摘要:

Auxin conjugates play a role in the regulation of free indole‐3‐acetic acid (IAA) content in plants. Not much is known about the enzymes involved in either conjugate synthesis or hydrolysis. In this study we have isolated and characterized an auxin conjugate hydrolase from Chinese cabbage seedlings and investigated it during the development of both the Chinese cabbage plants and the clubroot disease. The hydrolase isolated from light‐ and dark‐grown seedlings accepted the amide conjugates indole‐3‐acetic acid‐alanine (IAAla), IAA‐phenylalanine (IAPhe), but not IAA‐aspartate (IAAsp) as substrates. We also found a substantial amount of hydrolysis of an ester conjugate (IAA‐glucose, IAGlu) in our enzyme preparation. The tentative reaction product IAA was identified by HPLC and subsequent GC‐MS analysis. The pH optima for the different substrates were not identical, suggesting several hydrolase isoforms. After gel filtration chromatography we found at least two peaks containing different hydrolase isoforms. The isoform, which converted IAGlu to IAA, exhibited a molecular mass of ca 63 kDa, and an isoform of ca 21 kDa converted IAAla and IAPhe. The increased free IAA content in clubroot‐diseased roots of Brassicaceae can be due to either de novo synthesis or release of IAA from conjugates. To answer this question free, ester‐ and amide‐bound IAA was measured in 24‐ and 30‐day‐old leaves and roots of healthy andPlasmodiophora brassicae‐infected Chinese cabbage, and the hydrolase activity with different substrates measured in the same tissues. The amide conjugates were dramatically enhanced in infected roots, whereas free IAA was only slightly enhanced compared to the control tissue. Hydrolase activity was also enhanced in clubbed roots, but the substrate specificity differed from that found in the seedlings. Especially, IAAsp hydrolysis was induced after inoculation withP. brassicae.We conclude that different auxin conjugates can be hydrolyzed at different d

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00525.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Phosphate addition to P‐limited cells ofChlamydomonas reinhardtiiresulted in an immediate increase in the rate of respiratory O2consumption. The respiration rate continued to increase for several minutes after the addition of P1. Similar patterns of P1stimulation of respiratory O2consumption were observed in the presence of cyanide (cytochrome oxidase inhibitor) and propyl gallate (alternative oxidase inhibitor). Stimulation of O2consumption was accompanied by rapid changes in levels of glycolytic intermediates. These changes were consistent with activation of ATP‐dependent phosphofructokinase and pyruvate kinase. The adenylate pool exhibited only minor perturbations, P1, uptake resulted in extracellular acidification, which continued for several minutes after the exhaustion of added P1, whereas exhaustion of extracellular P1resulted in a rapid decline in the O2consumption rate. These results are consistent with control of respiration in P‐limited cells occurring largely at the level of glyco

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00526.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Several floral organ‐specific proteins in lily anthers do not accumulate to detectable levels until just before anthesis. Antisera were raised against three of these proteins. designated LLA, in pollen ofLilium longiflorumThunb. cv. Snow Queen. Monospecific antibodies were further prepared from antisera to investigate the specificity and distribution of these proteins during development. In an effort to study the function of these gene products, pollen protein was heat‐treated at 90°C for 10 min. Monospecific anti‐LLA‐32 and ‐23 antibodies recognized two of these heat‐stable proteins with molecular masses of 32 and 23 kDa. Accumulation of the two proteins in anther development was correlated with desiccation that occurred naturally in the pollen. Immunob‐lot analyses of total protein from floral and vegetative organs confirmed that both LLA‐32 and ‐23 proteins were pollen‐specific. The proteins showed consistent patterns of expression during development and their levels decreased when pollen germinated. The properties of the two proteins differed in responsiveness to both polyethylene glycol 8000 and abscisic acid, and in solubility characteristics. Analysis of amino acid composition indicates that both LLA‐32 and ‐23 proteins are rich in glutamic acid/glutamine and glycine, a characteristic of heat‐stable proteins. However, LLA‐23 has more polar amino acid residues with a polarity of 57%, two‐fold higher than that of the LLA‐32. Immunoblot analyses showed that LLA‐32 and ‐23 proteins were immunologically unrelated to the dehydrin‐like protein in lily seeds. It concluded that the two classes of pollen‐specific proteins have some features in common with each other and w

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00527.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Two methods of rehydrating red pine (Pinus resinosaAit.) shoots for pressure‐volume (PV) analysis were compared to clarify the effects of rehydration on estimated tissue water relations of shoots and fascicles. The commonly employed cut‐shoot method was compared to rehydration by means of water uptake through the roots of intact plants. Cut‐shoot rehydration and increased duration of rehydration significantly decreased estimates of tissue elasticity and relative water content at zero turgor for both shoots and fascicles. Rehydration of cut shoots for 2 days significantly increased the slope of the linear region of shoot pressure‐volume (PV) curves and decreased estimates of the apoplastic water fraction. Changes in these and estimates of other water relations attributes were correlated with increased initial water content during rehydration. Estimated apoplastic water fraction was higher for needle fascicles than shoots despite the large amount of woody stem tissue contained in shoots. Fascicle water status strongly influenced shoot water relations, in part due to apparent apoplastic loading with water of fascicles during rehy

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00528.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The effects of jasmonic acid (JA) on spore germination, early gametophyte development and sporophytic protoplast culture of the fernPlatycerium bifurcalum(Cav.) C. Chr. were investigated. JA and no influence on spore germination and primary rhizoid initiation, but significantly promoted early gametophyte development, which was evident from the longer primary rhizoids as well as the higher number of rhizoids and cells per gametophyte. Jasmonic acid (1 μM) also promoted the transition of gametophytes from a filamentous to a planar growth. Optimal primary rhizoid elongation and highest cell division activities in the gametophytes were observed at 0.01–1 μMJA, while the highest number of rhizoids on gametophytes was obtained at 0.1–1 μMJA. Jasmonic acid (0.01 μM) also stimulated initial protoplast divisions. Except for the experiment in which the effect of JA on germination was tested. JA concentrations exceeding 1 μMdid not promote cell elongation or cell division but were instead inhibitory. On the basis of these findings, we propose that JA may be involved in early stages ofP. bifurcatumdev

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00529.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

MaizeBt1is a structural gene for the major 39–44‐kDa amyloplast membrane polypeptides. Loss of BT1 in thebrittle1(bt1) mutant results in an 80% reduction in kernel starch. As an initial step toward the understanding of BT1 function, we investigated the relation of BT1 to starch accumulation in the two well‐characterized maize endosperm suspension‐cultured cell lines which were derived from 10 days post pollination (DPP) kernels of inbred A636 and 12‐DPP kernels of thewaxymutant in the A636 background. Starch in A636 endosperm cultures accounted for about 1.5% of the fresh weight of cells but BT1 was not detectable in amyloplast membranes or in microsomal membranes isolated from the cultured cells.Bt1transcripts were detected in 10‐ and 20‐DPP A636 kernels, but only a trace ofBt1transcripts was detected in the suspension‐cultured cells. Southern blotting indicated that theBt1gene was present in the genome of the cultured cells. TheBt1gene products in A636 endosperm cultures were not increased by treatments which enhance starch accumulation such as sucrose supplementation, chlorocholine chloride (CCC) addition to the medium, or both. A similar pattern of differentialBt1gene expression was found in thewaxyendosperm cultures. These results indicate that starch accumulation in the cultured cells is not correlated withBt1gene expression. The significance of these findin

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00530.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Seedlings of three species native to central North America, a C3tree,Populus tremuloidesMichx., a C3grass,Agropyron smithiiRybd., and a C4grass,Bouteloua curtipendulaMichx., were grown in all eight combinations of two levels each of CO2, O3and nitrogen (N) for 58 days in a controlled environment. Treatment levels consisted of 360 or 674 μmol mol‐1CO2, 3 or 92 nmol mol‐1O3, and 0.5 or 6.0 mMN. In situ photosynthesis and relative growth rate (RGR) and its determinants were obtained at each of three sequential harvests, and leaf dark respiration was measured at the second and third harvests. In all three species, plants grown in high N had significantly greater whole‐plant mass, RGR and photosynthesis than plants grown in low N. Within a N treatment, elevated CO2did not significantly enhance any of these parameters nor did it affect leaf respiration. However, plants of all three species grown in elevated CO2had lower stomatal conductance compared to ambient CO2‐exposed plants. Seedlings ofP. tremuloides(in both N treatments) andB. curtipendula(in high N) had significant ozone‐induced reductions in whole‐plant mass and RGR in ambient but not under elevated CO2.This negative O3impact on RGR in ambient CO2was related to increased leaf dark respiration, decreased photosynthesis and/or decreased leaf area ratio, none of which were noted in high O3treatments in the elevated CO2environment. In contrast,A. smithiiwas marginally negatively affecte

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00531.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The effects of atmospheric CO2enrichment and root restriction on photosynthetic characteristics and growth of banana (Musasp. AAA cv. Gros Michel) plants were investigated. Plants were grown aeroponically in root chambers in controlled environment glasshouse rooms at CO2concentrations of 350 or 1 000 μmol CO2mol‐1.At each CO2concentration, plants were grown in large (2001) root chambers that did not restrict root growth or in small (20 1) root chambers that restricted root growth. Plants grown at 350 μmol CO2mol‐1generally had a higher carboxylation efficiency than plants grown at 1 000 μmol CO2mol‐1although actual net CO2assimilation (A) was higher at the higher ambient CO2concentration due to increased intercellular CO2concentrations (Ciresulting from CO2enrichment. Thus, plants grown at 1 000 μmol CO2mol‐1accumulated more leaf area and dry weight than plants grown at 350 μmol CO2mol‐1.Plants grown in the large root chambers were more photosynthetically efficient than plants grown in the small root chambers. At 350 μmol CO2mol‐1, leaf area and dry weights of plant organs were generally greater for plants in the large root chambers compared to those in the small root chambers. Atmospheric CO2enrichment may have compensated for the effects of root restriction on plant growth since at 1 000 μmol CO2mol‐1there was generally no effect of root chamber size

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00532.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Aluminum (Al) stress was examined in three lines of wheat (Triticum aestivumL.) by measuring root lengths, protein synthesis and protein accumulation in seedling root tips grown in a hydroponic system. An Al‐sensitive, recurrent wheat parent (cv. Katepwa) showed very little root growth in low Al concentrations. In contrast, an Al‐tolerant near isogenic line (Alikat) and Al‐tolerant donor (cv. Maringa) had much greater root growth. Segregation data from an F2population (Katepwa × Alikat) showed that one major gene controlled Al tolerance based on root growth (X2= 0.651). All three lines showed an approximately 2‐fold increase in [35S]‐Met incorporation in root tips after 3 days in Al and a comparable increase in root‐tip dry weight. Maringa and Alikat root tips showed an increased total protein content while Katepwa root tips showed no increase in total protein content during the Al stress. Based on higher specific activities, insoluble proteins were preferentially translated in all three lines during Al stress. Proteinase activity in Katepwa root tips was 1.7‐fold higher during Al stress, with Maringa and Alikat showing no change in proteinase activity. The Al‐induced, increased proteinase activity in Katepwa appeared to inhibit soluble prot

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00533.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The aim of the experiment was to test the sensitivity of grasses from a subarctic region to a range of different ultraviolet‐B (UV‐B, 280–320 nm) levels. Seedlings ofCalama‐grostis lapponicaand tillers ofCalamagrostis purpureawere grown for 50 days in a greenhouse at 4 different levels of UV‐BBEradiation (no UV‐B, ambient UV‐B, UV‐B corresponding to 15 and 25% ozone depletion, respectively, at 68°N, northern Sweden on July 27th).InC. purpureatotal plant dry weight was significantly reduced at the 15% level compared to all other treatments, whilst tiller number was reduced when compared to the non UV‐B treatment only. Reduced growth at the 15% level was accompanied by significant increases in shoot to root ratio (S:R), leaf area ratio (LAR) and leaf weight ratio (LWR), which were due to changes in both specific leaf area (SLA) and root growth. Similarly, inC. lapponicathere were reductions in total dry weight at the 15% level, although differences in partitioning were only observed in LWR which was significantly greater than in the non UV‐B treatment.There was a difference in tiller number inC, lapponicabetween all treatments. A reduced number of tillers was observed with increasing UV‐B exposure from zero UV‐B to the 15% level, whilst tiller number was significantly higher at the 25% level than in all other treatments.InC, lapponica, differences were apparent in the amount of UV absorbing pigments. Plants exposed to ambient UV‐B and the 15% level had significantly more UV‐B absorbing compounds than those in the 25% and non UV‐B treatments.All these results suggest that the 15% ozone depletion level was the most harmful to plant growth and few damaging effects were observed at the hi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00534.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY