摘要:

Attached leaves of pumpkin (Cucurbita pepoL. cv. Jattiläismeloni) were exposed to high light intensity at room temperature (ca 23°C) and at 1°C. Fluorescence parameters and electron transport activities measured from isolated thylakoids indicated faster photoinhibition of PSII at low temperature. Separation of the α and β components of the complementary area above the fluorescence induction curve of dichlorophenyl‐dimethylurea‐poisoned thylakoids revealed that at low temperature only the α‐centers declined during exposure to high light intensity while the content of functional β‐centers remained constant. Freeze‐fracture electron microscopy showed no decrease in the density of particles on the appressed exoplasmic fracture face, indicating that the photoinhibited α‐centers remained in the appressed membranes at 1°C. Because of the function of the repair and protective mechanisms of PSII, strong light induced less photoinhibition at room temperature, but more complicated changes occurred in the α/β‐heterogeneity of PSII. During the first 30 min at high light intensity the decrease in α‐centers was almost as large as at 1°C, but in contrast to the situation at low temperature the decrease in α‐centers was compensated for by a significant increase in PSIIβ‐centers. Changes in the density and size of freeze‐fracture particles suggest that this increase in β‐centers was due to migration of phosphorylated light‐harvesting complex from appressed to non‐appressed thylakoid membranes while the PSII core remained in the appressed membranes. This situation, however, was only transient and was followed by

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00029.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Blue light gradients in the pulvini of soybean (Glycine maxvar. Northrup King S1346) leaves with different laminar orientations were examined with a fiber optic microprobe. The gradients changed markedly as a function of both incident light angle and leaf position and were determined largely by the amount of light present in the adaxial side of the pulvinus. The steepest gradient for inclined leaves was with light incident at 90° whereas for declined leaves it occurred when the light was incident at 150°. A proposed pulvinar mechanism which allows for the detection of light direction and leaf position by using the blue light gradient as an orientation signal could account for solar tracking by soybea

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00030.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Light Green, an apoplastic probe, was applied to the cut mesocotyl base or to the cut coleoptile apex of etiolated seedlings ofZea maysL. cv. Silver Queen. Probe transport was measured and its tissue distribution determined. In the mesocotyl, there is an apoplastic barrier between cortex and stele. This barrier creates two apoplastic domains which are non‐communicating. A kinetic barrier exists between the apoplast of the mesocotyl stele and that of the coleoptile. This kinetic barrier is not absolute and there is limited communication between the apoplasts of the two regions. This kinetic barrier effectively creates two sub‐domains. In the coleoptile, there is communication between the apoplast of the vascular strands and that of the surrounding cortical tissue. No apoplastic communication was observed between the coleoptile cortex and the mesocotyl cortex. Thus, the apoplastic space of the coleoptile cortex is a sub‐domain of the integrated coleoptile domain and is separate from that of the apoplastic domain of the mesocotyl c

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00031.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Carboxyfluorescein, a symplastic probe, was applied to the cut mesocotyl base or coleoptile apex of etiolatedZea mayscv. Silver Queen seedlings and its transport measured and tissue distribution determined. Long‐distance longitudinal symplastic transport of the carboxyfluorescein was mainly in the vascular stele. It moved laterally from the mesocotyl stele to the mesocotyl cortex but the presence of a weak barrier limited the movement. A partial symplastic barrier was also present near the coleoptile‐mesocotyl n

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00032.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The distribution of 4 key isoflavones (luteone, genistein, 2′‐hydroxygenistein and wighteone) in lupin (Lupinus albusL. cv. multolupa) hypocotyls shows a gradient that diminishes from young to old tissues. A spatial gradient occurs within the hypocotyl, and a temporal gradient in both the outermost vascular and epidermal tissues. Not only does a gradient exist in respect to the quantity of isoflavones, but there is also a gradient in respect to the type of isoflavone. Thus, wighteone is mainly associated with the non‐meristematic zones of the lupin hypocotyl. A close relationship was found between the distribution and the localization in the walls of phloem cells of both peroxidase (EC 1.11.1.7) and isoflavones. This observation suggests an in vivo peroxidase‐isoflavone interconnection. In fact, lupin isoflavones are able to inhibit the peroxidase‐catalyzed oxidation of the lignin precursor coniferyl alcohol, probably due to the co‐oxidation of isoflavones in the reaction media. The results are discussed on the basis of a possible role for isoflavones in controlling cell wallperoxidase activity involved in the lignification of p

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00033.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The role of high light stress in a natural environment was studied on spinach plants (Spinacia oleraceaL. cv. Wolter) grown in the field during the winter season. Fluorescence induction (at 293 K and 77 K) of leaves was used to characterize the stress effects. Night frost with minimum temperatures between – 1.5°C and –7.5°C (i.e. above the‘frost killing point’at ca. –11.5°C) led to impaired photosynthesis. This was seen as increased initial fluorescence (Fo), decreased ratio of variable to maximum fluorescence (FV/FM) and lowered rates of O2evolution. The freezing injury was reversible within several frostless days. Exposure to high light (about 900 mol m–2s–1) at chilling temperatures in the field caused photoinhibition, manifested as decreased variable fluorescence (FV) and FV/FMratio without changes in FO. The photoinhibitory fluorescence quenching was not stronger after frost than after frostless nights; synergism between light stress and preceding freezing stress was not observed. Fluorescence induction signals at 77 K showed that FVof photosystems I and II decreased to the same extent, indicating increased thermal deactivation of excited chlorophyll. Photoinhibition was fully reversible at +4°C within 1 h in low light, but only partially in moderate light. Preceding night frosts did not affect the recovery. The photoinhibition observed here is regarded as a protective system of thermal dissipation of ex

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00034.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A soluble anionic isoperoxidase (EC 1,11,1,7) was purified from peach (Prunus persicaL. Batsch cv. Merry) seeds. Purification was achieved by DEAE‐Sephacel, Sephacryl S‐300 and CM‐cellulose chromatography. The purified isoperoxidase de‐carboxylated indole‐3‐acetic acid (S0.50.13 mM, Hill coefficient 1.7). Molecular mass, determined by gel filtration and sodium dodecyl sulfate polyacrylamide gel electrophoresis, was ca 60 kDa. Polyclonal antibodies were raised in rabbit against this isoperoxidase. Using immunoprecipitation this isoenzyme was found to be immunologically different from other soluble anionic isoperoxidases isolated from

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00035.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Relationships between relative growth rate (RGR), endogenous gibberellin (GA) concentration and the response to application of gibberellic acid (GA3) were studied for two inbred lines ofPlantago majorL., which differed in RGR. A4, the fast‐growing inbred line, had a higher free GA concentration than the slow‐growing W9, as analyzed by enzyme immunoassay. GA3application increased total plant weight and RGR3particularly for the slow‐growing line. Chlorophyll a content and photosynthetic activity per unit leaf area were decreased, while transpiration rate was unaffected by GA3application. The increase in RGR by GA3application was associated with an increased leaf weight ratio; specific leaf area and percentage of dry matter in the leaves were only temporarily affected. Root respiration rate per unit dry weight was unaffected.The correlation between low RGR, low GA concentration and high responsiveness to applied GA3supports the contention that gibberellins are involved in the regulation of RGR. However, the transient influence of GA3application on some growth components suggests the involvement of other regulatory factors in addition

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00036.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

This work was done to test claims (Sangwan and Singh, Physiol. Plant. 73: 21–26) that the developing endosperm of wheat (Triticum aestivumL.) contains a cytosolic and a plastidic fructose‐ 1,6‐bisphosphatase (EC 3.1.3.11; FBPase). Repetition of the procedure of Sangwan and Singh with extracts of developing endosperm ofTriticum aestivumcv. Mercia produced two peaks of apparent FBPase activity on elution from DEAE‐cellulose. Both peaks showed high activity of pyrophosphate:fructose‐6‐phos‐phate 1‐phosphotransferase [EC 2.7.1.90; PFK(PPi)]. The apparent FBPase activity in both peaks was stimulated by 20 μMfructose‐2,6‐bisphosphate and inhibited by antibodies to PFK(PPi). Antibody to plastidic FBPase did not react positively in an immunoblot analysis with any protein of Mrcomparable to that of known FBPase in either peak. It is argued that the ability of each peak to convert fructose‐1,6‐bisphosphate to fructose‐6‐phosphate was due to PFK(PPi). and that there remains no substantiated evidence for the presence of a plastidic FBPase in the d

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00037.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The effects of microtubule inhibitors on the spectral properties of leaves of wheat (Triticum aestivumL. cv. Walde) and on the presence of plastid microtubule–like structures (MTLS) during etioplast to chloroplast transformation were examined. Amiprophos‐methyl (APM, 0.1 mM), fed to leaf sections of 7‐day‐old dark‐grown wheat, reduced the ration of phototransformable to non‐phototransformable proto‐chlorophyllide (PChlide), decreased the rate of the Shibata shift, and inhibited chlorophyll accumulation and grana stacking. The spectral properties of isolated etioplasts were not affected by APM. Colchicine (10 mM), fed to leaf sections, inhibited greening but had no effect on the PChlide ratio or the Shibata shift. MTLS were still visible on electron micrographs after treatment with APM or colchicine at frequencies similar to controls. A third inhibitor, vinblastine, had no effect on the spectral properties of non‐irradiated or irradiated etiolated leaves except at concentrations that produced visible tissue damage before the irradiation. The effects of APM and colchicine may reflect inhibitions of respiration and protein synthesis, respectively. It is concluded that MTLS are insensitive to microtubule inhibitors and thus are probably not comp

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1990.tb00038.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY