摘要:

AbstractYoung growth‐chamber‐grown cotton plants were subjected to a series of eight periods of soil water stress, which served as a preconditioning treatment. After preconditioning, water was withheld and changes in the stomatal resistance and leaf water potential were determined and compared with similar well watered control plants.The stomatal response of stress preconditioned plants adjusted such that the diffusion resistance of the lower surface of the leaf did not reach a value greater than 20 s cm−1until the leaf water potential dropped 14 bars below that required to reach the same resistance on previously unstressed plants. The resistance—leaf water potential relation for the adaxial surface was unaltered by the preconditioning treatment. Adjustment of the osmotic potential of the guard cells on the abaxial surface provides at least a partial explanation of this change in response. The lack of adjustment of stomatal response on the adaxial surface of the leaves was correlated with a lack of adjustment in osmotic potential of guard cells on that

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01863.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractA particulate enzyme displaying peroxidase activity has been extracted from the red algaCystoclonium purpureum(Huds.) Batt. The enzyme preparation was shown to contain ferri‐protoporphyrin IX through its formation of formic acid hemochromogen with absorption maxima at 399, 402, 555 and 600 nm. The preparation catalyses the formation of 3‐bromo‐p‐hydroxybenzyl alcohol fromp‐hydroxybenzyl alcohol in the presence of H2O2and NaBr at pH = 5.4. The formation of 3‐bromo‐p‐hydroxybenzyl alcohol was measured by gas chromato‐graphy‐mass spectrometry. At pH = 6.7, 4,5‐di‐hydroxybenzyl alcohol was formed. Addition of homogentisic acid stimulated the formation of dihydroxybenzyl alcohol and suppressed the brominating reaction. Iodide inhibits the enzyme. The results are consistent with a two

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01864.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe naturally occurring cytokinins, zeatin, zeatin riboside and dihydrozeatin did not promote the germination of celery (Apium graveolensL.) seeds and 6‐Δ2‐isopentenyladenine (2iPA) and its riboside were only moderately active. Of the synthetic cytokinins, kinetin, kinetin riboside, and the disubstituted urea, N‐phenyl‐N′‐pyridyl urea (NC5392) were moderately active, and 6‐benzyl‐aminopurine (BA) and its derivatives BA riboside and 6‐benzyl‐amino‐9(tetrahydropyran‐2yl)purine (SD8339) were the most active cytokinins tested. 6‐(o‐hydroxybenzyl)aminopurine (hyd‐BA) and its naturally occurring riboside inhibited germination under normally inductive conditions.All the cytokinins examined were more active in promoting germination of lettuce (Lactuca sativaL.) than celery seeds. BA, BA riboside and SD8339 were again the most active cytokinins. In contrast to the results with celery, zeatin and zeatin riboside were highly active. The other cytokinins also showed high activity with the exception of dihydrozeatin, hyd‐BA and hyd‐BA riboside which were less active. Cytokinin ribosides were less active than the corresponding free bases during the early period of the lettuce seed incubation but total

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01865.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThis study was conducted to compare the β‐glucosidase of cotyledons and fruits ofCucumis sativusL. cv. Chipper. The concentration of the enzyme was followed throughout the growth period of each organ. The greatest concentration of the enzyme did not correspond with the most rapid period of growth. Each enzyme was characterized kinetically. The Michaelis constant of the cotyledon β‐glucosidase forp‐NO2‐phenyl‐β‐D‐gluco‐pyranoside was 1.57 mM, and was 0.35 mM for the fruit enzyme. The enzymes from the two sources also differed in affinity for glucono‐1,5‐lactone, a competitive inhibitor of β‐glucosidases, susceptibility to inhibition by saccharides, and heat stability. The two organs apparently contain differe

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01866.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe photosynthesis and biomass production of two contrasting species,Salicornia rubraandDistichlis strictafrom the same habitat, were studied under different light intensities and osmotic conditions. Application of NaCl increased the biomass and succulence of Salicornia and decreased that of Distichlis. Ethylene glycol, EG mol. wt. 62.07, and 1:1 NaCl‐EG killed Salicornia and affected Distichlis adversely. The CO2uptake of both the species increased with increasing light intensity and was strongly influenced by the application of NaCl. All concentrations of NaCl stimulated the CO2uptake of Salicornia, but decreased that of Distichlis. NaCl significantly decreased the light compensation point of Salicornia but had no effect on that of Distichlis. The CO2efflux of the two species at 4.52 klx was not significantly different. The rate of CO2uptake of both the species declined with time at all levels of treatment. Salicornia had a more rapid decline in CO2uptake in absence of NaCl, whereas that of Distichlis was relatively unaffected by it.Although the tissue Na concentration of the two species increased with increasing NaCl concentration in the medium, the increase in Salicornia was 3.0 to 5.5 times greater than that of Distichlis. Increasing NaCl concentration decreased the chlorophyll concentration of Salicornia and increased that of Distichlis. This resulted in higher ratios of photosynthesis/chlorophyll concentration in Salicornia as against lower ratios in Distichlis. The tissue OP (osmotic potential) of both the species decreased with decreasing OP of the medium. In Salicornia the tissue OP decrease was concurrent with an increase in the CO2uptake, whereas the CO2uptake of Distichlis declined with decreasing OP of the medium despite a decrease in its tissue OP. It is concluded that Salicornia requires NaCl for its normal development, whereas Distichlis is adversely affected by it. Both species however, are better adapted to osmotic stress due to natural osmotic agents like NaCl, than to the osmotic stress due to artificial osmotic agents like ethylene glyco

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01867.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractApple rootstocks M.7 were given a nitrogen application either in the spring or in the preceding autumn. At the time of the spring application some rootstocks were ringed. During the 50‐day experimental period from bud‐break, shoot growth and the amount of nitrogen incorporated into the new shoots were slightly reduced in the spring‐treated trees and strongly reduced in the ringed trees of both treatments. Roots of unringed autumn‐fertilized trees showed higher levels of total and amino nitrogen than those of similar trees in the spring treatment; to a lesser degree, the reverse held for xylem sap from the stem. Ringing increased the amino‐nitrogen level in the roots, which suggests a reduced translocation rate.The nitrogen treatments led to marked differences in the percentage composition of the amino‐nitrogen fraction of roots and xylem sap. The distribution of amino acids and amides in the roots and that in xylem sap of the same trees was divergent, but arginine and asparagine often were the most important constituents. Aspartic acid was rather abundant in xylem sap. Ringing did not affect the composition of the amino‐nitrogen fraction in the roots quantitatively but increased the proportion of arginine in the sap.The possible relationship between the composition of xylem sap and soluble nitrogen in the roots is discussed. It is argued that especially in spring‐fertilized trees appreciable amounts of nitrogen must be translocated via the phloem in addition to the transpo

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01868.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractThe content of monogalactosyl diglyceride, digalactosyl diglyceride, sulfoquinovosyl diglyceride and phosphatidyl glycerol of gel‐filtrated etio‐chloroplasts isolated from greening barley seedlings was determined. The development of photosynthetic electron transport, measured as anthraquinone autooxidation, was simultaneously determined with an oxygen electrode.During the first hour of irradiation of the etiolated seedlings the lipid content of the plastids decreased rapidly. The decrease is interpreted as a chlorophyll sensitized photooxidation of the fatty acids of the diglycerides.With artificial electron donors an oxygen uptake was detected after 10 min of greening. With no donors added, a DCMU sensitive oxygen uptake was detected after 2 h. The level of DCMU inhibition increased as the plastid developed and total inhibition was obtained after 5 h.Between 2 and 6 h of greening the lipid content of the plastids stayed constant. During this greening period there was a correlation between the appearance of a DCMU sensitive electron transport and the accumulation of the trans‐3‐hexadecenoic acid of phosphatidyl glycerol. The trans‐3‐hexadecenoic acid was present already in the dark‐grown seedlings but an increase in content did not occur until after 3 h.The lipid content increased after 6 h of greening. This increase coincided well in time with the formation of grana. The fatty acid composition of the individual lipids, with the exception of phosphatidyl glycerol, and the monogalactosyl diglyceride to digalactosyl diglyceride ratios did not change fundamentally during

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01869.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractGeoperception in the Lentil Root Cap.— Previous analysis showed that, in its initial phase, the geotropic response ofLens culinarisL. roots cannot be explained by a simpleaction by sliding, pressure or contact of amyloplasts on a sensitive surface located along the longitudinal wall. In this study another mode of action is tested by considering the following parameters as functions of the roots inclination: (1) the distance (d) which the amyloplasts move; (2) their number of contacts (c̃) with parietal cytoplasm; (3) the variable (sin α) of the transversal component of the statolith weight (M̄×gsin α). It is shown that the initial rate of curvature (V̄), at the various angles, is related to the sedimentation of the amyloplasts by the equation V̄=alogbd̄c̄ sin α (whereaandbare constants). The results obtained prove that the geotropic stimulation is dependent upon the sine of the angle (α) of the root inclination and explain the sine rule deviation. The role of statoliths is discussed in the light of recent literature on growth inhibitors which are involved in the geotro

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01870.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractPhotochemical Activities of Etiochloroplasts Isolated from Plants Greened under Intermittent Light. I. Absorption of Oxygen.Oxygen exchange by isolated etiochloroplasts from wheat leaves (Triticum sativumLam. cv. Florence Aurore) has been studied with an oxygen electrode. The etiochloroplasts lack an oxygen evolving mechanism and show a light induced oxygen uptake with two components. One component, sensitive to 3‐(4‐chlorophenyl)‐1,1‐dimethylurea, results from electron flow through an active photosystem II and is suppressed by photosystem II electron donors. The other component is inhibited by quinones suggesting that it might represent some mechanism to trap and dissipate excitation energy from chlorophyll in competition with that produced by the presence of artificial traps. The results are discussed in order to explain the apparent lack of coupling between photosystem II, through which some electron flow is operating, and the active photosystem I present in these p

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01871.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

AbstractPhotochemical Activities of Etiochloroplasts Isolated from Plants Greened under Intermittent Light.II.Photobleaching of Pigments.Etiochloroplasts were isolated from wheat leaves (Triticum sativumLam. cv. Florence Aurore) greened under repeated flashes with intervals of 15 min of darkness. These plastids are unable to evolve oxygen and show a light‐induced bleaching of chlorophyll and carotenoids. This bleaching is inhibited by 3‐(4‐chlorophenyl)‐1,1‐dimethylurea and partially results from the presence of an active photosystem II.Pigment stabilization can be achieved after giving additional repeated flashes with short intervals of darkness (5 s) to the seedlings; but stabilization is then much lower than that obtained by continuous light when plastids with similar photochemical activity (Hill reaction) are compared.Pigment bleaching in etiochloroplasts is thus not only due to their inability to use water as photosystem II electron donor but results also from other structural or functional def

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1976.tb01872.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY