Effects of Osmotic Potential in Nutrient Solution on Diurnal Growth of Tomato Fruit

Tomato fruit on plants grown in circulating nutrient solutionexhibited a diurnal cycle in growth rate, measured as a changein diameter, with a maximum during thc day. The diurnal growthcycle was less evident in those fruit grown at high electricalconductivity (17 mS), or on days of reduced irradiance. Girdledfruit of low conductivity plants grew at a much reduced ratewith a diurnal cycle in reverse to that of ungirdled fruit,while girdled fruit of high conductivity plants showed no diurnalgrowth. The evidence suggests that phloem and xylem water transportinto fruit operate on opposite diurnal cycles. Partitioning of available xylem water in detached fruit betweenthe calyx and berry, as well as within the berry, was determinedby berry size and relative humidity in the air. Although berrytranspiration rate was unaffected by conductivity treatmentduring plant growth, water uptake capacity was greatly reducedin the berry from high conductivity plants, suggesting an increasedresistance in the xylem transport system within the fruit. Key words: Salinity, electrical conductivity, tomato fruit, xylem transport, transpiration     

Environmental Effects on the Diurnal Accumulation of 45Ca by Young Fruit and Leaves of Tomato Plants

Diurnal uptake and distribution of ⁴⁵Ca in young fruiting tomatoplants were assessed 12 or 24 h after ⁴⁵Ca was applied to thenutrient solution at the beginning of either the light (12 h)or the dark (12 h) period. During the experiment, the salinityof the nutrient solution (measured as electrical conductivity,EC) was either 2·5 or 17 mS cm^–1 and the relativehumidity (measured as vapour pressure deficit, VPD) was either0·2 or 0·6 kPa The uptake of ⁴⁵Ca by a tomato plant over 12 h was higher inthe light than in the dark but the difference was less at lowhumidity. More ⁴⁵Ca was transported from the roots to the shootin the light than in the dark. More than half of the ⁴⁵Ca inthe shoot was accumulated by the stem; the proportion of ⁴⁵Cain the stem was greater in the dark and was further enhancedby high humidity to more than 80% of the ⁴⁵Ca in the shoot.The accumulation of ⁴⁵Ca by the fruit truss in the dark wasgreater than in the light in all experimental conditions. Underlow humidity the accumulation of ⁴⁵Ca by young leaves was similarin both light and dark. In high humidity there was considerablyless accumulation of ⁴⁵Ca by the young leaves in the dark The uptake of ⁴⁵Ca continued over 24 h but the transport of⁴⁵Ca to individual organs in the second 12 h period was affectedby both light and humidity. Some of the ⁴⁵Ca accumulated byyoung leaves and fruit in the second period appears to havebeen derived from ⁴⁵Ca released from the xylem wall along thetransport pathway in the stem The roles of root pressure and transpiration in the diurnalaccumulation of calcium in young fruit and leaves are discussed Calcium, diurnal translocation, tomato, young fruit and leaves     

Effect of Short-Term Salinity on Lipid Metabolism and Ion Accumulation in Tomato Roots

To examine the ion accumulation and membrane lipid metabolism in response to salinity we compared two tomato cvs. Pera and Hellfrucht Fruhstamm (HF), considered to be salt-tolerant and sensitive respectively. Na⁺ and K⁺ accumulation was significantly higher in roots of cv. Pera after 24 h and 72 h of 100 mM NaCl. While in cv. HF, a temporary increase in K⁺ accumulation at 24 h was accompanied by a sustained increase in Na⁺ content. Both cultivars enhanced incorporation of [³²P]orthophosphate into phosphatidylinositol 4,5-bisphosphate at 24 h and 72 h of NaCl. In parallel to the increase of phosphatidylinositol 4,5-bisphosphate a decrease in phosphorylation of phosphatidic acid and phosphatidylcholine were observed in the sensitive cv. HF. Structural and signal lipid changes in response to salinity were more evident in the sensitive cv. HF. Salt tolerant cv. Pera accumulated Na⁺ ions in the roots without considerable modifications in lipid metabolism. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sucrose-to-Starch Metabolism in Tomato Fruit Undergoing Transient Starch Accumulation

Immature green tomato (Lycopersicon esculentum) fruits undergo a period of transient starch accumulation characterized by developmental changes in the activities of key enzymes in the sucrose (Suc)-to-starch metabolic pathway. Activities of Suc synthase, fructokinase, ADP-glucose (Glc) pyrophosphorylase, and soluble and insoluble starch synthases decline dramatically in parallel to the decrease in starch levels in the developing fruit. Comparison of "maximal" in vitro activities of the enzymes in the Suc-to-starch pathway suggests that these same enzymes are limiting to the rate of starch accumulation. In contrast, activities of invertase, UDP-Glc pyrophosphorylase, nucleoside diphosphate kinase, phosphoglucoisomerase, and phosphoglucomutase do not exhibit dramatic decreases in activity and appear to be in excess of starch accumulation rates. Starch accumulation is spatially localized in the inner and radial pericarp and columella, whereas the outer pericarp and seed locule contain little starch. The seed locule is characterized by lower activities of Suc synthase, UDP-Glc pyrophosphorylase, phosphoglucomutase, ADP-Glc pyrophosphorylase, and soluble and insoluble starch synthases. The outer pericarp exhibits comparatively lower activities of ADP-Glc pyrophosphorylase and insoluble starch synthase only. These data are discussed in terms of the developmental and tissue-specific coordinated control of Suc-to-starch metabolism.     

Pathways of Uptake and Accumulation of Sugars in Tomato Fruit

The route of sucrose unloading from the conducting tissue, theregulation of sucrose hydrolysis and the uptake and subsequentmetabolism of sugars were investigated in the rapidly growingtomato fruit. During the first two weeks of fruit enlargement, the vacuoleaccounted for more than 85% of the protoplast volume and theintercellular space accounted for 20% of the fruit placentaltissue. The plasmodesmatal frequency was highest between phloemparenchyma cells and lowest between phloem sieve cells and phloemparenchyma. The total invertase activity was about 8 µmolglucose g^–1 d. wt min^–1 during the rapid growingperiod and increased six-fold at ripening. The wall-bound invertaseaccounted for less than 11% of the total activity. Invertaseactivity increased with increasing sucrose concentrations (upto 50 mM) in the incubation medium, but decreased at higherconcentrations. Sucrose synthase activity could only be detectedwhen fruit was older than 19 d. The uptake and metabolism of sugars by fruit cells were investigatedby incubation of fruit slices with ¹⁴C-sugars for 3 h. The uptakeof sucrose increased with the sucrose concentration up to 200mM. The rate of glucose uptake and its conversion to the ethanol-insolublefraction were higher than those of sucrose. The uptake of sucrosedid not compete with that of glucose or vice versa, providedthe osmotic potential of the incubation solution was maintainedconstant. The uptake of sucrose was not inhibited by metabolicinhibitors such as PCMBS, CCCP, sodium azide or vanadate. TheATPase activity in the fruit tissue was low. These findings did not identify conclusively the mode of sucroseunloading. However, the uptake of sugars by fruit cells is non-specificand does not appear to require a membrane carrier or plasmalemmaATPase to provide energy for sucrose uptake. Fruit, invertase, Lycopersicon esculentum, phloem unloading, plasmodesmata, sucrose     

Ion Effects on Calcium Accumulation by Cardiac Sarcoplasmic Reticulum

The effects of monovalent cations on the active calcium-accumulating ability of cardiac sarcoplasmic reticulum were assessed. Grana prepared in an ion-free system accumulated calcium when ATP and Mg⁺⁺ were present. Sodium ion and to a lesser extent lithium but not K⁺ reduced the amount of calcium taken up. The reduction of calcium binding by Na⁺ is not due to inhibition of uptake but to a rapid release of the radiocalcium bound. The amount of calcium released by sodium does not appear to be enough to explain contraction on the basis of sodium influx into muscle, but may be significant in the regulation of tension.     

Tomato Mosaic Virus Infection in a Recirculating Nutrient Solution

We studied the behaviour of tomato mosaic tobamovirus (ToMV) in a recirculating nutrient solution. Particles of tomato mosaic virus were found in the nutrient solution 3 days after leaf inoculation of plants and we demonstrated that the level could increase to a concentration readily detectable by electron microscopy. Virions remained infective in nutrient solution for at least 6 months, could infect bait plants and induced systemic symptoms within 10 days. This is the first report of measurement of infective virions in recirculating nutrient solutions. Hydroponic producers should be aware of the potential for rapid spread of virus diseases in soilless growing systems as one infected plant can serve as a source of inoculum that can ultimately result in an epidemic.     

The Effects of Soil Salinity and Meloidogyne javanica on Tomato

A non-sodic, non-saline sandy loam soil was salinized to anion-cation ratios similar to those naturally occurring in Iraq and California. The interactions of saline soils (conductivities 4, 8, 12 and 16 mmhos/cm) with a moderately salt-tolerant plant (Lycopersicon esculentum ''Marimond'') and a plant parasitic nematode (Meloidogyne javanica) were investigated. Plant parasitic nematodes were shown to be an important modifying influence within the plant environment, either accentuating or ameliorating salinity stress effects.     

番茄果实不同发育阶段香气成分组成及变化

以陕西杨凌地区主栽的番茄品种'金棚1号'为试验材料,通过固相微萃取和GC/MS联用技术,对番茄果实不同成熟阶段的香气成分及其组成变化进行了研究.结果表明,'金棚1号'番茄果实共检测到54种香气成分,主要成分为醛类、酸类、醇类、酮类、酯类、酚类等.在果实的不同发育阶段,香味组分及其含量差异较大.醛类物质在绿熟期相对含量较高,为45.87%,在半熟期、硬熟期、完熟期的相对含量分别为12.65%、16.62%、17.15%,其中C6醛在绿熟期占43.7%,完熟期占15.27%,为醛类物质的主要成分;酸类物质含量在4个发育时期中先上升后下降,在半熟期含量达到最高,为15.2%,在完熟期酸类物质含量下降,为6.93%;酮类物质在完熟期含量达到最大,为18.27%;在绿熟期检测到4种重要的番茄特征香气物质,半熟期检测到5种番茄特征香气物质,硬熟期和完熟期各检测到6种番茄特征香气物质.说明随着果实的成熟,特征香气物质种类增多.     

Reversible Inhibition of Tomato Fruit Gene Expression at High Temperature (Effects on Tomato Fruit Ripening)

The reversible inhibition of three ripening-related processes by high-temperature treatment (38[deg]C) was examined in tomato (Lycopersicon esculentum L. cv Daniella) fruit. Ethylene production, color development, and softening were inhibited during heating and recovered afterward, whether recovery took place at 20[deg]C or fruit were first held at chilling temperature (2[deg]C) after heating and then placed at 20[deg]C. Ethylene production and color development proceeded normally in heated fruit after 14 d of chilling, whereas the unheated fruit had delayed ethylene production and uneven color development. Levels of mRNA for 1-aminocyclopropane-1-carboxylic acid oxidase, phytoene synthase, and polygalacturonase decreased dramatically during the heat treatment but recovered afterward, whereas the mRNA for HSP17 increased during the high-temperature treatment and then decreased when fruit were removed from heat. As monitored by western blots, the HSP17 protein disappeared from fruit tissue after 3 d at 20[deg]C but remained when fruit were held at 2[deg]C. The persistence of heat-shock proteins at low temperature may be relevant to the protection against chilling injury provided by the heat treatment. Protein levels of 1-aminocyclopropane-1-carboxylic acid oxidase and polygalacturonase also did not closely follow the changes in their respective mRNAs. This implied both differences in relative stability and turnover rates of mRNA compared to protein and nontranslation of the message that accumulated in low temperature. The results suggest that high temperature inhibits ripening by inhibiting the accumulation of ripening-related mRNAs. Ripening processes that depend on continuous protein synthesis including ethylene production, lycopene accumulation, and cell-wall dissolution are thereby diminished.     

花期减少施钙量对不同钙效率番茄果实钙形态和含量的影响

花期降低施钙量后,钙低效番茄品种L-402果实中钙含量显著降低,高效品种江蔬一号降低不显著,镁含量显著增加,钾含量有增加趋势。果实底端的钙含量高于顶端,降低施钙量后果实水溶性钙含量和比例显著提高,果胶酸钙含量和比例降低,磷酸钙含量也降低。钙低效品种L-402水溶性钙含量的增加,以及果胶酸钙和磷酸钙的降低程度,都大于高效品种江蔬一号,且降钙后果实顶端的革酸钙含量和比例增加。     

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.     

Chilling Injury Induces Lipid Phase Changes in Membranes of Tomato Fruit

Wide-angle x-ray diffraction has provided evidence for lipid phase separations in microsomal membranes from chill-injured tomato (Lycopersicon esculentum Mill. cv Caruso) fruit. Mature-green fruit stored for 20 d at 5[deg]C had not begun to ripen and were essentially free of chilling injury symptoms. Within 4 d of being returned to 25[deg]C, however, the fruit displayed characteristic symptoms of chilling injury, including translucent water-soaked patches, surface pitting, and irregular pigmentation. Membrane damage measured as electrolyte leakage from pericarp discs intensified after the fruit were returned to ambient temperature. Wide-angle x-ray diffraction patterns recorded at 25[deg]C for microsomal membranes isolated from untreated, mature-green fruit indicated that the membrane bilayers were exclusively liquid-crystalline. Diffraction patterns for microsomal membranes from fruit stored for 20 d at 5[deg]C showed only trace amounts of gel phase lipid, but within 4 d of subsequent exposure of the fruit to ambient temperature, there was evidence for a pronounced lateral phase separation of lipids within the membranes that would render them leaky. Inas-much as the phase separations were detectable at 25[deg]C and became pronounced only subsequent to the chilling episode, they appear to be an indirect rather than direct effect of exposure to low temperature. The diffraction data thus support the notion that the lipid phase changes observed here are not directly induced by low temperature but rather reflect subsequent biochemical changes in the bilayers that may contribute to the development of chilling symptoms.     

转反义PG基因番茄果实细胞结构变化的研究

经细胞学观察发现 ,转反义PG基因番茄果实在不同成熟期及存放前后 ,其果皮外面几层细胞的厚度都比未转基因的厚 1～ 5 μm ,细胞结构、细胞质和细胞核等的状态都有明显区别。尤以贮存后更为明显 ,未转基因果实的果皮细胞结构解体、细胞质凝聚、细胞核变的模糊程度都比转基因的严重。经外源乙烯处理后 ,转基因和未转基因果实的细胞结构也有相似的变化。结果表明 :反义PG基因的转入降低了PG活性 ,并且减弱了外源乙烯的作用 ,延缓了果实的衰老 ,提高了耐贮性能 ,从而起到果实保鲜作用     

Phosphorylation-Mediated Changes in Pyruvate Dehydrogenase Activity Influence Pyruvate-Supported Calcium Accumulation by Brain Mitochondria

Abstract: Changes in the activity of pyruvate dehydrogenase [pyruvate: lipoamide oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1, PDH], elicited by inhibition of the phosphorylation of its 40,000 M_rα-subunit, were compared with changes in pyruvate-supported calcium accumulation by rat brain mitochondria. Dichloroacetate (DCA) produces concentration-dependent inhibition of the phosphorylation of intramitochondrial PDH a-subunit, which is accompanied by stimulation of PDH activity and calcium accumulation. DCA did not affect succinate- or ATP-supported mitochondrial calcium accumulation. The concentration of DCA giving half-maximal inhibition of the phosphorylation was almost identical to that giving half-maximal stimulation of PDH activity and calcium accumulation. PDH activity and pyruvate-supported calcium accumulation showed similar dependence on pyruvate concentration with respective apparent affinities for pyruvate of 40 μ m and 30 μ m , and both activities exhibited positive cooperativity. DCA modified only the maximal activity of PDH or the maximal calcium accumulation without changing either the apparent affinities for pyruvate or calcium or the Hill coefficients. These data provide evidence that calcium accumulation by mitochondria is tightly linked to PDH activity and that changes in the phosphorylation of the PDH α-subunit can be reflected in changes in the calcium-buffering ability of mitochondria. This suggests a possible mechanism by which a variety of manipulations, such as repetitive synaptic stimulation, can alter the regulation of internal calcium levels.     

Effects of Various Concentrations of Iodine as Potassium Iodide on the Growth of Barley, Tomato and Pea in Nutrient Solution Culture

Iodine enhanced the height, number of tillers, fresh and dryweights of barley at concentrations of 0.5 and 1.0 ppm. With5.0 ppm the plants were indistinguishable from the untreatedcontrols. A dose of 10.0 ppm was inhibitory and induced symptomsof toxicity. In tomato, growth was increased at 0.5 ppm with maximum stimulationoccurring at 1.0 ppm. As in barley, 5.0 ppm exerted no effectand 10.0 ppm resulted in decreased growth, with toxicity symptomsevident. With pea, all iodine concentrations used led to reduced growth,the magnitude of the effect and the severity of the toxicitysymptoms increasing with concentration. The symptoms of toxicity in barley included general chlorosis,yellow intervenal patches, and brown necrotic spots. The lattertended to coalesce to form streaks. Death of some leaves resulted.Rather similar symptoms developed in tomato and pea, but nonecrotic spots were observed in the latter.     

Effects of Salinity and Nutrient Addition on Mangrove Excoecaria agallocha

Effects of salinity on seed germination and growth of young (1 month old) and old (2-year old) seedlings of Excoecaria agallocha were investigated. Combined effects of salinity and nutrient level were also examined on old seedlings. Seed germination was best at 0 and 5 psu salinity. 15 psu salinity significantly delayed root initiation and decreased final establishment rate. All seeds failed to establish at 25 psu salinity. Young seedlings performed best at 0 and 5 psu, but growth was stunned at 15 psu, and all seedlings died within 90 days at 25 psu. Old seedlings grew best at salinities below 5 psu and they survived the whole cultivation at 25 psu. This indicated that E. agallocha increased salt tolerance over time. Gas exchange was significantly compromised by salinities above 15 psu but evidently promoted by high nutrient. Proline accumulated considerably at high nutrient, and its contents increased from 0 to 15 psu but decreased at 25 psu salinity. Lipid peroxidation was aggravated by increasing salinity beyond 15 psu but markedly alleviated by nutrient addition. These responses indicated that E. agallocha was intolerant to high salinity but it can be greatly enhanced by nutrient addition.