摘要:

The linearly polarized reflectance from a leaf depends on the characteristics of the leaf surface. In the present study the leaf reflectance of a number of plant species with varying surface characteristics was measured at the Brewster angle with a polarization photometer having 5 visible and near‐infrared wavelength bands. We found that all leaf surfaces polarized incident light. Differences among species could be explained by variation in surface features. The results support our hypothesis that the polarized light is reflected by the leaf surface, not by its interior. Two mechanisms appeared responsible for the linearly polarized reflectance: (1) specular reflectance and (2) surface particle scattering. In most cases, large values of linearly polarized reflectance could be attributed to specular reflectance from the leaf surface. Attribution required knowledge of the optical dimensions of features on the leaf surfac

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01753.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The redox level and compartmentation of pyridine nucleotides was studied under photorespiratory and non‐photorespiratory conditions using rapid fractionation of barley (Hordeum vulgareL. cv. Gunilla, Svalöv) leaf protoplasts. From comparative measurements of the NADPH/NADP+ratio and the ATP/ADP ratio one acidic and one alkaline extraction medium was chosen which quenched the metabolism very efficiently. The mitochondrial NADH/NAD+was higher under photorespiratory conditions than under non‐photorespiratory conditions. Aminoacetonitrile, an inhibitor of the photorespiratory conversion of glycine to serine, lowered the mitochondrial NADH/NAD+ratio. This supports the hypothesis that glycine oxidation is coupled to oxidative phosphorylation to provide ATP to the cytosol. The chloroplastic NADPH/NADP+as well as the NADH/NAD+ratios were quite stable in saturating and limiting CO2as well as in the presence of aminoacetonitrile, although the triosephosphate/phosphoglycerate ratios changed. Thus, the redox level in the stroma seems to be tightly regul

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01754.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Peroxisomes and mitochondria were purified from potato tubers (Solanum tuberosumL. cv. Bintje) by differential centrifugation followed by separation on a continuous Percoll gradient containing 0.3Msucrose in the lower half and 0.3Mmannitol in the upper half. The peroxisomes band at the bottom and the mitochondria in the middle of this type of gradient. Mitochondrial contamination of the peroxisomes was only 2% [as judged by cytochromecoxidase (EC 1.3.9.1) activity]. Contamination by amyloplasts, plasma membrane and endoplasmic reticulum was also minimal. The peroxisomes were 80% intact as judged by malate dehydrogenase (MDH, NAD−‐dependent; EC 1.1.1.37) latency.The specific activity of NADH‐ferricyanide reductase and NADH‐Cytcreductase was 0.22 and 0.051 μmol (mg protein)−1min−1in freshly isolated peroxisomes, respectively. The active site of the reductase appeared to be on the inner surface of the membrane. The peroxisomes also contained ab‐type cytochrome. Frozen peroxisomes were subfractionated by osmotic rupture followed by centrifugation to separate the soluble proteins from the peroxisomal membrane. About half the MDH and 30% of the NADH‐ferricyanide reductase activity was associated with the membrane but only 6% of the catalase (EC 1.11.1.6) activity. A further wash removed 75% of the residual catalase with only a small loss of MDH or NADH‐ferricyanide reductase activity. MDH appears to be closely associated with the peroxisomal membrane.When the purified peroxisomal membrane was analyzed by SDS‐PAGE followed by silver staining, prominent bands at 22, 40, 41, 48, 53 and 74 kDa were observed. After immunoblotting the purified peroxisomal membrane, a band at 53 kDa showed strong cross‐reactivity with antibodies raised against NADH‐ferricyanide reductase. Since the NADH‐ferricyanide reductase activity in the peroxisomal membrane could be shown to be specific for the β‐hydrogen of NADH, the activity could not be due to contamination by endoplasmic reticulum where the reductase is α‐specific. We conclude that the peroxisomal membrane contains a short redox chain, consisting of a NADH‐ferricyanide reductase and ab‐type cytochrome, similar to that of e.g. the plasma membrane. The role of this

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01755.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Analyses of the esterification of newly formed chlorophyllide in irradiated dark‐grown leaves of wheat (Triticum aestivumL. cv. Kosack) suggest a translocation of chlorophyll synthetase activity from transforming prolamellar bodies to developing thylakoids. We have fractionated plastid inner membranes from dark‐grown leaves and from leaves irradiated for 5, 10, or 20 min and compared the in vitro esterification of chlorophyllide in two fractions, corresponding (in density) to the prolamellar body and the prothylakoid fraction of dark‐grown leaves. The relative amounts of chlorophyllide, and total protein, as well as the specific esterification activity, increased with irradiation time in the prothylakoid fraction. The esterification of chlorophyllide seems to depend on a transformation of the prolamellar body structure. The results are discussed also in relation to other events initiated by irradiation, such as the Shibata‐shift and the altered distribution of NADPH‐protochlorophyllide oxidoreductase (EC

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01756.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

With a reduced stratospheric ozone concentration, the generation of UV‐tolerant plants may be of particular importance. Among different crop plants there is large variation in sensitivity to UV‐B radiation. This study was undertaken to investigate the possibilities of using somaclonal variation and selection in vitro for improving UV‐B tolerance in sugar beet (Beta vulgarisL.).Sugar beet callus was exposed to UV radiation (280–320 nm, 0.863–5.28 kJ m‐2day‐1, unweighted) and resultant shoots were selected from surviving cells. After establishment of the plants, they were grown under either visible radiation (114 μmol m‐2s‐1PAR) or with the addition of UV radiation (6.3 kJ m‐2day‐1biologically effective UV‐B). Screening of regenerants in vivo for tolerance to UV radiation was undertaken 10 months after termination of the UV selection pressure. Screening was done visually and by using a number of physiological parameters, including chlorophyll fluorescence induction, ultraweak luminescence, pigment analysis and total content of UV‐screening pigments. A clear difference between the unselected and the UV‐selected somaclones was observed when visually studying the UV damage and other leaf injury. The observations were supported by the ultraweak luminescence measurements. Unselected plants showed significantly greater damage when subjected to subsequent UV radiation as compared to the selected plants. The clones subjected to UV selection pressure displayed a significantly higher concentration of UV‐screening pigments under subsequent UV radiation. The unselected plants under subsequent UV treatment showed a lower carotenoid concentration when compared to selected plants. However, no significant difference between treatments was found for chlorophylla/b, or F/Fmax, a measure o

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01757.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The source‐sink ratio of 1‐year‐old, potted sour cherry trees (Prunus cerasusL.) was altered by whold‐plant partial defoliation or continuous illumination to determine if trees were primarily sink limited and to elucidate the means whereby photosynthetic enhancement or inhibition occurs. Leaf xylem water potential was not affected by either treatment. Although stomatal conductance was reduced by 1 to 3 days of continuous illumination, internal CO2concentration was not significantly affected indicating that the enhanced physical limitation imposed by the stomata was of no physiological significance. Net CO2assimilation (A) was significantly higher 4 days after partial defoliation and lower from 1 to 4 days following continuious illumination. The increase in A in partially defoliated plants was associated with reduced leaf starch and increased surose and sorbitol concentrations. The decrease in A in continuously illuminated plants was associated with a decrease in variable fluorescence, photochemical efficiency of photosystem II (PSII) and an increase in instantaneous fluorescence, indicating that leaves were photoinhibited and that irreversible damage had occurred to PSII. In addition, leaves of continuously illuminated plants had 80% more starch and significantly less sucrose and sorbitol. These altered leaf carbohydrate concentrations indicate that the existing sink limitation may have been aggravated by continuous illumination leading to an insufficient utilization of sucrose from the leaf. Whether the altered photochemical and biochemical events occurred simultaneously and/or to the same degree to lead to the observed responses remains eq

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01758.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

In culture, the ectomycorrhiza‐forming fungiAmanita muscaria(Pers. ex Fries) Hock. andHebeloma crustuliniforme(Bull. ex Fries) Quel. only grow on media with glucose or fructose but not with sucrose as sole carbohydrate source. This is due to their lack of wall‐bound invertase activity. Therefore, utilization of sucrose by the fungi within a mycorrhizal association is believed to depend on the wall‐bound invertase activity of the host. This enzyme activity was studied in the apoplast of suspension cultured cells ofPicea abies(L.) Karst. An ionically and a tightly wall‐bound isoform of acid invertase were found that function as β‐d‐fructofuranoside‐fructohydrolases (EC 3.2.1.26). The ionically bound enzyme could be easily released from walls of intact cells with buffer of high ionic strength. In its native form, the ionically bound invertase isoform is a monomeric protein with a molecular mass of 61 kDa, as determined by gel filtration and SDS‐PAGE. Glycoprotein nature of the enzyme was demonstrated with antibodies directed against the digoxigenin‐labeled protein. The Kmvalues of both enzymes for sucrose, their natural substrate, are relatively high (ionically bound invertase Km= 16 mM, tightly bound invertase Km= 8.6 mM). Activity of both wall‐bound invertase isoforms strongly depends on the apoplastic pH. They have a narrow pH‐optimum and exhibit highest activity at pH 4.5. with elevated activity between pH 4.5 and 6.0. Furthermore, fructose acts as competitive inhibitor of both isoforms, whereas glucose is not inhibitory. Unloading of sucrose from host cells to the apoplastic interface of the Hartig net in ectomycorrhizae appears to depend on the rate of hydrolysis by the wall‐bound invertase of the host. Since the activity of the plant invertase depends on the actual pH value and the fructose concentration in the mycorrhizal interface, we suggest that the fungus can actively influence the activity of the plant invertase by acidification of the cell wall and by fructose uptake. Thus, the fungus itself can regulate its own supply

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01759.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The role of the embryonic axis in regulation of proteolysis of the main storage protein was studied in buckwheat (Fagopyrum esculentum) seed. Polyacrylamide gel electrophoresis (PAGE) analysis revealed that removal of the embryonic axis had no effect on the first stage of hydrolysis, that is proteolytic modification, of 13S globulin. This modification took place in the growing seedlings also in the presence of cycloheximide, i.e. it was due to an enzyme present in dry seed. However, in isolated cotyledons the 13S globulin was not degraded completely. Incubation of isolated cotyledons with cytokinins, gibberellic acid and indoleacetic acid could not replace the excised embryonic axis. At the same time, proteolysis of the 13S globulin in the growing seedlings was strongly inhibited by casein hydrolyzate. It is suggested that a complete proteolysis of the modified storage protein is regulated by the concentration of hydrolysis products at the site of hydrolysis. The embryonic axis serves, most probably, as a site of efflux of the products of protein hydrolysis in the cotyledons during seedling growth and thus regulates the course of proteolysis.Abscisic acid (10–100 μM) was without effect on modification of the 13S globulin, but suppressed the complete proteolysis of the protein by inhibiting, apparently, the synthesis of the cysteine proteinase in the growing seedlin

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01760.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The water fernAzolla pinnataR. Br. was fumigated for 1 week with either 25, 50 or 100 nl 1−1SO2. The symbiosis ofAzollawithAnabaena azollae(spp.) was severely damaged by atmospheric SO2even at concentrations as low as 25 nl 1−1, with significant reductions in growth, reduction of C2H2, NH3assimilation, protein synthesis, and heterocyst development. These disturbances appear to be mainly responsible for the extreme sensitivity of this fern to atmospheric SO2. Changes in violaxanthin/antheraxanthin and epoxy‐lutein/lutein ratios also indicate that free radical products are induced by atmospheric SO2. These results suggest that theAzolla‐Anabaenasymbiotic system is a very responsive and reliable lower plant model to study the detailed effects of total sulphur deposition upon the balances between various important plant metabolic pr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01761.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Haploid embryogenic lines ofLarix deciduawhich had been maintained on medium free of plant growth regulatiors were screened for chromosomal abnormalities. Chromosome squashes were prepared from fast‐growing suspension culture. alternatively, a method using burst protoplasts was devised for improving chromosome spreads. One line showed polyploidization with chromosome mumbers ranging from haploid to tetraploid. This line is presently predominantly diploid. Aneuploidization also occurred. The most effective method for counting chromosomes was from burst protoplasts. It is recommended that long‐term cultures of conifer tissues be checked for genetic stabil

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb01762.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY