Embryo-suspensor of Tropaeolum majus: Identification of gibberellin A63

Embryos and suspensors of Tropaeolum majus at the same stages of seed development were analysed for gibberellins by GC-MS. GA₆₃ was the only gibberellin present in both tissues. The amount of GA₆₃ in the suspensor is higher than in the embryo.     

Nectar Production and Floral Characteristics of Tropaeolum majus L. Grown in Ambient and Elevated Carbon Dioxide

Tropaeolum majus (nasturtiums) were grown from seed in growthcabinets, under 380 and 750 ppmv CO₂. Elevated CO₂significantlyincreased nectar secretion rate, both in flowers milked of nectardaily and in once sampled, 3-d-old flowers. Elevated CO₂didnot affect time to flowering, total number of flowers produced,pollen to ovule ratio, or the total or individual concentrationsof nectar amino acids. The dry weight and longevity of individualflowers was also unchanged. Nectar sugar content was unchangedby elevated CO₂in a subset of flowers used to assess the 3-d-oldnectar volume. This subset did not show the same increase innectar volume under elevated CO₂as the full set, resulting inthe concentration of sugars remaining unchanged. Overall, thequantity rather than the quality of the nectar changed underelevated CO₂while flower characteristics remained constant,implying that the identity of pollinators may remain the samewhile foraging behaviour (e.g. number of visits per plant, distancetravelled) may change in the future. Copyright 1999 Annals ofBotany Company Tropaeolum majus, nasturtiums, elevated CO₂, nectar, phenology, floral characteristics, amino acids, pollinator-plant interactions.     

Acid phosphatase activity in plastids (plastolysomes) of senescing embryo-suspensor cells

Autolysis of the suspensor, an embryonal haustorium, starts in the basal cells and proceeds in the direction of the embryo. InPhaseolus vulgaris, acid phosphatase activity is first found in transforming plastids, similar to the acid phosphatase activity inPh. coccineus [Nagl (1977) Z. Pflanzenphysiol.85, 45–51], although the ultrastructural details are different. InTropaeolum majus, autolysis begins in the most distal part of the suspensor, i.e., the chalazal or carpel haustorium. First the endoplasmic reticulum shows acid phosphatase activity, but neither the mitochondria, which undergo transformation similar to that observed in plastids ofPhaseolus, nor the leucoplasts show such activity. Later, however, the plastids exhibit low activity. Contrarily, the plastids in the suspensor cells adjacent to the embryo show increasing activity during senescence of the suspensor. During final autolysis, activity is found in all cytoplasmic membranes, while it is reduced in plastids. The visible ultrastructural transformations of various organelles into cytolysomes does not necessarily coincide with acid phosphatase activity. Our findings are a further indication of the high diversification and specialization of plastids during plant embryogenesis.     

The Complex Satellite DNA of Tropaeolum majus L.: Partial Characterization of Isolated and of Cloned Restriction Fragments

Satellite DNA (satDNA) was purified by repeated neutral CsCl,ethidium bromide/CsCl and actinomycin D/CsCl density centrifugationfrom total nuclear DNA of Tropaeolum majus. Digestion patternsof satDNA and main band DNA as generated with 22 different restrictionenzymes were partially characterized and hybridized by the Southernblot technique with Hpa II-generated satDNA fragments and aribosomal DNA fragment. Some restriction fragments were sequencedby the chemical method, either directly, or after cloning, andpossible secondary structures were determined. The results showthat the satellite is of high complexity and evidently composedof different, interspersed repeats, and is also interspersedwith ribosomal sequences. Some sequences of the satellite aredispersed throughout the Tropaeolum genome, and even found inthe chloroplast genome. Most of the restriction enzymes cutthe satDNA into many fragments of lengths between 14 bp and3000 bp. Hpa II cut the satellite DNA into at least 63 differentsized fragments (more than is known from any other plant satDNA).Sal I cut the satDNA into a single fragment of 1040 bp in size,which probably represented the superrepeat unit. Sequence analysisof satDNA restriction fragments and of cloned fragments isolatedat different times, indicated a rapid diversification in vivoand in vitro. Computer modeling of most likely secondary structuressuggest the occurrence of palindromic loops (cruciform structures).These could be the basis of rapid diversification in being sitesof preferred intragenomic recombination and rearrangement. Cloning, palindromic sequences, restriction analysis, satellite DNA complexity, Tropaeolum majus L, nasturtium     

New species of Alternaria from Marathwada (India)

Summary The paper deals with two new species ofAlternaria, Alternaria nyctanthi onNyctanthes arbortristis Linn. andAlternaria tropaeoli onTropaeolum majus L.     

