摘要:

We tested the hypothesis that, during propagation, the basal stem ofPinus banksianaLamb, cuttings contains a nonauxin endogenous root‐forming stimulus (ERS) whose effects are not replaced by auxin treatment; i.e., that auxin treatment of cuttings and surgical removal of their basal stems during propagation act additively on rooting, without significant interaction, as determined by analyses of variance. We studied the effects of ERS by severing the original basal (1 cm) stem from cuttings at days 3, 6 and 9 of a 30‐day period of propagation. To study treatment interaction, we applied the auxinN‐phenyl indolyl‐3‐butyramide to some surgically treated cuttings. Results for all variables (proportion of rooted cuttings, number of roots per cutting and fresh weight of basal stem plus roots, if any) indicated that removing the basal stem reduced rooting and that auxin treatment increased rooting, without significant treatment interaction. The results thus supported the hypothesis thatP. banksianaseedling cuttings contain ERS. However, neither the present nor previous tests have shown that ERS is a chemical stimulus rather than, for example, a biophysical or anato

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01304.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

InLemna pausicostataHegelm. 6746, light is required for sufficient acifluorfenmethyl (AFM) stimulation of protoporphyrin IX (Proto IX) accumulation to cause significant herbicidal action. In darkness, AFM causes Proto IX levels to increase for about 2 h, after which Proto IX content is stable at levels significantly lower than those accumulated in light. In darkness, sucrose cannot increase levels of AFM‐induced Proto IX. However, addition of δ‐aminolevulinic acid (ALA) increases Proto IX levels in AFM‐treated plants in darkness, demonstrating that the herbicide blocks the porphyrin pathway in darkness as it does in the light. Thus, Proto IX accumulation in darkness appears to be limited by ALA availability. This is supported by the finding that dioxoheptanoic acid caused more ALA to accumulate in light than in darkness. Heme is a feedback inhibitor of ALA synthesis, and heme synthesis is inhibited by AFM. However, total extractable heme levels were reduced by AFM by about the same amount in both light and darkness. Exogenously supplied hemin reduced AFM‐caused Proto IX accumulation and herbicidal damage in the light and also reduced Proto IX accumulation caused by AFM or AFM plus ALA in darkness. AFM‐stimulated Proto IX accumulation was inversely proportional to the log of the photon flux density between 5 and 500 μmol in m−2s−1. Reduced effects of higher photon fluxes on AFM‐stimulated Proto IX accumulation are probably due to both increased photobleaching of Proto IX and reduced porphyrin synthesis because of herbicidal damage. AFM‐stimulated Proto IX accumulation in darkness could not be demonstrated to be under phytochrome control, but it appeared to be under the negative influence of protoch

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01305.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The hypothesis was tested that the avoidance of acid subsoil by the velvet beanMucuna pruriensis based on a mechanism acting on the whole root system rather than on individual roots. In a split‐root experiment with circulating nutrient solution the growth of plants with Al‐containing (+/+) or Al‐free (0/0) solution on both sides of the root system was compared with that of plants which had a choice (0/+). Two levels of Al (110 and 185 μM) were tested at two levels of Ca (50 and 1250 μM). In the 185 μMAl treatment the concentration of monomeric Al varied between 53 μM, directly after refreshing the solution, and 5 μMat harvest time.An external Al concentration of 110 μMhad no effect on shoot and root dry weight, while 185 μMAl applied to both sides of the root system (+/+) increased root dry weight and reduced shoot dry weight and shoot/root ratio, compared with the 0/0 control. Application of 185 μMAl to half of the roots, ied to a significant shift in root growth in favour of the control side; this response is described here as Al avoidance. On the basis of total root length, root dry weight and root surface area, the ratio of 0/+ roots was 3.1, 2.8 and 2.4, respectively.Al avoidance at 185 μMAl was confirmed in another experiment, in which root response was measured to a local P source, supplied in a third compartment containing only KH2PO4. A significant increase in root length and dry weight in this compartment was observed, when other roots of the same plant were growing in the presence of Al. This result indicates that Al avoidance byMucunaroots is related t

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01306.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

An approach commonly employed to assess the potential role of the enzyme polygalacturonase (PG, EC 3.2.1.15) in tomato fruit cell‐wall pectin metabolism includes correlating levels of extractable PG with changes in specific characteristics of cell wall pectins, most notably solubility and molecular weight. Since information on these features of pectins is generally derived from analyses of subfractions of isolated cell wall, assurance of inactivation of the various isoforms of wall‐associated PG is imperative. In the present study, cell wall prepared from ripe tomato (Lycopersicon esculentumMill. cv. Rutgers) fruit was examined for the presence of active PG and for the ability of phenolic solvents to inactivate the enzyme. Using pectin solubility and Mr(relative molecular mass) changes as criteria for the presence of wall‐associated PG activity, pectins from phenol‐treated and nonphenol‐treated (enzymically active) cell wall from ripe fruit incubated in 50 mMNa‐acetate, 50 mMcyclohexanetrans‐1,2‐diamine tetraacetic acid (CDTA), pH 6.5 (outside the catalytic range of PG), were of similar Mrand exhibited no change in size with incubation time. Wall prepared without exposure to the phenolic protein‐denaturants exhibited extensive pectin solubilization and depolymerization when incubated in 50 mMNa‐acetate, 50 mMCDTA at pH 4.5, indicating the presence of active PG. Based on the changes in the Mrof pectins solubilized in 50 mMNa‐acetate, 50 mMCDTA, pH 4.5, active PG was also detected in wall exposed during isolation to phenolacetic acid‐water (PAW, 2:1:1, w/v/v), a solvent commonly employed as an enzyme denaturant. Although the depolymerization of pectins in PAW‐treated wall was extensive, oligouronides constituted minor reaction products. Interestingly, PAW‐treated wall did not exhibit PG‐mediated pectin release when incubated under conditions (30 mMNa‐acetate, 150 mMNaCl, pH 4.5) in which nonphenol‐treated cell wall exhibited high autolytic activity. In an alternative protocol designed to inactivate PG, cell wall was exposed to Tris‐buffered phenol (BP). In contrast to pectins released from PAW‐treated wall, pectins solubilized from BP‐treated wall at pH 4.5 were indistinguishable in Mrfrom those recovered from BP‐treated wall at pH 6.5 Even when incubated at pH 4.5 at 34°C, conditions under which pectins from PAW‐treated wall underwent more rapid and extensive depolymerization, pectins from BP‐treated wall exhibited no change in Mr, providing evidence that active PG was not present in these wall preparations. The implications of this study in interpreting the solubility and Mrof pectin

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01307.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The role of Cx‐cellulase (EC 3.2.1.4) in fruit ripening and softening is unknown. In the present study, avocado (Persea americana) fruit, a rich source of Cx‐cellulase, were examined to determine if the enzyme plays a role in ripening‐related hemicellulose metabolism. Hemicelluloses (4Malkali‐soluble) from avocado fruit exhibited a very broad distribution of polymer sizes and an overall decrease in Mrduring ripening. Polymers affected were primarily those of large Mr(relative molecular mass). The characteristic total hemicellulose Mrdistribution and changes with ripening were also evident for xyloglucan (XG), a putative substrate for avocado Cx‐cellulase. Hydrolytic activity toward hemicelluloses from preripe fruit was detected in crude buffer‐soluble protein extracts derived from ripe avocado mesocarp tissue. XG was also degraded, and in a pattern similar to that observed during ripening. Purified Cx‐cellulase also exhibited activity against specific components of isolated hemicelluloses; however, in contrast to the crude protein. Cx‐cellulase alone was without influence on the Mrdistribution of avocado XG. Protein depleted of Cx‐cellulase was capable of moderate XG depolymerization. We conclude from the present studies that the enzyme Cx‐cellulase is not involved in the ripening‐related depolymerization o

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01308.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The influence of 2,6‐dichlorobenzonitrile (DCB), an inhibitor of the synthesis of glucans, on the differentiation to tracheary elements of isolated mesophyll cells ofZinnia elegansand the formation of secondary cell walls was investigated. DCB caused a decrease in viability of the cells. The number of tracheary elements and the amount of lignin decreased with increasing concentrations of DCB in the medium. However, lignified tracheary elements were observed even in the presence of 5 μMDCB. In the presence of DCB, peroxidase activity and deposition of lignin were not always restricted to secondary cell‐wall thickenings but were observed all over the walls of tracheary elements. In addition, some of the cells without any obvious cell‐wall thickening were also lignified. The amount of total carbohydrate in cell walls decreased in the presence of DCB but the amount of uronic acids was barely affected. The amount of extracellular polysaccharide (ECP) increased in the presence of DCB. The effect of DCB on the incorporation of radiolabel from [14C]‐glucose into cell‐wall polysaccharides was examined. DCB specifically inhibited the synthesis of cellulose. These results suggest that the increase in the amount of ECP and the aberrant deposition of lignin caused by DCB were results of the perturbation of the assembly of cell‐wall materials caused by interference by DCB in the synthesis

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01309.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Upon treatment with abscisic acid (ABA) or as a result of water stress (desiccation) detached leaf segments of barley (Hordeum vulgareL. cv. Salome) synthesized proteins of Mr66000, 37000, 30000 and 23000 which had previously been characterized as abundant methyl jasmonate (JaMe)‐induced proteins. The time course of appearance of mRNAs encoding JaMe‐induced proteins was compared under the three different treatments, i.e. JaMe, ABA and desiccation. From the overall analysis by in vitro translation, a complex alteration in the leaf mRNA population became evident that depended on the treatment employed. mRNAs likewise induced by the various treatments could be discriminated from mRNAs appearing specifically after JaMe‐ or ABA‐treatment or in response to desiccation. For two mRNAs induced by JaMe, ABA and desiccation, sequence homology was suggested to transcripts encoding late embryogenesis abundant (LEA) proteins. The two transcript species of 2.17 kb and 1.28 kb detected with a syntheticLeagene‐specific probe in northern blot hybridizations appeared with different time courses and accumulated to different extents under the various treatments, highlighting the obvious diversity ofLeagene expression in response to ABA, JaMe and desiccation. We suggest a role of jasmonates in mediating water stress reactions in vegetative tissues

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01310.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The effects of ethidium bromide (EB) at 0.13 mMand of chloramphenicol (CAP) at 46 mMon the mitochondria and mitochondrial nucleoids inEuglena gracilis. Z strain, were examined by fluorescence microscopy and by electron microscopy. Ethidium bromide stopped the multiplication of cells and decreased their respiratory activity by 55% after treatment for 10 days. Most of the mitochondria became slender with few cristae and some became cup‐shaped with stacked cristac. Mitochondrial nucleoids decreased markedly in number after treatment with EB for more than 2 days. After treatment for 3 days with EB, mitochondrial nucleoids could not be detected in about half of all cells examined. Treatment with CAP for 10 days reduced the respiratory activity by 47%. Chloramphenicol did not decrease the number of mitochondrial nucleoids but it increased the number of cristae and the volume of mitochondri

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01311.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Protons pumps of the tonoplast may be involved in the regulation of cytosolic pH, but the effects of pH on the coupled activities of these transporters are poorly understood. The effects of pH on the activities of the H+‐translocating pyrophosphatase (PPiase) and vacuolar‐type H+‐translocating adenosine triphosphatase (H+‐ATPase) from maize (Zea maysL. cv. FRB 73) root membranes were assessed by model that simultaneously considers proton transport by the pump and those processes that reduce net transport. The addition of either pyrophosphate or ATP to either microsomal or tonoplast membranes generated a pH gradient. The pH gradient generated in the presence of both substrates was not the sum of the gradients produced by the two substrates added separately. When membranes were separated by sucrose density gradient centrifugation, pyrophosphate (PPi)‐dependent proton transport was associated with light density membranes having tonoplast H+‐ATPase activity. These results indicate that some portion of the PPiase was located on the same membrane system as the tonoplast ATPase; however, tonoplast vesicles may be heterogeneous, differing slightly in the ratio of ATP‐ to PPi‐dependent transport. Proton transport by both the PPiase and ATPase had maximal activity at pH 7.0 to 8.0 Decreases in proton transport by the ATPase at pH above the optimum were associated with increases in the processes that reduce net transport. Such an association was not observed at pH values below the optimum. These results are discussed in terms of in situ regulation of cytoplasmic pH b

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01312.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

In dark‐grown Douglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings, the steady‐state level of the major light‐harvesting chlorophylla/bbinding proteins mRNA (cab mRNA) was about 25% of the level that accumulated in light‐grown seedlings. A single, 5‐min irradiance with red light up‐regulated expression transiently, so that cab mRNAs accumulated to a Jevel approaching that determined for light‐grown seedlings. The response was reversible by far‐red light to the dark level, indicating that the up‐regulation was a phytochrome‐mediated response. Phytochrome action also up‐regulated genes that encode ribulose bisphosphate carboxylase/oxygenase (EC 4.1.1.39) (rbcS) in Douglas‐fir seedlings, but the maximal rbcS mRNA level that was attained after the red light treatment was several‐fold lower than the expression level deternined for light‐grown seedlings. Genes that produce ubiquitin and ubiquitin‐fusion transcripts were differentially expressed in dark‐ and light‐grown seedlings, but the genes did not

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb01313.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY