摘要:

Abstract.Coated vesicles are organelles frequently encountered in many plant cell types often in association with the plasma membrane, Golgi apparatus, partially coated reticulum and multivesicular bodies. They are readily identified by a characteristic cage or basket composed of interlocking triskelions of the protein clathrin which are bound to the surface of the vesicle membrane. Although their transport function has been well studied and characterized in mammalian systems, the possible importance of coated vesicles as transport organelles in plant cells is only just beginning to be explored. In this review, the authors describe the structure of higher plant coated vesicles and discuss their possible involvement in the endocytosis of marcromolecules, in exocytosis and in the intracellular transport of material between cytoplasmic compartments. Their possible role in maintaining the macromolecular composition of the plasma membrane whilst allowing recycling of excess lipid bilayer and their potential application as vehicles for the introduction of foreign macromolecules into plant cells are discussed.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01150.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Seedlings ofEucalyptus paucifloraSieb. ex. Spreng. were stressed by withholding water. They were then rewatered, and the time course of recovery of photosynthesis was followed. Recovery always followed a distinct bi‐phasic pattern. A first, rapid, stage of recovery commenced between 5 and 60 min after rewatering and was completed by between 30 min and four h after rewatering. Recovery in this stage always involved concurrent increases in stomatal conductance and the leaf's capacity to assimilate CO2at any intercellular partial pressure of CO2[A(pi)relationship]. This stage of rapid recovery was followed either by a constant or gradually declining rate of photosynthesis for the remainder of the light period. In plants kept to a normal diurnal cycle, a second stage of recovery occurred and was completed during the night following rewatering. In this second stage of recovery, theA(Pi)relationship recovered to 90–100% of prestress values. In contrast, the recovery of stomatal conductance was not complete by the first day after rewatering. In darkness, complete recovery of theA(pi)relationship required as little as five h. If plants were kept in continuous high light, then between six and 16 h elapsed after rewatering before the second stage of recovery commenced. After this lag, almost complete recovery of theA(pi)relationship was possible. These results indicate that water stress has two independent and parallel effects on the mesophyll capacity for photosynthesis. The first may be simply reversible when the plant is rewatered, while the second may involve damage to the photosynthetic machinery that requires protein synthesis for its rever

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01151.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Isothermal heat‐conductance calorimetry was used to monitor responses of tomato and carrot metabolism to changes in temperature and oxygen concentrations. Calorimetric measurements of metabolic heat evolution from tissue segments and cultured cells was found to be a sensitive, nondestructive estimate of metabolic rates. Short‐term measurements of metabolic rates of cells in culture correlate well with calorimetric measurements made on tissue sections. The results accurately predict the growth properties of intact plants based on the generally recognized characteristics of these two species. The calorimetric method provides another means for rapid evaluation of plant responses to physical and chemical stresses and is of value for screening and select

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01152.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The response of apple twig tissue to a freezing stress was examined using a combination of low temperature scanning electron microscopy and freeze substitution techniques. Bark and wood tissues responded differently. In the bark, large extracellular ice crystals were observed in the cortex. The adjacent cortical cells collapsed and a large reduction in cell volume was observed. The extent of cell collapse throughout the bark was not uniform. Cells in the periderm, phloem and cambium exhibited little change in cell volume compared to cortical cells. Large extracellular ice crystals were not observed in the xylem or pith tissues. The xylem ray parenchyma and pith cells did not collapse in response to a freezing stress, but retained their original shape. The pattern of ice formation and cell response was not observed to change with season or the level of cold acclimation. This study supported the concept that bark and xylem tissues exhibit contrasting freezing behaviour. The observations were consistent with the idea that water in bark freezes extracellularly while water in xylem ray parenchyma and pith cells may supercool to temperatures approaching –40 °C prior to freezing intracellular

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01153.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Wheat (Triticum aestivumL. var. TAM‐W101) leaf segments exhibited an acquired protection against metal toxicity following exposure of the seedlings to heat shock temperatures in the dark. The acquired protection of the leaf segments to cadmium was 400‐fold greater than leaf segments from seedlings kept at 25°C and exhibited the greatest change in protection of the five metals tested. Increased protection against aluminium and iron toxicity was also detected in the leaf segments from heat shocked seedlings. The concentration of aluminium at which a 50% loss of 2,3,5‐triphenyltetrazolium chloride reduction occurred was 5.5 mol m−3in control leaf segments and 20 mol m−3in the leaf segments from heat shocked seedlings. The 50% loss of 2,3,5‐triphenyltetrazolium chloride reduction in the leaf segments from heal shocked seedlings was four‐fold higher for iron. A small, yet reproducible change in the 2,3,5‐triphenyltetrazolium chloride reduction was observed for copper and no change in reduction was observed for zinc treatments in the leaf segments from heat shocked seedlings. These data indicate that exposure of wheat seedlings to heat shock temperatures results in the acquisition of protection against metal toxicity to otherwise lethal concentrations of aluminium, c

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01154.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.A method for isolating protoplasts from leaves of the submerged aquatic angiospermPotamogeton lucensL. is described. The protoplasts are produced enzymatically from leaf strips using 1.5% (w/v) Cellulysin, 0.3% (w/v) Macerozyme R10, and 2.5% (v/v) β‐glucuronidase at 27°C in the dark. Subsequently the protoplasts are purified on a discontinuous Ficoll gradient. The yield obtained is approximately 20% of the starting material on a chlorophyll basis. The viability is high, namely more than 90% as estimated with Evans Blue. Cells of the intact leaves ofP. lucenscan use HCO3−for photosynthesis.14CO2fixation experiments at pH 6.0 and 8.5 suggest that these isolated protoplasts can also use bicarbonate as a carbon s

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01155.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Significant levels of nitrogenase activity (nitrogen fixation) were demonstrated in three species of Arctic legumes (Oxytropis maydelliana, O. arctobia and Astragalus alpinus) growing in high tundra at Sarcpa Lake, Melville Peninsula, N.W.T. Nitrogenase activity of intact plants was correlated with the number of nodules per plant, with field soil temperatures and limited by water shortage. Activity in freshly detached nodules showed a plateau of maximum activity between 10°C and 25°C and a near linear decline with temperature down to 0°C. Unusually, the segmented nodules of all three species are perennial in which growth and leghaemoglobin production resumes each spring from an overwintering apical meristem. Nodules are most numerous in the warmer soil stratum (2–10 cm. depth). Other studies indicate that the arctic rhizobia belong to a single cold‐adapted species which has co‐evolved with the legumes o

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01156.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Silver ions effectively inhibited both the initiation and the continuation of tomato (Lyeopersicon esculentumMill) ripening. Studies of protein synthesisin vivoshowed that application of 2 mol m−3silver thiosulphate to mature green fruit prevented the appearance of several novel proteins associated with ripening, including the softening enzyme polygalacturonase. However, total protein synthesis, as judged by the incorporation of [35S] methionine into proteins, continued unabated after silver treatment. Ripening was also arrested when silver was supplied after ripening had begun. The accumulation of several ripening‐related mRNAs, including that for polygalacturonase, was studied by translationin vitroand using cDNA clones as hybridization probes. Silver was shown to prevent the appearance of polygalaturonase mRNA when supplied to mature green fruit and to cause a rapid reduction in the concentration of mRNA for polygalacturonase and other ripening‐related proteins when supplied after ripening had begun. It is proposed that silver exerts its effects due to interaction with the ethylene perception mechanism. The results suggest that perception of ethylene is vital not only for the initiation of ripening but also for the continued expression of genes required for rip

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01157.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Deuterium‐labelled ABA‐aldehyde was fed to various tomato genotypes. Normal andnotabilismutant plants incorporated substantial amounts of the label into ABA. In contrast, two ABA‐deficient mutants,flaccaandsitiens, reduced ABA‐aldehyde to a mixture ofcis‐andtrans‐ABA alcohol rather than oxidizing it to ABA. It was concluded that ABA‐aldehyde is the immediate precursor of ABA in higher plants. It appears that theflaccaandsitienslesions both act to block the last step of the ABA biosynthetic pathway. The mutant gene loci are likely to be involved in coding for different sub‐units of the same dehyd

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01158.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.A monoclonal antibody prepared against barley (Hordeum vulgareL., cv. Himalaya) nuclease (EC 3.1.30.2) was characterized with solid‐state enzyme‐linked immunosorbent assays and immuno‐blotting. The antibody was specific for intracellular and secreted nuclease. Hormonal regulation of the synthesis and secretion of nuclease in isolated aleurone layers was investigated by immunoprecipitation of biosynthetically‐labelled nuclease using polyclonal antibodies and by immunoblot analyses using the monoclonal antibody, respectively. Gibberellic acid (GA3) induced thede novosynthesis and secretion of nuclease in a time‐and concentration‐dependent manner. Nuclease was detected in aleurone layers incubated in 1 mmol m−3GA3, after 24 h. The maximum rates of nuclease synthesis and secretion occurred 36–48 h after hormone treatment. A minimum concentration of 10−6mol m−3GA3was required for nuclease synthesis and secretion, whereas the maximum rate of nuclease secretion occurred at concentrations of 10−5mol m−3and higher. In the presence of abscisic acid, the synthesis and secretion of nuclease from GA3‐treated aleurone layers was almost completely inhibited. Based on these findings, the authors conclude that all nuclease within and secreted from aleurone layers treated with GA3is the resu

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01159.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY