摘要:

The relationships between free ABA levels and shoot elongation were investigated in shoots ofScirpus mucronatusL. Under submergence, shoot elongation increased but free ABA levels decreased. The extent of the increase in length and the decrease in free ABA in submerged shoots increased with the increase of water depth. When the shoots were transferred to air after 12 days of submergence, they ceased to elongate and the free ABA levels recovered to the values of air‐grown shoots. ABA, at concentrations from 1 μMto 1 mM, inhibited the submergence‐induced shoot elongation. In ambient air, fluridone, an inhibitor of ABA biosynthesis, at 7 μMdecreased the free ABA levels in shoots but increased shoot elongation. The effects could be reversed by 10 μMABA. These results indicate that ABA is an internal inhibitor of shoot growth inS

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00470.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Manifestations of aluminium (Al) toxicity in two cultivars of wheat (Triticum aestivumL. cvs Kadett [relatively Al‐resistant] and WW 20299 [relatively Al‐sensitive]) were investigated at two root zone temperatures (RZT) that may occur in the field. The plants were grown for 9 days at 10 or 25°C RZT. Mineral nutrients other than CaSO4were supplied daily in exponentially increasing amounts to meet the demand of the plants. Al was added as Al2(SO4)3at the beginning of the culture period at concentrations ranging from 0 to 100 μM. pH was kept constant at 4.1. Experimental data were analysed for interactions between Al and RZT on a fresh weight basis by the nonlinear Weibull function. Cultivar Kadett, when grown at 25°C RZT, was more resistant to Al than when grown at 10°C RZT. Cultivar WW 20299 was equally sensitive to Al at 10 and 25°C RZT but generally more sensitive to Al than cv. Kadett. It is suggested that cv. Kadett, in contrast to cv. WW 20299, possesses a mechanism for Al resistance that is less effective at 10°C than at 25°C RZT and therefore may be metabolically dependent. In roots, the concentrations of K, P, Mg and Ca were not negatively affected by Al or by RZT. In shoots of both cultivars the concentrations of Ca and Mg became comparatively low when the plants were treated with Al or at low RZT, the effect being larger for Ca than for Mg. At 10°C RZT under Al stress, the Ca concentrations in shoots approached the critical concentration where growth may be inhibited. As no Al was detected in the shoots, it is suggested that Al in the roots inhibits shoot growth by reducing transport of Ca from root

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00471.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The effect of salt on ascorbate peroxidase (EC 1.11.1.11) activity and mRNA level in radish (Raphanus sativusL. cv. Fakir) was investigated. cDNA encoding a radish ascorbate peroxidase was obtained and sequenced. Sequence data analysis showed that the coding region was well conserved among higher plants. The radish cDNA was used as a probe to measure the steady‐state level of ascorbate peroxidase mRNA in plants subjected to salt stress (100 mMNaCl). The levels of transcripts encoding ascorbate peroxidase were almost identical in control or salt‐grown radish plants in both leaves and roots. The activity of soluble ascorbate peroxidase was enhanced by the salt treatment in both leaves and roots. The salt‐induced increase in ascorbate peroxidase activity requires days to become significant and can be considered as a late response. The increase in activity, but not in mRNA level, suggests that the salt‐induced ascorbate peroxidase expression is probably the consequence of post‐transcription

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00472.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The heterophyllous macrophyte waterchestnut (Trapa natansL.) produces floating and submerged leaves which are strikingly different in morphology. In the present work,we compared, through cytological, cytochemical and immunocytochemicalanalyses, the nuclear features of the shoot meristem in floating and submerged buds that produce the different leaves. The occurrence of DNA polymorphism in the two types of leaves was studied by using the random amplified polymorphic DNA (RAPD) approach. The light microscope study of chromatin organization revealed an articulate structure of the nuclei, with prominent chromocentres in both floating and submerged buds. However, the meristematic nuclei of floating buds, as compared to those of submerged buds, displayed peculiar features which seem to be related to a higher proportion of A‐T‐ricn sequences and a higher level of DNA methylation of the nuclear genome. Moreover, RAPD analysis showed polymorphism between the genomic DNAs of floating and submerged leaves. These results show that organs of an individual plant living in different environmental conditions undergo changes in genome organization which may predispose those organs to function more effectively in different environme

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00473.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The relationship between seed phenolics and appearance of seed coat–imposed dormancy during seed development inCynoglossum officinaleL. was studied. Up to 24 days after anthesis, seeds failed to germinate upon imbibition in Petri dishes at 25°C. At 44 days after anthesis, seeds were fully germinable; removal of seed coats did not improve their germination or O2uptake. At 72 days after anthesis, mature seeds at the base of the cyme did not germinate unless their coats were removed. Removal of seed coat also stimulated O2uptake at this harvest date. The methanol‐soluble phenolic content of the seeds increased during the early stages of seed development, in both the seed coat and the embryo. As seed development continued, the methanol‐soluble phenolic content of the embryo stabilized, but that of the seed coat declined. This decline was associated with an increase in the thioglycolic acid–soluble phenolics, presumably lignins, in the seed coat. These results suggest that polymerization of methanol–soluble phenolics into lignins in the seed coat during later stages of seed development renders the seed coat of C.officinaleimpermeable to 03, and thus keeps the se

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00474.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The ability to measure the pH of the apoplast in situ is of special interest as a test of the cell wall acidification theory. Optical sectioning of living seedlings of corn roots using the laser scanning confocal microscope (LSCM) permits us to make pH measurements in living tissue. The pH of the apoplast of corn roots was measured by this method after infiltration with CI‐NERF, a pH‐sensitive dye, along with Texas Red Dextran 3000, a pH‐insensitive dye, as an internal standard. In the elongation zone of corn roots, the mean apoplastic pH was 4.9. Upon gravitropic stimulation, the pH on the convex side of actively bending roots was 4.5. The lowering of the apoplastic pH by 0.4 units appears to be sufficient to account for the increased growth on that side. This technique provides site‐specific evidence for the acid growth theory of cell elongation. The LSCM permits measurements of the pH of living tissues, and has a sensitivity of approximately 0.2 p

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00475.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Extracts from several rice cultivars (Oryza sativaL. cvs IR58, 74586 and SC33) infected with the sheath blight pathogenRhizoctonia solani, were analyzed to determine the isozyme distribution of chitinases (EC 3.2.1.14) and β‐l,3‐glucanases (EC 3.2.1.39). Upon infection by the fungal pathogen, two chitinases of 28 and 35 kDa and two β‐l,3‐glucanases of 30 and 32 kDa were shown to be induced in all cultivars. They resolved into multiple isozymes under nondenaturing electrophoretic conditions. Wounding, but not bacterial infection, resulted in the induction of these hydrolytic enzymes. Even though fungal infection resulted in induction of chitinases and β‐glucanases in all cultivars, some cultivars that were moderately resistant toR. solaniappeared to have higher levels of specific isozymes. A chitinase cDNA clone was identified by screening a library, prepared from RNA isolated fromR. solani‐infected rice plants, with an antibody to a bean chitinase. This cDNA encoded a 35‐kDa chitinase which was significantly different in amino acid sequence from other rice chitinases described so far. Northern blot analysis of RNA from infected rice plants indicated that transcripts corresponding to this chitinase gene were induced upon

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00476.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Positive influences of high concentrations of dissolved inorganic carbon (DIC) in the growth medium of salinity‐stressed plants are associated with carbon assimilation through phosphoenolpyruvate carboxylase (PEPc) activity in roots; and also in salinity‐stressed tomato plants, enriched CO2in the rhizosphere increases NO−3uptake. In the present study, wild‐type and nitrate reductase‐deficient plants of barley (Hordeum vulgareL. cv. Steptoe) were used to determine whether the influence of enriched CO2on NO−3uptake and metabolism is dependent on the activity of nitrate reductase (NR) in the plant. Plants grown in NH4+and aerated with ambient air, were transferred to either NO3−or NH4+solutions and aerated with air containing between 0 and 6 500 μmol mol−1CO2. Nitrogen uptake and tissue concentrations of NO3−and NH4+were measured as well as activities of NR and PEPc.The uptake of NO−3by the wild‐type was increased by increasing CO2. This was associated with increased in vitro NR activity, but increased uptake of NO3−was found also in the NR‐deficient genotype when exposed to high CO2concentrations; so that the influence of CO2on NO3−uptake was independent of the reduction of NO3−and assimilation into amino acids. The increase in uptake of NO3−in wild‐type plants with enriched CO2was the same at pH 7 as at pH 5, indicating that the relative abundance of HCO3−or CO2in the medium did not influence NO3−uptake. Uptake of NH4+was decreased by enriched CO2in a pH (5 or 7) independent fashion. Thus NO3−and NH+4uptakes are influenced by the CO2component of DIC independently of anaplerotic carbon provision for amino acid synthesis, and CO2may directly affect the uptake of NO3−and NH4+in ways

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00477.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The net flow in vascular and transpirational components of the grape berry water budget was evaluated during water deficits imposed at different stages of fruit development. Diurnal fluctuations in berry diameter were measured on field‐grown grapevines (Vitis viniferaL. cv. Cabernet Sauvignon) by using electronic displacement transducers. Water deficits were imposed by withholding irrigation, and water potentials of mid‐shoot leaves, basal stem xylem and clusters were determined with a pressure chamber. The relative net flows through pedicel xylem and phloem and through berry transpiration were estimated pre‐veraison and post‐veraison. The xylem functioned nearly exclusively in providing net inflow pre‐veraison, while the phloem was clearly dominant post‐veraison. Accordingly, the amplitude of diurnal contraction was markedly smaller post‐veraison than pre‐veraison. The amplitude of diurnal contraction increased dramatically with decreasing plant water status pre‐veraison, yet exhibited little sensitivity to low vine water status post‐veraison. Measurements of the difference in water potential between clusters and source stems did not provide evidence of a gradient that would elicit significant water movement from the cluster to the stem at any time of the day. This was true for both irrigated and non‐irrigated vines, although the non‐irrigated vines exhibited a smaller gradient favoring inflow throughout much of the day. The gradient for xylem water transport to the cluster was considerably smaller post‐veraison than pre‐veraison. The results showed that berry transpiration functioned as the primary pathway for water loss

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00478.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Changes in polyamine biosynthesis and elongation of etiolated rice coleoptiles (Oryza sativaL. cv. Taichung Native 1) in response to fusicoccin (FC) and indoleacetic acid (IAA) were investigated. FC stimulated coleoptile elongation at concentrations higher than 1 μMbut caused a decrease in the levels of free putrescine, spermidine and sper‐mine, as well as in the activities of arginine decarboxylase (ADC, EC 4.1.1.19) andS‐adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50). The extent to which FC caused these effects was dependent on its concentration. Treatment with 100 μMIAA also induced coleoptile elongation and resulted in a decrease in free spermidine/sper‐mine and SAMDC activity. However, treatment with IAA resulted in an increase in free putrescine levels and ADC activity. The extent of coleoptile elongation and putrescine accumulation also depended on IAA concentration. α‐Difluoromethylarginine (DFMA), an irreversible inhibitor of ADC. but not α‐difluoromethylornithine (DFMO). an irreversible inhibitor of ODC (EC 4.1.1.17), inhibited the LAA‐stimulated coleoptile elongation and putrescine accumulation. Addition of putrescine could not reverse the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00479.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY