Triacontanol-supported micropropagation of woody plants

 The effectiveness of triacontanol in the micropropagation of two woody, economically important fruit plant species was investigated. Triacontanol was added to the routine multiplication and rooting media of apple (Malus domestica cv. JTE-E4) and sour cherry (Cerasus fruticosa cv. Probocskai) rootstocks at concentrations of 2, 5, 10 and 20 μg/l. It was found to increase the number of shoots and the fresh weight of apple in the multiplication phase and to enhance root number and chlorophyll content in the rooting phase. The addition of indole-3-butyric acid (IBA) to the media further improved the effect of triacontanol. A less pronounced effect could be seen in the multiplication phase of sour cherry, although there was an enhancement of shoot proliferation. In the rooting phase, however, the application of triacontanol caused a significant increase in the number of roots per plant, and this effect was further improved when triacontanol was combined with 0.5 mg indole-3-butyric acid/l. Received: 29 March 2000 / Revision received: 1 September 2000 / Accepted: 4 September 2000     

Subgroups of Paediatric Acute Lymphoblastic Leukaemia Might Differ Significantly in Genetic Predisposition to Asparaginase Hypersensitivity

L-asparaginase (ASP) is a key element in the treatment of paediatric acute lymphoblastic leukaemia (ALL). However, hypersensitivity reactions (HSRs) to ASP are major challenges in paediatric patients. Our aim was to investigate genetic variants that may influence the risk to Escherichia coli-derived ASP hypersensitivity. Sample and clinical data collection was carried out from 576 paediatric ALL patients who were treated according to protocols from the Berlin—Frankfurt—Münster Study Group. A total of 20 single nucleotide polymorphisms (SNPs) in GRIA1 and GALNT10 genes were genotyped. Patients with GRIA1 rs4958351 AA/AG genotype showed significantly reduced risk to ASP hypersensitivity compared to patients with GG genotype in the T-cell ALL subgroup (OR = 0.05 (0.01–0.26); p = 4.70E-04), while no such association was found in pre-B-cell ALL. In the medium risk group two SNPs of GRIA1 (rs2055083 and rs707176) were associated significantly with the occurrence of ASP hypersensitivity (OR = 0.21 (0.09–0.53); p = 8.48E-04 and OR = 3.02 (1.36–6.73); p = 6.76E-03, respectively). Evaluating the genders separately, however, the association of rs707176 with ASP HSRs was confined only to females. Our results suggest that genetic variants of GRIA1 might influence the risk to ASP hypersensitivity, but subgroups of patients can differ significantly in this respect.     

Interactions between plant hormones and thiol-related heavy metal chelators

Upon toxic metal stress numerous defence mechanisms have been induced, including the synthesis of metal-binding ligands and plant hormones or plant growth regulators in plants. As several elements in the promoter region of the heavy metal-responsive genes can be activated by plant hormones and growth regulators, understanding and revealing possible and special relationships between these regulator compounds and the metal chelator phytochelatins, which are in the first line of heavy metal defence mechanism is of great important. Phytochelatins are synthetized from glutathione and have a structure of [(γ-Glu-Cys)_n]-Gly, where n is the number of repetition of the (γ-Glu-Cys) units. Evidences for the role of PCs in heavy metal tolerance are very strong; however, little information is available on how plant growth regulators influence the phytochelatin synthesis at molecular or even gene expression level. In the present review we provide an overview of the role and synthesis of phytochelatins in metal-tolerance mechanism from a new point of view, i.e. their relation to the plant growth regulator molecules, with special regard also on those cases, when close direct relationship exists because of the partly overlapped synthesis pathways of plant growth regulators and glutathione/phytochelatins.     

The newly synthesized plant growth regulator <Emphasis Type="Italic">S</Emphasis>-methylmethionine salicylate may provide protection against high salinity in wheat

High salinity is one of the major environmental factors limiting the productivity of crop species worldwide. Improving the stress tolerance of cultivated plants and thus increasing crop yields in an environmentally friendly way is a crucial task in agriculture. In the present work the ability of a new derivative, S-methylmethionine-salicylate (MMS), to improve the salt tolerance of wheat plants was tested parallel with its related compounds salicylic acid and S-methylmethionine. The results show that while these compounds are harmful at relatively high concentration (0.5 mM), they may provide protection against high salinity at lower (0.1 mM) concentration. This was confirmed by gas exchange, chlorophyll content and chlorophyll-a fluorescence induction measurements. While osmotic adjustment probably plays a critical role in the improved salt tolerance, neither Na or K transport from the roots to the shoots nor proline synthesis are the main factors in the tolerance induced by the compounds tested. MMS, S-methylmethionine and Na-salicylate had different effects on flavonol biosynthesis. It was also shown that salt treatment had a substantial influence on the SA metabolism in wheat roots and leaves. Present results suggest that the investigated compounds can be used to improve salt tolerance in plants.     

Hydroponic treatment with salicylic acid decreases the effects of chilling injury in maize (Zea mays L.) plants

The addition of 0.5 mM salicylic acid (SA) to the hydroponic growth solution of young maize (Zea mays L.) plants under normal growth conditions provided protection against subsequent low-temperature stress. This observation was confirmed by chlorophyll fluorescence parameters and electrolyte leakage measurements. In addition, 1 d of 0.5 mM SA pre-treatment decreased net photosynthesis, stomatal conductivity and transpiration at the growth temperature (22/20 °C). Since there was only a slight decrease in the ratio of variable to maximal fluorescence (F_v/F_m) the decrease in photosynthetic activity is not due to a depression in photosystem II. The analysis of antioxidant enzymes showed that whereas SA treatment did not cause any change in ascorbate peroxidase (EC 1.11.1.11) and superoxide dismutase (EC 1.15.1.1) activities, there was a decrease in catalase (EC 1.11.1.6) activity, and an increase in guaiacol peroxidase (EC 1.11.1.7) and glutathione reductase (EC 1.6.4.2) activities after the 1-d SA treatment at 22/20 °C. In native polyacrylamide gels there was, among the peroxidase isoenzymes, a band which could be seen only in SA-treated plants. It is suggested that the pre-treatment of maize plants with SA at normal growth temperature may induce antioxidant enzymes which lead to increased chilling tolerance. Received: 4 June 1998 / Accepted: 23 November 1998     

Use of beta-blocker therapy in older patients after acute myocardial infarction in Ontario.

BACKGROUND: Despite its proven efficacy, beta-blocker therapy remains underused in elderly patients after myocardial infarction (MI). The objectives of this study were to identify undertreated groups of seniors and to determine whether older and frailer patients are being selectively dispensed low-dose beta-blocker therapy. METHODS: From a comprehensive hospital discharge database, all people aged 66 years or more in Ontario who survived an acute MI between April 1993 and March 1995 were identified and classified into those who did not receive beta-blocker therapy and those dispensed low, standard or high doses of this agent. Logistic regression models were used to study the effect of age, sex, comorbidity, potential contraindications to beta-blocker therapy and residence in a long-term-care facility on the odds of not being dispensed a beta-blocker. Among beta-blocker users, the odds of being dispensed low relative to standard or high doses of this agent were evaluated. RESULTS: Of the 15,542 patients, 7549 (48.6%) were not dispensed a beta-blocker. Patients 85 years of age or more were at greater risk of not receiving beta-blocker therapy (adjusted odds ratio [OR] 2.8, 95% confidence interval [CI] 2.5-3.2) than were those 66 to 74 years. Having a Charlson comorbidity index of 3 or greater was associated with an increased risk of not receiving beta-blocker therapy (adjusted OR 1.5, 95% CI 1.3-1.8) compared with having lower comorbidity scores. Patients who resided in a long-term-care facility were at increased risk of not being prescribed beta-blocker therapy (adjusted OR 2.6, 95% CI 2.0-3.4). Among the 5453 patients with no identifiable contraindication to beta-blocker therapy, women were significantly less likely than men to receive this agent (p = 0.005). Of the 6074 patients who received beta-blockers, 2248 (37.0%) were dispensed low-dose therapy. Patients aged 85 years or more had an increased risk of being dispensed low-dose therapy (adjusted OR 1.6, 95% CI 1.3-2.0) compared with those aged 66 to 74 years. Compared with those who had the lowest comorbidity scores, patients with the highest comorbidity scores were more likely to be dispensed low-dose beta-blocker therapy (adjusted OR 1.3, 95% CI 1.0-1.8). INTERPRETATION: Almost half of Ontario patients aged 66 or more who survived an MI, particularly those who were older or frailer, did not receive beta-blocker therapy. Among those dispensed beta-blocker therapy, older and frailer patients were more frequently dispensed low-dose therapy.     

Exogenous treatment with salicylic acid attenuates cadmium toxicity in pea seedlings

The present study investigated the possible mediatory role of salicylic acid (SA) in protecting plants from cadmium (Cd) toxicity. The exposure of pea plants to increasing Cd concentrations (0.5, 1.0, 2.0 and 5.0 μM) during early stages of their establishment, caused a gradual decrease in shoot and root fresh weight accumulation, the rate of CO₂ fixation and the activity of ribulose-1,5-bisphosphate carboxylase (RuBPC, E.C. 4.1.1.39), the effect being most expressed at higher Cd concentrations. In vivo the excess of Cd-induced alterations in the redox cycling of oxygen-evolving centers and the assimilatory capacity of the pea leaves as revealed by changes in thermoluminescence emission after flash illumination. The levels of some important parameters associated with oxidative stress, namely lipid peroxidation, electrolyte leakage and proline production were increased. Seed pretreatment with SA alleviated the negative effect of Cd on growth, photosynthesis, carboxylation reactions, thermoluminescence characteristics and chlorophyll content, and led to decrease in oxidative injuries caused by Cd. The data suggest that the beneficial effect of SA during an earlier growth period could be related to avoidance of cumulative damage upon exposure to cadmium thus reducing the negative consequences of oxidative stress caused by heavy metal toxicity. In addition, the observed high endogenous levels of SA after treatment with Cd suggests that SA may act directly as an antioxidant to scavenge the reactive oxygen species and/or indirectly modulate redox balance through activation of antioxidant responses.Taken together these evidences could explain at some extend the protective role of SA on photochemical activity of chloroplast membranes and photosynthetic carboxylation reactions in Cd-stressed pea plants.     

Atnoa1 mutant Arabidopsis plants induce compensation mechanisms to reduce the negative effects of the mutation

Alterations in temperature adaptation processes and changes in the content of stress-related compounds, polyamines and salicylic acid were evaluated in Atnoa1 (NO-associated 1) Arabidopsis mutant. The F_v/F_m chlorophyll-a fluorescence induction parameter and the actual quantum yield were significantly lower in the Atnoa1 mutant than in the wild-type. In the wild-type Col-0, the fastest increase in the non-photochemical quenching (NPQ) occurred in plants pre-treated at low temperature (4 °C), while the slowest was in those adapted to 30 °C. The NPQ showed not only a substantially increased level in the light-adapted state, but also more rapid light induction after the dark-adapted state in the Atnoa1 mutant than in the wild-type. The results of freezing tests indicated that both the wild-type and the mutant had better freezing tolerance after cold hardening, since no significant differences were found between the genotypes. The level of putrescine increased substantially, while that of spermine decreased by the end of the cold-hardening (4 °C, 4 d) period. The quantity of spermidine in Atnoa1 was significantly higher than in Col-0, at both control and cold-hardening temperatures. A similar trend was observed for spermine, but only under control conditions. The mutant plants showed substantially higher salicylic acid (SA) contents for both the free and bound forms. This difference was significant not only in the control, but also in the cold-hardened plants. These results suggest that there is a compensation mechanism in Atnoa1 mutant Arabidopsis plants to reduce the negative effects of the mutation. These adaptation processes include the stimulation of photoprotection and alterations in the SA and polyamine compositions.