摘要:

Cell division and root initiation of excised juvenile, mature and half‐expanded mature (My) leaf petioles ofHedera helixL. cultured in vitro were studied to determine whether these processes were correlated with localized expression of a proline‐rich protein (PRP) gene. Petioles of all three types showed cell divisions at day 5 of culture in auxin‐treated petioles but not in non‐auxin‐treated petioles. No cell division occurred in non‐auxin‐treated petioles even after day 9 of culture. Juvenile and one population of My auxin‐treated petioles formed root primordia after 9 days of culture. Mature petioles and another population of My petioles formed only callus in response to auxin. The spatial and temporal expression pattern of a gene encoding a PRP was analyzed by in situ hybridization. The PRP mRNA was not detectable in petioles of any developmental phase immediately after excision. In both juvenile and mature petioles the PRP mRNA preferentially accumulated in the phloem parenchyma, the inner cortex adjacent to the phloem, and in cells surrounding ducts. Cell division was not required for PRP gene expression since both auxin‐treated and non‐treated juvenile and mature petioles had expression. Steady state levels of PRP mRNA were much lower in juvenile relative to mature petioles cultured in vitro. Auxin treatment reduced the steady state levels of PRP mRNA in My petioles but not in mature or juvenile petioles. These data are consistent with an inverse relationship between competence to form adventitious roots and PRP mRNA levels in the specific cell types from which root primordia form. Alternatively, the PRP mRNA level may serve as a molecular marker for developmental plasticity

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02219.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The objective of this study was to compare whole plant growth and physiological responses to salt stress of twoAcacia niloticasubspecies (ssp.cupressiformisand ssp.tomentosa). Salt stress was induced by adding NaCl at different concentrations to the nutrient solution: 0, 75, 100 and 200 mM. After one month under such stress, plants were still healthy and actively growing in both subspecies up to 100 mMNaCl. Water potential (Ψ) and osmotic potential (π) decreased with salinity and the lower π enabled the plants to maintain turgor. Höfler diagrams confirmed that osmotic adjustment had occurred under all treatments. Furthermore, the point of zero turgor occurred at a higher relative water content. An increase in the elastic modulus (ɛ) was observed under stress (low elasticity of the cell wall). Both osmotic adjustment and a high ɛ modified the capacity of both subspecies to maintain a positive water balance. Accumulation of ions (Na+, K+and Cl−) and proline could explain such osmotic adjustment.Acacia niloticassp.cupressiformisshowed a higher absorption of K+than ssp.tomentosaup to 100 mMNaCl tr

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02220.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Wounded tuber tissue of potato (Solanum tuberosumL. cv. Gloria) exposed to the monoterpene S‐carvone did show neither suberization nor cambium layer formation, whereas these processes started after 2–4 days in control tissue. Suberized tissue was clearly visible 24 days after the start of the S‐carvone treatment, when the concentrations of S‐carvone and its bioconversion products in the tissue were almost zero and cambium layer formation had not yet started. The inhibition of wound healing coincided with a lack of induction of 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase (HMGR, EC 1.1.1.34). The wounded potato tissue used as control, showed a transient induction of HMGR activity.In S‐carvone treated tissue, the activities of GR (glutathione reductase, EC 1.6.4.2) and AP (ascorbate peroxidase, EC 1.11.1.11) were induced, and the level of glutathione increased fou

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02221.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

In this paper the effects of indole‐3‐acetic acid (IAA) on growth ofTagetes patulahairy root cultures and secondary product formation are presented. The biosynthesis of thiophenes, sulfurous compounds with nematicidal activity, was inhibited by IAA application, as was evident from a decrease of [35S] sulfur incorporation. The inhibition only occurred after the roots had developed numerous laterals as a result of auxin action. However, in roots cultured in the absence of IAA, there was no significant correlation between branching and thiophene accumulation. Therefore, development of lateral roots is not a sufficient condition for a low capacity to synthesize thiophenes. The highest rate of thiophene accumulation in the roots culture is at its maximum. Hence, growth and the production of thiophenes appear to be compatible inT. Patulahair ro

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02222.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Multiple activity peaks of neutral invertase (EC 3.2.1.26) were found in chicory roots (Cichorium intybusL. var. foliosum cv. Flash). The main activity peak was purified by a combination of anion‐exchange chromatography, hydrophobic interaction chromatography, chromatofocusing and gel filtration. This protocol produced a 77‐fold purification and a specific activity of 1.6 μmol (mg protein)−1min−1. The mass of the enzyme was 260 kDa as estimated by gel filtration and 65 kDa on SDS‐PAGE. Optimal activity was found between pH 7 and 7.5. The purified enzyme exhibited hyperbolic saturation kinetics with a Kmbetween 10 and 20 mM for sucrose. No other products than glucose and fructose could be detected. Raffinose was hydrolyzed at a rate of 2.4% relative to sucrose whereas the enzyme did not hydrolyze maltose, cellobiose, trehalose, 1‐kestose, 1.1‐nystose or inulin. Neutral invertase activity was completely inhibited by HgCl2and AgNO3and partially inhibited by CoCl2, and ZnSO4(1 mM). Pyridoxal phosphate (Ki≅ 500 μM), Tris (Ki≅ 1.2 mM), glucose and fructose (Ki≅ 16 mM) were strong inhibitors of the enzyme. Fructose and Tris behaved as competitive inhibitors. A possible role for the enzyme's activity

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02223.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

NADPH‐, NADH‐, and KNO3‐eluted fractions of nitrate reductase (NR) were isolated from roots of winter wheat (Triticum aestivumL. cv. Mironovskaya 808) grown under low temperature or high salinity. All three fractions exerted activity with either NADPH or NADH as electron donor. The NADPH‐eluted fraction showed the highest activity with NADPH, whereas the NADH‐ and KNO3‐eluted fractions were most active with NADH. The NADH‐ and NADPH‐dependent activities in the NADH‐ and KNO3‐eluted fractions were the ones that changed the most in response to low temperature. The inhibitory effect of salt stress was the same for both activities in each of the NADH‐ and KNO3‐eluted fractions. The NADPH‐eluted NR was the one least affected

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02224.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Micromolar concentrations of potassium ferricyanide inhibit light‐induced stomatal opening. The extent of the inhibition is dependent on the presence of carbon dioxide and the concentration of potassium ferricyanide needed to obtain 50% inhibition of stomatal opening is 40‐fold higher in CO2‐free air than in normal air. The fungal toxin, fusicoccin (1 μM), overcame the ferricyanide inhibition of stomatal opening indicating that the electron acceptor may interact more or less directly with the activity of the plasma membrane H+‐ATPase. Although potassium ferricyanide strongly inhibited stomatal opening, it had only minor effects on stomatal maintaining or stomatal closure due to darknes

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02225.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Ferredoxin‐dependent glutamate synthase (EC 1.4.7.1) catalyzes an essential step in the pathway of glutamate biosynthesis. Exposing detached tomato (Lycopersicon esculentum) leaves for 6 h to 12 g l−1NaCl resulted in a significant two‐fold increase in the activity of ferredoxin‐dependent glutamate synthase extracted from the leaves. Western blot studies demonstrated that salt treatment also increased the ferredoxin‐dependent glutamate synthase content of the leaves. A similar effect of salt on the concentration of this enzyme was found in the leaves of hydroponically‐grown tomato plants. The induction of ferredoxin‐dependent glutamate synthase under salt stress may provide the glutamate required for the proline synthesis which is a common response t

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02226.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Four maize cultivars, which differ in tolerance to acid soils under field conditions (Zea maysL., acid soil‐tolerant C 525 M, BR 201 F and Adour 250, and acid soil‐sensitive HS 7777) were used to study the influence of pH (4.3 and 6.0) and Al (0, 20 and 50 μM) on the elongation of seminal roots in nutrient solution. Root elongation was inhibited by high H+concentrations (pH 4.3) in cultivars C 525 M, Adour 250 and HS 7777 but not in BR 201 F. After 20 h exposure to Al, root elongation rates were more inhibited in cultivars BR 201 F and HS 7777 than in C 525 M and Adour 250. The use of a computerized linear displacement transducer system with high resolution (1 μm) allowed the monitoring of short‐term responses of root elongation to Al. In the three cultivars affected by H+toxicity, but not in the acid‐tolerant BR 201 F, Al supply caused an immediate, but transient increase of relative root elongation rates. This result supports the hypothesis that Al‐induced growth stimulation is caused by amelioration of proton toxicity. The time required for 20 μMAl to induce a 5% decrease of root elongation rates was shorter in the Al‐sensitive BR 201 F (33 min) and HS 7777 (86 min) than in the Al‐tolerant C 525 M (112 min) and Adour 250 (146 min) cultivars. However, the response‐time to Al may be overestimated in the proton‐sensitive cultivars, due to the transient stimulation of root elongation rates induced by Al. According to our results, experiments intended to investigate primary mechanisms of Al toxicity should be started after less than 30 min exposure to toxic Al concentrations, using pH conditions which avoid Al‐induced growth stimulation due to ameliorat

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02227.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Control by light and nitrate of the appearance of nitrite reductase (NIR; EC 1.7.7.1) activity was investigated in turions ofSpirodela polyrhizaduring the pre‐germination period to establish the nature of the coaction between these factors. A cDNA clone coding for tobacco NIR was available as a probe. In the period immediately after transfer from after‐ripening conditions (5°C. darkness) to germination conditions (25°C; phase 1, from 0 to 72 h after start of the experiments) a nitrate‐dependent increase in NIR activity was observed, presumably because of the temperature shift. During this phase light had no effect on the nitrate‐dependent increase in NIR activity. In contrast, after a pre‐treatment of 72 h in darkness at 25°C following cold afterripening responsiveness to phytochrome appeared, with light inducing a nitrate‐dependent increase in NIR activity (phase II, from 72 to 120 h after start of the experiments). Application of nitrate (10 mM) in phase II also resulted in an increase of NIR activity in light or darkness although highest NIR activities were observed in the presence of light. Ammonium did not affect the appearance of NIR activity. In all experiments, a single isoform of NIR was detectable in both phases. It was concluded that the mode of coaction between light (via phytochrome) and nitrate is different in phase I and phase II and depends on the developmental state of the plant organs. Furthermore, the response patterns of nitrate reductase and NIR activities to both factors is so similar in turions that co‐regulation of both enzymes can be assumed, as found previously in tobacco seedlings. Northern blot analyses revealed a low NIR transcript level in the absence of nitrate in darkness during phase II. Both light and nitrate alone were sufficient to stimulate the NIR mRNA steady state level and the highest transcript level was detectable in the presence of both stimulators. This demonstrates a synergistic effect of both factors on steady state NIR

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1995.tb02228.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY