The Effect of Quercetin on the Accumulation of Carbohydrates and Amino Acids in Tomato Fruits

We studied the effects of low concentrations of quercetin on the contents of sugars and amino acids in ripe tomato (Lycopersicon esculentumMill.) fruits. In treated plants, the content of glucose increased by 1.5–4.5 times, whereas the total content of amino acids decreased by 1.5 times. The glucogenic amino acids, glutamic and aspartic acid, decreased most substantially, viz. by 1.7 and 1.6 times, respectively. The mechanism of the quercetin-induced enhancement of gluconeogenesis and suppression of glycolysis, both resulting in the accumulation of glucose, are discussed.     

NaCl stress causes changes in photosynthetic pigments,proteins, and other metabolic components in the leaves of a true mangrove,<Emphasis Type="Italic">Bruguiera parviflora</Emphasis>, in hydroponic cultures

We studied salt stress-induced biochemical changes in young, hydroponically grown plants of mangrove,Bruguiera parviflora (Rhizophoraceae). Our focus was on the effect of NaCI (applied at 100, 200, 400, or 500 mM) on leaf pigments, total soluble proteins, total free amino acids, carbohydrates, polyphenols, and proline. The total Chi content increased for 14 d after treatment with 100 mM NaCI, then gradually stabilized. At 400 mM, the total Chi content slowly decreased over the 45-d test period. However, the Chia:b ratio remained unchanged in isolated chloroplasts and in leaf tissue. Percent changes in the carotenoids content followed the same trend as for Chi, except for a 1.5-fold decrease during the 400-mM NaCI treatment, compared with the control. The total sugar content increased by 2.5-fold by Day 45 after treatment with 400 mM NaCI, whereas the starch content measured in the same treatment decreased by 40 to 45%. Leaf protein content decreased as salinity increased, which suggests either a possible disruption in the protein synthesis mechanism or, more likely, an increase in proteolytic activity. The total amino-acid pool increased steadily, by four-fold, in the 45-d, 400-mM treatment Both proline and polyphenols accumulated with increasing levels of salinity, which confirms the role of proline as a stress-induced protective metabolite in the adaptive process of this species. Our results showed that a true mangrove such as 8.parviflora can easily be sustained and propagated under low-salinity conditions. At high levels of salinity (~400 mM, beyond which they could not survive), the plants became adapted to salt stress after two to three weeks. During this adaptive period, changes in pigment and protein levels also occurred. The accumulation of proline and polyphenols played a key role in the plant’s stressinduced adjustment to NaCI under hydroponic culture conditions.     

Nitrogen deficiency induced changes of free amino acids and coumarin contents in the leaves of Matricaria chamomilla

Through o-hydroxycinnamic acids, the biosynthesis of coumarins is connected with aromatic amino acid metabolism and nitrogen uptake. Therefore the quantitative changes in levels of some free amino acids and coumarins (herniarin and its glucosidic precursors (Z) - and (E)-2-β-D-glucopyranosyloxy-4-methoxycinnamic acids; umbelliferone) in the leaf rosettes of chamomile (Matricaria chamomilla L.) subjected to nitrogen deficiency were studied. Nitrogen content decreased in the leaf rosettes and in the roots of N-deficient plants during the course of the experiment, but these plants produced significantly higher root biomass. Among secondary metabolites, the sum of 2-β-D-glucopyranosyloxy-4-methoxycinnamic acids increased sharply, herniarin increased slowly and the content of umbelliferone was low in N-deficient plants. We have concluded that nitrogen deficiency is not an inducing factor for stress accumulation of herniarin and umbelliferone. A decrease in levels of all detected amino acids, besides histidine, was found. Within aromatic amino acids, tyrosine was the most abundant. The content of free phenylalanine was significantly lower in both, control and N-deficient plants when compared to the content of tyrosine. In this view, the increase of herniarin glucosidic precursors is apparently due to enhancing phenylalanine ammonia-lyase activity under nitrogen deficiency and nitrogen-free carbon skeletons are shunted in to the phenylpropanoid metabolism, including biosynthesis of (Z)-and (E)-2-β-D-glucopyranosyloxy-4-methoxycinnamic acids.     

Effects of exogenous quercetin on the levels of carbohydrates and amino acids in fruits ofLycopersicon esculentum

Low doses of the exogenous flavonoid quercetin increased the content of sugars in tomato fruits of various cultivars. The content of glucose in tomato fruits of cv.Ukrainskii teplichnyi increased from 3.62 to 11.24% per unit dry weight. Increases in the content of glucose were found in all tomato cultivars examined. An analysis of qualitative and quantitative compositions of amino acids showed that their levels were markedly decreased in fruits of quercetin-treated plants. Our studies and data found in the literature suggest that this effect is due to the synthesis of sugars from amino acids by gluconeogenesis. The reverse process of sugar hydrolysis does not occur because exogenous quercetin inhibits the activity of pyruvate kinase.     

Improving the nutritive value of tubers: elevation of cysteine and glutathione contents in the potato cultivar White Lady by marker-free transformation

The amino acids that limit the nutritive value of potato are the sulfur containing amino acids methionine and cysteine. Manipulation of the targeted amino acid biosynthesis is a way to circumvent this problem. Cysteine is synthesised from O-acetyl-l-serine formed by serine acetyltransferase (SAT). To increase the cysteine content of the commercial potato cultivar White Lady the chimeric SAT-coding cysE gene from Escherichia coli under the control of the constitutive CaMV 35S promoter and fused to the chloroplast targeting rbcS 5'-transit peptide sequence was introduced into the White Lady genome. Novelty of the approach was the application of marker-free transformation. Two transgenic lines were obtained that accumulated the cysE mRNA in high amounts. Crude leaf extracts of these plants exhibited up to 80- and 20-fold higher SAT activity in leaves and tubers, respectively, than those prepared from non-transformed plants. Levels of cysteine and glutathione both in leaves and tubers were 1.5-fold higher in average than in control plants. The alterations observed had no effect on tuber yield and sprouting behaviour. Gas chromatography coupled to mass spectrometry showed that all other amino acids than cysteine were unaffected. Here we demonstrate for the first time that the cysteine content of tubers can be enhanced by metabolic engineering.     

Effect of Light Quality on Nitrogen Metabolism of Radish Plants

The long-term action of blue or red light on nitrogen metabolism was studied in radish (Raphanus sativus L.) plants. The potential activity of nitrate reductase (NR) in vivo and its maximum activity in vitro, the content of soluble protein and free amino acids were determined in the course of the growth of a third leaf of radish plants. The effect of light quality on NR activity was found to depend significantly on the stage of leaf development. Blue light (BL) stimulated NR activity in leaves, when their areas were about 11–13% of the fully developed leaves. The efficiency of red light (RL) was significantly lower, because the maximum NR activity was observed in the leaves developed to the stage, when their areas were 38–40% of the final one. The comparative analysis of the pool of free amino acids in expanding leaves of BL- or RL-grown plants revealed significant changes in the contents of individual amino acids. Despite a higher accumulation of two amino acids in the leaves of BL-grown plants, namely, Asp (27% as compared to 13–16% in the RL-grown leaves) and Gly (5% against 2.5% in RL-grown leaves), the BL-grown leaves also demonstrated a significant decrease in Ala (10% as compared to 23% in the RL-grown leaves) and some decrease in the amounts of Ser and Gly. The content of soluble protein in a juvenile BL-grown leaf was observed to decrease gradually during leaf development. However, the protein content in the BL-grown leaf was always higher than in the RL-grown leaf of the same age. We concluded that the photoregulatory action of BL on NR activity determined the different rates of nitrogen assimilation in BL- and RL-grown plants.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 3, 2005, pp. 349–356.Original Russian Text Copyright © 2005 by Maevskaya, Bukhov.     

Stress-induced changes in the free amino acid composition in transgenic soybean plants having increased proline content

Following drought stress at supraoptimal temperature the increase in proline (Pro) content in transgenic (T) soybean [Glycine max (L.) Merr. cv. Ibis] plants overexpressing the gene coding for the last enzyme of Pro biosynthesis, L-Δ¹-pyrroline-5-carboxylate reductase, was much greater than in wild type (W) plants (105-fold versus 19-fold after 7 d). Under control conditions arginine accounted for nearly 60 % of the total free amino acid content. After stress treatment the content of Pro was more than 50 % in both T and W genotypes, and at the end of recovery the γ-aminobutyrate content reached 27 and 53 % in the W and T plants, respectively. Without stress treatment there was only a 2-fold difference between T and W in the tyrosine content. However, during the stress period and the subsequent recovery a similar difference was found for many amino acids. The present results indicate that manipulating of the content of a single amino acid influences the whole free amino acid composition in soybean.     

Changes in Mulberry Leaf Metabolism in Response to Water Stress

A series of experiments were conducted to characterize the water stress-induced changes in the activities of RuBP carboxylase (RuBPCO) and sucrose phosphate synthase (SPS), photosystem 2 activity, and contents of chlorophylls, carotenoids, starch, sucrose, amino acids, free proline, proteins and nucleic acids in mulberry (Morus alba L. cv. K-2) leaves. Water stress progressively reduced the activities of RuBPCO and SPS in the leaf extracts, the chlorophyll content, and PS2 activity in isolated chloroplasts. Plants exposed to drought showed lower content of starch and sucrose but higher total sugar content than control plants. While the soluble protein content decreased under water stress, the amino acid content increased. Proline accumulation (2.5-fold) was noticed in stressed leaves. A reduction in the contents of DNA and RNA was observed. Reduced nitrogen content was associated with the reduction in nitrate reductase activity. SDS-PAGE protein profile showed few additional proteins (78 and 92 kDa) in the water stressed plants compared to control plants.     

Mulberry Leaf Metabolism under High Temperature Stress

Effects of high temperature on the activity of photosynthetic enzymes and leaf proteins were studied in mulberry (Morus alba L. cv. BC2-59). A series of experiments were conducted at regular intervals (120, 240 and 360 min) to characterize changes in activities of ribulose-1,5-bisphosphate carboxylase (RuBPC) and sucrose phosphate synthase (SPS), photosystem 2 (PS 2) activity, chlorophyll (Chl), carotenoid (Car), starch, sucrose (Suc), amino acid, free proline, protein and nucleic acid contents in leaves under high temperature (40 °C) treatments. High temperature markedly reduced the activities of RuBPC and SPS in leaf extracts. Chl content and PS 2 activity in isolated chloroplasts were also affected by high temperature, particularly over 360 min treatment. Increased leaf temperature affected sugar metabolism through reductions in leaf starch content and sucrose-starch balance. While total soluble protein content decreased under heat, total amino acid content increased. Proline accumulation (1.5-fold) was noticed in high temperature-stressed leaves. A reduction in the contents of foliar nitrogen and nucleic acids (DNA and RNA) was also noticed. SDS-PAGE protein profile showed few additional proteins (68 and 85 kDa) in mulberry plants under heat stress compared to control plants. Our results clearly suggest that mulberry plants are very sensitive to high temperature with particular reference to the photosynthetic carbon metabolism.     

Enhanced glucotropaeolin production in hairy root cultures of Tropaeolum majus L. by combining elicitation and precursor feeding

We have studied the effects of precursor amino acids (phenylalanine and cystein), elicitors (salicylic and acetylsalicylic acids, methyl jasmonate, β-aminobutyric acid, yeast extract), PAL-inhibitor (1-amino-2-phenylethylphosphonic acid) applied alone or in combination on glucotropaeolin production and myrosinase activity in hairy root cultures of Tropaeolum majus. Short, 24-h treatment, and subsequent transfer of hairy roots to the fresh medium enabled avoiding detrimental effect of studied stimulators on biomass growth. In control cultures the highest glucotropaeolin content, 58.1 ± 6.7 mg g⁻¹ DW, was detected on the 3rd day after transfer of the roots to the fresh medium but glucotropaeolin yield (mg 100 ml^–1 culture volume) had been increasing until the 9th day after transfer as a result of continuous biomass growth. Glucotropaeolin content and yield were 2-fold enhanced after treatment with precursor amino acids or PAL-inhibitor alone, but their combination additively led to 4-fold increase in glucotropaeolin production. Among the studied elicitors acetylsalicylic acid induced the highest, 3-fold increase in glucotropaeolin production, it also enhanced myrosinase activity, but to a smaller extend (by about 50%). Acetylsalicylic acid also potentiated induced by precursors, PAL-inhibitor, methyl jasmonate and yeast extract production of glucotropaeolin. The highest, 4.8-fold increase in glucotropaeolin production was found after combined acetylsalicylic acid and precursors treatment. Additive effect of acetylsalicylic acid-combined treatment on myrosinase activity was not detected. The obtained results indicate that amino acid precursors, phenylalanine and cystein, availability may be a limiting factor in the process of stimulation of glucotropaeolin production in T. majus hairy root cultures.     

Effects of NaCl-salinity on amino acid and carbohydrate contents of Phragmites australis

The effects of NaCl-salinity on growth, free amino acid and sugar content and composition were assayed in roots, rhizomes and leaves of Phragmites australis (Cav.) Trin. ex Steud. Juvenile plants produced from freshwater clones, were cultured under greenhouse hydroponic conditions for 21 days. Relative growth rates were highest at a salinity level of 0 and 1.5‰, respectively, but decreased significantly at 10‰. All plants cultured at 35‰ salinity died. The osmolality in rhizomes and leaves increased with salinity. The total contents of free amino acids were highest in rhizomes>leaves>roots. In rhizomes, the amino acid content increased significantly up to four-fold from 0 to 10‰ salinity. This increase was caused by up to 200-fold increase of proline and 11-fold increase of glutamine at 10‰, whilst the share of asparagine and glutamate decreased. Leaves showed a similar response to salinity with increasing amino acid contents, and shares of proline and glutamine whereas roots did not react significantly. The contents of sucrose, glucose and fructose were highest in leaves>rhizomes>roots. In rhizomes of all three clones, the sugar contents increased up to 3.5-fold from 1.5 to 10‰ salinity level, but were lower at 1.5‰ versus the control (0‰). Sugar contents were lowest (roots) and highest (leaves) at 1.5‰ salinity. The sugar composition did not vary significantly except for leaves where the fraction of sucrose decreased with increasing salinity level at all three clones from 89.1 to 61.7% of total dissolved sugar (pooled data). The importance of free amino acids and sugars as osmolytes was similar in rhizomes and leaves (13–15% of total osmolality at 10‰). In rhizomes, free amino acids were more important as osmolyte than sugars, while the opposite was true for leaves. Proline contributed up to 2.7% to total osmolality. It is hypothesised that a strong proline accumulation indicates the exceeding of a critical salinity level.     

槲皮素对氧化应激大鼠肝细胞氨基酸代谢的影响

通过检测原代培养的大鼠肝细胞培养液中18种氨基酸含量的变化情况,探讨槲皮素对氧化应激大鼠肝细胞氨基酸代谢的影响。结果表明,与对照组相比,槲皮素组氨基酸质量浓度无明显变化;H2O2组、槲皮素+H2O2组培养液中丙氨酸、蛋氨酸和组氨酸的质量浓度显著减少(P<0.05),而牛磺酸的质量浓度显著增加(P<0.05),上述变化槲皮素+H2O2组较H2O2组更明显,槲皮素+H2O2组M et和H is的质量浓度显著低于H2O2组(P<0.05)。说明槲皮素可影响氧化应激肝细胞某些氨基酸,尤其是含硫氨基酸的代谢。这种影响可能是槲皮素抗氧化应激作用的机制之一。     

Phloem-specific expression of pyrophosphatase inhibits long distance transport of carbohydrates and amino acids in tobacco plants

As reported in a previous paper [Lerchl et al. (1995) Plant Cell, 7, 259–270], expression of Escherichia coli inorganic pyrophosphatase in the cytosol under the control of the phloem-specific rolC promoter from, Agobacterium rhizogenes results in decreased growth of transgenic tobacco plants. In this paper we investigate the effect of the phloem-specific expression of pyrophosphatase on phloem metabolism, and on plant growth and allocation. A small decrease in the hexose phosphate/UDP-glucose ratio, the ATP/ADP ratio and the respiration rate in the midribs of the transformants provides evidence Hint mobilization of sucrose via pyrophosphate-dependent reactions is necessary for phloem energy metabolism. The source leaves of the transformants had higher levels of carbohydrates and amino acids and a much higher glutamine/glutamate ratio than the wild type, showing that export was inhibited and that the growth inhibition was not due to a lack of photoas-similates or organic nitrogen in the leaves. The accumulation of photoassimilates was paralleled by a decrease in photosynthesis, chlorophyll content and ribulose bisphosphate carboxylase/oxygenase (Rubisco) activity, a small increase in hexose phosphates and triose phosphates and a decrease in glycerate 3-phosphate in the source leaves. There was a decrease of soluble sugars and amino acids in sink leaves of the transformants. In sink leaves amino acids decreased more than carbohydrates and a decrease in the glutamine/ glutamate ratio was observed. This was accompanied by a large decrease of nitrate. Sugars and amino acids were also reduced in the root tips of the transformants. The carbohydrate /amino acid ratio decreased 5-fold in the root tips, indicating a particularly smile shortage of carbohydrates. Relatively high levels of sugars and amino acids in the basal regions of the root and the increase in sugars in the midrib indicate that there is also increased leakage of assimilates out of the phloem during long-distance transport. Metabolism is required to maintain phloem function along the transport route, as well as for the initial step of loading. The transformants showed decreased stem and root growth. The growth inhibition was largest in conditions allowing rapid growth of the wild type (high light and nitrogen supply).     

Prey-induced changes in the accumulation of amino acids and phenolic metabolites in the leaves of <Emphasis Type="Italic">Drosera capensis</Emphasis> L

Effect of prey feeding (ants Formica fusca) on the quantitative changes in the accumulation of free amino acids, soluble proteins, phenolic metabolites and mineral nutrients in the leaves of carnivorous plant Drosera capensis was studied. Arginine was the most abundant compound in Drosera leaves, while proline was abundant in ants. The amount of the majority of amino acids and their sum were elevated in the fed leaves after 3 and 21 days, and the same, but with further enhancement after 21 days, was observed in ants. Accumulation of amino acids also increased in young non-fed leaves of fed plants. Soluble proteins decreased in ants, but were not enhanced in fed leaves. This confirms the effectiveness of sundew’s enzymatic machinery in digestion of prey and suggests that amino acids are not in situ deposited, but rather are allocated within the plant. The content of total soluble phenols, flavonoids and two selected flavonols (quercetin and kaempferol) was not affected by feeding in Drosera leaves, indicating that their high basal level was sufficient for the plant’s metabolism and prey-induced changes were mainly N based. The prey also showed to be an important source of other nutrients besides N, and a stimulation of root uptake of some mineral nutrients is assumed (Mg, Cu, Zn). Accumulation of Ca and Na was not affected by feeding.     

Fe2O3 nanoparticles induced biochemical responses and expression of genes involved in rosmarinic acid biosynthesis pathway in Moldavian balm under salinity stress

The effect of iron oxide nanoparticle (NP) at four concentrations (0, 30, 60 and 90 ppm) and salinity at three levels (0, 50 and 100 mM) were investigated on rosmarinic acid (RA) production in 5-week-old Moldavian balm (Dracocephalum moldavica L.) plants. Salinity and spraying iron oxide NPs significantly affected tyrosine (Tyr), phenylalanine (Phe) and proline (Pro) amino acids content, Phenylalanine Ammonia-Lyase (PAL), Tyrosine Aminotransferase (TAT) and Rosmarinic Acid Synthase (RAS) genes expression levels, RA content, Polyphenol Oxidase (PPO), PAL and Superoxide Dismutase (SOD) activities, malondialdehyde (MDA) content and DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity. PAL, TAT and RAS genes expression rate and content of RA were enhanced in Moldavian balm plants exposed by NaCl + NPs. The results of high performance liquid chromatography (HPLC) revealed that simultaneous application of 50 mM NaCl and 90 ppm NPs increases the RA content in leaf by 81.15% as compared to control plants. The Tyr and Phe contents decreased in Moldavian balm plants exposed to salt stress. Application of NPs had a positive effect on the content of these amino acids. Proline content increased under salinity stress and application of iron NPs induced a significant increase in the Pro content of leaf. The results revealed that PAL, PPO and SOD enzymes activities increased under salinity conditions. The highest activity of PPO and SOD was observed in 100 mM NaCl + 60 ppm NPs treatment. Simultaneous application of 100 mM NaCl + 90 ppm NPs increased the MDA content and DPPH radical scavenging activity compared to control plants. It can be concluded that the application of appropriate levels of NPs moderates the effect of salinity stress in D. moldavica L. and results in an increased amount of RA compared to control plants.     

Redox regulation of free amino acid levels in Arabidopsis thaliana

Abiotic stresses induce oxidative stress, which modifies the level of several metabolites including amino acids. The redox control of free amino acid profile was monitored in wild‐type and ascorbate or glutathione deficient mutant Arabidopsis thaliana plants before and after hydroponic treatment with various redox agents. Both mutations and treatments modified the size and redox state of the ascorbate (AsA) and/or glutathione (GSH) pools. The total free amino acid content was increased by AsA, GSH and H₂O₂ in all three genotypes and a very large (threefold) increase was observed in the GSH‐deficient pad2‐1 mutant after GSH treatment compared with the untreated wild‐type plants. Addition of GSH reduced the ratio of amino acids belonging to the glutamate family on a large scale and increased the relative amount of non‐proteinogenic amino acids. The latter change was because of the large increase in the content of alpha‐aminoadipate, an inhibitor of glutamatic acid (Glu) transport. Most of the treatments increased the proline (Pro) content, which effect was due to the activation of genes involved in Pro synthesis. Although all studied redox compounds influenced the amount of free amino acids and a mostly positive, very close (r > 0.9) correlation exists between these parameters, a special regulatory role of GSH could be presumed due to its more powerful effect. This may originate from the thiol/disulphide conversion or (de)glutathionylation of enzymes participating in the amino acid metabolism.     

Time course of the content of folates and free amino acids in leaves of Pisum sativum L. after irradiation with ultraviolet C

The effect of irradiation with UV-C on the time course of the content of total folates and free amino acids in leaves of pea (Pisum sativum L.) cultivar Neistoshchimyi was studied. It was shown that photolysis of folates is a rapid response to exposure to ultraviolet, as a result of which the plant produces a stable compound, pterin-6-carboxylic acid, with a relative fluorescence quantum yield 2.0 at 20°C (total value, 0.58). Presumably, this compound may be involved in the pterin-mediated photosensitization of singlet oxygen production. The kinetics of changes in the composition of free amino acids after exposure to UV-C has been studied. Exposure to UV-C for 0.5 and 1 min induced utilization of free amino acids, suggesting activation of the synthesis of hormones and alkaloids that may facilitate resistance to the stressor. Greater doses as a result of exposure to radiation for 10 and 40 min decreased the content of free hydrophobic amino acids. This phenomenon could be due to the formation of covalent cross-links in membranes, which decrease the accessibility of hydrophobic amino acids. It is concluded that the changes in the qualitative and quantitative composition of free amino acids in leaves of irradiated plants were due to glycolysis.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 2, 2005, pp. 155–161.Original Russian Text Copyright © 2005 by Stakhov, Ladygin, Stakhova.     

Engineering of the aspartate family biosynthetic pathway in barley (Hordeum vulgare L.) by transformation with heterologous genes encoding feed-back-insensitive aspartate kinase and dihydrodipicolinate synthase

In prokaryotes and plants the synthesis of the essential amino acids lysine and threonine is predominantly regulated by feed-back inhibition of aspartate kinase (AK) and dihydrodipicolinate synthase (DHPS). In order to modify the flux through the aspartate family pathway in barley and enhance the accumulation of the corresponding amino acids, we have generated transgenic barley plants that constitutively express mutant Escherichia coli genes encoding lysine feed-back insensitive forms of AK and DHPS. As a result, leaves of primary transformants (T₀) exhibited a 14-fold increase of free lysine and an 8-fold increase in free methionine. In mature seeds of the DHPS transgenics, there was a 2-fold increase in free lysine, arginine and asparagine and a 50% reduction in free proline, while no changes were observed in the seeds of the two AK transgenic lines analysed. When compared to that of control seeds, no differences were observed in the composition of total amino acids. The introduced genes were inherited in the T₁ generation where enzymic activities revealed a 2.3-fold increase of AK activity and a 4.0–9.5-fold increase for DHPS. T₁ seeds of DHPS transformants showed the same changes in free amino acids as observed in T₀ seeds. It is concluded that the aspartate family pathway may be genetically engineered by the introduction of genes coding for feed-back-insensitive enzymes, preferentially giving elevated levels of lysine and methionine.     

Seasonal Evolution of the Quality of Fresh Glasshouse Tomatoes under Mediterranean Conditions, as Affected by Air Vapour Pressure Deficit and Plant Fruit Load

Changes in yield and quality of fresh tomatoes in response toair vapour pressure deficit (VPD) and plant fruit load werestudied under Mediterranean summer conditions. Plants thinnedto three or six fruits per truss were grown in two compartments,one at a VPD below 1.5 kPa, the other without VPD control. Theseasonal trend in fruit yield and quality was assessed fromApril to September by weekly measurement of number, fresh weightand dry matter content of harvested fruits, together with theoccurrence of blossom-end-rot (BER) and cracking. On two occasions,in July and September, sugar and acid content was measured atthree ripening stages. The seasonal decrease in fresh yieldwas attenuated at low VPD, because of higher individual fruitfresh weight, especially at low fruit load. Low VPD decreasedoccurrence of BER but like low fruit load, it increased fruitcracking. Fruit dry matter content was lower at low VPD, butwas unaffected by fruit load. Sugar content and the ratio ofsugars:acids was increased at high VPD and low fruit load, withinteractive effects depending on season and ripening stage.The influence of VPD on acid content differed with fruit loadand also changed during ripening and between seasons. Resultsshowed that water was the main limiting factor for growth offruits picked in July; at this time, reducing fruit load topromote mean fruit size had negative effects on BER and cracking.Reducing VPD reduced BER but had a negative effect on crackingand diluted both the dry matter and sugar content. For fruitsharvested later in summer, these negative effects were attenuatedbecause fruit growth was also carbon limited. Copyright 2000Annals of Botany Company Lycopersicon esculentum Mill., tomato, water and carbon stress, yield, quality, dry matter, sugar, acid, BER, volatile composition     

Effect of exogenous quercetin on the level of carbohydrates and amino acids in Lycopersicon esculentum fruit

Low doses of the exogenous flavonoid quercetin increased in contents of sugars in tomato fruits of various cultivars. The content of glucose in tomato fruits of cv. Ukrainskii teplichnyi increased from 3.62 to 11.24% per unit dry weight. Increases in the content of glucose were found in all tomato cultivars examined. An analysis of qualitative and quantitative compositions of amino acids showed that their levels were markedly decreased in fruits of quercetin-treated plants. Our studies and data found in the literature suggest that this effect is due to the synthesis of sugars from amino acids by gluconeogenesis. The reverse process of sugar hydrolysis does not occur because exogenous quercetin inhibits the activity of pyruvate kinase.