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Pathogenic fungi use secreted effector proteins to suppress immunity and support their infection, but effectors have also been reported from fungi that engage in nutritional symbioses with plants. Sequence-based effector comparisons between pathogens and symbiotic arbuscular mycorrhizal (AM) fungi are hampered by the huge diversity of effector sequences even within closely related microbes. To find sequence-divergent but structurally similar effectors shared between symbiotic and pathogenic fungi, we compared secreted protein structure models of the AM fungus Rhizophagus irregularis to known pathogen effectors. We identified proteins with structural similarity to known Fusarium oxysporum f. sp. lycopersici dual domain (FOLD) effectors, which occur in low numbers in several fungal pathogens. Contrastingly, FOLD genes from AM fungi (MycFOLDs) are found in enlarged and diversified gene families with higher levels of positive selection in their C-terminal domains. Our structure model comparison suggests that MycFOLDs are similar to carbohydrate-binding motifs. Different MycFOLD genes are expressed during colonisation of different hosts and MycFOLD-17 transcripts accumulate in plant intracellular arbuscules. The exclusive presence of MycFOLDs across unrelated plant-colonising fungi, their inducible expression, lineage-specific sequence diversification and transcripts in arbuscules suggest that FOLD proteins act as effectors during plant colonisation of symbiotic and pathogenic fungi.

El tiempo de floración es un proceso fundamental en el desarrollo de las plantas. En Arabidopsis thaliana (A. thaliana), la duración del día (fotoperiodo) presenta un papel crucial en la transición floral, y en concreto, el gen CONSTANS (CO) tiene una función central estrechamente regulada a nivel transcripcional y postraduccional. El objetivo de este trabajo es aplicar los resultados observados en A. thaliana sobre el papel de CO en la floración y senescencia floral a la planta modelo ornamental, Petunia hybrida (P. hybrida). Se llevó a cabo la identificación de un gen ortólogo a CO en P. hybrida, PhCO, y la caracterización del mismo, analizando su expresión génica y niveles proteicos durante 24h. El patrón de expresión de PhCO sugiere que éste está sometido a una regulación circadiana similar a la de CO. La clonación de PhCO en los vectores de expresión pMDC32 y pMDC43 y la posterior transformación de ambas construcciones en A. thaliana co-10, nos permitirá realizar un análisis de la floración y senescencia floral y comprobar si PhCO es realmente el gen ortólogo de CO. La expresión génica y niveles de proteína de PhCO también varían en función del fotoperiodo, con una mayor expresión en condiciones de día largo. Además, P. hybrida presenta una floración acelerada en condiciones de día largo con respecto a condiciones de día corto. Estos hechos sugieren, como sucede en A. thaliana, una inducción fotoperiódica de la floración por PhCO en P. hybrida.

[ES]: Containerized ornamental plant production is facing several environmental challenges. One of them is to replace the widely used, but with questionable sustainability, peat based substrates and another is to avoid water contamination by chemicals leaching from the nursery. Therefore, as have been verified that petunia and pelargonium plants can be produced in peat-based growing media partially replaced by vermicompost (V) and biochar (B) without decreasing commercial quality, this study has focused on analyzing the leachate from a standard peat-based substrate as a control, used for producing these two ornamental species, and those from the same substrate to which different proportions in volume of V (10% and 20%) and B (4% and 12%) have been added. The amount of nitrogen leached from the mixed substrates was reduced compared to the control one in both species (on average 37%). Nitrogen was leached mainly as nitrate-nitrogen (89% in Petunia and 97% in Pelargonium). In Petunia phosphorous leaching was also decreased (30%) for the treatment with 10% V and 4% B, while potassium leaching in substrate containing 20% V and 12% B increased by 100%. Our results show that these two organic materials tested (V and B) can help producers to reduce the use of peat and chemical fertilizers as well as the risk of contamination by chemicals, mainly nitrate., [PO]: A produção de plantas ornamentais em contêineres está enfrentando vários desafios ambientais. Um deles é substituir os substratos amplamente utilizados, mas com sustentabilidade questionável, baseados em turfa, e outro é evitar a contaminação da água por produtos químicos lixiviados do viveiro. Verificou-se que as plantas de petúnia e gerânio podem ser produzidas em meios de crescimento baseados em turfa parcialmente substituídos por vermicomposto (V) e biochar (B) sem diminuir a sua qualidade comercial. Este estudo concentrou-se na análise do lixiviado de uma turfa padrão como controle, utilizado para a produção destas duas espécies ornamentais, e o mesmo substrato ao qual foram adicionados diferentes proporções em volume de V (10% e 20%) e B (4% e 12%). Verificou-se que a quantidade de nitrogenio lixiviado dos substratos misturados foi reduzida em comparação com a testemunha em ambas as espécies (em média 37%). O nitrogênio foi lixiviado principalmente como nitrato-nitrogênio (89% em Petunia e 97% em Pelargonium). Na Petunia a lixiviação de fósforo também foi reduzida (30%) para o tratamento com 10% de V e 4% de B, enquanto a lixiviação de potássio em substrato contendo 20% de V e 12% de B aumentou em 100%. Nossos resultados mostram que esses dois materiais orgânicos testados (V e B) podem ajudar os produtores a reduzir o uso de turfa e fertilizantes químicos, bem como diminuir o risco de contaminação por substâncias químicas, principalmente nitrato.

[EN] Biochar and hydrochar have been proposed as novel materials for providing soilless growth media. However, much more knowledge is required before reliable advice can be given on the use of these materials for this purpose. Depending on the material and the technology applied (pyrolysis or hydrothermal carbonization), phytotoxicity and greenhouse gas emissions have been found for certain chars. In this study, our aim was to assess the feasibility of three chars as substrate constituents. We compared two biochars, one from forest waste and the other from olive mill waste, and a hydrochar from forest waste. We studied how chars affected substrate characteristics, plant performance, water economy and respiratory CO2 emission. Substrates containing biochar from forest waste showed the best characteristics, with good air/water relationships and adequate electrical conductivity. Those with biochar from olive mill waste were highly saline and, consequently, low quality. The substrates with hydrochar retained too much water and were poorly aerated, presenting high CO2 concentrations due to high respiratory activity. Plants performed well only when grown in substrates containing a maximum of 25 % biochar from forest waste or hydrochar. After analyzing the char characteristics, we concluded that biochar from forest waste could be safely used as a substrate constituent and is environmentally friendly when applied due to its low salinity and low CO2 emission. However, biochar from olive mill waste and hydrochar need to be improved before they can be used as substrate constituents.

[EN] Biochar and hydrochar have been proposed as novel materials for providing soilless growth media. However, much more knowledge is required before reliable advice can be given on the use of these materials for this purpose. Depending on the material and the technology applied (pyrolysis or hydrothermal carbonization), phytotoxicity and greenhouse gas emissions have been found for certain chars. In this study, our aim was to assess the feasibility of three chars as substrate constituents. We compared two biochars, one from forest waste and the other from olive mill waste, and a hydrochar from forest waste. We studied how chars affected substrate characteristics, plant performance, water economy and respiratory CO2 emission. Substrates containing biochar from forest waste showed the best characteristics, with good air/water relationships and adequate electrical conductivity. Those with biochar from olive mill waste were highly saline and, consequently, low quality. The substrates with hydrochar retained too much water and were poorly aerated, presenting high CO2 concentrations due to high respiratory activity. Plants performed well only when grown in substrates containing a maximum of 25 % biochar from forest waste or hydrochar. After analyzing the char characteristics, we concluded that biochar from forest waste could be safely used as a substrate constituent and is environmentally friendly when applied due to its low salinity and low CO2 emission. However, biochar from olive mill waste and hydrochar need to be improved before they can be used as substrate constituents.

Vermicompost is a product derived from the accelerated biological degradation of organic wastes by earthworms and microorganisms. Biochar is a by-product of the C-negative pyrolysis technology for bio-energy production from organic materials. Containerized plant production in floriculture primarily utilizes substrates such as peat moss. Environmental concerns about draining peat bogs have enhanced interests in research on complementary products that can be added to peat. A comparative greenhouse study was conducted to assess the suitability of biochar (B) and vermicompost (V) as partial substitutes for peat-based growing media for ornamental plant production. Different blends of B at a volume fraction of 0, 4, 8, 12 % and V at 0, 10, 20, 30, 40, 50 % were compared to a baseline peat substrate (S) as control in the cultivation of geranium (Pelargonium peltatum) and petunia (Petunia hybrida). Substrates were characterized for physical and chemical properties, plant growth, and flower production. Mixtures with low-medium V levels (10-30%) and high B level (8-12 %) in Petunia and Pelargonium induced more growth and flower production than that of the control. The results obtained with different B and V associations are of interest to those who want to reduce peat consumption for the production of ornamental plants in containers and to reduce carbon footprint of this commercially productive sector

El ritmo circadiano de una planta es controlado por una red compleja de genes, expresados por la mañana, al mediodía y por la noche, con interacciones tanto al nivel de transcripción y traducción. El reloj circadiano afecta a muchos aspectos del desarrollo de planta, incluyendo el crecimiento y el tiempo de floración, resistencia al frío, apertura de la flor, la emisión de volátiles y por lo tanto la atracción de polinizadores y la repulsión de herbívoros. La emisión de volátiles florales en Petunia, una especie polinizada por insectos activos durante la noche, tiene un pico hacia la noche y es más baja durante el día. Uno de los principales genes de reloj es Zeitlupe (ZTL), lo que significa cámara lenta. La proteína ZTL tiene tres dominios, un dominio está especializada en la detección de luz, un dominio media la interacción proteína-proteína y el tercer dominio se dirige a otras proteínas para la degradación a través del sistema ubiquitina-proteasoma. La función específica de ZTL es la degradación proteasomal del gen “TIMING OF CAB EXPRESSION 1 (TOC1)”, otro gen del reloj del núcleo. En caso del gen ZTL, la abundancia de ARNm no está regulada por el reloj, pero los niveles de la proteína tienen su pico en anochecer. Nuestro objetivo es analizar cómo los genes del reloj circadiano controlan aspectos del desarrollo vegetativo y florales en Petunia hybrida. La comprensión del control genético sobre el desarrollo floral es un aspecto importante de la interacción con polinizadores.

[no abstract]

Petunia hybrida is a popular bedding plant that has a long history as a genetic model system. We report the whole-genome sequencing and assembly of inbred derivatives of its two wild parents, P. axillaris N and P. inflata S6. The assemblies include 91.3% and 90.2% coverage of their diploid genomes (1.4 Gb; 2n = 14) containing 32,928 and 36,697 protein-coding genes, respectively. The genomes reveal that the Petunia lineage has experienced at least two rounds of hexaploidization: the older gamma event, which is shared with most Eudicots, and a more recent Solanaceae event that is shared with tomato and other solanaceous species. Transcription factors involved in the shift from bee to moth pollination reside in particularly dynamic regions of the genome, which may have been key to the remarkable diversity of floral colour patterns and pollination systems. The high-quality genome sequences will enhance the value of Petunia as a model system for research on unique biological phenomena such as small RNAs, symbiosis, self-incompatibility and circadian rhythms.

The expression of transgenes in plant genomes can be inhibited by either transcriptional gene silencing or posttranscriptional gene silencing (PTGS). Overexpression of the chalcone synthase-A (CHS-A) transgene triggers PTGS of CHS-A and thus results in loss of flower pigmentation in petunia. We previously demonstrated that epigenetic inactivation of CHS-A transgene transcription leads to a reversion of the PTGS phenotype. Although neomycin phosphotransferase II (nptII), a marker gene co-introduced into the genome with the CHS-A transgene, is not normally silenced in petunia, even when CHS-A is silenced, here we found that nptII was silenced in a petunia line in which CHS-A PTGS was induced, but not in the revertant plants that had no PTGS of CHS-A. Transcriptional activity, accumulation of short interfering RNAs, and restoration of mRNA level after infection with viruses that had suppressor proteins of gene silencing indicated that the mechanism for nptII silencing was posttranscriptional. Read-through transcripts of the CHS-A gene toward the nptII gene were detected. Deep-sequencing analysis revealed a striking difference between the predominant size class of small RNAs produced from the read-through transcripts (22 nt) and that from the CHS-A RNAs (21 nt). These results implicate the involvement of read-through transcription and distinct phases of RNA degradation in the coincident PTGS of linked transgenes and provide new insights into the destabilization of transgene expression.

La cuantificación de la expresión génica de forma precisa mediante RTPCR cuantitativa requiere utilizar como genes normalizadores aquéllos cuyo nivel de expresión sea constante, al menos bajo unas determinadas condiciones experimentales. Por ello, debe analizarse de forma absoluta la abundancia de los genes normalizadores putativos para cada especie y bajo distintas condiciones, a fin de escoger los más apropiados para cada caso. Existen trabajos realizados en los que se han determinado genes de referencia para Arabidopsis thaliana, vid, arroz o patata. Sin embargo, no se han identificado genes con expresión estable para estudios de desarrollo meristemático y floral. En este estudio analizamos la idoneidad de nueve genes de Petunia hybrida, como sistema modelo para Solanáceas, bajo distintos estados de desarrollo vegetativo y reproductivo.

Petunia plants that exhibit a white-flowering phenotype as a consequence of chalcone synthase transgene-induced silencing occasionally give rise to revertant branches that produce flowers with wild-type pigmentation. Transcription run-on assays confirmed that the production of white flowers is caused by post-transcriptional gene silencing (PTGS), and indicated that transgene transcription is repressed in the revertant plants, providing evidence that induction of PTGS depends on the transcription rate. Transcriptional repression of the transgene was associated with cytosine methylation at CpG, CpNpG and CpNpN sites, and the expression was restored by treatment with either 5-azacytidine or trichostatin A. These results demonstrate that epigenetic changes occurred in the PTGS line, and these changes interfere with the initiation of transgene transcription, leading to a reversion of the PTGS phenotype.

Petunia hybrida ‘Red Star’ is a variety whose flowers exhibit a star-type red and white bicolor pattern. We analyzed the mRNA levels of six genes involved in anthocyanin biosynthesis. Only the level of chalcone synthase (CHS) mRNA was depressed in the unpigmented flower sectors. Both transcriptional activity and the accumulation of short interfering RNA of CHS in the unpigmented sectors were detected. Viral infection blocked the generation of CHS-silenced sectors. These results indicate that sequence-specific degradation of CHS RNA is the primary cause of the formation of white sectors in ‘Red Star’ flowers.

Petunia hybrida ‘Red Star’ is a variety whose flowers exhibit a star-type red and white bicolor pattern. We analyzed the mRNA levels of six genes involved in anthocyanin biosynthesis. Only the level of chalcone synthase (CHS) mRNA was depressed in the unpigmented flower sectors. Both transcriptional activity and the accumulation of short interfering RNA of CHS in the unpigmented sectors were detected. Viral infection blocked the generation of CHS-silenced sectors. These results indicate that sequence-specific degradation of CHS RNA is the primary cause of the formation of white sectors in ‘Red Star’ flowers.

Petunia hybrida ‘Red Star’ is a variety whose flowers exhibit a star-type red and white bicolor pattern. We analyzed the mRNA levels of six genes involved in anthocyanin biosynthesis. Only the level of chalcone synthase (CHS) mRNA was depressed in the unpigmented flower sectors. Both transcriptional activity and the accumulation of short interfering RNA of CHS in the unpigmented sectors were detected. Viral infection blocked the generation of CHS-silenced sectors. These results indicate that sequence-specific degradation of CHS RNA is the primary cause of the formation of white sectors in ‘Red Star’ flowers.

Homeotic genes specify the identity of different plant tissues and organs. Mutations in of these genes results in replacement of a specific organ or tissue by another plant body part or tissue, which is normally formed at a different position. An important group of homeotic genes in plants is represented by members of the MADS box family of transcription factors. The first members isolated from this large family were involved in specifying the identity of floral organs. Based on the genetic and molecular analysis of these genes the "ABC(DE)" model of floral development was established. Meanwhile, MADS box transcription factors with other kind of functions were identified, like the regulation of flowering time.To gain insight in the molecular mechanisms underlying MADS box transcription factor functioning, the MADS box family of the model species Petunia hybrida has been analysed. MADS box proteins are active as homo- or heterodimers and even higher-order ternary and quaternary complex formation have been shown recently. Therefore, this study focuses mainly on the characterisation of protein-protein interactions. Initially, some new members of the petunia MADS box family were isolated from inflorescence and ovary cDNA-libraries, bringing the total number of identified petunia MADS box genes up-to 23. Members of this family are either named FLORAL BINDING PROTEINs ( FBPs ) or PETUNIA MADS ( pMADS ). The 23 members were all characterised by expression pattern analysis, phylogenetic comparison and yeast two-hybrid screenings for the identification of protein-protein interactions. The obtained results were compared with data from MADS box transcription factor families of other species, like Antirrhinum majus and Arabidopsis thaliana . This comparison demonstrated that MADS box genes and their functions are largely conserved among flowering plants and therefore, functions could be predicted for some unknown petunia and Arabidopsis MADS box proteins. Furthermore, some of t

