摘要:

AbstractThe action of gibberellins on celery (Apium graveolensL.) seed germination and the release of reducing sugars from barley (Hordeum vulgareL.) seed endosperm were enhanced by decreasing the pH of the incubation solution to below the pKa point. In most cases, low pH was obtained by mixing the solution with weak acids such as succinic acid 2.2 dimethylhydrazide (SADH), 2‐chloroethylphosphonic acid (CEPA), or citric acid. However, lowering the pH of the gibberellin solution with strong acid (HCl) also increased markedly the activity of low concentrations of GA4/7. The synergistic action of ethylenediaminetetraacetic acid (EDTA) with gibberellin was not dependent on the pH level of the incubation solution. The response of celery seeds to gibberellins was increased when their distal ends were removed: solution pH and EDTA had no effect on this response.The possible explanations of the synergism between low pH compounds and gibberellins are discusse

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03965.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractChlorophyll degradation inCucumisleaf discs was measured at different temperatures between 1 and 25°C in the light and in darkness, and in the presence or absence of sucrose. Two different processes of chlorophyll degradation could be distinguished, a light‐requiring process operating at 1 and 5°C and another, light and sucrose enhanced degradation process which was evident at 25°C. Degradation of leaf pigments at low temperatures was of a photo‐oxidative nature since there was no degradation in the dark. The chlorophyll a/b ratio was decreased, carotene was degraded at a faster rate than chlorophyll, and 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU) and triphenyltetrazolium chloride (TTC) which prevent photo‐oxidation, protected against chlorophyll degradation. The light and sucrose enhanced chlorophyll degradation at 25°C was of an enzymatic nature since it occurred in the dark as well as in the light. The chlorophyll a/b ratio was not affected, and carotene and chlorophyll degradation occurred at the same rate. Since DCMU completely inhibited the light enhancement at 25°C and experimentation in a low oxygen atmosphere also protected chlorophyll against the effect of light and sugar application, it is suggested that the enhancement of chlorophyll degradation by light and sucrose at 25°C may be due to increased sugar uptake of the chloroplasts and consequently excessive starch formatio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03966.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe movement of auxin through tendril segments ofPassiflora caerulcaL. has been investigated using IAA‐2‐14C. It has been shown that (1) flux of IAA through the segments is strongly polarized basipetally: (2) the amount of14C recovered in the basal receiver blocks increases linearly within a transport period of 6 h; (3) velocity of basipetal transport is 14.5 mm h−1; (4) at least 70% of the radioactivity in the receiver blocks is confined to the IAA molecule: approximately 55% of14C from methanolic extracts of the segments is IAA: (5) at low temperatures (2–4°C) the basipetal transport is abolished; (6) white light promotes basipetal transport, and this effect is abolished in a CO2‐free atmosphere; (7) no difference could be detected in14C content between dorsal and ventral halves of tendril segments nor among individual dorsal and ventral recei

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03967.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractCell suspensions of carrot,Datura, tobacco and soybean subjected to −20°C, −70°C and −196°C in the presence of a suitable cryoprotective agent, and stored for various lengths of time have been revived. After revival these cells divided to form callus masses. Direct immersion in liquid nitrogen invariably killed the cells, whereas cooling at the rate of 1 or 2°C/min, or pre‐freezing briefly at −20 and −70°C, followed by freezing at −196°C retained the viability. Depending on the plant species up to 70% of the cell clumps could withstand ultra‐cooling. Tobacco andDaturacell suspensions were more sensitive to cold treatment than were those of carrot. Actively growing cell suspensions containing small cell‐clumps revived rapidly, while filtered cell‐suspensions of free cells only occasionally survived. Calli of tobacco and carrot obtained from frozen suspensions have bee

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03968.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractSeedlings ofPicea sitchensis(Bong.) Carr. (Sitka spruce) have been grown in four different light regimes in growth chambers. Chloroplast fragments have been isolated from the needles and Photosystem I and Photosystem II activities measured. Measurements were made at eight photon flux densities giving light response curves for photosystem activity in needles grown in the four different light regimes. Chlorophyll concentration was higher in needles from the low cultivation light environments than in those from the high light environments. Photosystem activity was higher in needles from the high cultivation light environments. Evidence that Photosystem I was limiting photosynthesis in needles grown in the high light environments was obtained.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03969.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractFractions of acetone extracts from heartwood, sapwood and wood from the reaction zone in roots of Norway spruce, attacked by Fomes annosus, were tested concerning their effect on the activity of cellulase, polygalacturonase, aryl‐β‐glucosidase and laccase, obtained from culture filtrates of the same fungus. A specific inhibition of polygalacturonase was recorded with the resinous fractions. The hydrolysing enzymes were more inhibited by the lignans of the reaction zone in the presence of fungal laccase than in the absence of laccase. The pH dependence of the inhibiting effect of phenols varied among the enzymes. The four enzymes were inhibited by partly different lignan fractions, and synergistic effects between minor compounds were indicated. The phenolic fractions inhibited weakly the biosynthesis of the enzymes. It was obvious that results from enzyme inhibition studiesin vitrodo not reflect the complicated mutual interrelationships between production and activity of the extracellular fungal enzymes and the chemical constituents of the hostin

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03970.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractSeedlings of Norway spruce (Picea abiesL.) have been found to synthesize anthocyanins in the root tips as well as in the hypocotyls upon irradiation with white light when kept at 4°C for 6–8 days. In addition, it has also been found that the elongation and the geotropic curvature of spruce roots are dependent on the light conditions.The course of the geotropic curvature in spruce roots containing anthocyanins has been followed during a period of 5 h, in which the seedlings were geotropically stimulated continuously in the horizontal position. When the stimulation was performed in white light and in darkness at 21°C, significantly larger curvatures were observed in the roots pretreated at 4°C in darkness than in the roots containing anthocyanins. The specific curvature (curvature in degrees per mm elongation), however, was approximately the same in both types of roots stimulated in white light. This was due to a retarded elongation of the roots pretreated with light at 4°C and containing anthocyanins. A smaller difference in elongation rate between roots with and without anthocyanins was observed in the dark than in the light, but even in the dark the anthocyanin‐containing roots grew more slowly than roots without anthocyanins.In order to find out if it is the anthocyanin content or the illumination which affects the elongation and geotropic curvature in the roots, a series of similar experiments was performed using cress seedlings grown at 4°C in light or darkness. Roots of cress seedlings cultivated under conditions which would induce anthocyanin formation in spruce roots exhibited the highest geotropic responses both in light and darkness as compared to cress seedlings grown at 4°C in darkness.As in the case of spruce roots an increase in elongation was observed in cress roots illuminated during the geotropic stimulation. These similarities in the behaviour made it relevant to compare the development of the geotropic curvature in cress and spr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03971.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe ability ofl‐phenylalanine ammonia‐lyase (E.C. 4.3.1.5) to metabolizedl‐m‐,dl‐o‐ anddl‐p‐fluorophenylalanine inAvena sativahas been examined. Although all three amino acid analogues served as substrates for this enzyme, there was a marked difference in the behavior of the meta isomer from that of the para and ortho species. The Michaelis constant for the meta analogue was similar to that obtained for the natural substrate,l‐phenylalanine, but distinct from the kinetic data for the para and ortho isomers. In addition,in vivoanalyses demonstrated that bothl‐phenylalanine and the meta‐fluoro‐derivative served to protect against chlorogenic acid loss, whereas previous studies have shown that the para and ortho species depressed levels of this phenolic derivative. Finally, treatment of coleoptile apices with either the meta isomer orl‐phenylalanine reverseddl‐p‐fluorophenylalanine stimulated growth and attendant reduction in chlorogenic acid content. These findings provide further clarification of the effects of fluorophenylalanines uponl‐phenylalanine ammonia‐lyase mediated biosynthesis of low

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03972.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe rate of leaf elongation in radiata pine (Pinus radiata) and wheat seedlings was closely related to the osmotic potential of the rooting solution. Sudden stress application and removal treatments caused immediate changes in the leaf elongation rate and a new steady‐state rate independent of the old was quickly established. The osmotic potential in the active elongation zones of a leaf differed from that of the remainder of the leaf and was considered more appropriate for deriving turgor pressure to be related to leaf elongation. Shifts in elongation rate were associated with corresponding shifts in total leaf water potential in both species and with corresponding shifts in turgor pressure in wheat.There was a linear correlation between the pitch of the helical thickenings in the protoxylem of radiata pine needles and their elongation rate. A record of elongation rate is, therefore, preserved in the needle. Developmental aspects of the deposition of the helix are discusse

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03973.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractGalactose has long been known to inhibit growth in certain plant systems and more recently to promote abscission. These same systems are similarly affected by ethylene. The mung bean (Phaseolus aureusRoxb.) hypocotyl system was employed to ascertain whether the inhibitory effects of galactose might be regulated through ethylene. Galactose alone (at 10 and 100 mM) of the many carbohydrates tested elicited high rates of ethylene evolution (1.5–4.0 nl/g fresh weight x h) as determined by gas chroma‐tography. Hook opening, pigment formation, and hypocotyl elongation were inhibited by this resultant ethylene. Galactose and auxin were found to act synergistically with respect to ethylene induction. Use of an auxin antagonist and auxin transport inhibitor revealed that galactose‐induced ethylene formation is auxin dependent. Time course studies indicate that this effect may be auxin‐sparing. Methionine appears to be the substrate of galactose‐induced ethylene. since a methionine antagonist [L‐2‐amino‐4‐(2′‐amino ethoxy)‐trans‐3‐butenoic acid] abolished the induction. Potential interrelationships between galactose and ethyl

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb03974.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY