摘要:

AbstractIsolated stem segments ofPinus silvestrisL. produce new xylem in sterile culture for 5 weeks if sucrose and IAA are present in the medium. The response of cambium varies in the course of the season and along the tree stem. The cambium is more sensitive in spring and in the stem portion closer to tree apex than later in the season and closer to the stem base. Spring initiation of cambial activity in adult pine trees under natural conditions could not be correlated with any consistent concentration gradient of natural auxin extracted from the cambial region. Thus, the relation between concentration of auxin and the activity of cambium is complex and involves changes of cambial responsivity. Interaction with gibberellic acid or kinetin and changing concentration of sucrose were studied during the season, but none of these substances alone appeared to be responsible for the observed variation in cambial response to auxin.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04826.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractNatural auxin content has been determined in the cambial region of largePinus silvestrisL. trees at various dates during the year. The tissue was collected from the stem of intact or ring‐barked trees and from stumps remaining after the trees were cut down at breast height in early summer or late autumn. No seasonal decrease of concentration of the extractable auxin in the cambial region could be detected. Decapitation or ring‐barking produced severe reduction in auxin content and arrested cambial division. In the next season the auxin level and the cambial activity remained completely depressed. It is concluded that without tissue continuity in the region external to xylem and without basipetal supply of substances, no mechanism operated by roots or remaining stem tissue near the tree base can ensure a high level of auxin in the cambial region or activate and maintain the cambial division. The activity of extracted pine auxin was found not to be identical with the stimulatory potential of authentic IAA determined by standard bioassays. The possibility of interaction with other extracted substances is discus

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04827.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractIAA oxidase/peroxidase active fractions were separated using concanavalin A‐sepharose into glycoprotein and non‐glycoprotein fractions. No IAA oxidase peak was separable from peroxidase activity. The development of these fractions were followed in pea roots over a four day period. Initially the nonglycosylated IAA oxidase/peroxidase was the dominant fraction with the IAA oxidase/peroxidase ratio remaining close to unity. The glycosylated fraction developed later with IAA oxidase the dominant activity. Differential carbohydration of IAA oxidase/peroxidase fractions may determine the intracellular sites of activity of this molecular spec

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04828.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractUptake of alkali cations, metal ions, chloride, and boric acid is shown by reanalysis of available data to be mediated by single, multiphasic mechanisms which may be fundamentally similar in a variety of plants and tissues.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04829.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractHeat treatments of two minutes at 46 to 47°C to root systems ofNicotiana rusticaandPhaseolus vulgarisaffected roots and shoots. Xylem exudate of Phaseolus was collected, and it was found that heat treatment reduced cytokinin levels and increased abscisic acid levels in the exudate. Shoot and root growth of both species was reduced. Root membrane integrity of Nicotiana was measured and was found to be impaired. It is suggested that the changes in hormone activity due to heat treatment regulate the reduction in shoot growth. Cell wall metabolism and glucosyl transferases making β‐glucans were investigated in Phaseolus leaves. Incorporation of14C from14CO2into wall constituents was slightly inhibited but neither photosynthesis nor extracted β‐glucan synthetases were affected during the first 12 hours after tre

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04830.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractCitrate synthase of wheat (Triticum aestivumL.), bean (Phaseolus vulgarisL.), cauliflower (Brassica oleraceaL.), and a marine blue‐green alga (Coccochloris elabens) is inhibited by sulfhydryl binding reagents. The inhibitions are partially reversed by dithiothreitol. Pig heart citrate synthase is only slightly inhibited by the same reagents and this is completely reversed by dithiothreitol.All citrate synthases in this study are inhibited by adenosine triphosphate. The inhibition is relieved by increasing the concentration of acetyl coenzyme A.Citrate synthase of wheat, cauliflower, bean, and pig heart was estimated by gel filtration to have a molecular weight of 100,000 daltons. The Coccochloris citrate synthase was estimated to have a molecular weight greater than 250,000 daltons.The evolutionary implications of these findings are discussed.This enzyme is comparable in size to the 100,000 dalton mammalian enzyme (Singhet al.1970) making it somewhat larger than the 65,000 dalton mango enzyme (Srereet al.1971). The PHMB‐treated enzyme also shows changes in its electrophoretic properties (Greenblatt and Sarkissian unpublished).The evidence presented here demonstrates that citrate synthase of various plants is sensitive to sulfhydryl reagents suggesting that sulfhydryl reactivity is a not unusual property of plant citrate synthase. In addition we show that molecular weight as large as or larger than that reported in microbial systems can occur in a blue‐green

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04831.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractThe compound 5‐methyl‐7‐chloro‐4‐ethoxycarbonylmethoxy‐1,2,3‐benzothiadiazole inhibited the uptake and translocation of auxin, promoted bean hook opening and inhibited abscission of florets and epinastic responses in plants. The inhibition of epinasty was not eliminated by rectifying the ethylenepromoted unequal distribution of auxin normally thought to be responsible for epinas

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04832.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractComparative field studies of water potential and relative water content in needles of Scots pine,Pinus sylvestrisL., were carried out in September‐October 1965, in June 1966 and in July‐August 1968. The sample trees were grafts, planted in 1946 and belonging to two clones, growing in close proximity and under the same environmental conditions. The main subject of the investigation was to determine whether differences in water potential and/or relative water content existed between these two clones, and if these differences could be correlated to the growth differences and thus aid in the development of selection criteria. The results obtained demonstrate such differences in water potential but not in relative water content. The differences were not consistent through the experimental periods. The clone which had the highest water potentials in June 1966, had the lowest in September‐October 1965 and in July‐August 1968. The results revealed that the clone which showed the fastest total growth, normally had the lowest water potentials when irradiated. In 1968 the current and the previous season's needles were separately investigated. The water potential and relative water content were always higher in the current season's needles. Highly significant negative correlations between water potential or relative water content and irradiance, temperature, and vapour pressure deficit wer

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04833.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractLight‐dark synchronizedChlorella fuscawas used to study the incorporation of radioactive uracil into the trichloroacetic acid insoluble fraction.In autospores the incorporation measured in darkened cells usually started immediately after uraci addition, and the time course showed three distinct linear phases with abrupt transitions between them. Chromatographic analyses of the radioactive pool components showed that the total amounts of monophosphate, diphosphate and triphosphate nucleotides of uracil did not limit the incorporation and thus did not cause the abrupt rate shifts.In autospores, 5, 9 and 14 h old cells, the initial incorporation rate increased with increasing initial uracil concentration to reach a constant value above 0.5 μ.M. Addition of glucose to the cells increased the incorporation rate over the whole uracil concentration range tested with autospores, but did not influence the rates of the other cells.The incorporation rate varied during the synchronous cycle in a manner which closely resembled the pattern for uptake and degradation rates, with the most pronounced similarity from 9 h onwar

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04834.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

AbstractQualitative changes of cytokinins in leaves of different ages fromPopulusxrobusta(Schneid.) have been determined, together with seasonal changes in cytokinin activity in mature leaves and xylem sap. Chromatography on Sephadex LH‐20 has shown that total cytokinin activity and diversity are at a maximum in expanding leaves. As leaves age, the amount and number of cytokinins decrease, with yellow senescent leaves having only one detectable cytokinin, thought to be a glucoside.Seasonal changes were followed by chromatography of the extracts on paper in butan‐2‐ol: 25 % NH4OH (4:1). Maximum cytokinin levels, due to Fraction Z (Rf 0.5–0.8), in leaves and xylem sap were found in mid‐summer. Prior and subsequent to cessation of shoot elongation growth, fraction Z decreased and fraction N (Rf 0–0.2) increased to predominate in senescent leaves. Removal of the apex resulted in an increase of fraction N in leaves from decapitated plants when compared to similar leaves from intact plants. It is suggested that, once apical sink activity has ceased, cytokinins in the xylem sap are diverted into leaves and converted to a cytokinin glucoside, possibly a storage form of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1973.tb04835.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY