Vegetable grafting confers soil-borne disease resistance through the use of selected rootstocks. Additional costs associated with grafted vegetable seedling propagation limit grower access to this technology. The use of low temperature storage in grafted seedling production reduces labor costs and allows propagators to meet the seasonal and narrow-window demand of growers. For the first part of the experiment 22 genotypes of Solanaceae or Cucurbitaceae seedlings were evaluated in low temperature storage conditions (5 or 12°C). Seedling performance was better in 12°C storage than in 5°C storage. For the second part of the experiment watermelon, the most low-temperature sensitive species found in our first study, was grafted onto two different commercial rootstocks or on to other watermelon seedlings and stored at 12°C for two and four weeks. Both 'Strong Tosa' and 'Emphasis' rootstocks conferred chilling tolerance during storage to watermelon scions, allowing storage of grafted plants for two weeks.

The greenhouse industry is interested in light emitting diodes (LEDs) as a light source supplement to solar light to improve plant growth and development. Before LEDs can be adopted as supplemental light for greenhouse crops, plant responses to LED spectral quality need to be investigated. Tomato and cucumber seedlings were grown under different supplemental blue and red photon flux ratios (B:R ratios) under high (16-19 mol m⁻² d⁻¹) and low (5-9 mol m⁻² d⁻¹) solar daily light integrals (DLIs). The supplemental daily light integral was 3.6 mol m⁻² d⁻¹. A treatment without supplemental light served as a control. Both tomato and cucumber seedlings had increased growth rate and improved morphology when grown under the supplemental LED light compared to the control. However, no significant differences were observed for any growth and morphological parameters measured in this study between the different B:R ratios for both cucumber and tomato transplants under high DLI conditions. Cucumber seedlings showed a tendency to decrease dry mass, leaf number and leaf area under low DLI conditions with increasing B:R ratio. Tomato seedlings did not show any differences between the different B:R ratios under low DLI conditions. Seedlings growth and morphology under supplemental LED light were compared to those under supplemental high pressure sodium (HPS) light. Cucumber seedlings under supplemental HPS light had greater shoot dry mass than those under the supplemental red LED light. Tomato shoot dry mass showed no differences between the HPS and red LED supplemental light treatments. Cucumber seedlings were also grown under supplemental LED pulsed lighting and supplemental LED continuous lighting. Cucumber seedlings showed no differences in shoot dry mass and net photosynthetic rate between the treatments. Collectively, these studies concluded that red LED is preferred for supplemental lighting and the increase of blue light does not offer any benefits unless the efficiency of blue LEDs largely exceeds the red LEDs. The results of this research can be used for fixture development by LED manufactures and as a decision making tool for the adoption of supplemental LED lighting by greenhouse growers.

The Wealden ghyll woodlands are associated with unique plant assemblages that include nationally rare bryophyte species with oceanic affiliations. The identification and monitoring of this type of 'priority' habitat, recognised as important in terms of regional and national biodiversity, is a central facet of the UK Biodiversity Action Plan (UKBAP). Despite the acknowledged importance of ghyll woodlands for non-vascular plant species, previous studies attempting to examine and characterise the ghyll woodlands have neglected to include these bryophyte communities. This research identifies and characterises the Wealden ghyll woodlands through an examination of the spatial and temporal distributions of bryophyte and flowering plant species. The research also seeks to provide baseline data against which biodiversity levels can monitored. In order to identify and contextualise the importance of ghyll woodland in terms of regional biodiversity, survey data was collected from other types of ancient woodland throughout the region for comparative analysis. The study involved the collection of species and environmental data from a total of 1440 random quad rats from 60 survey sites situated throughout the Weald, as well as the use of archive survey data collected during two 20 year periods (1951-1970 and 1976-1995). A number of statistical approaches including general linear modelling, ANOSIM, MannWhitney U and Spearman rank correlation analysis were used to identify the environmental correlates of spatial and temporal changes in species distributions. Spatial analysis indicated that ghyll woodland is restricted to the stream valleys themselves which were significantly richer in bryophyte and flowering plant species than the surrounding woodlands. NVC classifications assigned to the ghylls indicated the presence of 'oceanic' plant communities that are associated with damp, humid microclimatic conditions. A number of authors have explained the presence of oceanic bryophytes within the ghylls as being the result of a damp, humid microclimate present within the stream valleys. However, the study found no significant differences between climatic conditions within the ghyll valleys and those in the surrounding ancient woodlands. ANOSIM analysis indicated that community composition was influenced by site substrate, with clay and sandstone ghyll woodlands containing significantly different plant communities. Chi-squared analysis identified a temporal increase in the ratio of oceanic bryophytes and ancient woodland indicator flowering plant species during the study period. Analysis of Ellenberg indicator values indicated a move towards more shadetolerant plant communities within the ghyll woodlands. The patchily distributed ghyll woodlands were examined for signs of habitat fragmentation through genetic analysis of the bryophyte Conocephalum conicum (Great Scented Liverwort) using the random amplification polymorphic DNA technique (RAPD). Wright's fixation index (FST) and Nei 's coefficient of gene variation (GST) both indicated a loss of genetic diversity characteristic of genetic isolation. A Mantel test based on Nei 's genetic distance values indicated that the genetic isolation observed was not correlated with the geographical distance between populations. The study indicated that temporal changes are occurring in the composition of ghyll woodland plant communities and that bryophyte populations are displaying symptoms of genetic isolation. The study illustrates the importance of some form of monitoring program if the biodiversity value of these sites is to be maintained.

É conhecido que a utilização repetitiva e consecutiva dos mesmos herbicidas, ou de herbicidas diferentes, porém com mesmo mecanismo de ação, exerce uma pressão de seleção sobre as populações de plantas daninhas controladas. As duas formas principais de resposta das populações de plantas daninhas resultantes da pressão de seleção dos herbicidas são a mudança da flora pela seleção de espécies de plantas daninhas tolerantes, ou a seleção de biótipos de plantas daninhas resistentes aos herbicidas. Na prática têm sido observadas, pelos produtores de cana-de-açúcar, mudanças de flora pela seleção de algumas espécies de capim-colchão (Digitaria spp), as quais não têm sido controladas eficientemente pelos herbicidas normalmente recomendados para o seu controle. Suspeita-se que estas populações selecionadas são constituídas por diferentes espécies de capim-colchão, que apresentam níveis maiores de tolerância aos herbicidas. Sendo assim, os objetivos desta pesquisa foram: (i) identificar taxonomicamente as espécies de capim-colchão infestante da cultura da cana-de-açúcar no Estado de São Paulo, e avaliar a eficácia de herbicidas no controle de Digitaria nuda a nível de campo; (ii) comparar a suscetibilidade das espécies D. nuda e D. ciliaris aos herbicidas do grupo químico das triazinas, uréias substituídas, imidazolinonas, triazinonas e aos herbicidas, cujo mecanismo de ação é a inibição da síntese de caroteno, e quantificar o nível de tolerância das espécies através da elaboração de curvas de dose-resposta; (iii) determinar, com a utilização de 14C-herbicida, a absorção e translocação pelas espécies Digitaria nuda e Digitaria ciliaris dos herbicidas diuron (via folha) e imazapyr e metribuzin (via raiz). A identificação das espécies de capim-colchão (Digitaria spp) foi efetuada seguindo chave de identificação existente na literatura. No estudo da eficácia de herbicidas no controle de Digitaria nuda a nível de campo, foram utilizados oito tratamentos herbicidas, aplicados em condições de pré-emergência. As avaliações de controle foram realizadas aos 15, 30 e 60 dias após a aplicação (DAA). O estudo da eficácia de herbicidas no controle das espécies Digitaria nuda e Digitaria ciliaris, foram conduzidos em casa-de-vegetação. Foram utilizados oito tratamentos herbicidas, aplicados em condições de pré-emergência. As avaliações de controle foram realizadas aos 14 e 21 (DAA). O estudo do nível de tolerância foi realizado em casa-de-vegetação do Departamento de Produção Vegetal da ESALQ/USP, Piracicaba/SP, através de curvas de dose-resposta. Os estudos de absorção e translocação foram conduzidos em câmara de crescimento, e as análises realizadas no Laboratório de Ecotoxicologia do Centro de Energia Nuclear na Agricultura (CENA/USP), em Piracicaba, SP, utilizando-se 14C-herbicida, medindo-se a radioatividade em diferentes partes das plantas. Os resultados permitiram concluir que: (i) a espécie Digitaria nuda foi selecionada pela aplicação repetitiva dos herbicidas utilizados no controle de capim-colchão na cultura da cana-de-açúcar; demonstrando ser mais tolerante aos herbicidas dos grupos químicos das imidazolinonas e uréias substituídas, quando comparada à Digitaria ciliaris; (ii) a partir das curvas de dose-resposta, pode ser verificado que a Digitaria nuda demonstrou ser mais tolerante que a Digitaria ciliaris aos herbicidas diuron, imazapyr e tebuthiuron; (iii) a absorção e translocação não foram os mecanismos responsáveis pela tolerância apresentada pela Digitaria nuda aos herbicidas diuron e imazapyr. / It is known that the repetitive and successive use of the same or differents herbicides, but with same mechanism of action, impose a selection pressure on the weed population controled. The two main forms of weed population response resulted from the selection pressure of the herbicide is, weed species shifts, through selection of the tolerant species of weed, or selection of resistant biotipes within the population. It has been observed by sugarcane growers weed species shifts whitin the genus (Digitaria spp). It is suspected that the populations selected are constituted by different crabgrass species, with higher level of herbicide tolerance. The objectives of the research were: (i) identify taxonomically the crabgrass infesting the sugarcane crop in São Paulo state – Brazil, and to study herbicide efficacy in the control of the Digitaria nuda in field conditions; (ii) compare the susceptibility of D. nuda and D. ciliaris to herbicides of the chemical groups triazine, substituted urea, imidazolinone, triazinone, and inhibitors of carotene synthesis, and quantify the level of susceptibility of the species, through dose-response curves; (iii) determine, by using 14C-herbicide, the absorption and translocation by the species Digitaria nuda and Digitaria ciliaris of herbicides diuron (by leaf), and imazapyr and metribuzin (by root). The identification of the crabgrass species (Digitaria spp) was carry out following a identification key published in the literature. In the study of herbicides efficacy in the control of Digitaria nuda in field conditions, eight herbicide treatments, applied in pre-emergence were used, and the control percentage was evaluated at 15, 30 and 60 days after herbicide application (DAA). The study of herbicide efficacy to control the species Digitaria nuda and Digitaria ciliaris were conducted in greenhouse. Eight herbicide treatments, applied in pre-emergence were used, and the control percentage was evaluated at 14 and 21 days after herbicide application (DAA). The study of the level of tolerance was conducted in the greenhouse of the Department of Crop Science, University of São Paulo, Piracicaba/SP – Brazil, through dose-response curves; The study of absorption and translocation were conducted in a growth chamber, and the 14C-herbicide analysis was done in the Laboratory of Ecotoxicology of the Center of Nuclear Energy Applied to Agriculture, Piracicaba/SP, Brazil, using 14C-herbicide, measuring radioactivity in different plant parts. The results allowed to conclud that: (i) the specie Digitaria nuda was selected by repetitive applications of the herbicides used in the control of the crabgrass in the sugarcane crop, showing that the specie is more tolerant to the herbicides of the chemical group of imidazolinone and substituted urea, when compared to Digitaria ciliaris; (ii) From the dose-response curves study, it was observed that Digitaria nuda showed more tolerance than Digitaria ciliaris to the herbicides diuron, imazapyr and tebuthiuron; (iii) The absorption and translocation were not the mechanism responsible for the tolerance showed by Digitaria nuda to the herbicides diuron and imazapyr.

Estudo fitoquímico dos extratos de folhas e galhos de Peperomia villipefiola (\"hierba de la plata\"), coletada no Peru, resultou no isolamento e caracterização da miristicina (3-metoxi-4,5-metilenedioxi-alil-benzene) e sete novos cromenos. Os cromenos tiveram suas estruturas elucidadas através de análises espectroscópicas como sendo: 5-hidroxi-7-metil-2,2-dimetil-2H-1-cromeno-6-carboxilato de metila (PVL1), 7-metil-5-metoxi-2,2-dimetil-2H-1-cromeno-8-carboxilato de metila (PVL2), 7-hydroxy-5-metil-2,2-dimetil-2H-1-cromeno-6-carboxilato de metila (PVL3), 5-metil-7-metoxi-2,2-dimetil-2H-1-cromeno-6-carboxilato de metila (PVL4), ácido 7-hidroxi-5-metanol-2,2-dimetil-2H-1-cromeno-6-carboxílico (PVL5), ácido 5-metanol-7-metoxi-2,2-dimetil-2H-1-cromeno-6-carboxílico (PVL6) e 5-acetoximetanol-7-hidroxi-2,2-dimetil-2H-1-cromeno-6-carboxilato de metila (PVL7). Uma proposta biossintética foi sugerida, no qual o anel aromático seria formado pela via policetídica enquanto que a porção isoprênica poderia ser oriunda tanto da via do mevalonato quanto da via do fosfato de metileritriol. / The leaves and stems extracts from the Peperomia villipetiola (\"herb of the silver\"), collected in Peru, yielded myristicine (3-methoxy-4,5-methy/enedioxy-allylbenzene) and seven new chromenes. The chromenes, all new compounds, had their structures elucidated by means of spectroscopic analysis as: methyl 5-hydroxy-7-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (PVL1), methyl 5-methoxy-7-methyl-2,2-dimethyl-2H-1-chromene-8-carboxylate (PVL2), methyl 7-hydroxy-5-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (PVL3), methyl 7-methoxy-5-methyl-2,2-dimethyl-2H-1-chromene-6-carboxylate (PVL4), 5-methanol7-hydroxy-2 ,2-dimethyl-2H-1-chromene-6-carboxylic acid (PVL5), 5-methanol-7-methoxy-2,2-dimethyl-2H-1-chromene-6-carboxylic acid (PVL6), and methyl 5-acetoxymethanol-7-hydroxy-2,2-dimethyl-2H-1-chromene-6-carboxylate (PVL7). A biosynthetic scheme was suggested in which the aromatic ring should be formed by polyketide pathway while the isoprenyl moiety either from mevalonic acid or methylerythriol phosphate pathway.

Certain varieties of snap bean, Phaseolus vulgaris L. , seeds are very susceptible to cracks that develop naturally across the cotyledons during pre-harvest, storage, or germination. This phenomenon is commonly known as cotyledonal cracking and may cause serious yield reductions on plants developing from affected seeds. Cotyledonal cracking susceptibility of six white and six colored seeded varieties of snap beans were compared. Considerable differences were found in cracking susceptibility, but there was little or no relationship between seed coat color and cracking susceptibility. An experiment was conducted to determine if a metabolic stress of the plant during the time of pod set could be involved in cotyledonal cracking. Blossoms were tagged on individual plants beginning with the day of first blossom, and tagging was continued for 21 days as blossoms emerged . Individual pods were harvested at maturity and maintained under controlled conditions throughout a simulated weathering treatment to follow. Seeds of each pod were classified according to the amount of cotyledonal cracking sustained. It was concluded that if a stress were involved, it apparently affected the seed several days after pod initiation and that an increase in cotyledonal cracking was negatively correlated to an increase in the number of pods set during one day. Simulated weathering tests were made of seeds remaining in the pod and seeds from the same varieties that were shelled. The results indicated that the pod provides about equal cotyledonal cracking protection for all varieties tested. Apparently the pod is not an important cause of cracking resistance in certain varieties of snap beans. Seed coat permeability was measured and compared for the 12 varieties . A technique was employed by which the bean seed coat served as a semipermeable membrane between a distilled water and a sucrose solution. Sucrose dilution was measured refractometrically and the rate of water penetration calculated. There was little relationship between seed coat permeability and cracking susceptibility among the varieties. The rate of imbibition and drying for seeds of six varieties having varying degrees of cracking susceptibility was tested. Imbibition and drying conditions were closely controlled and weight changes were recorded at regular intervals during imbibition and drying. Results indicated that some of the varieties expressing the most rapid moisture changes were also the most resistant to cracking. It was concluded that the rate of change of seed moisture was not the primary factor controlling cotyledonal cracking susceptibility. Rate of imbibition was tested for two susceptible and two resistant varieties. When the pre-imbibition seed moisture was above 10 percent, a ll varieties imbibed water freely. When pre-imbibition moisture was below 10 percent, several seeds of resistant varieties became slowly permeable while nearly all seeds of the susceptible varieties imbibed freely. This suggested the possibility that a hard seed tendency of the resistant varieties may be one source of protection against cotyledonal cracking. Preliminary data suggested that the seed coats of susceptible varieties remain permeable even at moisture levels below 10 percent, while many seed coats of the resistant varieties become rather impermeable at low moisture levels. Microscopic examination of cotyledonal cracks from four different varieties indicated that the splitting occurred across cotyledonal cell walls more rapidly than between cell walls. This suggested that a weakness of the intercellular middle lamella is not responsible for cotyledonal cracking susceptibility. Further microscopic examination and comparison of the cotyledonal cell structure of two susceptible and two resistant varieties failed to show any structural differences between varieties that could account for differences in cotyledonal cracking susceptibility.

No description available.

A study was conducted to determine (1) the N contribution of lentil (<i>Lens culinaris</i> Medikus) and its effect on subsequent wheat (<i>Triticum aestivum</i> L.) crops in the Dark Brown and Brown soil zones of Saskatchewan, (2) if synchronization of available N contributes to the rotation benefit, and (3) N fertilizer replacement value of the N effect of lentil on the subsequent wheat crop. Two approaches were used: a landscape-scale study established at Dinsmore in 1994, and a repeated small-plot study established at several locations (Dinsmore, 1993 and 1994; Clavet, Conquest, Eston and Zealandia, 1995). In the landscape-scale study, N2 fixation by lentil ranged from 28 to 46 kg ha-1, with an average of 34 kg ha -1 N and an N balance of -36 kg ha-1. In the small-plot study, N2 fixation ranged from 10 to 112 kg ha -1 with an average of 59 kg ha-1 N and an N balance of -22 kg ha-1. In the landscape-scale study, preseeding available N on the rotation that incorporated lentil was 29 and 61% higher than in the monocropped wheat in the first and second subsequent crops, respectively. The corresponding values for the small-plot study were 59 and 14%, respectively. N availability was well synchronized with the period of maximum N demand by the wheat crop in both rotations. However, both lentil-residue N and wheat-residue N were poorly synchronized with the period of maximum N demand by the wheat. The rotation effect was exhibited in higher grain yield (23% higher in the landscape-scale study, and 21% higher in the small-plot study). Approximately 10 and 70% of the rotation benefit in the landscape-scale and small plot studies, respectively, were attributed to the N effect. Nitrogen fertilizer replacement value ranged from 47 to 89 kg ha-1 N. Therefore, lentil can fix enough N and indirectly contribute to greater available N in subsequent crops than in crops following non-legumes. However, the actual amount of N derived from lentil residue is small. The greater available N is attributed to spared N and enhanced soil N mineralization. Hence, under the conditions of this study, enhancement of available N contributed more to the rotation benefit than synchronization. The high NFRV show that inclusion of lentil in the rotation can enhance available N in the cropping system and potentially reduce fertilizer N application.

An efficient system for or 'Agrobacterium'-mediated transformation of <i>Brassica carinata</i> was used together with a promoterless <i> gus</i>::<i>nptII</i> gene fusion to isolate putative promoter sequences. Cotyledonary petioles were transformed using the promoterless gene fusion construct. Only transformation events in which the promoterless gene fusion had integrated downstream from plant regulatory sequences were expected to produce viable tissue under kanamycin selection. Forty-two transgenic plants were recovered. Transformation efficiency was approximately 0.6%. Regenerated plants were screened for GUS expression in different tissues and organs by histological and fluorometric assays. Tissue-specific GUS expression was detected (stigmas, seed coat, leaf edges and vascular tissue) in some plants, while strong constitutive GUS expression was detected in others (based on GUS histological assays). Using subgenomic libraries, putative promoter fragments were isolated from the plants which exhibited GUS expression in stigmas, leaf edges and constitutively. A putative promoter fragment from a plant which exhibited GUS expression only in the stigma was fused with the gus gene and reintroduced by <i>Agrobacterium </i> -mediated transformation into <i>B. napus, B. carinata, Arabidopsis' and tobacco </i>. GUS expression was observed in the stigma of <i>B. napus </i> but not in ' B. carinata'. In <i>Arabidopsis </i> and tobacco GUS expression. was not tissue specific (weakly constitutive or restricted to two or more tissues). The 3' DNA sequence (15 kb) flanking the <i> gus</i>::<i>nptII </i> insert in the plant with GUS expression in the stigma was also isolated using a subgenomic library. A gene for a cytochrome P450 like protein was discovered on the minus DNA strand of the 3' sequence with a start codon approximately 6.5 kb from the T-DNA left border.

Meadow bromegrass (<i>Bromus riparius</i> Rehm.) is a recently introduced pasture grass in western Canada. Its leafy production and rapid regrowth have made it the most widely used grass species for pasturing beef animals in this region. As relatively little breeding work has been done on this species, there is little information on its breeding behaviour. The main objective of this study was to estimate genetic parameters and assess breeding methodologies for meadow bromegrass. Forty-four meadow bromegrass genotypes from the three available cultivars and forty half-sib (polycross (PX) and open-pollinated (OP)) and selfed (S1) progenies were evaluated for morphological and agronomic characters, and molecular (RAPD) markers. Genetic variation for total biological yield, head weight, seed yield, harvest index, height, growth habit, spread, and volume was significant in the OP and S1 tests. Genetic variation estimates for dry matter yield were negative (PX), not significant (OP), or moderate (S1). Estimated geneticvariation for quality traits and those characters which were visually evaluated was not significant, except for growth habit (OP and S1) and acid-detergent fiber (ADF) (S1). Among progeny lines, RAPD marker variation found in the half-sib progenies accounted for about 15% of the total variation. In the S1 test the variation among progeny lines was twice that of the half-sib progenies. Correlations between the different characters demonstrated that is possible to simultaneously improve both seed and forage yield. Since leafiness was found to be correlated with dry matter yield but not with seed yield it may be possible to simultaneously improve all three characters. Rankings of progenies by the half-sib tests for forage and seed yield were not changed by the use of the synthetic parental value (SVi) which includes information from selfed progeny. The PX progeny test did not discriminate parents as well as the OP and S1 tests, which may be due to non-random pollination in the polycross. The S1 progeny test showed the highest predicted response to selection, followed by the OP test. Heritability estimates from the OP and S1 tests for total biological yield, seed yield, harvest index, and height, were similar to those found in the clonal evaluation test. Therefore, a clonal evaluation test will provide sufficient information to choose parents for breeding an improved synthetic cultivar for these characters. Observed dissimilarity of ranking of progeny lines over progeny tests for some traits (head weight, seed yield, and harvest index) was due to discrepancies between the PX and OP tests. No differences in progeny line ranking among the progeny tests were observed for all other traits. Analysis of variance on marker frequency means showed that interaction between genotypes and progeny lines was also not significant.