at 2°C. It is suggested that Rb+(K+) influx became adjusted to low temperature and that abscisic acid (ABA) may be involved in this mechanism. It is also suggested that extrusion of Ca2+was impaired and/or Ca2+channels were activated at 2°C in roots of plants grown in the full‐strength solution and that extrusion was gradually restored and/or Ca2+channels were closed un

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02072.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Recently considerable progress has been achieved in the elucidation of the origin of thermoluminescence in chloroplasts. The assignment of 2 of the thermoluminescence bands, peaking at around +5°C (Q or D band) and +30°C (B band), to the recombination of charges, originating from the oxidzed species of the oxygen evolving complex (the so‐called S states) and to the reduced primary and secondary quinone acceptors QAand QB, respectively, has aided in the investigation of reactions involving both the electron donor and acceptor sides of photosystem II. In this paper we review recent thermoluminescence results concerning the deactivation of S states, temperature and pH dependence of S state transition, and the activity of the water oxidizing system after removal of Cl−, manganese or the 33 kDa protein. Reports on the use of thermoluminescence in investigations on the sites of action of herbicides and redox changes of QBconferred by herbicide resistance are also discussed. The effect of pH, bicarbonate, and Acceleration of Deactivation Reaction of enzyme “Y” (ADRY) reagents on the photosystem II reactions are presented in the light of thermoluminescence observations. Further possible applications of thermoluminescence promising better understanding of the photosynthetic processes are

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb02073.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY