ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00329.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractRecent evidence suggests that octadecanoid derived metabolites, notably jasmonic acid and/or methyl jasmonate, are involved in the reaction of touch‐sensitive tendrils to mechanical stimulatio

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00330.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe exact ion gradients across cellular membranes and their changes due to metabolic or transport processes can be best studied with the use of ion‐selective microelectrodes. The last decade of research using ion‐selective microelectrodes in intact cells has proven this technique to be indispensable for the investigation of a variety of physiological questions of regulatory processes, membrane transport, cellular signalling, developmental biology and plant nutrition. Their application to selected problems has led to numerous exciting observations, many of which have changed our view concerning cellular responses to environmental stimuli and in many instances have led to a new understanding of plant cell physiology. Since, with these electrodes, intracellular as well as extracellular free ion concentrations can be simultaneously detected with electrical transport parameters such as membrane potential and membrane conductance, they can be powerful tools in the hands of many plant cell biologi

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00331.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe aqueous two‐phase partitioning technique was utilized to isolate a plasma membrane (PM) fraction from etiolated seedlings ofArabidopsis thaliana. The purification procedure adopted yielded a fraction highly enriched in PM as compared to inner membranes, with a recovery of about 30%, as judged from the activities of PM markers such as vanadate‐sensitive ATPase, FC binding and UDP‐glucose sterol glucosyltransferase. The purified PM fraction displayed vanadate‐sensitive H+pumping activity. Its purity was confirmed by the biochemical characteristics of its ATPase activity assayed in the absence of Ca2+: sensitivity to vanadate (IC50ca. 1 μM), Mg2+‐dependence, insensitivity to molybdate, oligomycin and nitrate, pH optimum at 6.6.The PM H+‐ATPase activity was stimulated by fusicoccin and by a controlled treatment of the PM with trypsin. In both cases stimulation was much stronger on the activity assayed at pH 7.5 than on the activity at pH 6.6. Moreover, neither fusicoccin nor the treatment with trypsin stimulated the portion of activity (30 to 40% at pH 7.5) which decayed upon preincubation of the PM in assay medium

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00332.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe transport and hydrolytic activities of the plasma membrane (PM) Ca2+pump were characterized in a PM fraction purified from seedlings ofArabidopsis thalianaby the aqueous two‐phase partitioning technique.Ca2+uptake could be energized by ATP and by ITP (at about 70% the rate sustained by ATP). This characteristic was used to measure the hydrolytic activity of the enzyme as Ca2+‐dependent ITPase activity. The PM Ca2+pump displayed a broad pH optimum around pH 7.2, was drastically inhibited by erythrosin B (EB), and was half‐saturated by 60 μM ITP. It was stimulated by CaM, specially at low, non‐saturating Ca2+concentrations. All of these characteristics closely resemble those of the PM Ca2+pump in other plant materials.Analysis of the effects of EB and other fluorescein derivatives (eosin Y and rose bengal) showed that: i) EB behaved as a competitive inhibitor with respect to ITP; ii) the PM Ca2+pump was drastically inhibited by concentrations of fluorescein derivatives (submicromolar), much lower than those required to inhibit the PM H+‐ATPase; iii) the different fluorescein derivatives were diversely efficient in inhibiting the activities of the Ca2+pump and of the H+‐ATPase of the PM (eosin Y was about 10000‐fold, EB 1000‐fold and rose bengal only 50‐fold more active on the Ca2+pump than on the H+‐ATPase); and iv) the effectiveness of EB in inhibiting the Ca2+pump was strongly affected by the protein concentration

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00333.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractUsing the patch‐clamp technique K+channels could be observed in the plasma membrane of protoplasts from pollen grains ofLilium longiflorum. With depolarizing membrane potentials the open probability of the different K+channels increased. Two K+channel populations occurring occasionally had a single channel conductance of 120 pS and 42 pS, respectively. The most often observed K+channel had a single channel conductance of 19 pS which showed an increase of channel activity with increasing free cytoplasmic Ca2+concentration. This channel population might be involved in the pathway of endogenous transcellular K+currents which are activated during pollen tube tip extensio

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00334.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe various types of plastids occurring in assimilatory and non‐green tissues ofTaxus baccataL. were investigated with respect to their ultrastructure and their content of starch, chlorophyll, Rubisco and the plastidic coupling factor CF1. Chlorophyll was estimated from fluorescence intensity, and the presence of both enzymes was examined by electron microscopy after immunogold labelling.All kinds of plastids, irrespective of their location in the tree, contained stromal membranes. Due to their content of CF1and chlorophyll (except those of the roots) these membranes were addressed as thylakoids. Since the plastids also contain Rubisco, they represent chloroplasts. However, a decreasing gradient of all investigated chloroplastic characters from the plastids of the assimilatory tissue of the needles to those of axial tissues and of the roots was obvious. All kinds of plastids accumulated large amounts of starch especially in spring prior to bud burst but were virtually free of starch during the winter month

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00335.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAmmonia (NH3) is the third most abundant N species in the atmosphere and, due to various natural and anthropogenic sources, can reach high concentrations in some areas. While some plants show effects of toxicity, others are capable of using this N‐form and grow well without any utilization of soil‐N. Acquisition of atmospheric NH3will affect the acid‐base balance of the plants as absorption and dissolution causes an alkalinisation (production of OH−) and assimilation of NH3results in an acidification (generation of H+). As there is only a limited capacity for biochemical disposal of excess H+in shoots, pH regulation may involve H+/OH−extrusion into the media via roots and transport of (in)organic ions between roots and above‐ground parts of the plant.Our aim therefore was to assess NH3acquisition byLolium perenneand to study the effects of gas phase NH3on growth, acid‐base balance and mineral composition of the plants. The experiments therefore included application of a range of14NH3to the shoots and of15N as NO3−, NH4+or NH4NO3to the roots, from which the amount of gas phase NH3acquisition could be quantified. Analysis of the mineral composition provided data for calculation of acid‐base balance as well as for water use efficiencies of the plants.The results indicate that over the range of NH3supplied, plants from all treatments could utilize gas‐phase NH3as demonstrated by increases in growth and in N and C use efficiencies. Plants receiving NO3−via their roots had a higher capacity to use gaseous NH3than those growing with NH4+. NH3assimilation in shoots reduced both the acid load with NH4+nutrition and the alkaline load with NO3−supply to the roots. The results of the experiments are discussed in relation to possible acid‐base regulation mech

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00336.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPolar cell growth is regulated by auxin (Klämbt et al., 1992). It is essentially dependent upon exocytosis. Is exocytosis directly regulated by auxin?Aleurone cells secrete amylases, as well as other hydrolases, by exocytosis. In preliminary experiments, with 22 h of incubation, increasing concentration of N‐1‐naphthylphthalamic acid (NPA) parallels the inhibition of amylase secretion.A model system for secretion was designed. Barley aleurone layers, previously incubated in 1 μM GA3for 16 h, then washed extensively in the presence of 10 μM NPA for 10 min, were incubated finally for 2 h in GA3, NPA and/or auxins. NPA inhibits amylase secretion. Auxins completely abolished secretion inhibition at the optimal concentration of 1 μM.Aleurone layers contain 1.5 to 3 μM endogenous indole‐3‐acetic acid (IAA) and have a high capacity to accumulate and retain IAA. A 7‐fold accumulation occurred within 3 h after application of 20 μM radiolabeled IAA. A loss of about 10% could be measured within the following 4 h period in fresh media, independent of the presence of NPA.The inhibition of amylase secretion by NPA is not due to an inhibition of protein biosynthesis which was tested by the use of [

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00337.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractAccording to the acid growth theory of auxin action, it has been proposed that auxin decreases root growth by inhibiting the proton pump, thus causing an alkalinization of the apoplast. This paper critically tests this hypothesis with corn (Zea maysL.) roots. It was found that: i) the pH‐growth curve for roots exhibits a broad optimum ranging from pH 4.5 to 9. ii) Any acid‐induced growth is of very short duration, iii) The low sensitivity of root growth to external pH is independent of both the pump activity and the buffer capacity of the bathing solution, iv) Neither incubation in acidic buffer nor stimulation of the proton pump reverts the auxin‐induced root growth inhibition. It is concluded that the auxin‐induced root growth inhibition is not mediated by cell wall alkalin

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00338.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY