Electrophoretic Variation in Esterases, Peroxidases and Acid Phosphatases in Some Native Greek Taxa of the Genera Hordeum and Taeniatherum

Horizontal starch gel electrophoresis has been applied to thestudy of esterase, peroxidase and acid phosphatase patternsin seven taxa, namely Hordeum diploids (2n=14) (H. marinum,H. marinum I and H. hystrix), tetraploids (2n=28) (H. bulbosumand H. murinum subsp. leporinum) and Taeniatherum (2n=14) (T.caput-medusae and T. caput-medusae I) in order to elucidatetheir phylogenetic relationships. On the basis of our experimentalresults the seven taxa may be placed in the following threegroups; (1) diploid Hordeum (H. marinum, H. marinum I, H. hystrix);(2) tetraploid Hordeum (H. bulbosum, H. murinum subsp. leporinum);(3) Taeniatherum (T. caput-medusae, T. caput-medusae I). Esterase, peroxidase and acid phosphatase patterns of the twoHordeum diploid taxa (H. marinum and H. marinum I) are verysimilar suggesting their close phylogenetic relationship; thesame is true for both the taxa of the genus Taeniatherum (T.caput-medusae and T. caput-medusae I). The taxa of the Taeniatherumgroup compared with the diploid Hordeum (H. marinum, H. marinumI, H. hystrix) and the tetraploid Hordeum (H. bulbosum, H. murinumsubsp. leporinum) show a lower degree of phylogenetic relationshipand seem to be equally distant from them. The tetraploid Hordeumgroup shows a higher phylogenetic relationship with diploidHordeum group than with the Taeniatherum group. These results confirm that the genus Taeniatherum, previouslyconsidered as part of the genus Hordeum, should be regardedas a separate genus. Gramineae (Poaceae), Hordeum L., Taeniatherum Nevski., esterase, peroxidase and acid phosphatase patterns, phylogenetic relationships     

Estimating the capacity for improvement in risk prediction with a marker

Consider a set of baseline predictors X to predict a binaryoutcome D and let Y be a novel marker or predictor. This paperis concerned with evaluating the performance of the augmentedrisk model P(D = 1|Y,X) compared with the baseline model P(D= 1|X). The diagnostic likelihood ratio, DLR_X(y), quantifiesthe change in risk obtained with knowledge of Y = y for a subjectwith baseline risk factors X. The notion is commonly used inclinical medicine to quantify the increment in risk predictiondue to Y. It is contrasted here with the notion of covariate-adjustedeffect of Y in the augmented risk model. We also propose methodsfor making inference about DLR_X(y). Case–control studydesigns are accommodated. The methods provide a mechanism toinvestigate if the predictive information in Y varies with baselinecovariates. In addition, we show that when combined with a baselinerisk model and information about the population distributionof Y given X, covariate-specific predictiveness curves can beestimated. These curves are useful to an individual in decidingif ascertainment of Y is likely to be informative or not forhim. We illustrate with data from 2 studies: one is a studyof the performance of hearing screening tests for infants, andthe other concerns the value of serum creatinine in diagnosingrenal artery stenosis.     

Existence of a Common Glycoprotein Homologous to S-Glycoproteins in Two Self-incompatible Homozygotes of Brassica campestris

S-Glycoproteins (S-locus-specific glycoproteins) in Brassicaspecies are present only in stigmas and thought to play an importantrole in self-incompatibility system. The stigma extract containsalso several other glycoproteins reacting with the antiserumto S-glycoproteins, among which some glycoproteins from S₈S₈-and S₉S₉-homozygotes have the same pI value. Both of the glycoproteinswhich were tentatively termed NS₈- and NS₈S₉-glycoproteins,respectively, were isolated and analyzed. Those were revealedto be identical. Its amino acid sequence was homologous withthe S-glycoproteins in Brassica species. The NS-glycoproteinswere expressed at the same time and only in stigma as S-glycoproteins. (Received July 19, 1988; Accepted September 7, 1988)     

The GUS reporter-aided analysis of the promoter activities of Arabidopsis ACC synthase genes AtACS4, AtACS5, and AtACS7 induced by hormones and stresses

Ethylene biosynthesis in higher plants is regulated developmentallyand environmentally. To investigate the regulation of ACC synthasegene expression, the promoters of Arabidopsis ACS genes, AtACS4,AtACS5, and AtACS7, were fused to a GUS reporter gene, and therecombinant transgenes were introduced into Arabidopsis to producethree groups of AtACS::GUS transgenic plants. Histochemic andfluorometric study of these transgenic plants revealed thatpromoters of AtACS4, AtACS, and AtACS7 are all active in dark-germinatedseedlings. AtACS5 has the highest promoter activity in leavesof 2-week-old light-grown seedlings among the three AtACS genesstudied. In the mature leaves, AtACS4 and AtACS7 genes are expressedin both veins and areoles, whereas AtACS5 is expressed at ahigher level in the areoles and epidermal cells surroundingtrichomes. The promoter activities of all these AtACS genesare found in the reproductive organs. AtACS5 and AtACS7 arehighly expressed in petals, sepals, carpels, stamens, caulineleaves, inflorescence stems, and siliques, while AtACS4 expressionis undetectable in the petals of open flowers. All three AtACSgenes are expressed in root tissue. In the 2-week-old light-grownArabidopsis, the AtACS4 promoter is responsive to the planthormones IAA, ethylene, and ABA, and to darkness and wounding;the AtACS5 promoter to IAA, ABA, salt, high temperature, andwounding; and the AtACS7 promoter to GA₃, ethylene, and ABA,and to darkness and salt. Low-temperature treatment abolishesthe darkness-induced AtACS7 gene expression, but not that ofAtACS4. Each AtACS gene has a unique expression profile duringgrowth and development. It appears that at any developmentalstage or any growth period of Arabidopsis, there is always amember of AtACS multigene family that is actively expressed. Key words: ACC synthase, Arabidopsis, ethylene, gene expression, GUS histochemical staining, reporter, stress treatments     

The FLOWERING LOCUS T/TERMINAL FLOWER 1 family in Lombardy poplar

Genes in the FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1)family have been shown to be important in the control of theswitch between vegetative and reproductive growth in severalplant species. We isolated nine members of the FT/TFL1 familyfrom Lombardy poplar (Populus nigra var. italica Koehne). Sequenceanalysis of the members of the FT/TFL1 family revealed considerablehomology within their coding regions both among family membersand to the members of the same family in Arabidopsis, tomatoand grapevine. Moreover, members of this family in all fourspecies examined display a common exon–intron organization.Phylogenetic analysis revealed that the genes fall into fourdifferent clades: two into the TFL1 clade; five into the FTclade; and one each into the MOTHER OF FT AND TFL1 and BROTHEROF FT AND TFL1 clades. One gene in the TFL1 clade, PnTFL1, isexpressed in vegetative meristems, and transgenic Arabidopsisthat ectopically expressed PnTFL1 had a late-flowering phenotype.The expression patterns of two genes in the FT clade, PnFT1and PnFT2, suggested a role for them in the promotion of flowering,and transgenic Arabidopsis that ectopically expressed eitherPnFT1 or PnFT2 had an early-flowering phenotype.     

Effect of Radiation and Temperature on Efficiency of Cereal Leaves during Grain Growth

Grain: leaf ratio, G (the ratio of grain yield to leaf areaduration between ear emergence and maturity), in 15 experimentson wheat and barley in different seasons (Group A experiments)was highly correlated with mean daily radiation, R, mean dailytemperature, T_µ, and mean daily maximum temperature, T_max,during the grain growth period. The regression of G on R accountedfor 81 per cent of the variance of G, and introducing T_µto the regression significantly increased this to 88 per cent.The regression of G on T_max alone accounted for 87 per cent,perhaps because T_max effectively integrates radiation and temperature. When R was varied artificially by shades in two experimentson wheat in different years (Group B experiments) the relationshipbetween G and R was approximately linear in both, but the slopeof the line was less in one year, when R and temperature wereless, than in the other. For this second year, when R and temperatureswere about the middle of the ranges found in Group A experiments,the calculated relationship agrees with the Group A resultsafter correcting values of G for differences of Tu from itsvalue in the shading experiment. A formula relating G and Rderived from the results of both Group B experiments and theobserved correlation of R and temperature in the field, assumingthat the regression of G on R depends on temperature, agreeswith the relationship between G and R in the Group A experiments. It is concluded that differences in radiation and temperatureare about equally responsible for the differences in G foundbetween seasons. The positive effect of temperature on G suggeststhat factors other than leaf photosynthesis, e.g. translocationrate or capacity of the grain to accumulate carbohydrate, areimportant in determining G.     

Water Import Rate in Tomato Fruit: A Resistance Model

A model of the water import rate in tomato fruit is proposed.It compares the fruit to a hollow sphere (P) with external radiusR and internal radius R_G, corresponding to pericarp, and containingan internal spherical part (G). The pathway limiting water inputrate at any point I at a distance r from the fruit centre wasassumed to be proportional: (a) in P, to the length of the arcwhich has a radius r and which goes from I to the pedicel extension;(b) in G, to r. The water input rate at I was modelled basedon a law similar to Darcy's law which takes into account thedifference between the water potential at entry of fruit andthe water potential at point I. This latter potential was thesum of fruit osmotic potential and pressure potential due toresistance of tissue to deformation. This potential was proportionalto R-r or R_G -r. The model was expressed at fruit level by alaw such that water mass imported per unit time per unit surfacearea of fruit (f_rw) was a linear function of R. The model wascompared to linear regressions of this rate in terms of R whichhad been found during fruit swelling from published results,and which were obtained at different values of nutrient solutionsalinity. The results suggested that water input in tomato fruitis conditioned by passive forces depending on fruit size.Copyright1994, 1999 Academic Press Fruit, growth, model, resistance, salinity, size, tomato, transfer, water     

Leaf Properties Related to the Photosynthetic Response to Drought in Upland and Lowland Rice Varieties

Four upland and two lowland varieties were grown on floodedand dry soil in pots in a glasshouse. Photosynthetic rate (P),transpiration rate (T), and water content (W) of the secondexpanded leaf from the top of the main stem were measured undercontrolled aeration and illumination in a leaf chamber in thelaboratory, together with leaf area (La), dry matter content(DM), nitrogen content (N), stomatal frequency (Sf), and totalvessel cross-sectional area at the base of the leaf blade (Va).P/La was positively related to T/La and Sf/La among six varietieswhen they were grown on flooded soil. IR 8, a semidwarf indicalowland variety, showed the highest P/La with the highest Sf/Laand T/La. When grown on dry soil P/La was positively correlatedwith W/DM, the latter being negatively related to T/Va. Twoupland varieties, African Moroberekan and Brazilian IAC 1246,showed the highest P/La on dry soil, keeping a higher W/DM witha lower T/La and a lower T/Va. Daytime leaf diffusive conductance(l/r_L) and leaf water potential (_L) measured on the same orthe same stage leaf in the glasshouse were positively correlatedwith the W/DM measured in the laboratory among varieties grownon dry soil. Simultaneous observation of P, T and W in the laboratoryindicated nonstomatal reduction in P/La due to leaf water deficitin sensitive varieties, although these varieties also showeda markedly lower daytime l/r_L in the glasshouse as comparedwith resistant varieties. Oryza sativa L., rice, drought resistance, photosynthesis, transpiration, water deficit, stomatal frequency, vessel size     

Intergeneric and Interspecific Relationships in Araceae tribe Caladieae and Development of Molecular Markers using Amplified Fragment Length Polymorphism (AFLP)

Since amplified fragment length polymorphism (AFLP) analysishas proved useful in distinguishing cultivars of Caladium, itwas used to assess the status of species of Caladium vs. Xanthosoma,both in tribe the Caladieae, and to reassess the position ofHapaline in the same tribe. AFLP analysis using three primercombinations was carried out on four species of Caladium(C.bicolor, C. humboldtii, C. lindenii and C. schomburgkii). Resultsshowed that AFLP can distinguish between the different speciesby their unique and different banding patterns. AFLP analysisconfirmed that C. humboldtii is a species distinct from C. bicolorand that C. lindenii is a true Caladium species and does notbelong to Xanthosoma. UPGMA cluster analysis showed that C.bicolor and C. schomburgkii are most similar and that C. humboldtiiis closer to the C. bicolor / C. schomburgkii cluster comparedwith C. lindenii. Genetic relationships between Caladium, Xanthosoma,Hapaline, Alocasia and Protarum were also examined by AFLP analysisusing eight primer combinations. Several useful molecular markerswere specific either to Caladium orXanthosoma , so that AFLPcan be used to distinguish species of these two genera. Geneticanalysis of the genera examined confirms that the Caladieaeand Colocasieae tribes are distinct and that Hapaline fallswithin the tribe Caladieae and that Protarum is most distantfrom all the genera examined. Copyright 2000 Annals of BotanyCompany Araceae, Caladium, Xanthosoma, Hapaline, Alocasia, Protarum, AFLP DNA fingerprinting, diversity, AFLP markers     

Identification of Stylar RNases Associated with Gametophytic Self-Incompatibility in Almond (Prunus dulcis)

Stylar proteins of 13 almond (Prunus dulcis) cultivars withknown S-genotypes were surveyed by IEF and 2D-PAGE combinedwith immunoblot and N-terminal amino acid sequence analysesto identify S-RNases associated with gametophytic self-incompatibility(SI) in this plant species. RNase activities corresponding toS_a and S_b, two of the four S-alleles tested, were identifiedby IEF and RNase activity staining. The S_a-RNase band reactedwith the anti-S₄serum prepared from Japanese pear (Pyrus serotina);no reaction with the antiserum was observed with the s_bRNaseband. When the s_a-RNase band was excised from an IEF gel stainedfor RNase activity, subjected to SDS-PAGE, and detected by immunoblotting,it appeared that this band consisted of a single protein thatreacted with the anti-s₄serum with M_r of about 28 kDa. With2D-PAGE and silver staining of the stylar extracts, all fourS-proteins could be successfully distinguished from each otherin the highly basic zone of the gel. Although S_b-, S_c-, andS_dproteins had roughly the same M_r of about 30 kDa, the S_c-proteinseemed to be slightly smaller than the S_b-protein and slightlylarger than the S_aprotein. In 2D-PAGE profiles as well, theS_a-protein had M_r of about 28 kDa, apparently smaller than theother three proteins. A bud sport, in which one of the two S-allelesof the original cultivar is impaired, was visualized as a lossof S_cprotein, which is consistent with the previous pollinationstudy. All four S-proteins reacted with the anti-S₄serum, probablybecause of the differing conformations of these S-proteins inthe IEF and 2D-PAGE gels. The S_a-protein in 2D-PAGE appearedto be identical to S_a-RNase in IEF; both bad the same M_r andwere reactive with the anti-S₄-serum. N-terminal amino acidsequence analysis of the four 5-proteins revealed that theywere highly homologous to each other and similar to the 5-RNasesof Malus, Pyrus, Scrophulariaceae, and Solanaceae. Taken together,RNases in the style are strongly suggested to be associatedwith the gametophytic SI of al- mond. This is the first reportidentofiying and characterizing S-RNase in almond. (Received July 11, 1996; Accepted December 26, 1996)     

Potential Dry Matter and Water Import Rates in the Tomato Fruit in Relationship to Fruit Size

The tomato fruit was compared to a sphere with a radius R. Radialgrowth rates in the fruit (F_IW and F_ID) due to water importor to dry matter import, respectively, which are also the waterimport rate or dry matter import rate per unit surface areaof fruit, were calculated from two sets of published results.This data referred to fruits which swelled in such a way thatthe availability of assimilates had little effect on growth.Two varieties differentiated the two series of results and inone series, three trials were differentiated by the salinityof the nutrient solution. In all trials, it was found that F_IW and F_ID decreased whenR increased. Two phases were observed for F_IW: after a firstphase, F_IW decreased more quickly and almost linearly when Rincreased. F_ID was constant or decreased with respect to R.Except at the beginning of growth at the greatest salinity,there were clearly linear regressions between F_IW and F_ID suchas F_ID = aF_IW-b; where b was lower with higher salinity. Thechanges of the concentration of imported dry matter (F_ID/F_IWwere examined in terms of R and F_IW/R. The mechanisms controllingthe changes in F_IW and F_ID were discussed. The results suggestedfruit radius was an important parameter of these mechanisms.Thus, water import rate and dry matter import rate could eachbe considered to be the product of two factors: fruit surfacearea, which is directly dependent on fruit radius, and waterimport rate or dry matter import rate per unit of fruit surfacearea.Copyright 1993, 1999 Academic Press Dry matter, fruit growth, logistic model, sink size, tomato, water transfer     

