Flower Formation In vitro by Hypocotyl Explants of Cucumber (Cucumis sativus L.)

Hypocotyl explants of cucumber (Cucumis sativus L.) producedcallus when grown in Murashige and Skoog medium with 0.5 or1.0 µM benzyladenine and 1.5 or 5.0 µm 2, 4-D. Somaticembryos and adventitious buds were formed when callus was transferredto medium without growth regulators. Flowers that were formedin vitro were either staminate or pistillate. Cucumis sativus L, cucumber, embryogenesis, organogenesis, flowering in vitro     

Effects of Sink Demand on Photosynthesis in Cucumber

In Cucumis sativus L. net photosynthesis of leaf number 12 increaseduntil 12 d after its unfolding and then decreased gradually. Sink demand was varied by imposing the number of fruits perplant without changing the number of leaves per plant. Net leafphotosynthesis did not respond to sink demand during the first16 d of fruit growth. Subsequently, a substantial reductionin photosynthesis was found only when all fruits were removed.This reduction was accompanied by a decrease in the rate oftranspiration, indicating a higher stomataL resistance. Neither starch nor mono- and disaccharides accumulated noticeablyat reduced sink demand, suggesting that there was no end-productinhibition of photosynthesis. Dry matter content of the leaves increased and specific leafarea decreased when sink demand was reduced. When modelling cucumber production, effects of sink demand onleaf photosynthesis can be ignored. Key words: Cucumis sativus, photosynthesis, sink-source, sink demand     

Effect of Vanadate on Microsomal ATPase Activity, Acidification of the Medium and Auxin-stimulated Growth in Pea and Cucumber

The relationship between ATPase activity, medium acidificationand auxin-stimulated growth in segments of pea stem (Pisum sativumL., cv. Alaska) and cucumber hypocotyl (Cucumis sativus L.,cv. Long Green Ridge) was investigated using sodium orthovanadate,widely used as a selective inhibitor of plasma membrane-associatedATPase activity. ATPase activity of cucumber microsomal preparationswas about seven times lower than similar preparations from pea(on a mg microsomal protein basis) and was much more effectivelyinhibited by vanadate. Similarly, acidification of the mediumby abraded cucumber segments occurred to a lesser extent thanwith pea and showed a greater inhibition by vanadate. Both growthin controls and auxin-stimulated growth of cucumber segmentswere strongly inhibited by vanadate, whereas in pea auxin-stimulatedgrowth was reduced by only half and controls showed little inhibition.Acidification of the medium by segments of both species wasfound to occur readily even in controls and showed little promotionin the presence of IAA, although growth in both species wasrapidly and significantly promoted by IAA. These results indicatethat acidification is brought about by a plasma membrane-associatedATPase, and suggest that while acidification is an essentialfactor for auxin-stimulated growth it may not be the mechanismby which the growth rate is controlled. ATPase, Cucumis sativus, indole-3-acetic acid, Pisum sativum, vanadate     

Infection of Cucumber Cotyledons by Cucumber Mosaic Virus and the Participation of Chlorophyllase in the Development of Chlorotic Lesions

Cotyledon infection of cucumber (Cucumis sativus L. cultivarImproved Telegraph) results in abnormal growth and the appearanceof chlorotic lesions leading to general chlorosis of the cotyledons.The disease causes increased chlorophyll degradation and chlorophyllaseactivity. Virus-induced perturbations in chlorophyllase activityare discussed in relation to current concepts of the role ofthis enzyme in vivo.     

Canopy Photosynthesis of Tomato, Cucumber and Sweet Pepper in Greenhouses: Measurements Compared to Models

Two models for canopy photosynthesis (modified versions of thoseof Acock et al. , 1978 and of Thornley, 1976) were examinedby comparison with experimental photosynthesis data of cucumber(Cucumis sativus L.), sweet pepper (Capsicum annuum L.) andtomato (Lycopersicon esculentum Mill.). The data were obtainedin six large-scale, long-term, semi-commercial cultivationsin greenhouses (Nederhoff and Vegter, 1994). Measured environmentalconditions and measured LAI were input to the model. The emphasiswas on the models' sensitivity to the prevailing CO₂ concentration. The (modified) Acock model with 'standard' (originally published)parameters underestimated the photosynthesis rate. This modeltuned to one of our experimental data sets did not fit verywell to the other data sets. As expected, if the model was tunedto each particular data set, it was fairly in agreement withthe measurements, but the fitted parameter values were sometimesquestionable. With the (modified) Thornley model it was obligatoryto estimate or tune the light extinction. The model performedreasonably if all parameters were tuned and also if only thelight extinction was tuned. The modified models were considered usable for practical applications,after parameter tuning. As the sensitivity to CO₂ was not alwaysequal among the models and the measurements, care should betaken when applying the models for CO₂ supply control.Copyright1994, 1999 Academic Press Canopy photosynthesis, Capsicum annuum L., carbon dioxide, cucumber, CO₂, Cucumis sativus L., glasshouse, greenhouse, Lycopersicon esculentum Mill., measurements, model, sweet pepper, tomato     

The Effects of a Hydrogel Polymer on the Growth of Certain Horticultural Crops under Saline Conditions

The effects of incorporating a hydrogel polymer into sand onthe development of selected horticultural plants grown undersaline conditions has been demonstrated. In separate experiments,the seeds of tomato (Lycopersicon esculentum Mill.), lettuce(Lactuca sativa L.) and cucumber (Cucumis sativus L.) were germinatedin sand/swollen hydrogel polymer mixture (25: 75, v: v) withadded Hoagland nutrient solution. At cotyledon + first trueleaf stage, the plantlets were transplanted into polythene growbagscontaining a range of sand/swollen hydrogel polymer combinations(0: 100, 25: 75, 50: 50, 75: 25 and 100: 0, v: v). Saline solutionscontaining NaCl, CaCl² and MgCl² were prepared as molar solutionsand applied at combined concentrations as follows; Control (Hoagland),2000, 4000, 8000, and 32 000 ppm. Application of the appropriatesolution to the growbags was made twice per week, alternatingwith a comparable watering regime. Harvesting was carried outafter 14 and 28 d. Polymer incorporation encouraged growth ofall species under all saline conditions, the order of effectivenessof the polymer contents being as follows; 75%>50% 25% 100%>0%.At high salinity (32 000 ppm) plants of the test species werereduced in growth but appeared to be tolerant at all levelsof polymer incorporation; in pure sand the level of tolerancein tomato and cucumber was <8000 ppm and in lettuce <4000 ppm. Generally, dry weight, leaf area, succulence, chloroplastpigments (chlorophyll a, chlorophyll b, and carotenoids), photosyntheticactivity, total amino acids, proline, and protein contents wereincreased with polymer incorporation compared with pure sand.This hydrogel polymer appears to be highly effective for useas a soil conditioner in horticulture, to improve crop toleranceand growth in a sand or light gravel substrate under salineconditions. It is intended to confirm the results of these studiesby field trials. Key words: Tomato (Lycopersicon esculentum Mill.), lettuce (Lactuca sativa L.), cucumber (Cucumis sativus L.), salinity, hydrogel, polymer, salt tolerance, growth, free amino acid, free proline, and protein     

Cucumis sativus Cryptic Virus, a New Virus in Cucumber

Isometric virus-like particles (VLPs) have been purified from cucumber leaf tissue. Three dsRNA segments with estimated molecular weights of 1.8, 1.1 and 1.0 × 10⁶d have been isolated from VLPs occurring in CsCl density gradient fractions but were also readily detected in preparations from as little as 1 g of fresh leaf tissue. The VLPs resemble dsRNA containing cryptic viruses and have been named Cucumis sativus cryptic virus (CsCV).     

Intergeneric Translocation of Floral Stimulus across a Graft in Monoecious Cucurbitaceae with Special Reference to the Sex Expression of Flowers

The effect of floral stimulus on flower sex expression in monoeciouscucurbits was examined using a qualitative short-day plant,Sicyos angulatus L. Sicyos was induced to flower not only bygrafting it onto a flower-induced plant of the same speciesbut also by intergeneric grafting Onto the day-neutral plantCucumis sativus L. or the quantitative short-day plant Luffacylindrica Roem under noninductive long-day conditions. Sicyosplant grafted onto various cucumber varieties having differentgenetic backgrounds for their sex expression developed bothstaminate and pistillate inflorescences with similar sex expression.When the availability of floral stimulus was restricted as inthe case of grafting of Sicyos onto young cucumber seedlingsat the cotyledonary stage, most inflorescences appearing onthe Sicyos were staminate ones. Pistillate flowers formed onthe cucumber receptors substantially increased when they weregrafted onto Sicyos donors which had a sufficient number ofleaves induced by short-days as compared with those graftedonto noninduced ones. These results suggest that the availabilityof floral stimulus participates in the sex expression of flowersin Cucurbitaceae. Undeveloped pistillate inflorescences, whichoccasionally appear on Sicyos scion, flowered normally whenN⁶-benzylaminopurine was directly applied to the inflorescence. (Received February 27, 1981; Accepted October 16, 1981)     

Comparative Requirement for Endogenous Ethylene during Seed Germination

Requirement for endogenous ethylene during seed germinationof the following ten species was determined: Lycopersicon esculentumMill, (tomato), Allium cepa L. (onion), Avena fatua L., dormantpure line AN-51 (wild oats), Cucumis sativus L. (cucumber),Sinapis arvensis L. (wild mustard), Tagetes erecta L. (marigold),Raphanus sativus L. (radish), Triticum aeslivum L. (wheat),Catharanthus roseus L. (periwinkle), and Phaseolus aureus L(mung bean). Experiments were done under controlled conditionssuited for the germination of each species. Criteria used todetermine the need for endogenous ethylene were: (i) temporalrelationship between ethylene production and seed germination;(ii) parallel inhibition of ethylene synthesis and seed germinationby L-     

Hydrogen sulfide emission by cucumber leaves in response to sulfate in light and dark

Young leaf discs of cucumber (Cucumis sativus) emit H₂S at 50–100 pmol/min/cm² in response to 25 mM K₂SO₄ and light. The light-de     

The Effects of Silicon Supplementation on Cucumber Fruit: Changes in Surface Characteristics

Addition of silicate to hydroponic nutrient media has been shownto increase resistance of cucumber to powdery mildew. As a sideeffect of this treatment, the fruit surface developed an unusualdull appearance, or bloom. The effects of silicate supplementationon cucumber fruit were observed using scanning and transmissionelectron microscopy, energy-dispersive X-ray analysis, and colourimetricassays. Changes in the fruit trichome morphology occurred: trichomesfrom + Si fruit had a coarse outer appearance compared to -Si fruit where the trichomes were smooth. X-ray mapping showedhigh Si content in trichomes but not in the surrounding epidermisor fleshy mesocarp and endocarp tissues. Sections through theepidermal layer reveal that the silica is restricted to thetrichomes, primarily in the epicuticular wax.Copyright 1993,1999 Academic Press Cucumber, Cucumis sativus L., fruit, silica, energy dispersive X-ray analysis, trichomes     

Ethylene Production by Fe-deficient Roots and its Involvement in the Regulation of Fe-deficiency Stress Responses by Strategy I Plants

Species that showed marked morphological and physiological responsesby their roots to Fe-deficiency (Strategy I plants) were comparedwith others that do not exhibit these responses (Strategy IIplants). Roots from Fe-deficient cucumber (Cucumis sativusL.‘Ashley’), tomato (Lycopersicon esculentumMill.T3238FER) and pea (Pisum sativumL. ‘Sparkle’) plantsproduced more ethylene than those of Fe-sufficient plants. Thehigher production of ethylene in Fe-deficient cucumber and peaplants occurred before Fe-deficient plants showed chlorosissymptoms and was parallel to the occurrence of Fe-deficiencystress responses. The addition of either the ethylene precursorACC, 1-aminocyclopropane-1-carboxylic acid, or the ethylenereleasing substance, Ethephon, to several Fe-sufficient StrategyI plants [cucumber, tomato, pea, sugar beet (Beta vulgarisL.),Arabidopsis(Arabidopsis thaliana(L.) Heynh ‘Columbia’), plantago(Plantago lanceolataL.)] promoted some of their Fe-deficiencystress responses: enhanced root ferric-reducing capacity andswollen root tips. By contrast, Fe-deficient roots from severalStrategy II plants [maize (Zea maysL. ‘Funo’), wheat(Triticum aestivumL. ‘Yécora’), barley (HordeumvulgareL. ‘Barbarrosa’)] did not produce more ethylenethan the Fe-sufficient ones. Furthermore, ACC had no effecton the reducing capacity of these Strategy II plants and, exceptin barley, did not promote swelling of root tips. In conclusion,results suggest that ethylene is involved in the regulationof Fe-deficiency stress responses by Strategy I plants.Copyright1999 Annals of Botany Company. Arabidopsis (Arabidopsis thaliana(L.) Heynch), barley (Hordeum vulgareL.), cucumber (Cucumis sativusL.), ethylene, iron deficiency, maize (Zea maysL.), pea (Pisum sativumL.), plantago (Plantago lanceolataL.), ferric-reducing capacity, sugar beet (Beta vulgarisL.), tomato (Lycopersicon esculentumMill.), wheat (Triticum aestivumL.).     

Effect of Extractive Substances and Total Glycoside Fraction from Panax ginseng C. A. Meyer on Root Growth of Cucumis sativus L. Seedlings

We studied the effect of extractive substances (ES) and total glycoside fraction (TGF) from Panax ginseng on plant cell growth. The seeds of cucumber Cucumis sativus L., KIT variety, were used for the biological assay. The tested substances inhibited the primary root growth in Cucumis sativus seedlings. Actively growing seedlings were most sensitive to this effect.     

Development and characterization of microsatellite markers in Cucumis

This study provides a set of useful SSR markers and describes their development, characterization and application for diversity studies.Sixty one Cucumis SSR markers were developed, most of them (46) from melon (Cucumis melo L.) genomic libraries. Forty of the markers (30 melon and 10 cucumber SSRs) were evaluated for length polymorphism in a sample of 13 melon genotypes and 11 cucumber (Cucumis sativus L.) genotypes. PCR-amplification revealed up to six size alleles among the melon genotypes and up to five alleles among the cucumber genotypes, with mean gene-diversity values of 0.52 and 0.28 for melon and cucumber, respectively. These differences are in accordance with the known narrower genetic background of the cucumber. SSR data were applied to phylogenetic analysis among the melon and cucumber genotypes. A clear distinction between the ’exotic’ groups and the sweet cultivated groups was demonstrated in melon. In cucumber, separation between the two sub-species, C.sativus var. sativus and C.sativus var. hardwickii,was obtained. Conservation of SSR loci between melon and cucumber was proven by sequence comparisons. Received: 17 April 2000 / Accepted: 16 May 2000     

Antagonistic and Synergistic Interactions between Ancymidol and Gibberellins in Shoot Growth of Cucumber (Cucumis sativus L. )

Effects of the plant growth retardant, ancymidol, on the growthand morphology of the shoot system of cucumber (Cucumis sativusL. ) were investigated. Ancymidol inhibited stem elongation,reducing both number and length of internodes. Reduction inleaf area, attributable to a reduction in both cell size andnumber, was accompanied by an increase in chlorophyll per unitarea. The retardant decreased apical dominance and delayed anthesis.Gibberellic acid fully reversed ancymidol-induced inhibitionof stem elongation, internode length and production, and leafexpansion. GA_4/7 and ancymidol gave a synergistic promotionof stem elongation by increasing elongation of younger internodesand increasing internode production. Synergistic promotion ofpetiole elongation by this combination was also observed. Ancymidol,applied 7 d previously either to the shoot or root, severelyreduced the level of gibberellin-like activity in bleeding sapcollected from decapitated plants.     

Stimulation of Net Photosynthesis in Cucumber Leaf Discs: Effect of K-Glyoxylate and KCL

Incubation of leaf discs of Cucumis sativus in 15 mol m^–3K-glyoxylate (pH 4.6) doubled the rate of net photosynthesisat limiting CO₂ or HCO^–₃ compared with discs floated ondistilled water. When both control and treated discs were incubatedin Mes-TMAOH buffer at pH 5.0, K-glyoxylate still increasednet photosynthesis by as much as 70%. The tetramethylammoniumsalt (TMA-glyoxylate) was without effect but KCl enhanced netphotosynthesis. Both KCl and K-glyoxylate increased stomatalaperture at pH 5.0. At pH 7.5 (Mops-TMAOH), neither stomatalaperture or photosynthesis was altered by K-glyoxylate, KClor TMA-glyoxylate. None of these salts was found to stimulatephotosynthesis in isolated cucumber mesophyll cells over a rangeof pH values although the cells incorporated as much ¹⁴C-glyoxylateas did leaf discs. The data suggest that enhanced photosynthesisin leaf discs is not due directly to a stimulation of mesophyllcell photosynthesis but rather is a consequence of increasedCO₂ availability and decreased stomatal resistance at low pHin the presence of potassium. Key words: Cucumber, Photosynthesis, Potassium glyoxylate     

Photosynthesis of Stands of Tomato, Cucumber and Sweet Pepper Measured in Greenhouses under Various CO2-concentrations

The rate of net photosynthesis (P) of whole plant stands oftomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativusL.) and sweet pepper (Capsicum annuum L.) was measured in sixlong-term experiments in large greenhouses under normal operatingconditions and CO₂-concentrations between 200 and 1200 µmolmol^-1. The objective was to quantify the responses to lightand carbon dioxide and to obtain data sets for testing simulationmodels. The method of measuring canopy photosynthesis involvedan accurate estimation of the greenhouse CO₂ balance, usingnitrous oxide (N₂O) as tracer gas to determine, on-line, theexchange rate between greenhouse and outside air. The estimatedrelative error in the observed P was about ± 10%, exceptthat higher relative errors could occur under particular conditions. A regression equation relating P to the photosynthetically activeradiation, the CO₂ concentration and the leaf area index explained83-91% of the variance. The main canopy photosynthesis characteristicscalculated with the fitted regression equations were: canopyP_max 5-9 g m^-2 h^-1 CO₂ uptake; ratio P_max/LAI 1·5-3 gm^-2 h^-1; light compensation point 32-86 µmol s^-1 m^-2;light use efficiency (quantum yield) at low light 0·06-0·10µmol µmol^-1 and CO₂ compensation point 18-54 µmolmol^-1. The results were related to the prevailing conditions.Copyright1994, 1999 Academic Press Canopy photosynthesis, Capsicum annuum L., carbon dioxide, CO₂, CO₂ balance, CO₂ use efficiency, cucumber, _{Cucumis sativus} L., glasshouse, greenhouse, light use efficiency, Lycopersicon esculentum Mill., sweet pepper, tomato, tracer gas     

Thick Root Syndrome in Cucumber (Cucumis sativus L.): A Description of the Phenomenon and an Investigation of the Role of Ethylene

In commercial growth of horticultural plants in greenhouses,high financial losses are being suffered due to the so-calledthick root syndrome (TRS), a phenomenon characterized by severedeterioration of the root system. The early symptoms of TRSin cucumber (Cucumis sativus L.) are strongly curving rootsthat are swollen and superficially damaged. Research focusedon ethylene, as both the culture practice of cucumber and theknown effects of ethylene on root growth point to a possiblerole for this phytohormone in TRS. Ethylene induced root curvatureand swelling as well as damage of the epidermal layer and outercortex of roots of cucumber plants similar to TRS symptoms.Formation of root hairs was stimulated and root elongation wasalso severely inhibited by exogenous ethylene. However, basedon experiments with the ethylene inhibitor     

Modelling Light Absorption and Canopy Net Photosynthesis of Glasshouse Row Crops and Application to Cucumber

A model of light absorption and photosynthesis applicable toglasshouse row crops is constructed and applied to cucumber.Light absorption is calculated using a method suggested fordiscontinuous canopies; photosynthesis is modelled with a non-rectangularhyperbola. The predictions of this model are compared with experimentaldata in the preceding paper. Here the model is used to simulateresponses to light and CO₂ concentration and especially to examinethe effects of varying the parameters of the crop that can becontrolled by the grower. These include the number of plantsin each row, the number and width of the rows, the gap betweenrows, and the height of the crop. For example, it is shown that,for high values of crop net photosynthesis, the number of rowsis more important at high light than at low light, whereas cropheight is more important at low light than at high light. Theimplications of these and other findings are discussed. Key words: Cucumis sativus L., glasshouse crops, cucumber, model, light absorption, photosynthesis, CO₂, row crops, simulation