摘要:

The effects of supplemental Ca2+supply and NaCl salinity on the ionic relations and levels of proline and other amino acids in the primary root ofSorghum bicolor(cv. Hegari) seedlings were investigated. Two days of exposure to 150 mMNaCl resulted in a 50‐fold increase in the proline level in the 0–10 mm root tips of seedlings supplied with 5.0 mMCa2+, but only a 4‐fold increase in seedlings with 0.5 mMCa2+. In contrast to the high levels of proline in the root tip, proline accumulation was only modest in the expanded tissues of the root. The enhancement of proline accumulation in the root tip of salinized seedlings with the Ca2+supplement may be related to their more favorable tissue K to Na ratio. Thus, elevated Ca2+may mitigate the NaCl‐induced inhibition ofS. bicolorroot growth via the maintenance of net K to Na selectivity and the enhancement of proline accumulation in the r

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00498.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The effects of perturbation and excision on net NO‐3, uptake, influx and efflux in roots of 8‐day‐old barley (Hordeum vulgareL.) seedlings induced with NO‐3or NO‐2were determined. Perturbation was simulated by mechanically striking the intact roots with a glass rod. Perturbation or excision of roots and subsequent division into small segments had little effect on NO‐3influx, but briefly inhibited net uptake which recovered within a few min. While in perturbed roots net uptake rates recovered to the same level as in control roots, full recovery did not occur in excised roots. Inhibition of net uptake was due to stimulation of NO‐3efflux. The recovery time and level of inhibition of net NO‐3uptake and/or stimulation of efflux were a function of extent of perturbation, or the number of segments following excision, and root NO‐3concentration. NO‐3efflux was further stimulated when roots were perturbed after cytoplasmic NO‐3had been depleted, indicating that both the plasmalemma and tonoplast may be affected. In excised roots both NO‐3influx and efflux decreased with age due to depletion of energy sources. The results indicate that root perturbation and excision had no effect on NO‐3influx but inhibited net upt

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00499.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

To clarify the roles of auxin‐binding proteins (ABPs) in the action of auxin, soluble auxin‐binding proteins were isolated from an extract of etiolated mung bean hypocotyls by affinity chromatography on 2,4‐dichlorophenoxyacetic acid (2,4‐D)‐linked Sepharose 4B. A 39‐kDa polypeptide was retained on the affinity column and eluted with a solution containing IAA or 2,4‐D, but not with a solution containing benzoic acid. The protein was then purified by several column‐chromatographic steps. The apparent molecular mass of the protein was estimated to be 77 kDa by gel filtration and 39 kDa by SDS‐PAGE. We designated this protein ABP39. The partial amino acid sequences of ABP39, obtained after chemical cleavage by CNBr, revealed high homology with alcohol dehydrogenase (ADH; EC 1.2.1.1). While the ABP39 was not capable of oxidizing ethanol, it did catalyze the reduction of indole‐3‐acetaldehyde (IAAld) to indole‐3‐ethanol (IEt) with an apparent Kmof 22 μM.The IAAld reductase (EC 1.2.3.1) is specific for NADPH as a cofactor. The ABP39 also catalyzed the reduction of other aldehydes, such as acetaldehyde, benzaldehyde, phenylacetaldehyde and propionealdehyde. Indole‐3‐aldehyde was a poor substrate. The enzyme activity was inhibited by both indole‐3‐acetic acid and 2,4‐D in a competitive manner. Therefore, the enzyme is considered to be retained on the affinity colu

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00500.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

For the elucidation of the mechanisms of floral transition in indifferent plants, cucumber seedlings (Cucumis sativuscv. Rennsei or cv. Shimoshirazu‐jibai) were grafted onto squash seedlings (Cucurbita maximaDuchesne XC. moschataDuchesne cv. Shintosa‐ichigou) of which the meristems had been removed, and the effect on flower induction on the cucumber scion was examined. In both cultivars, the grafted cucumber bore no flowers, whereas control plants developed flowers above the second to fourth nodes. The inhibition of flower formation on the grafted cucumber scion occurred even when the root of cucumber was left with the squash root on the grafted plant, and flower formation occurred after removal of the squash stock. The inhibitory effect of the squash stock in the presence of the cucumber root was abolished by removal of the squash root. Neither the dry weight of stem plus leaf nor the chlorophyll content of the leaf, as indicators of vegetative growth, were correlated with flower formation on cucumber plants that had been grafted in the presence of cucumber roots on whole, cotyledon‐free or root‐free squash stock. These results indicate that flower formation in cucumber was inhibited by a factor produced by squash roots, an inhibition probably not involved in the modulation of vegetative growth. The root may control floral transition by the production of inhibitory factors in some day‐neutral Cucurbitace

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00501.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Plasma membranes from the green algaChlamydomonas reinhardtiiwere purified by differential centrifugation and two‐phase partitioning in an aqueous polymer system. The isolated plasma membranes were virtually free from contaminating chloroplasts, mitochondria, endoplasmic reticulum and Golgi membranes as shown by marker enzyme and pigment analysis. The isolated plasma membranes exhibited vanadate sensitive ATPase activity, indicating the presence of a P‐type ATPase. This was verified by using antibodies against P‐type ATPase fromArabidopsis, which crossreacted with a protein of 109 kDa. The ATPase activity was inhibited to more than 90% by vanadate (Ki= 0.9 μM) but not affected by inhibitors specific for F‐ or V‐type ATPases. demonstrating the purity of the plasma membranes. Mg‐ATP was the substrate, and the rate of ATP‐hydrolysis followed simple Michaelis‐Menten kinetics giving a Km= 0.46 mM. Free Mg2+stimulated the activity, K1/2= 0.68 mM. Maximal activity was obtained at pH 8. The ATPase activity was latent but stimulated 10 to 20‐fold in the presence of detergents. This indicates that the isolated plasma membrane vesicles were tightly sealed and mostly right‐side‐out, making the ATPase inaccessible to the hydrophilic substrate ATP. In the presence of the Brij 58, the isolated plasma membranes performed ATP dependent H+‐pumping as shown by the optical pH probe acridine orange. H+‐pumping was dependent on the presence of valinomycin and K+ions and completely abolished by vanadate. Addition of Brij 58 has been shown to produce 100% sealed inside‐out vesicles of plant plasma membranes (Johansson et al. 1995, Plant J. 7: 165–173) and this was also the case for plasma membranes from the green

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00502.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Expansion of root‐cap mucilage during hydration was followed by cryo‐scanning analytical microscopy of soil‐grown roots ofdiploperennisandZea mays.Roots examined directly from the soil have no expanded mucilage. Their condensed, unexpanded mucilage is in three domains, periplasmic, intercellular and peripheral to the cap tissue. Carbon concentration is the same in the three domains. During hydration there is no change in carbon concentration as the condensed mucilage moves through these three domains; however there is a sharp drop at the periphery where a gel phase transition occurs. The rate of expansion of the mucilage blob around the root tip is limited by the rate of this gel phase trans

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00503.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Developing and germinating pea seeds contain high levels of ubiquitin conjugated to proteins as detected on western blots. In contrast, the level of dry seed protein‐ubiquitin conjugates in vivo appears low, with mainly free ubiquitin present. The ubiquitination of endogenous dry pea seed proteins is observed in vitro, relying only on already present endogenous ubiquitin, suggesting the enzymatic machinery for ubiquitination is present in the dry seed. Energy source in the form of ATP increased the formation of large molecular mass conjugates, although some conjugation took place without added ATP. The usefulness of dry seeds, having low levels of ATP which can then be manipulated in the in vitro reaction is discussed. ATP and ubiquitin degrading activities are detected in the crude in vitro system, pointing to the need to purify the individual components, or to seek specific inhibitors of the undesirable secondary reaction

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00504.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Pollination greatly accelerates petal senescence. The first observed event after pollination is an increase in the flower's sensitivity to ethylene, followed by an increase in ethylene biosynthesis. Our objectives were to study the mode of action of the increase in ethylene sensitivity and the possible involvement of short‐chain saturated fatty acids (SCSFAs) in this process. Application of SCSFAs, ranging in chain length from 7 to 10 carbons onto stigmas ofPhalaenopsis (Phalaenopsishybrid, cv. Herbert Hager) flowers increased their sensitivity to ethylene in the same way as pollination. Following pollination, there was a significant increase in the endogenous content of these fatty acids in the flower's column and perianth, with octanoic acid (C8) being the main SCSFA observed. The increase in SCSFA content was observed as early as 6 h after pollination and began to decline 6 h later. Incorporation of octanoic acid into liposomes or microsomal membranes isolated fromPhalaenopsispetals resulted in a decrease in lipid order that was detected by fluorescence polarization of dansyl pyrrolidine (DNSP) but not of 1,6‐diphenyl‐1,3,5‐hexatriene (DPH). At peak ethylene sensitivity, 10 h after pollination, there was a significant decrease in the lipid order of microsomal membranes isolated fromPhalaenopsiscolumns and perianths, again as detected by DNSP but not by DPH. Stigmatic application of octanoic acid mimicked the effect of pollination on membrane lipid order. We suggest that SCSFAs may be the ethylene ‘sensitivity factors’ produced following pollination, and that their mode of action involves a decrease in the order of specific regions in the membrane lipid bilayer, consequently altering ethy

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00505.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Asparaginyl‐endopeptidase activity was detected in endosperms of maturing and germinating wheat seeds. The highest activity was found during maturation before the maximal accumulation of storage proteins. The enzyme activity then decreased in the dry seeds and increased again during germination. The increase of activity during germination required the presence of the embryo. In fact, the activity found in detached endosperms was lower than that found in attached ones. The localization at tissue level of the enzyme reveals differences between maturation and germination: the enzyme was about equally located in the aleurone layer and starchy endosperm during maturation, but solely in the aleurone layer during germination. The asparaginyl enzymes from maturing and germinating seeds had many similar properties, such as pH optimum, pH stability, thermal stability and sensitivity to thiol reagents and to thiol compounds. The results suggest that asparaginyl endopeptidases may be involved in the modification of proproteins of storage proteins during seed maturation and in the degradation of storage proteins deposited in the aleurone layer during germinatio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00506.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A comparison of rooting ability of stem cuttings made from hypocotyls and epicotyls from 50‐day‐old seedlings of loblolly pine (Pinus taeda L.) reveals a dramatic decline by epicotyl cuttings, which do not root at all in 20–30 days in the presence or absence of auxin. In contrast, almost all the hypocotyls root during this time, but only in the presence of exogenously applied auxin. The failure of epicotyls to root does not appear to be due to differences in [14C]‐labeled auxin uptake, transport, metabolism, or tissue distribution in the two types of cuttings. At the cellular level, initial responses to auxin, such as differentiation of the cambium into parenchyma, occur in both types of cuttings, but localized rapid cell division and root meristem organization are not observed in epicotyls. Autoradiography revealed that radioactivity froma‐naphthalene acetic acid is bound in the cortex but not concentrated at sites of root meristem organization prior to the organization of the meristem in hypocotys. During the development of the epicotyl. cellular competence to form roots appears to be lost. Although this loss in competence is not associated with a concurrent loss in ability to transport auxin polarly, the latter process appears to play a key role in rooting other than to move auxin to the site of root formation. The phytotropin N‐(1‐naphthyl)phthalamic acid inhibits rooting if applied during the first 3 days after the cutting is made, but does not affect auxin concentration or metabolism at the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00507.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY