摘要:

The presence of a living root of tomato (Lycopersicon esculentumMill. cv. Panase F) had a strong positive effect on growth in vitro of hyphal fragments ofCantharellus cibariusFr. This was observed for 12 out of 14 fungal strains tested. Initial re‐growth of hyphae was independent of the presence of a root, but for the further development of strong mycelial growth 7 strains completely depended on the presence of a root. Five strains showed a considerably prolonged lag phase in the absence of a root and only 2 strains were independent. The presence of a root had no influence on the specific growth rates. Hyphal fragments of the totally root‐dependent strain S1 grew strongly in the absence of a root if they were brought into intimate mutual contact. Factor(s) stimulating growth were apparently produced by both roots and fungus. Volatiles from donor cultures of tomato roots ofC. cibarius, Boletus edulis, andTylopilus felleusstimulated growth of hyphal fragments in root‐less receiver cultures. This effect was prevented by the presence of a KOH solution. Donor cultures could be replaced by 0.5

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05050.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The growth period ofSalix viminalisL. (clone 683) plants near Stockholm, Sweden, (59.5°N, 18.3°E) started in April with flowering and ended in October with abscission of the shoot tips. Cell divisions in the vascular cambium started almost two months before sprouting and ceased at about the same time as the elongation growth of the shoots. Phloem cells were apparently produced before flowering, while new xylem production started at the time of flushing. Cytodifferentiation in immature xylem continued until November. Thick‐walled cells with protoplasm were observed adjacent to xylem mother cells in the cambium during the winter. The number of radially arranged cells in the cambial zone increased from 3–4 during dormancy to about 18 during the mitotic maximum in July. Seasonal variation was apparent in vacuolization, wall thickness and presence of storage material in the cells. Lipid bodies and protein bodies occurred in both fusiform and ray initials, while starch was observed in ray initials, ray cells and in the phloem. In September the ultrastructure of the cambium showed anatomical features characteristic for both active and dormant cells. Dictyosomes with vesicles and rough ER were present in thick‐walled cells that contained lipid bodies and starch granules. Nuclear divisions in the cambium ended in

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05051.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

NADP+‐isocitrate dehydrogenase (EC 1.1.1.42) was purified more than 1500‐fold from the host‐plant cytosol ofMedicago sativaL. cv. Saranac root nodules by ion exchange and affinity chromatography. The forward reaction was characterized. The enzyme exhibited an absolute requirement for a divalent cation (preferably Mn2+), had a broad activity optimum from pH 7.5 to 9.0, and was most stable at pH 7.5. The apparent Arrhenius energy of activation was 70.7 kJ mol−1(20 to 30°C) indicating that the reaction rate of the enzyme was relatively sensitive to temperature. The Kmfor isocitrate was 20 μMand for NADP+10.7 μM. Initial velocity and end product inhibition studies of the forward reaction indicate a random bi ter mechanism. End product studies indicated that NADPH was a competitive inhibitor and α‐ketoglutarate was a non‐competitive inhibitor with respect to isocitrate and NADP+. Citrate was a competitive inhibitor with respect to isocitrate. Glutamine was identified as a positive effector when assays were conducted at non‐saturating isocitrate concentrations. The potential significance of glutamine regulation of α‐ketoglutarate production in a dinitrogen‐fixi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05052.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Highbush blueberry plants (Vaccinium corymbosumL. cv. Bluecrop) growing in containers were flooded in the laboratory for various durations to determine the effect of flooding on carbon assimilation, photosynthetic response to varying CO2and O2concentrations and apparent quantum yield as measured in an open flow gas analysis system. Hydraulic conductivity of the root was also measured using a pressure chamber. Root conductivity was lower and the effect of increasing CO2levels on carbon assimilation less for flooded than unflooded plants after short‐(i‐2 days), intermediate‐(10–14 days) and long‐term (35–40 days) flooding. A reduction in O2levels surrounding the leaves from 21 to 2% for unflooded plants increased carbon assimilation by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO2fixed (mol CO2)−1. Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O2, averaging 0.005 mol CO2fixed (mol CO2)−1. Apparent quantum yield decreased from 2.2 × 10−1mol of CO2fixed (mol light)−1for unflooded plants to 2.0 × 10−3and 9.0 × 10−4for intermediate‐ and long‐term flooding durations, respectively. Shortterm flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carbox

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05053.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Rubbing‐induced inhibition of elongation inBryonia dioicawas completely prevented by 10−7Mcobalt chloride. Cellular redistribution of peroxidases, mainly characterized by transiently enhanced membrane‐binding of soluble peroxidases, occurred as an immediate consequence of rubbing and was not inhibited by Co2+. Ethylenesynthesisand 1‐aminocyclopropane‐1‐carboxylic acid (ACC) conversion readily increased upon rubbing and fell soon afterwards, but ACC conversion then increased again progressively. Co2+did not drastically counteract these changes, except for the second rise in ACC conversion which was completely eliminated. The rubbing‐induced rise in ethyiene production and ACC conversion was closely correlated to microsomal ACC conversion and peroxidase activity, but only during the first hours after rubbing. The presented approach enables us to correlate stress‐induced ethylene production to membrane‐binding of peroxidases. It is suggested that ACC conversion inBryonia dioicais triggered by two different, sequentially ordered mechanisms. The difference in the effects of Co2+on elongation and ethylene production is discussed with respect to the role of ethylene in t

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05054.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

High neutral metallocarboxypeptidase activity (EC 3.4.17) has earlier been detected in young seedlings of rice (Oryza sativaL.) using benzyloxycarbonyl‐L‐phenylalanyl‐L‐alanine (Z‐Phe‐Ala) as substrate at pH 7. This finding was confirmed, and it was observed that the activity could be assayed with higher specificity and sensitivity by using Z‐Gly‐Ala or Z‐Gly‐Phe as substrate at pH 6.5–7. No corresponding activity was detected in seedlings of barley (Hordeum vulgareL. cv. Himalaya), oats (Avena sativaL.) or maize (Zea maysL.). The seedlings of the four cereals possessed similar activities of acid carboxypeptidases (EC 3.4.16; hydrolysis of Z‐Phe‐Ala and Z‐Ala‐Phe at pH 5.2 and of Z‐Ala‐Arg at pH 5.7). However, in endosperms of germinating rice and maize these activities were only about 1–5% of those in barley and oats. A corresponding, although less pronounced, difference was evident between the scutella of the two pairs of cereals. The possible relationship between neutral carboxypeptidase activity and ability to grow i

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05055.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Activities of six enzymes from extracts of separated embryos and gametophytes of tamarack [Larix laricina(Du Roi) K. Koch] seeds were assayed at various stages of imbibition and germination. On a per seed part basis, activities of 6‐phosphogluconate dehydrogenase (6‐PGD, EC 1.1.1.44), glucose‐6‐phosphate dehydrogenase (G‐6‐PD, EC 1.1.1.49), malate dehydrogenase (NAD+–MDH, EC 1.1.1.37), isocitrate dehydrogenase (NADP+–IDH, EC 1.1.1.42), soluble peroxidase (PER, EC 1.11.1.7), and acid phosphatase (ACP, EC 3.1.3.2) from both the embryo and gametophyte tissues generally increased slowly, following cold stratification for 30 days and imbibition under germinating conditions for 5 days, but then increased at a faster rate with emergence of the radicle and subsequent growth of the seedling. The rate of increase of enzyme activity was highest for PER. Soluble protein levels also increased with imbibition and germination, with about 3 times greater levels present in the gametophyte than in the embryo. Heat inactivation experiments showed that, except for G‐6‐PD, activities were stable up to 40°C. Inactivation occurred at lower temperatures for G‐6‐PD, while higher temperatures were required for PER. Incubation of extracts for 7 days at 4°C indicated that loss of enzyme activity was greatest for G‐6‐PD (3.9% remaining) and least for PER and ACP (94 and

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05056.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

We investigated the effect of Ca2+on ethylene production in 2‐cm long apical segments from primary roots of corn (Zea maysL., B73 × Missouri 17) seedlings. The seedlings were raised under different conditions of Ca2+availability. Low‐Ca and high‐Ca seedlings were raised by soaking the grains and watering the seedlings with distilled water or 10 mMCaCl2, respectively. Segments from high‐Ca roots produced more than twice as much ethylene as segments from low‐Ca roots. Indoleacetic acid (IAA; 1 μM) enhanced ethylene production in segments from both low‐Ca and high‐Ca roots but auxin‐induced promotion of ethylene production was consistently higher in segments from high‐Ca roots. Addition of I‐aminocyclopropane‐I‐carboxylic acid (ACC) to root segments from low‐Ca seedlings doubled total ethylene production and the rate of production remained fairly constant during a 24 h period of monitoring. In segments from high‐Ca seedlings ACC also increased total ethylene production but most of the ethylene was produced within the first 6 h. The data suggest that Ca2+enhances the conversion of ACC to ethylene. The terminal 2 mm of the root tip were found to be especially important to ethylene biosynthesis by apical segments and, experiments using45Ca2+as tracer indicated that the apical 2 mm of the root is the region of strongest Ca2+accumulation. Other cations such as Mn2+, Mg2+, and K+could largely substitute for Ca2+. The significance of these findings is discussed with respect to recent evidence for gravity‐induced Ca2+redistribution and its relationship to the establishment of asymmetric grow

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05057.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Passive influx of45Ca2+into non‐growing corn root tissue (Zea maysL.) was increased as a result of actions (cutting, rubbing, chilling, heating, acidifying) or agents (cyanide, uncouplers) known to depolarize the cell membrane, and was decreased by actions (washing) or agents (fusicoccin) known to hyperpolarize it. These responses indicate the presence of Ca2+channels which are voltage controlled. If the injuries were extensive, however, voltage control was lost and hyperpolarization with fusicoccin was expressed by increased45Ca2+influx. Control could be regained by tissue washing, and millimolar levels of external Ca2+would protect against loss of control. Influx of Ca2+was strongly inhibited by La3+, but only weakly by verapamil. Intact roots showed greater cold shock sensitivity in maturing cells than in growing cells. We conclude that corn roots normally restrict Ca2+influx by a mechanism linked to hyper‐polarization of the plasmalemma.Calcium ions which enter cold‐shocked tissue are partially extruded during the early phase of recovery by a process stimulated by fusicoccin and subject to uncou

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05058.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The role of gibberellins in the germination of seeds ofAmaranthus caudatusL. was examined. Tetcyclacis (BAS 106), an inhibitor of gibberellin biosynthesis, inhibited germination of the seeds. The inhibition caused by BAS 106 was antagonised by gibberellin A4+7(GA4+7). Ethephon (2‐chloroethylphosphonic acid) and 1‐aminocyclopropane‐1‐carboxylic acid (ACC) could replace GA4+7. Ethephon and ACC counteracted also the side effects of BAS 106 that are not reversible by GA4+7. The rate of seed germination was not increased by gibberellin in the presence of aminoethoxyvinylglycine (AVG). AVG increased the effect of BAS 106. GA4+7could not reverse the effect of BAS 106 when AVG was simultaneously applied. The results indicate that the biosynthesis of endogenous gibberellins may be required for germination ofA. caudatusseeds and that main physiological effects of GA4+7on seed germination may depend on ethylene biosy

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1986.tb05059.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY