Evidence for Physically Distinct Systemic Signalling Pathways in the Wounded Tomato Plant

The physical pathway of a systemic signal linking local woundingand systemic synthesis of proteinase inhibitors was investigatedin tomato (Lycopersicon esculentum Mill. ‘Moneymaker’)plants. Lucifer Yellow was used to visualize wound induced flowin the xylem. Cuts under water or severe wounds (heat or largecrushing wounds) induced flows in the xylem to other parts ofthe plant in a pattern determined by the vascular architecture.The detailed distribution of systemic proteinase inhibitor activityfollowing these wounds was similar to the pattern of wound inducedflow in the xylem. Steaming the petiole of the wounded organdid not prevent the systemic induction of proteinase inhibitorby a severe wound. It was concluded that elicitors releasedby a severe wound were distributed systemically in the xylem.Small crushing wounds did not induce systemic flow in the xylembut did induce proteinase inhibitor activity in organs importingvia the phloem. Steaming the petiole of the wounded leaf preventedsystemic induction of proteinase inhibitor by small crushingwounds, a result which is consistent with the translocationof elicitors in the phloem. These results indicate the participationof more than one signalling pathway in the systemic inductionof proteinase inhibitor synthesis by wounding. Copyright 1999Annals of Botany Company Elicitors, proteinase inhibitors, Lycopersicon esculentum, signal pathway, vascular anatomy, wound response.     

Protein Phosphorylation in Plastids from Ripening Tomato Fruits {Lycopersicon esculentum)

Incubation of plastids isolated from ripening tomato fruits(Lycopersicon esculentum) with [     

RNA-dependent RNA Polymerase Activities in Tomato Plants Susceptible or Resistant to Tobacco Mosaic Virus

RNA-dependent RNA polymerase activities were measured in healthyand tobacco mosaic virus (TMV)-infected tomato plants, to investigatethe possibility that altered activity might be involved in theoperation of the Tm-I gene for resistance to TMV. Healthy, susceptibleand resistant plants had similar levels of enzyme activity.Infection with TMV strain 0, which is inhibited by Tm-I, causeda 2-fold increase in activity in susceptible plants but no increasein Tm-I plants. Infection with a number of strain 1 isolates,which overcome Tm-I resistance, led to a 2 to 4-fold increasein enzyme activity in resistant plants. RNA-dependent RNA polymerase, Tm-I resistance gene, tobacco mosaic virus, tomato, Lycopersicon esculentum     

Pressure -Flow Relationships, Xylem Solutes and Root Hydraulic Conductance in Flooded Tomato Plants

Roots of month-old tomato plants (Lycopersicon esculentumMill.)were flooded for up to 36h. Shoots were removed just below thecotyledonary node, and the roots subjected to external pneumaticpressures (     

Ultrastructure of Protein Crystals in Potato and Tomato Trichomes

Large protein crystals were located in the leaf and stem trichomesof Solanum tuberosum L. and Lycopersicon esculentum Mill. Inpotato the crystals ranged from 1.05 to 4.5 µm (average2.3 µm) on a side and in tomato they ranged from 1.16to 3.5 µm (average 2.7 µm) on a side. The proteinnature of the crystals was determined by histochemical stainingwith Coumassie brilliant blue R250 and aniline blue black. Thecrystalline structure of the inclusions was observed in ultrathinsections using electron microscopy. In potato, in cleared areasof the cytoplasm, ribosomes were observed scattered among proteinfilaments. The filaments were approximately 7 nm in diameter.Morphologically similar crystals were observed in the tomatotrichomes but the protein filaments were smaller (approximately4 nm in diameter). Protein crystals were also observed in palisadeand spongy parenchyma and epidermal leaf cells in tomato. Protein crystals, trichomes, potato, Solanum tuberosum L., tomato, Lycopersicon esculentum Mill., ultrastructure     

Structure and expression of a cDNA encoding a putative neoxanthin cleavage enzyme (NCE), isolated from a wilt-related tomato (Lycopersicon esculentum Mill.) library

Oxidative cleavage of a 9-cis xanthophyll probably representsthe key regulatory step in abscisic acid (ABA) biosynthesis.A transposon tagged maize (Zea mays) mutant vp14, provided theoriginal DNA sequence data needed to design a VP14 fusion proteincapable of catalysing this reaction in vitro. A cDNA encodinga similar protein has now been isolated from a wilt-relatedtomato (Lycopersicon esculentum Mill.) library. The tomato cDNAand derived amino acid sequence have been compared to thoseof maize and of other enzymes catalysing broadly similar oxidativecleavage reactions. The results of Northern analysis in tomatoindicated that mRNA levels of this vp14 homologue increaseddramatically in response to water stress. Key words: ABA biosynthesis, oxidative cleavage step, tomato     

Regulation of Leaf Shape in the Solanifolia Mutant of Tomato (Lycopersicon esculentum) by Plant Growth Substances

The solanifolia mutant (sf/sf) of tomato (Lycopersicon esculentum)produces leaves consisting of leaflets with entire margins,unlike the lobed leaflets of normal plants. Normal plants treatedwith gibberellic acid (GA₃) produced leaves with entire marginswhereas mutant plants exposed to 2-chloroethyl-trimethyl ammoniumchloride (CCC)—an inhibitor of gibberellin biosynthesis—producedlobing of leaflets. The leaf area of the mutant was significantlygreater than that of the normal, but was not significantly differentfrom GA₃-treated normal leaves. Similarly, in CCC-treated mutantleaves the leaf area was not different from that of normal untreatedleaves. These observations suggest that the sf/sf mutation affectsthe leaf shape through its effect on endogenous gibberellinsand/or inhibitory substances. Leaf shape, Lycopersicon esculentum, plant growth substances, tomato     

Thigmomorphogenesis: the Effect of Mechanical Perturbation and Ethrel on Stem Pithiness in Tomato [Lycopersicon esculentum (Mill.) Plants]

The stems of ‘Y’-shaped (double stemmed) tomato(Lycopersicon esculentum Mill.) plants were mechanically perturbed(MP) by stroking for 6 successive days. The treatment reducedelongation of the two stems by 40 per cent. When only one branchof the pair was treated, its length was reduced to the sameextent as the two branches in the previous treatment, whilethe elongation of the untreated branch was increased by 60 percent over that of the control. Withholding irrigation induced stem pithiness due to droughtstress in non-MP-plants. However, in MP-pretreated plants, thenumber of pithy internodes was markedly less and the degreeof severity of the disorder was reduced. Ethrel applicationmimicked the effects of MP on pithiness. In some unknown way,the plants are hardened by MP or Ethrel. Lycopersicon esculentum Mill, tomato, drought stress, thigmomorphogenesis, ethylene, pithiness     

Morphology of Leaf Surfaces of Tomato Cultivars in Relation to Possible Invasion into the Leaf by Pseudomonas syringae pv. tomato

The role of morphological characteristics of tomato leaves inthe infection process of the pathogen Pseudomonas syringae pv.tomato was studied in 15 cultivars of varying susceptibility.Natural openings such as stomata, broken trichomes and cuticularcracks were counted. It was found that susceptibility increasedin proportion to the number of these potential penetration sites.However, their role is probably limited because even in thehighly resistant cultivars there are enough natural openingsto enable successful bacterial penetration. Bacterial speck of tomato, Lycopersicon esculentum, phytopathogenic bacteria, plant morphology, Pseudomonas syringae pv. tomato, tomato     

The pathway for systemic electrical signal conduction in the wounded tomato plant

The pathway of a systemic electrical signal possibly linking wounding and the systemic synthesis of proteinase inhibitor was investigated in tomato (Lycopersicon esculentumMill. cv. Moneymaker) plants. Heat, causing wounding to a cotyledon, was used to induce both a travelling electrical signal and systemic proteinase inhibitor activity. Intracellular recordings of changes in the membrane potential of different cell types were measured in the petiole of leaf 1, the first true leaf, and impaled cells were identified by injection of fluorescent dye (Lucifer Yellow CH). No difference was found between the membrane potentials of the different cell types; the mean membrane potential of all the cell types was -148 ± 3 mV. Only sieve-tube elements and companion cells produced large (79 ± 3.3 mV) action-potential-like depolarisations following wounding, although smaller (23 ± 1.6 mV) depolarisations were observed in other cell types. It was concluded that the electrical signal possibly linking a wound stimulus in a cotyledon with the induction of systemic proteinase inhibitor synthesis was propagated in the sieve-tube element/companion cell complex.Abbreviations LYCH Lucifer Yellow CH - PI proteinase inhibitor This work was supported by the Biotechnology and Biological Sciences Research Council (UK).     

Analysis of Low-temperature Tolerance of a Tomato (Lycopersicon esculentum) Cybrid with Chloroplasts from a more Chilling-tolerant L. hirsutum Accession

Growth and photosynthesis of an alloplasmic tomato (cybrid),i.e. line AH47, containing the nuclear genome of the chilling-sensitivecytoplasmic albino mutant of L. esculentum Mill. ‘LargeRed Cherry’ (LRC) and the plastome of a more chilling-toleranthigh-altitude accession of the related wild species L. hirsutumHumb. & Bonpl. LA 1777, were investigated at an optimal(25/20°C) and suboptimal (16/14°C) day/night temperatureregime and their performance compared with that of both euplasmicparents. The cybrid shoot had a similar biomass and developmentrate to the nuclear tomato (L. esculentum) parent at both temperatureregimes. Compared with the biomass production of shoots grownat optimal temperature, the reduction in shoot biomass at suboptimaltemperature was smaller for L. hirsutum than for L. esculentumand the cybrid. This difference was related to a stronger inhibitionof leaf area expansion in L. esculentum and the cybrid in thesuboptimal temperature regime than in L. hirsutum. Irrespectiveof the temperature regime under which the plants were grown,photosynthetic performance and leaf pigment, carbohydrate andsoluble-protein contents of the cybrid resembled those of thenuclear parent. No advantages of the alien L. hirsutum chloroplastwith respect to growth and photosynthesis-related characteristicswere observed in the cybrid in the suboptimal temperature regime,indicating that the temperature sensitivity of the photosyntheticapparatus is regulated by nuclear genes. An adverse consequenceof interspecific chloroplast transfer was the increased susceptibilityto chill-induced photoinhibition of the cybrid. It is concludedthat cybridization is not a useful tool for improving low-temperaturetolerance of tomato. Copyright 2000 Annals of Botany Company Alloplasmic tomato, chloroplast, cybrid(ization), growth, low-temperature tolerance, Lycopersicon esculentum, L. hirsutum, photosynthesis, plastome, tomato     

Production of phenocopies of the lanceolate mutant in tomato using polar auxin transport inhibitors

Germinating seeds and regenerating shoot apical meristems oftomato exposed to the polar auxin transport inhibitors NPA andHFCA converted normal indeterminate growth of the shoot to thatof a determinate pattern. The inhibitors produced linear, tendril-likeshoots which phenocopied several forms of the homozygous lanceolatemutant in tomato. Key words: Tomato, Lycopersicon esculentum, tendril, IAA transport inhibitor, indoleacetic acid, NPA, HFCA     

Invertase Activity, Soluble Carbohydrates and Inflorescence Development in the Tomato (Lycopersicon esculentum Mill.)

The concentration of reducing sugars in the developing firstinflorescence of the tomato (Lycopersicon esculentum Mill.)increased steadily between the macroscopic appearance of theflower buds and the initial stages of fruit expansion. Overthis period sucrose concentrations remained relatively constant.The rise in reducing sugar concentration was accompanied byan increase in the activity of an acid invertase. In individualflower buds invertase activity rose to a maximum shortly beforeanthesis and declined sharply as the anthers dehisced. Increased planting densities and removal of source leaves reducedthe rate of dry matter accumulation by the first inflorescenceand increased the incidence of flower bud abortion. These changeswere correlated with reductions in reducing sugar concentrations,in reducing sugar/sucrose ratios and in acid invertase levels.Removal of young leaves at the shoot apex significantly increasedthe relative growth rate of the inflorescence and led to a substantialincrease in its invertase content. These treatments had relativelylittle effect on sucrose concentration in the inflorescence. The data are consistent with the operation of an invertase-mediatedunloading mechanism for transported sucrose at sinks in theflower buds. It is suggested that the retarded development ofthe first inflorescence and the high incidence of flower budabortion observed under conditions of reduced photoassimilateavailability are causally related to the decline in invertaseproduction in the flower buds. Possible mechanisms for the regulationof invertase synthesis in the flowers are discussed. Lycopersicon esculentum Mill, tomato, inflorescence development, invertase, sink activity     

Effects of Kinetin and Salinity on Germination of Tomato, Barley and Cotton Seeds

The effects of kinetin and the interaction between kinetin andsalinity on seed germination of three plant species namely Lycopersiconesculentum, Hordeum vulgare and Gossypium hirsutum were studiedKinetin was applied exogenously to the seeds in order to determinewhether this growth-promoting hormone would promote germinationand to see if osmotically-induced dormancy caused by NaCl couldbe alleviated The results indicate that kinetin is capable ofbreaking dormancy in these species and there is a significantinteraction with salinity in tomato and cotton Kinetin, germination, salinity, water stress, salt stress, Lycopersicon esculentum Mill, tomato, Hordeum vulgare L, barley, Gossypium hirsutum L, cotton     

Effects of Heat Stress on Carbon Transport from Tomato Leaves

Export of radioactive carbon from two cultivars of tomato, (Lycopersiconesculentum Mill.) leaves was inhibited in response to heat stress.Increasing temperatures resulted in a marked decrease in leafstarch levels. The depletion of starch concentration in theleaves was primarily due to hydrolysis and an inhibition ofstarch formation. At high temperatures, starch hydrolysis wasinhibited in Roma VF, a heat sensitive cultivar, while Saladette,a heat tolerant cultivar was not similarly affected. Calloseformation was found on phloem sieve tube plates of leaf petiolesexposed to 72 h of high temperatures. More sieve tube plateswere covered with a thicker callose layer in Roma VF than inSaladette. Lycopersicon esculentum (Mill.), tomato, carbon translocation, starch hydrolysis, callose, heat stress     

Ribulose-1,5-bisphosphate carboxylase from plants adapted to extreme environments

The K_m and V_max of ribulose-1,5-bisphosphate carboxylase (RuBPCase)in selenium absorbing plants (Astragalus flavus Barn., Astragalusrafaelensis Barn. and Stanleya pinnata Bril.) were similar toRuBPCase from tomato (Lycopersicon esculentum L. var. tropic).The pH optima for RuBPCase activity was 8.0 for L. esculentumand A. flavus and 7.0 for A. rafaelensis and S. pinnata. TheActivation Energy (E) values for the enzymes were as follows:A.flavus (21.37), S.pinnata (19.85), A. rafaelensis (19.12)and L. escudentum (18.58). The energy of activation was higherfor the desert plants as compared to the tomato. The Arrheniusplot curves were linear to 50?C far the desert plants as comparedto 45?C for tomato. Enzyme kinetics of RuBPCase from halophytic plants (Salicorniapacifica Stand., var. utahensis (Tidestrom) Munz. and Salicorniarubra Nels.) indicated the enzyme was at least as sensitiveto NaCl concentrations as the enzyme from tomato. (Received November 9, 1976; )     

Ethylene production and peroxidase activity during tomato fruit ripening

Peroxidase activity and enzymic production of ethylene werestudied in tomato fruits (Lycopersicon esculentum MILL.) at3 ripeness stages. As the fruit ripens, one isoperoxidase disappears,and 3 new ones are formed. Activity of peroxidase and of ethylene-formingenzyme both increased 3 to 4 times as the fruit ripened. Histochemicalstaining showed that peroxidase is confined to the outermostand innermost layers of the pericarp, the placental tissue andvascular tissues; stained particles were neither mitochondrianor plastids. (Received October 27, 1969; )     

Effect of Disbudding on Root Cytokinin Export and Leaf Senescence in Tomato and Tobacco

Bud removal and decapitation (disbudding) of plants of tomato(Lycopersicon esculentum Miller) and tobacco (Nicotiana tabacumL.) resulted in an increase in both the concentration and thetotal flux of cytokinin in bleeding xylem sap. There was a retardationin the rate of chlorophyll loss from leaves of disbudded plantsof both species. Ultrastructural examination of the chloroplastsof disbudded tomato plants revealed a maintenance of chloroplastintegrity, compared with chloroplasts from control plants. Itis suggested that the delaying of leaf senescence observed indisbudded plants is due to an increased availability of cytokininto these leaves.     

Effect of Heat Stress on Assimilate Metabolism in Tomato Flower Buds

Assimilate import by flower buds in two cultivars of tomato(Lycopersicon esculentum Mill.) was inhibited by heat stress.With increasing temperature, levels of sucrose in the sourceorgan increased while levels of starch decreased. The transportof radioactive carbon was correlated with the starch contentof the flower buds. In Saladette, a heat-tolerant cultivar,conversion of the imported carbon to starch occurred to a greaterextent than in Roma VF, a heat-sensitive cultivar. Uptake ofsucrose from agar medium by detached flower buds was negativelycorrelated with their internal ratio of sucrose to hexoses.Glucose uptake from agar medium by detached flower buds decreasedwith increasing temperatures. Sucrose hydrolysis was negativelyaffected by high temperatures, and this was more pronouncedin the heat-sensitive than in the heat-tolerant cultivar. Theeffect of heat stress on assimilate translocation from the leavesto the sink organ is discussed. Lycopersicon esculentum Mill., starch, sucrose, heat stress     

Differentiation of the Tapetum During Microsporogenesis in Tomato (Lycopersicon esculentum Mill.), with Special Reference to the Tapetal Cell Wall

During microsporogenesis and pollen maturation, the tapetumin anthers of tomato (Lycopersicon esculentum) underwent severalultrastructural changes and ultimately degenerated. The changesobserved related to the secretory function of the tapetum andto the transfer of materials from the cytoplasm to the surfaceof tapetal cells. Electron dense deposits, initially in thevacuoles, disappeared coincident with the appearance of orbiculeson the cell wall. The fibrillar wall of the tapetal cells loosened,presumably to facilitate transfer of materials through the wall.In Addition, membranous fragments were a consistent featurein the tapetum wall and may play a role in transport of materials.The cells of the inner tapetum (towards the connective) andouter tapetum (towards the epidermis) had different ultrastructuralfeatures. The cytoplasm of the outer tapetum was more electrondense and had a higher proportion of dictyosomes and mitochondriathan the inner tapetum, indicating the greater secretory natureof the outer tapetum. The plastids and mitochondria also differedin morphology between the two regions. Degenerations of thetapetal cytoplasm began by the vacuolate microspore stage. Atanthesis, cytoplasm was absent but the orbicular wall of thetapetum remained appressed to the wall of the middle layer ofthe anther.Copyright 1993, 1999 Academic Press Lycopersicon esculentum, microsporogenesis, pollen development, tapetum development, tomato, ultrastructure