Relationships Between Climate and Flowering of Eight Herbs in a Swedish Deciduous Forest

Effects of annual variation in rainfall, temperature and humidityon flowering abundance of eight temperate woodland plants (Anemonenemorosa, Cardamine bulbifera, Lamiastrum galeobdolon,Oxalisacetosella , Ranunculus ficaria, Stellaria holostea, Viola reichenbachianaand Viola riviniana) were studied during 12 consecutive years(1989–2000) in a hornbeam (Carpinus betulus) forest insoutheast Sweden. Above-average rainfall/humidity in late summerto early autumn of the preceding year increased flowering abundancein L. galeobdolon, O. acetosella, V. reichenbachiana, V. rivinianaand, especially, in R. ficaria, but not in S. holostea and A.nemorosa. Moreover, flowering of R. ficaria and O. acetosellawas positively related to rainfall/humidity during several partsof, or the entire, preceding year. On the contrary, floweringof S. holostea and A. nemorosa was closely related to low valuesof rainfall/humidity in autumn and/or winter of the precedingyear and also to low humidity in the current year in A. nemorosa.Two long periods (3–4 years) of increasing rainfall deficitcoincided with decreasing flowering abundance in most of thespecies, but not with decreasing vegetative development. Temperaturevariability was less consistently related to flowering. A coolperiod during the preceding summer or autumn seemed importantfor flowering in L. galeobdolon, O. acetosella and the Violaspecies, although these relations were, at least partly, causedby interactions with rainfall/humidity. No significant (P <0.05) correlations were found between flowering and the conditionsprevailing in April to May—the main flowering season—ofthe current year. Copyright 2001 Annals of Botany Company Climate, flowering, rainfall, temperature, Anemone nemorosa, Cardamine bulbifera, Lamiastrum galeobdolon, Oxalis acetosella, Ranunculus ficaria, Stellaria holostea, Viola reichenbachiana, Viola riviniana     

The Regulatory Functions of the rolB and rolC Genes of Agrobacterium rhizogenes are Conserved in the Homologous Genes (Ngrol) of Nicotiana glauca in Tobacco Genetic Tumors

To compare patterns of expression between the Ngrol genes ofN. glauca and the Rirol genes of Agrobacterium rhizogenes, weperformed fluorometric and histochemical analysis of transgenicgenetic tumors on the hybrid of Nicotiana glauca x N. langsdorffü(Fl) that harbored a rß- glucuronidase (GUS) reportergene fused to the promoter of NgrolB, NgrolC, RirolB or RirolC The promoters of NgrolB and NgrolCNgrolC had 2- to 3-fold loweractivity than those of RirolB and RirolC However, the changesin patterns of GUS activity caused by deletion of NgrolB andNgrolCpromoters were similar to those of RirolB and RirolC promoters.This result suggests that the cis-acting sequences that regulatethe level of expression of RirolB and RirolC are conserved inthe NgrolB and NgrolC promoters. Furthermore, an auxin dependent(NAA-dependent) increase in GUS activity was observed in thecase of NgrolB-GUS and RirolB-GUS. Histochemical analysis showedGUS activity encoded by both NgrolB-GUS and RirolB-GUS in normal-typeFl transgenic plants was located in meristematic zones, whilethat encoded by NgrolC-GUS and RirolC-GUS was detected mainlyin vascular systems of various organs. Thus, the patterns ofexpression of the Ngrol genes were the same as those of theRirol genes in terms of promotion by auxin and tissue-specificity,indicating that regulatory mechanisms for both sets of geneshave been conserved during the evolution of the genus Nicotianaafter transfer from a progenitor of Agrobacterium to that ofNicotiana. (Received May 2, 1995; Accepted June 13, 1995)     

VINYL PHEOPORPHYRIN A5 IN THE INNER SEED COATS OF PUMPKINS

The pigments contained in the inner seed coats of Cucurbitapepo, C. maxima and C. moschata were investigated spectroscopicallyusing both intact tissues and their ether extracts. The pigment(s) contained in C. pepo and C. maxima was inferred to be "protochlorophyll"and/or Mg vinyl pheoporphyrin a₅ which are indistinguishablefrom each other by mere spectroscopic observations. The coatsof C. moschata were found to contain Mg-free vinyl pheoporphyrina₅ which has so far been reported to exist only in some Chlorellamutants. The spectra of these pigments in intact tissues wereremarkably different from those of the ether extracts, indicatingthe profound difference in their physical states in vitro andin vivo. It was discussed that the "protochlorophyll b" reportedearlier by SEYBOLD and EGLE might have been vinyl pheoporphyrina₁. (Received July 14, 1960; )     

Four TFL1/CEN-Like Genes on Distinct Linkage Groups Show Different Expression Patterns to Regulate Vegetative and Reproductive Development in Apple (Malusxdomestica Borkh.)

Recent molecular analyses in several plant species revealedthat TERMINAL FLOWER1 (TFL1) and CENTRORADIALIS (CEN) homologsare involved in regulating the flowering time and/or maintainingthe inflorescence meristem. In apple (Malusxdomestica Borkh.),four TFL1/CEN-like genes, MdTFL1, MdTFL1a, MdCENa and MdCENb,were found and mapped by a similar position on putatively homoeologouslinkage groups. Apple TFL1/CEN-like genes functioned equivalentlyto TFL1 when expressed constitutively in transgenic Arabidopsisplants, suggesting that they have a potential to complementthe TFL1 function. Because MdTFL1 and MdTFL1a were expressedin the vegetative tissues in both the adult and juvenile phases,they could function redundantly as a flowering repressor anda regulator of vegetative meristem identity. On the other hand,MdCENa was mainly expressed in fruit receptacles, cultured tissuesand roots, suggesting that it is involved in the developmentof proliferating tissues but not in the control of the transitionfrom the juvenile to the adult phase. In contrast, MdCENb wassilenced in most organs probably due to gene duplication bythe polyploid origin of apple. The expression patterns of MdTFL1and MdCENa in apple were also supported by the heterologousexpression of β-glucuronidase fused with their promoterregions in transgenic Arabidopsis. Our results suggest thatfunctional divergence of the roles in the regulation of vegetativemeristem identity may have occurred among four TFL1/CEN-likegenes during evolution in apple.     

Efficacy of Fungicides for Control of Phytophthora Leaf Blight of Taro

Six fungicides were evaluated under greenhouse, laboratory,and dryland field conditions for control of Phytophthora leafblight of taro incited by P. colocasiae. Five separate criteriawere utilized to evaluate these fungicides: fungicidal activityin vitro; and fungicidal activity in vivo under conditions ofsimulated dew, simulated rainfall, greenhouse, and dryland fieldenvironments. In in vitro tests zoospores were killed at thefollowing concentrations: Dithane M-45, 5 ppm; Difolatan, 9ppm; Polyram, 65 ppm; Tribasic Copper Sulphate, 145 ppm; Benlate,210 ppm; and Dyrene, 260 ppm. Excellent control was obtainedwith Difolatan; good control with Dithane M-45 and Polyram;and poor control with Benlate, Tribasic Copper Sulphate, andDyrene. Results of in vivo tests correlated with those of thein vitro tests. Difolatan, Benlate, and Dyrene were the mostphytotoxic while Tribasic Copper Sulphate, Polyram, and DithaneM-45 were the least phytotoxic.     

Native or Exotic? Double or Single? Evaluating Plants for Pollinator-friendly Gardens

In a series of dawn-to-dusk studies, we examined the natureand accessibility of nectar rewards for pollinating insectsby monitoring insect visits and the secretion rate and standingcrop of nectar in the British native plant species Salvia pratensis,Stachys palustris, S. officinalis, Lythrum salicaria, Linariavulgaris, the non-native Calendula officinalis, Petunia x hybrida,Salvia splendens, and the possibly introduced Saponaria officinalis.We also compared single with double variants ofLotus corniculatus, Saponaria officinalis, Petunia x hybrida andCalendula officinalis. All the British species studied are nectar-rich and are recommendedfor pollinator-friendly gardens. They showed maximal secretionrates of about 10–90 µg sugar per flower h^-1, andmost had mean standing crops of about 5–60 µg sugarper flower. In all British species studied, the corolla wasdeep enough for the relatively long-tongued bumblebee Bombuspascuorum, but the shallower flowers of Lythrum salicaria werealso much visited by shorter-tongued bees and hoverflies, aswell as by butterflies. The exotic Salvia splendens, presumablycoevolved with hummingbirds in the Neotropics, has such deepflowers that British bees cannot reach the nectar except bycrawling down the corolla. With a secretion rate approaching300 µg sugar per flower h^-1and little depletion by insects,S. splendens accumulated high standing crops of nectar. S. splendens,and single and double flowers of the two probably moth-pollinatedspecies Petunia x hybrida and Saponaria officinalis, receivedfew daytime visits despite abundant nectar but Calendula waswell visited by hoverflies and bees. We compared single anddouble variants of Lotus corniculatus,Petunia x hybrida andCalendula officinalis, and also Saponaria officinalis, the lastbeing probably introduced in Britain (Stace, 1997 New floraof the British Isles. 2nd edn. Cambridge: Cambridge UniversityPress). In Petunia, Saponaria and Lotus, double flowers secretedlittle or no nectar. In Calendula, where doubling involved achange in the proportion of disc and ray florets rather thanmodification of individual flower structure, double and singlecapitula had similar standing crops of nectar. Except inCalendula, exotic or double flowers were little exploited by insect visitors.In the exotics, this was probably due to the absence or scarcityof coevolved pollinators, coupled, in double flowers, with theabsence of nectar. Copyright 2001 Annals of Botany Company Salvia pratensis, Salvia splendens, Stachys palustris, Stachys officinalis,Lythrum salicaria , Linaria vulgaris, Lotus corniculatus, Saponaria officinalis,Petunia x hybrida, Calendula officinalis, wild flowers, double flowers, gardens, nectar, secretion rate, standing crop, pollinators, bumblebees, Bombus, honeybees, Apis, hoverflies, butterflies,Anthidium manicatum     

Reproductive Isolation in a Native Population of Petunia sensu Jussieu (Solanaceae)

Reproductive isolation was studied in four syntopic speciesof Petunia sensu Jussieu (Solanaceae) at a site in Rio Grandedo Sul State, Brazil. Reciprocal artificial crossing experimentsconfirmed that a genetic barrier exists between Petunia(P. axillarisand P. integrifolia) andCalibrachoa (C. parviflora and C. heterophylla),and also between C. parviflora andC. heterophylla . Petuniaaxillaris(white, nocturnally scented flower) is geneticallycompatible with the syntopic and allotopic P. integrifolia(coloured,unscented flower). Reproductive isolation appears to be maintainedby the two species having different pollinators: nocturnallyactive hawkmoths (Manduca contracta andM. diffissa subsp. petuniae)pollinate P. axillaris while a diurnally active bee (Hexanthedasp.) pollinates P. integrifolia. Flowers of P. integrifoliaexhibit diurnal opening and closing movements synchronous withthe activity period of the bee. Other than a probable nectarrobber (a carpenter bee, Xylocopa augusti), no insect visitedflowers of P. axillaris in the day. Amounts of floral nectarin P. axillaris and P. integrifolia were within the range ofhawkmoth- and bee-pollinated flowers, respectively. Reproductiveisolating mechanisms in the genus Petunia sensu Jussieu arediscussed. Copyright 2001 Annals of Botany Company Calibrachoa, hawkmoth, Petunia, Petunia axillaris, Petunia integrifolia, pollinator, reproductive isolation, Solanaceae