Breaking-off tissue specific activity of the oil palm metallothionein-like gene promoter in T1 seedlings of tomato exposed to metal ions

Metallothioneins (MTs) are cysteine-rich metal-binding proteins that are involved in cell growth regulation, transportation of metal ions and detoxification of heavy metals. A mesocarp-specific metallothionein-like gene (MT3-A) promoter was isolated from the oil palm (Elaeis guineensis Jacq). A vector construct containing the MT3-A promoter fused to the β-glucuronidase (GUS) gene in the pCAMBIA 1304 vector was produced and used in Agrobacterium-mediated transformation of tomato. Histochemical GUS assay of different tissues of transgenic tomato showed that the MT3-A promoter only drove GUS expression in the reproductive tissues and organs, including the anther, fruit and seed coat. Competitive RT-PCR and GUS fluorometric assay showed changes in the level of GUS mRNA and enzyme activity in the transgenic tomato (T₀). No GUS mRNA was found in roots and leaves of transgenic tomato. In contrast, the leaves of transgenic tomato seedlings (T₁) produced the highest GUS activity when treated with 150 μM Cu²⁺ compared to the control (without Cu²⁺). However, Zn²⁺ and Fe²⁺ treatments did not show GUS expression in the leaves of the transgenic tomato seedlings. Interestingly, the results showed a breaking-off tissue-specific activity of the oil palm MT3-A promoter in T₁ seedlings of tomato when subjected to Cu²⁺ ions.     

Central nervous system activities of two diterpenes isolated from Aloysia virgata

Using the guide of a competitive assay for the benzodiazepine binding site in the γ-aminobutyric acid type A receptor (GABA_A), two active diterpenes were isolated from the aerial parts of Aloysia virgata (Ruíz & Pavón) A.L. Jussieu var. platyphylla (Briquet) Moldenke. These compounds, identified as (16R)-16,17,18-trihydroxyphyllocladan-3-one (1) and (16R)-16,17-dihydroxyphyllocladan-3-one (2) on the basis of spectral data, competitively inhibited the binding of [³H]-FNZ to the benzodiazepine binding site with K_i ± S.E.M. values of 56 ± 19 μM and 111 ± 13 μM, respectively. The behavioral actions of these diterpenes, intraperitoneally (i.p.) administered in mice, were examined in the plus-maze, holeboard, locomotor activity and light/dark tests. Compound 1 exhibited anxiolytic-like effects in mice evidenced by a significant increase of the parameters measured in the holeboard test (the number of head dips at 0.3 mg/kg and 3 mg/kg, the rears at 1 mg/kg and the time spent head-dipping at 3 mg/kg), in the plus-maze assay (the percentage of open arm entries at 1 mg/kg) and in the light/dark test (the time in light and the number of transitions at 1 mg/kg). Compound 2 augmented the number of rearings in the holeboard apparatus (at 0.3 mg/kg and 1 mg/kg) and the locomotor activity (at 1 mg/kg). These results reveal the presence of neuroactive compounds in Aloysia virgata.     

Novel dammarane-type sapogenins from Panax ginseng berry and their biological activities

Three new dammarane-type sapogenins (1, 3, and 5) together with two known ones (2 and 4) were isolated from the total hydrolyzed saponins extracted from Panax ginseng berry. Their structures were elucidated using a combination of 1D and 2D ¹H and ¹³C NMR spectra and mass spectroscopy as 20(R)-25-methoxyl-dammarane-3β,12β,20-triol (1), 20(R)-25-methoxyl-dammarane-3β,6α,12β,20-tetrol (2), 20(R)-20-methoxyl-dammarane-3β,12β,25-triol (3), 20(R)-20,25-dimethoxyl-dammarane-3β,12β-diol (4), and (12R,20S,24S)-20,24-; 12,24-diepoxy-dammarane-3β-ol (5). Their antitumor activities were evaluated in six human cancer cell lines. The novel compounds 1 and 3 showed significant cytotoxic activity against the six cell lines. The IC₅₀ values of 3 against HepG2, Colon205, and HL-60 were the lowest (8.78, 8.64, and 3.98 μM, respectively). Compounds 1 and 20(S)-25-OCH₃-PPD, which are a pair of configuration isomers, showed a 10- to 100-fold greater growth inhibition than ginsenoside-Rg₃ (an anti-cancer clinical agent in China). The data presented here may be useful for the development of novel anti-cancer agents.     

Hydraulic resistance of developing Actinidia fruit

Background and Aims

Xylem flows into most fruits decline as the fruit develop, with important effects on mineral and carbohydrate accumulation. It has been hypothesized that an increase in xylem hydraulic resistance (R_T) contributes to this process. This study examined changes in R_T that occur during development of the berry of kiwifruit (Actinidia deliciosa), identified the region within the fruit where changes were occurring, and tested whether a decrease in irradiance during fruit development caused an increase in R_T, potentially contributing to decreased mineral accumulation in shaded fruit.

Methods

R_T was measured using pressure chamber and flow meter methods, the two methods were compared, and the flow meter was also used to partition R_T between the pedicel, receptacle and proximal and distal portions of the berry. Dye was used as a tracer for xylem function. Artificial shading was used to test the effect of light on R_T, dye entry and mineral accumulation.

Key Results

R_T decreased during the early phase of rapid fruit growth, but increased again as the fruit transitioned to a final period of slower growth. The most significant changes in resistance occurred in the receptacle, which initially contributed 20 % to R_T, increasing to 90 % later in development. Dye also ceased moving beyond the receptacle from 70 d after anthesis. The two methods for measuring R_T agreed in terms of the direction and timing of developmental changes in R_T, but pressure chamber measurements were consistently higher than flow meter estimates of R_T, prompting questions regarding which method is most appropriate for measuring fruit R_T. Shading had no effect on berry growth but increased R_T and decreased dye movement and calcium concentration.

Conclusions

Increased R_T in the receptacle zone coincides with slowing fresh weight growth, reduced transpiration and rapid starch accumulation by the fruit. Developmental changes in R_T may be connected to changes in phloem functioning and the maintenance of water potential gradients between the stem and the fruit. The effect of shade on R_T extends earlier reports that shading can affect fruit vascular differentiation, xylem flows and mineral accumulation independently of effects on transpiration.     

Non-synonymous polymorphisms in the P2RX 4 are related to bone mineral density and osteoporosis risk in a cohort of Dutch fracture patients

In the present study we investigated whether single nucleotide polymorphisms (SNPs) in the P2RX₄, which alter the P2X₄R function, are associated with the development of osteoporosis and whether an interaction between the P2X₄R and P2X₇R confer a synergistic effect of these two receptors on osteoporosis risk. Patients with fracture (690 females and 231 males, aged ≥50 years) were genotyped for three non-synonymous P2X₄R SNPs. Bone mineral density (BMD) was measured at the total hip, lumbar spine, and femoral neck. Subject carrying the variant allele of the Tyr315Cys polymorphism showed a 2.68-fold (95 % CI, 1.20–6.02) higher risk of osteoporosis compared with wild-type subject. Furthermore, significant lower lumbar spine BMD values were observed in subjects carrying the Cys315 allele as compared with wild-type (0.85 ± 0.17 and 0.93 ± 0.17 g/cm², respectively; p < 0.001). Assuming a recessive model, carriers of the variant allele of the Ser242Gly polymorphism showed increased BMD values at the lumbar spine compare to wild-type subject (1.11 ± 0.35 and 0.92 ± 0.17 g/cm², respectively; p = 0.0045). This is the first study demonstrating an association of non-synonymous polymorphisms in the P2RX₄ and the risk of osteoporosis, suggesting a role of the P2X₄R in the regulation of bone mass.

Electronic supplementary material

The online version of this article (doi:10.1007/s11302-012-9337-0) contains supplementary material, which is available to authorized users.     

Dynamics of transparent exopolymeric particles (TEP) production by Phaeocystis globosa under N- or P-limitation: a controlling factor of the retention/export balance

The concentration of transparent exopolymeric particles (TEP) was monitored during Phaeocystis globosa blooms that developed in mesocosms under different initial N:P ratios (from N- to P-limited conditions). TEP concentration was measured using the microscopic (TEP_micro, ppm) and the colorimetric (TEP_color, Xanthan equiv. L⁻¹) methods. TEP concentrations varied from 5 to >75 ppm and from 60 to >1500 μg Xanthan equiv. L⁻¹, and were relatively low until the mesocosms reached nutrient (either N or P) depletion and then increased abruptly. From the TEP_micro versus TEP_color concentrations comparison and from their relation to chlorophyll a concentrations, two phases for the dynamics of TEP production were identified: (1) production through active release of precursors during the growth phase of P. globosa — defined as TEP₁ — and their integration into the TEP pool through coagulation processes; (2) release of large TEP from the mucilaginous matrix of P. globosa colonies subsequent to disruption caused by nutrient depletion — defined as TEP₂ — and their direct integration into the TEP pool outside the constraint of coagulation. The formation of a multiorigin TEP pool during P. globosa blooms may have implications for the fate of the blooms, due to difference in TEP bioreactivity according to their source and to difference in timing and intensity of TEP₁ versus TEP₂ production according to N- or P-depletion. For P. globosa blooms developing under N-limiting conditions, the transition from the first source (i.e. TEP₁) to the second one (i.e. TEP₂) was a slow and continuous process. In contrast, the P. globosa bloom developing under P-limiting conditions showed the sudden formation of heavy mucous aggregates when P became depleted, that may have been caused by a massive release of TEP₂. Our study suggests that the nutrient regime may control the export vs. retention balance during P. globosa blooms, via production of a multiorigin TEP pool.     

The anaphase promoting complex activator CCS52A,a key factor for fruit growth and endoreduplication in tomato

Tomato fruit growth is characterized by the occurrence of numerous rounds of DNA endoreduplication in connection to cell expansion and final fruit size determination. Endoreduplication occurs as an impairment of mitosis, which can originate from the selective degradation of M-phase-specific cyclins via the ubiquitin-mediated proteolytic pathway, requiring the E3 ubiquitin ligase Anaphase Promoting Complex/Cyclosome (APC/C). In plants CCS52A is the ortholog of CDH1/FZR proteins from yeast, drosophila and human, belonging to the WD40-repeat protein family. During fruit development, the SlCCS52A gene expression is specifically associated to endoreduplication in tomato. Altering SlCCS52A expression in either negative or positive manner impacts the extent of endoreduplication in fruit and affects fruit size. When SlCCS52A is down-expressed endoreduplication is impaired during fruit growth leading to reduced fruit growth. However when SlCCS52A is overexpressed, endoreduplication is initially delayed, accounting for the altered final fruit size, but resumes and is even enhanced leading to fruit growth recovery, pointing at the physiological role of endoreduplication in growth induction during tomato fruit development.Key words: anaphase promoting complex, CCS52A, endoreduplication, fruit development, growth, tomatoEndoreduplication represents the most common mode of cell endopolyploidization in plants and is estimated to occur in over 90% of Angiosperms.^1,2 This process is an endonuclear DNA stock duplication leading to the production of chromosomes with 2n chromatids without any change in chromosome number.^3,4 As a consequence hypertrophying nuclei arise from successive cycles of DNA replication.In fruits of Cucurbitaceae and Solanaceae, mesocarp cells commonly undergo six rounds of DNA duplication (endocycle), and the highest ploidy levels for these cells being reached in tomato fruits where eight endocycles (up to 512C) can be observed.⁵ This high level of endopolyploidy in tomato fruits and the numerous data reported on this process in this species,^6–9 makes it an outstanding model for studying endopolyploidization and its physiological role during fruit development.     

Predicting the carcass chemical composition and describing its growth in live pigs of different sexes using computed tomographys

The aims of this study were (1) to evaluate the ability of computed tomography (CT) to predict the chemical composition of live pigs and carcasses, (2) to compare the chemical composition of four different sex types at a commercial slaughter weight and (3) to model and evaluate the chemical component growth of these sex types. A total of 92 pigs (24 entire males (EM), 24 surgically castrated males (CM), 20 immunocastrated males (IM) and 24 females (FE)) was used. A total of 48 pigs (12 per sex type) were scanned repeatedly in vivo using CT at 30, 70, 100 and 120 kg and slaughtered at the end of the experiment. The remaining 44 were CT scanned in vivo and slaughtered immediately: 12 pigs (4 EM, 4 CM and 4 FE) at 30 kg and 16 pigs each at 70 kg and 100 kg (4 per sex type). The left carcasses were CT scanned, and the right carcasses were minced and analysed for protein, fat, moisture, ash, Ca and P content. Prediction equations for the chemical composition were developed using Partial Least Square regression. Allometric growth equations for the chemical components were modelled. By using live animal and carcass CT images, accurate prediction equations were obtained for the fat (with a root mean square error of prediction (RMSEP_CV) of 1.31 and 1.34, respectively, and R²=0.91 for both cases) and moisture relative content (g/100 g) (RMSEP_CV=1.19 and 1.38 and R²=0.94 and 0.93, respectively) and were less accurate for the protein (RMSEP_CV=0.65 and 0.67 and R²=0.54 and 0.63, respectively) and mineral content (RMSEP_CV from 0.28 to 1.83 and R² from 0.09 to 0.62). Better equations were developed for the absolute amounts of protein, fat, moisture and ash (kg) (RMSEP_CV from 0.26 to 1.14 and R² from 0.91 to 0.99) as well as Ca and P (g) (RMSEP_CV=144 and 71, and R²=0.76 to 0.66, respectively). At 120 kg, CM had a higher fat and lower moisture content than EM. For protein, CM and IM had lower values than FE and EM. The ash content was higher in EM and IM than in FE and CM, while IM had a higher Ca and P content than the others. The castrated animals showed a higher allometric coefficient for fat and a lower one for moisture, with IM having intermediate values. However, for the Ca and P models, IM presented higher coefficients than EM and FE, and CM were intermediate.     

Soil TPH Concentration Estimation Using Vegetation Indices in an Oil Polluted Area of Eastern China

Assessing oil pollution using traditional field-based methods over large areas is difficult and expensive. Remote sensing technologies with good spatial and temporal coverage might provide an alternative for monitoring oil pollution by recording the spectral signals of plants growing in polluted soils. Total petroleum hydrocarbon concentrations of soils and the hyperspectral canopy reflectance were measured in wetlands dominated by reeds (Phragmites australis) around oil wells that have been producing oil for approximately 10 years in the Yellow River Delta, eastern China to evaluate the potential of vegetation indices and red edge parameters to estimate soil oil pollution. The detrimental effect of oil pollution on reed communities was confirmed by the evidence that the aboveground biomass decreased from 1076.5 g m⁻² to 5.3 g m⁻² with increasing total petroleum hydrocarbon concentrations ranging from 9.45 mg kg⁻¹ to 652 mg kg⁻¹. The modified chlorophyll absorption ratio index (MCARI) best estimated soil TPH concentration among 20 vegetation indices. The linear model involving MCARI had the highest coefficient of determination (R ² = 0.73) and accuracy of prediction (RMSE = 104.2 mg kg⁻¹). For other vegetation indices and red edge parameters, the R² and RMSE values ranged from 0.64 to 0.71 and from 120.2 mg kg⁻¹ to 106.8 mg kg⁻¹ respectively. The traditional broadband normalized difference vegetation index (NDVI), one of the broadband multispectral vegetation indices (BMVIs), produced a prediction (R ² = 0.70 and RMSE = 110.1 mg kg⁻¹) similar to that of MCARI. These results corroborated the potential of remote sensing for assessing soil oil pollution in large areas. Traditional BMVIs are still of great value in monitoring soil oil pollution when hyperspectral data are unavailable.     

Bimetallic copper(II) and zinc(II) complexes of acyclic Schiff base ligands derived from amino acids

The acyclic Schiff-base ligands (2-(OH)-5-(R³)C₆H₂-1,3-(HCNC(R¹)(R²)CO₂H), derived from the dialdehyde 2-hydroxy-5-R-1,3-benzenedicarboxaldehyde (R = Me or t-Bu) and two equivalents of the amino acids glycine, 2,2-diphenylglycine or phenylalanine, have been reacted with the metal acetates M(OAc)₂ (M = Cu, Zn) in the presence of triethylamine, affording the complexes [HNEt₃][M₂(CH₃CO₂)₂(2-(O)-5-(t-Bu)C₆H₂-1,3-(HCNC(R¹)(R²)CO₂)₂] (M = Cu, R¹ = R² = C₆H₅, R³ = Me (1); M = Zn, R¹ = R² = H, R³ = t-Bu (2); M = Zn, R¹ = R² = C₆H₅, R³ = t-Bu (3); M = Zn, R¹ = H, R² = CH₂C₆H₅, R³ = t-Bu (4)) in good yields. The crystal structures of 1·MeCN, 2·, 3·2MeOH, and 4·3MeOH have been determined.     

Gibberellins Increase Cuticle Deposition in Developing Tomato Fruit

Effects of the gibberellins A₄₊₇(GA₄₊₇) and A₃(GA₃), benzyladenine (BA) and forchlorfenuron (CPPU) on deposition of the cuticular membrane (CM) in developing tomato (Lycopersicon esculentum L.) fruit were investigated. Growth regulators were applied when fruit development within trusses ranged from the flower to the mature stage. Developmental stage of fruit at the time of application was indexed by fruit diameter. Fruit were harvested at maturity, the CM isolated enzymatically on an individual fruit basis and mass of CM per unit fruit surface area calculated. In mature fruit, mass of CM per fruit increased with fruit size, but mass of CM per unit surface area was independent of fruit size, position within a truss and position of the truss on the plant. GA₄₊₇ and GA₃ increased CM mass per unit fruit surface area at concentrations up to 300 mg l⁻¹. Young fruit (5–10 mm diam. at time of application) was most responsive. Responsiveness decreased as fruit development at application progressed towards maturity. There was no consistent effect of GA₄₊₇ or GA₃ on fruit mass. BA (up to 100 mg l⁻¹) or CPPU (up to 3 mg l⁻¹) had no significant effect on CM mass per unit surface area regardless of developmental stage. Higher concentrations of BA or CPPU decreased CM mass per unit surface area. There was no effect of BA or CPPU on fruit mass. Potential mechanisms and benefits of a gibberellin induced increase in CM deposition are discussed.     

Mechanisms Involved in Calcium Deficiency Development in Tomato Fruit in Response to Gibberellins

Although gibberellins (GAs) have been shown to induce development of the physiological disorder blossom-end rot (BER) in tomato fruit (Solanum lycopersicum), the mechanisms involved remain largely unexplored. BER is believed to result from calcium (Ca) deficiency, but the relationship between Ca content and BER incidence is not strong. Our objectives were to better understand how GAs and a GA biosynthesis inhibitor affect BER development in tomato fruit. Tomato plants of two BER-susceptible cultivars, ‘Ace 55 (Vf)’ and ‘AB2,’ were grown in a greenhouse environment and subjected to Ca-deficiency conditions. Plants were treated weekly during fruit growth and development with 300 mg L^?1 GA₄₊₇, 300 mg L^?1 prohexadione-calcium (Apogee^®, a GA biosynthesis inhibitor), or water beginning 1 day after flower pollination. GA₄₊₇ treatment induced an increase in BER incidence in both cultivars up to 100%, whereas ‘Ace 55 (Vf)’ and ‘AB2’ plants treated with Apogee did not show BER incidence. The number of functional xylem vessels was higher in the placental and pericarp tissue of tomato fruit treated with Apogee at the early stages of fruit growth. Treatment with Apogee also increased fruit pericarp Ca concentration. GA₄₊₇ treatment enhanced the expression of the putative CAX and Ca-ATPase genes, that code for proteins involved in Ca movement into storage organelles. The lowest water-soluble apoplastic Ca concentration and the highest membrane leakage values were observed in the pericarp of GA₄₊₇-treated fruit. These results suggest that GAs consistently reduced fruit Ca uptake and water-soluble apoplastic Ca concentration, leading to leakier plasma membranes and an increase in BER development in fruit tissue of both tomato cultivars.     

Assessing crop N status of fertigated vegetable crops using plant and soil monitoring techniques

Evaluation of crop N status will assist optimal N management of intensive vegetable production. Simple procedures for monitoring crop N status such as petiole sap [NO₃^?–N], leaf N content and soil solution [NO₃^?] were evaluated with indeterminate tomato and muskmelon. Their sensitivity to assess crop N status throughout each crop was evaluated using linear regression analysis against nitrogen nutrition index (NNI) and crop N content. NNI is the ratio between the actual and the critical crop N contents (critical N content is the minimum N content necessary to achieve maximum growth), and is an established indicator of crop N status. Nutrient solutions with four different N concentrations (treatments N1–N4) were applied throughout each crop. Average applied N concentrations were 1, 5, 13 and 22 mmol L^?1 in tomato, and 2, 7, 13 and 21 mmol L^?1 in muskmelon. Respective rates of N were 23, 147, 421 and 672 kg N ha^?1 in tomato, and 28, 124, 245 and 380 kg N ha^?1 in muskmelon. For each N treatment in each crop, petiole sap [NO₃^?–N] was relatively constant throughout the crop. During both crops, there were very significant (P < 0.001) linear relationships between both petiole sap [NO₃^?–N] and leaf N content with NNI and with crop N content. In indeterminate tomato, petiole sap [NO₃^?–N] was very strongly linearly related to NNI (R² = 0.88–0.95, P < 0.001) with very similar slope and intercept values on all dates. Very similar relationships were obtained from published data of processing tomato. A single linear regression (R² = 0.77, P < 0.001) described the relationship between sap [NO₃^?–N] and NNI for both indeterminate and processing tomato, each grown under very different conditions. A single sap [NO₃^?–N] sufficiency value of 1050 mg N L^?1 was subsequently derived for optimal crop N nutrition (at NNI = 1) of tomato grown under different conditions. In muskmelon, petiole sap [NO₃^?–N] was strongly linearly related to NNI (R² = 0.75 – 0.88, P < 0.001) with very similar slope and intercept values for much of the crop (44–72 DAT, days after transplanting). A single linear relationship between sap [NO₃^?–N] and NNI (R² = 0.77, P < 0.001) was derived for this period, but sap sufficiency values could not be derived for muskmelon as NNI values were >1. Relationships between petiole sap [NO₃^?–N] with crop N content, and leaf N content with both NNI and crop N content had variable slopes and intercept values during the indeterminate tomato and the muskmelon crops. Soil solution [NO₃^?] in the root zone was not a sensitive indicator of crop N status. Of the three systems examined for monitoring crop/soil N status, petiole sap [NO₃^?–N] is suggested to be the most useful because of its sensitivity to crop N status and because it can be rapidly analysed on the farm.     

Colored Mulches Affect Yield of Fresh-market Tomato Infected with Meloidogyne incognita

The effects of different-colored polyethylene mulches on the quantity and spectra of reflected light, earliness of fruit set, fruit yield and quality, and root-knot disease were studied in field-grown, staked tomato (Lycopersicon esculentum). White mulch reflected more photosynthetic light and a lower far-red-to-red ratio than red mulch, whereas black mulch reflected less than 5 percent of any color. Soil temperatures and fruit yields were recorded for tomato plants inoculated with Meloidogyne incognita race 3 at initial populations of 0, 1,000, 10,000, 50,000, or 100,000 eggs/plant and grown over black, white, or red plastic mulch in both spring and fall. Soil temperatures were lower under white mulch than under red or black mulch. Tomato yields declined as inoculum level increased. Plants grown over red mulch in the spring and inoculated with 50,000 eggs of M. incognita had greater early marketable yields than similarly inoculated plants grown over black or white mulch. Tomato plants inoculated with 100,000 eggs and grown over white mulch or red mulch in the spring had greater total yields per plot than similar plants grown over black mulch (7.39 kg and 7.71 kg vs. 3.65 kg, respectively).     

Properties and Partial Purification of 1-Aminocyclopropane-1-carboxylate Synthase

We studied the regulation of 1-aminocyclopropane-1-carboxylate (ACC) synthase activity in tomato (Lycopersicon esculentum Mill.) fruit tissue and attempted the purification of this enzyme. The increase of ACC synthase activity in wounded tomato pericarp was inhibited by cordycepin and cycloheximide. Density labeling studies showed a 0.75% increase in the buoyant density of ACC synthase isolated from tomato pericarp tissue that had been incubated on ²H₂O as compared to ACC synthase from H₂O-treated tissue. These data are consistent with the hypothesis that ACC synthase is synthesized de novo following wounding of tomato pericarp tissue. SDS-gel electrophoresis and fluorography showed that the pattern of incorporation of l-[³⁵S]methionine into protein changed with time after wounding of the tissue. Radioactive protein bands that were not detected 1 hour after wounding, became apparent 2 to 3 hours after wounding.     

Analysis of Crop Losses in Tomato Due to Pratylenchus penetrans

The effects of Pratylenchus penetrans upon yields of ''Veebrite'' tomato were studied at initial soil population densities (P_i) of 360, 2,010, 4,580, and 14,360 nematodes/kg of soil in 20-cm (i.d.) clay-tile microplots. The lowest P_i appeared to stimulate fruit production. Higher P_i''s suppressed fruit production (total weight of marketable tomatoes and numbers of intermediate- and large-sized fruits), in comparison to control yields, the highest P_i resulted in 38% fewer fruits which weighed 44% less. These losses were at least partly due to a delay in fruit ripening, caused by the nematodes, which did not become apparent until the fourth week. Nematode populations in the soil increased at all but the highest P_i; final populations were around 7,000/kg of soil. Nematode populations in roots ranged from 230-590/gm of root at the completion of the experiment. Nematode control by fumigation would definitely be warranted at soil population densities of 2,000/kg or higher; with 500-2,000/kg, the decision to fumigate would depend on soil type and economic and hiological factors.     

Synthesis and structure of dichloropalladium(II) complexes of heteroleptic N,S- and N,Se-donor ligands based on the 2-organochalcogenomethylpyridine motif, and Mizoroki-Heck catalysis mediated by complexes of N,S-donor ligands

Ligands containing the 2-organochalcogenomethylpyridine motif with substituents in the 4- or 6-position of the pyridyl ring, R⁴,R⁶-pyCH₂ER¹ [R⁴ = R⁶ = H, ER¹ = SMe (1), SeMe (2), SPh (6), SePh (7); R⁴ = Me, R⁶ = H, ER¹ = SMe (3), SPh (8), SePh (9); R⁴ = H, R⁶ = Me, ER¹ = SMe (4), SPh (10), SePh (11); R⁴ = H, R⁶ = Ph, ER¹ = SMe (5), SPh (12), SePh (13)] are obtained on the reaction of R⁴,R⁶-pyMe with LiBuⁿ followed by R¹EER¹. On reaction with PdCl₂(NCMe)₂, the ligands with a 6-phenyl substituent form cyclopalladated species PdCl{6-(o-C₆H₄)pyCH₂ER¹-C,N,E} (5a, 12a, 13a) with the structure of 13a (ER¹ = SePh) confirmed by X-ray crystallography; other ligands form complexes of stoichiometry PdCl₂(R⁴,R⁶-pyCH₂ER¹). Complexes with R⁶ = H are monomeric with N,E-bidentate configurations, confirmed by structural analysis for 3a (R⁴ = Me, ER¹ = SMe), 7a (R⁴ = H, ER¹ = SePh) and 9a (R⁴ = Me, ER¹ = SePh). Two of the 6-methyl substituted complexes examined by X-ray crystallography are oligomeric with trans-PdCl₂(N,E) motifs and bridging ligands, trimeric [PdCl₂(μ-6-MepyCH₂SPh-N,S)]₃ (10a) and dimeric [PdCl₂(μ-6-MepyCH₂SePh-N,Se)]₂ (11a). This behaviour is attributed to avoidance of the Me···Cl interaction that would occur in the cis-bidentate configuration if the pyridyl plane had the same orientation with respect to the coordination plane as observed for 3a, 7a and 9a [dihedral angles 8.0(2)-16.8(2)°]. When examined as precatalysts for the Mizoroki-Heck reaction of n-butyl acrylate with aryl halides in N,N-dimethylacetamide at 120 °C, the complexes exhibit the anticipated trends in yield (ArI > ArBr > ArCl, higher yield for electron withdrawing substituents in 4-RC₆H₄Br and 4-RC₆H₄Cl). The most active precatalysts are PdCl₂(R⁴-pyCH₂SMe-N,S) (R = H (1a), Me (3a)); complexes of the selenium containing ligands exhibit very low activity. For closely related ligands, the changes SMe to SPh, 6-H to 6-Me, and 6-H to 6-Ph lead to lower activity, consistent with involvement of both the pyridyl and chalcogen donors in reactions involving aryl bromides. The precatalyst PdCl₂(pyCH₂SMe-N,S) (1a) exhibits higher activity for the reaction of aryl chlorides in Buⁿ₄NCl at 120 °C as a solvent under non-aqueous ionic liquid (NAIL) conditions.     

Sensitivity of Meloidogyne incognita and Rotylenchulus reniformis to Abamectin

Avermectins are macrocyclic lactones produced by Streptomyces avermitilis. Abamectin is a blend of B_1a and B_1b avermectins that is being used as a seed treatment to control plant-parasitic nematodes on cotton and some vegetable crops. No LD₅₀ values, data on nematode recovery following brief exposure, or effects of sublethal concentrations on infectivity of the plant-parasitic nematodes Meloidogyne incognita or Rotylenchulus reniformis are available. Using an assay of nematode mobility, LD₅₀ values of 1.56 μg/ml and 32.9 μg/ml were calculated based on 2 hr exposure for M. incognita and R. reniformis, respectively. There was no recovery of either nematode after exposure for 1 hr. Mortality of M. incognita continued to increase following a 1 hr exposure, whereas R. reniformis mortality remained unchanged at 24 hr after the nematodes were removed from the abamectin solution. Sublethal concentrations of 1.56 to 0.39 μg/ml for M. incognita and 32.9 to 8.2 μg/ml for R. reniformis reduced infectivity of each nematode on tomato roots. The toxicity of abamectin to these nematodes was comparable to that of aldicarb.     

Preparation, properties and crystal structure of two isomers of R,R,S,S- and R,S,R,S-[chloro(1,3,10,12,16,19-hexaazatetracyclo[17,3,1,1,0]tetracosane)copper(II)]

Two isomers (R,S,R,S- and R,R,S,S-) of five coordinate complex [Cu(L)Cl]⁺ have been separated and characterised. These two isomers have significantly different spectrochemical and electrochemical properties. Absorption maximum of R,S,R,S-[Cu(L)Cl]⁺ shifts to longer wavelength and its reduction potential shifts to more positive direction comparing those of R,R,S,S-[Cu(L)Cl]⁺. R,S,R,S-[Cu(L)Cl]⁺ is significantly distorted to trigonal-bipyramidal structure, whereas R,R,S,S-[Cu(L)Cl]⁺ retains almost square-planar geometry. The average bond distance of Cu-N in basal plane of R,S,R,S-[Cu(L)Cl]⁺ is longer by 0.024 Å than that of R,R,S,S-[Cu(L)Cl]⁺, whereas the bond distance of Cu-Cl in former is shorter by 0.200 Å than that in latter. The isolated square-planar complexes of R,R,S,S- and R,S,R,S-[Cu(L)](ClO₄)₂ are converted to the R,R,S,S- and R,S,R,S-[Cu(L)Cl]⁺ by the addition of Cl⁻ in nitromethane solution with the rate constants, k=1.70 (±0.02) and 8.31 (±0.07) M⁻¹ s⁻¹, respectively.     

Purification and partial characterization of a membrane-associated lipoxygenase in tomato fruit

Membrane-associated lipoxygenase from green tomato (Lycopersicon esculentum L. cv Caruso) fruit has been purified 49-fold to a specific activity of 8.3 μmol·min⁻¹·mg⁻¹ of protein by solubilization of microsomal membranes with Triton X-100, followed by anion- exchange and size-exclusion chromatography. The apparent molecular mass of the enzyme was estimated to be 97 and 102 kD by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size-exclusion chromatography, respectively. The purified membrane lipoxygenase preparation consisted of a single major band following sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which cross-reacts with immunoserum raised against soluble soybean lipoxygenase 1. It has a pH optimum of 6.5, an apparent K_m of 6.2 μm, and V_max of 103. μmol·min⁻¹·mg⁻¹ of protein with linoleic acid as substrate. Corresponding values for the partially purified soluble lipoxygenase from tomato are 3.8 μm and 1.3 μmol·min⁻¹·mg⁻¹ of protein, respectively. Thus, the membrane-associated enzyme is kinetically distinguishable from its soluble counterpart. Sucrose density gradient fractionation of the isolated membranes indicated that the membrane-associated lipoxygenase sediments with thylakoids. A lipoxygenase band with a corresponding apparent mol wt of 97,000 was identified immunologically in sodium dodecyl sulfate-polyacrylamide gel electrophoresis-resolved proteins of purified thylakoids prepared from intact chloroplasts isolated from tomato leaves and fruit.