The Suspensor Haustoria of Some Species of Crotalaria Linn

The structure and function of the suspensor has been studiedin eight species of Crotalaria, in all of which it shows a differentiationinto an upper and a lower part. The peripheral cells of thelower part project out and act as haustorial structures forthe absorption of nutrition from the surrounding endosperm.In G. retusa and G.striata these processes are very long andtubular attacking the surrounding endosperm and nucellar tissuesand extending even into the integumental layers. Remains ofthe suspensor are recognizable even in the mature seed. Thecells of the suspensor possess chloroplasts so that this organalso has a photosynthetic function in addition to its haustorialactivity.     

1-Nitro-2-phenylethane,a possible intermediate in the biosynthesis of benzylglucosinolate

Results have been obtained consistent with the hypothesis that aci tautomers of nitro compounds are precursors of glucosinolates. When dl-[3-¹⁴C]phenylalanine and [¹⁴C]1-nitro-2-phenylethane were fed to shoots of Tropaeolum majus L., the incorporation of tracer from each compound into benzylglucosinolate was found to be similar. Conversion of ¹⁴C from 1-nitro-2-phenylethane into the aglycone moiety of benzyl-glucosinolate was specific. The natural occurrence of 1-nitro-2-phenylethane in T. majus and its formation in this plant from [1-¹⁴C]phenylacetaldoxime were demonstrated by gas chromatography and by means of a trapping experiment.     

Evidence for Genetic Change in the Antirrhinum Rust (Puccinia antirrhini)

The available data on the resistance of Antirrhinum majus L.to rust, Puccinia antirrhini Dietel and Holway, are reviewed.There is evidence for one or more genetic changes in the pathogen.In one instance it can be demonstrated that this change is likelyto have been by mutation. The chronology of the changes is:in the U.S.A., east of the Rockies between 1921 and 1935 andin California during 1936; in Europe between 1936 and 1954 andin Britain between 1958 and 1962. A virulent race was presentin Australia by 1954. Puccinia antirrhini Dietel and Holway, rust, Antirrhinum majus L., mutation, virulence, resistance     

Changes in Nuclear DNA Content, Cell and Nuclear Size, and Frequency of Cell Division in the Cotyledons of Brassica napus L. during Embryogenesis

Cellular behaviour was examined during embryogenesis in Brassicanapus to test whether or not polyploidy occurs in the cotyledonsduring the phase of oil deposition. Nuclear DNA content, nuclearand cell size, and the mitotic index were measured in the cotyledonson various days post anthesis (dpa). In squashed monolayersfrom 15 dpa cotyledons, a polyploid (>5C) population wasdetected together with a substantial number of cells in G2 (4C).Nuclear volume was measured on sectioned tissues and, at 15dpa, the range of values from the cotyledons (40–500 *m³)contrasted with that in the vestigial suspensor and endosperm(50–> 600 µm³). At 15 dpa the nuclear volumedata suggest that whilst cells in the cotyledons were in Gland G2 many endosperm and suspensor cells were polyploid. Thus,polyploidy observed in the squashed monolayers was probablydue to contaminating endosperm/suspensor cells. At 25 and 35dpa, polyploidy was not detected; all cells were in Gl (2C)and cell area increased. The mitotic index peaked at 20 dpabefore declining and given the narrower distribution of nuclearvolumes at 25 and 35 dpa (50–300 µm³), these dataare consistent with cell arrest in Gl. Thus, polyploidy wasnot detected in the cotyledons of B. napus which differs fromwhat is known about cellular development in legume cotyledons. Key words: Brassica napus L., DNA, nuclear volume     

745. TROPAEOLUM MINUS

Tropaeolum minus L. was the first nasturtium to appear in European gardens. It was already widespread in the 16th century, and hence it must have been among the first American plants to be cultivated widely in European gardens. It is a smaller species than T. majus L., the well‐known garden nasturtium, and has lost popularity since the latter was introduced. Its cultivation and uses are discussed.     

Isolation and Characterization of a cDNA Clone of UDP-Galactose: Flavonoid 3-0-Galactosyltransferase (UF3GaT) Expressed in Vigna mungo Seedlings

Four cDNA clones were isolated from Vigna mungo seedlings bythe screening with cDNA encoding UDP-glu-cose:flavonoid 3-0-glucosyltransferase(UF3GT) of Antirrhinum majus as a probe; the product of thegene corresponding to one cDNA was more highly expressed inthe first simple leaves than in stems. Nucleotide sequence analysisrevealed 1,691 bp (including 326 bp non-reading) containingan open reading frame of 455 amino acids. The deduced aminoacid sequence showed 42% and 23% identity with those of A. majusUDP-glucose:flavonoid 3-O-glucosyltransferase (UF3GT) and Petuniahybrida UDP-rhamnose:anthocyanidin 3-0-glucoside rhamnosyltrans-ferase(RT), respectively. One region of the cDNA (amino acids 325to 387) showed similarity to ceramide UDP-galac-tosyltransferasesof mice, rats and humans. A crude extract from Escherichia coli,in which the protein was expressed from the cDNA, showed highUF3GaT activity but low UF3GT activity, and was similar in K_m,optimal pH and substrate specificity to UF3GaT from V. mungo.We conclude that we have obtained UDP-galactose:flavonoid 3-0-galactosyltransferase(UF3GaT) cDNA from V. mungo. 4 Deceased.     

Changes in endogenous growth regulators in nasturtium leaves during senescence

Summary By use of lettuce-hypocotyl and wheat-coleoptile bioassay, the presence of both gibberellin (GA)-like and abscisic-acid(ABA)-like components in acidic ethyl-acetate extracts of fully expanded nasturtium (Tropaeolum majus) leaves has been shown. During senescence of detached leaves there was a progressive decline in GA-like components and an increase in ABA-like components. Pretreatment of detached leaves with GA₃ or kinetin prevented changes in the levels of endogenous growth regulators and delayed senescence. The observations provide experimental verification for the concept that senescence is associated with changes in endogenous growth regulators.     

Manifestation et Mode de Conservation de Leveillula taurica, Agent de l'Oïdium de la Tomate au Maroc

Manifestation and conservation of Leveillula taurica on tomatoes in Morocco Powdery mildew of tomato, caused by Leveillula taurica, was considered a minor disease until 1978 when serious outbreaks occurred. These outbreaks coincided with periods of a draught and the introduction of new hybrids from Europe. The pathogen infects a variety of plants, including eleven cultivated and five wild species. Infections of tomato plants were obtained by isolates collected from cultivated plants (Cynara cardunculus, Cicerarietinum, Medicago sativa, Capsicum annuum, Tropaeolum majus) and wild species (Chenopodium ambrosioides, Sonchus asper, Oxalis cemua, Urtica urens).     

Origin and Development of Somatic Embryoids Formed Directly on Immature Embryos of Trifolium repens In Vitro

When immature zygotic embryos of Trifolium repens are culturedin vitro in the presence of 0.05 mg 1^–1 BAP, the cellsof the hypocotyl epidermis proliferate to produce somatic embryoidsdirectly without an intervening callus phase. The young epidermalcells show features of proembryogenic cells, and the first signof embyroid induction is a shift from regular equational, anticlinaldivisions to irregular, periclinal and oblique quantal divisions.Multicellular budding and single-cell initiation apparentlyboth occur, with multicellular budding being the more frequentpattern in the present study. Most early proembryoids resembleglobular zygotic proembryos but appear to lack a suspensor.It is suggested that the subtending embryonic tissue fulfilsthe role of a suspensor or proembryonal complex. Secondary proliferationsfrom the young cotyledon and hypocotyl epidermis of primaryembryoids are formed by processes similar to those producingprimary embryoids, and also from structures initially resemblingepidermal hairs. These hair-like structures arise from singlesuperficial cells which show evidence of cutinisation and callosedeposition suggesting some degree of physical separation fromneighbouring cells. Trifolium repens, tissue culture, somatic embryogenesis, embryoid, legume     

Ultrastructural Changes of the Egg Apparatus Associated with Fertilization and Proembryo Development of Soybean, Glycine max (Fabaceae)

As part of a study involving pod retention in soybean, Glycinemax (L.) Merr., we investigated changes occurring in the eggapparatus of non-abscised flowers from the time immediatelypreceding fertilization through early embryogeny. Prior to theentry of the pollen tube into the embryo sac, one of the synergidsbegins to degenerate as evidenced by increased electron densityand a loss of volume. This cell serves as the site of entryfor the pollen tube. The cytoplasm of the second, or persistentsynergid, remains unaltered until after fertilization. Bothsynergids contain, in addition to a filiform apparatus, a singleunidentified inclusion of flocculent material located in thechalazal portion of each cell. The zygote can be distinguishedfrom the egg by its consistently narrow wall; and it dividesto form a proembryo, a mass of cells not yet differentiatedinto embryo proper and suspensor. The basal cells of the proembryoare more vacuolate than the apical ones, characteristic of thebasal vacuolation of both egg and zygote. Cells of the proembryoare connected to one another via plasmodesmata, and with theexception of the basal-most cell, are isolated symplasticallyfrom the surrounding endosperm. Wall ingrowths frequently occurin certain cells of the proembryo, notably those cells in contactwith the degenerate synergid and embryo sac wall. At a laterstage of ontogeny, by which time the globular embryo properhas become distinct from the suspensor, the wall ingrowths areconcentrated in the suspensor. Glycine max, soybean, embryogeny, synergids     

Embryology ofCymbidium sinense:the Microtubule Organization of Early Embryos

InCymbidium sinense, the pattern of embryo development is unusualin that oblique cell divisions result in the formation of severalsuspensor cells prior to the development of the embryo proper.Characteristic changes in microtubular distribution can be foundwithin the zygote and the proembryo during their development.After fertilization, the ellipsoid-shaped zygote has randomlydistributed microtubules within its cytoplasm. As the zygotetakes on a more rounded appearance, microtubules organize intoa dense meshwork. Furthermore, microtubule bundles appear atthe chalazal region of the cell prior to the first mitotic divisionof the zygote. At the preprophase stage of mitosis, a preprophaseband of microtubules appears in the cytoplasm of the zygote.The zygote divides obliquely and unequally and gives rise toan apical cell and a slightly larger basal cell. Many randomly-alignedmicrotubules can be found in the cortex of the basal cell. Theincrease in the abundance of microtubules coincides with theisotropic expansion of the basal cell. The early division ofthe basal cell and subsequent division of the apical cell resultsin the formation of a four-celled embryo, of which three cellsnear the micropylar pole develop as suspensor cells. In thesuspensor cells, the microtubules tend to orient in the samedirection as the long axis of the cell. In addition, prominentmicrotubules can also be found near the adjoining cell wallsof the four-celled embryo. The terminal cell is highly cytoplasmicwith abundant microtubules within the cell. Subsequent divisionsof the terminal cell give rise to additional suspensor cellsand the embryo proper. In the mature embryo, five suspensorcells are usually present; one eventually grows through themicropyle of the inner integument and four grow towards thechalazal pole. The cortical microtubules of suspensor cellsredistribute from a longitudinal to a transverse direction asthey grow towards their respective poles.Copyright 1998 Annalsof Botany Company Embryogenesis, endosperm, microtubules, preprophase band, suspensor cells,Cymbidium sinense(Andr.) Willd.     

Embryology of Cymbidium sinense: Embryo Development

Embryo development inCymbidium sinense is characterized by twoconsecutive oblique divisions resulting in the formation ofa four-celled embryo. Three of the four cells towards the micropylebegin to vacuolate while the remaining cell located at the terminusremains cytoplasmic. The three cells towards the base becomesuspensor cells, and they continue to elongate and expand bythe process of vacuolation. The terminal cytoplasmic cell continuesto divide and give rise to the embryo proper and additionalsuspensor cells. Nile red staining indicates the absence ofcuticular material in the walls of the suspensor cells. A positivereaction towards nile red can be detected in the embryo properafter periclinal divisions have ceased in the surface layer.In the mature embryo, storage protein and lipid are presentin the cells of the embryo proper. Embryo; orchid; suspensor; cuticle; Cymbidium sinense (Andr.) Willd.     

Gibberellin-like activity in suspensors of Tropaeolum majus L. and Cytisus laburnum L.

Gibberellins in the embryo-suspensor system have been considered so far only in Phaseolus coccineus. We present in this report the localization of gibberellin-like substances in the suspensors of Tropaeolum majus L. and Cytisus laburnum L. The total gibberellin activity (expressed as gibberellic-acid equivalent in the -amylase bioassay) in 2000 suspensors (106 mg fresh weight; FW) of C. laburnum and in 600 suspensors (236 mg FW) of T. majus were 50.9 g g^-1 FW and 8.9 g g^-1 FW respectively.Abbreviation GA gibberellin     

Regeneration of zygotic-like microspore-derived embryos suggests an important role for the suspensor in early embryo patterning

The inaccessibility of the zygote and proembryos of angiospermswithin the surrounding maternal and filial tissues has hamperedstudies on early plant embryogenesis. Somatic and gametophyticembryo cultures are often used as alternative systems for molecularand biochemical studies on early embryogenesis, but are notwidely used in developmental studies due to differences in theearly cell division patterns with seed embryos. A new Brassicanapus microspore embryo culture system, wherein embryogenesishighly mimics zygotic embryo development, is reported here.In this new system, the donor microspore first divides transverselyto form a filamentous structure, from which the distal cellforms the embryo proper, while the lower part resembles thesuspensor. In conventional microspore embryogenesis, the microsporedivides randomly to form an embryonic mass that after a whileestablishes a protoderm and subsequently shows delayed histodifferentiation.In contrast, the embryo proper of filament-bearing microspore-derivedembryos undergoes the same ordered pattern of cell divisionand early histodifferentiation as in the zygotic embryo. Thisobservation suggests an important role for the suspensor inearly zygotic embryo patterning and histodifferentiation. Thisis the first in vitro system wherein single differentiated cellsin culture can efficiently regenerate embryos that are morphologicallycomparable to zygotic embryos. The system provides a powerfulin vitro tool for studying the diverse developmental processesthat take place during the early stages of plant embryogenesis. Key words: Brassica napus, microspore embryogenesis, pattern formation, polarity, suspensor, zygotic embryogenesis     

Fitness of the parasitoid Diadegma insulare is affected by its host's food plants

The diamondback moth, Plutella xylostella (L.) is considered a specialist on Brassicaceae, but it is capable of expanding its food range by incorporation of non-brassicaceous plants into its diet. The use of a new food plant may change food availability and vulnerability of P. xylostella to its natural enemies, especially specialist parasitoids. In this laboratory study, we evaluated the bottom-up effects of two Brassicaceae viz. Brassica napus L. and Descurainia sophia (L.) Webb ex Prantl and two non-Brassicaceae viz. Tropaeolum majus L. and Cleome hassleriana Chodat on several fitness correlates of the specialist parasitoid, Diadegma insulare (Cresson) reared on P. xylostella larvae. Percentage of parasitism of host larvae by D. insulare varied among the plant species and was highest on T. majus and lowest on D. sophia. Values of several fitness correlates for D. insulare differed when the host was feeding on various plant species. Egg to adult development was fastest on B. napus followed by C. hassleriana, D. sophia and T. majus. Female wasps reared on C. hasseleriana lived the longest in absence of food. The response of D. insulare to potential food-plant expansion by its host P. xylostella is discussed.