In this thesis we have examined the spatial and temporal aspects of gene expression and the position induced differences in transgene expression between individual transformants. For this purpose we imaged luciferase ( luc ) gene expression driven by three different promoters that are active throughout a leaf tissue of transgenic petunia plants. The Cauliflower Mosaic Virus (CaMV) 35S promoter, a modified CaMV 35S promoter (m35S) and an Arabidopsis thaliana lipid transfer protein (LTP) were studied. We observed differences in in planta luciferase activity between individual transformants, but also between leaves within a plant and within a single leaf. The luciferase activity within a leaf of a single transformant could differ up to a factor 300. Moreover, the way in which in planta luciferase activity varies within a plant is different in independent transformants expressing the same transgene.The local differences in inplanta luciferase activity cannot be attributed to possible artefacts of the reporter system. Local limitations of luciferin, ATP or oxygen, which are all required for the luciferase reaction, might contribute to these artefacts. Pre-spraying the plants three to five times with luciferin is sufficient to obtain a steady state light production in "undisturbed" luciferase reporter plants, similar to feeding luciferin through the vascular system. We calculated that the ATP consumed by the luciferase reaction in planta is very small compared to the ATP steady state levels within leaf cells, while the cellular ATP concentration is far above the Km of luciferase for ATP. Furthermore, it was shown that oxygen levels could not be limited physiologically, resulting in changes in the local differences in luciferase activity within a leaf. We showed that the in planta activity of accumulated luciferase is rapidly declining after the first application of luciferin, indicating that in planta either no or very little regeneration of luciferase (activity) occurs d

Am "Max-Planck-Institut für Züchtungsforschung Köln-Vogelsang" wurde Mitte der achtziger Jahre in eine weißblühende Linie von Petunia hybrida Hort. (Vilm.) ein Anthocyansynthese-Gen von Zea mays L. transferiert. Unter den nach diesem Gentransfer entstandenen ziegelrot blühenden Pflanzen befand sich auch ein Typ, der ein Sternmuster in der Blüte zeigt. In der vorliegenden Arbeit konnte diese Musterbildung auf eine chimärische Konstitution zurückgeführt werden: Die Instabilität des A1-Gens in der Petunie resultiert in einen Farbstoffausfall in der alleinig farbstofführenden Epidermis, die von der ersten Scheitelschicht (L1) des Sproßscheitels gebildet wird. Subepidermale Gewebe können als genetisch intakt im Sinne einer potentiellen Fähigkeit zur Farbstoffsynthese charakterisiert werden. Deutlich wird das unter anderem an den partnerinduktiven Wirkungen, die von subepidermalem, L2-bürtigen Gewebe ausgehen und die Anthocyanbildung in der benachbarten, farbstoffdefekten Epidermis veranlaßt. Da die L1 am Kronblattrand alle Gewebe, also auch das Mesophyll bildet, bleiben diese Bereiche weiß gefärbt. Nur im Binnenfeld der Petalen, wo L2-bürtiges, intaktes Gewebe an die Epidermen anschließt, treten diese partnerinduktiven Wirkungen auf. Das Resultat ist ein Sternmuster der aus fünf Petalen zusammengewachsenen Kronröhre. Spontan und nach in-vitro-Kalluskultur entmischen die Pflanzen in ihre einzelnen Komponenten, so daß rot und weiß blühende Typen entstehen, die mit ihrer Blütenfarbe und ihrem Ploidiegrad (unterscheidbar bei Ploidiemarkierung) die jeweilige Scheitelschicht repräsentieren, von der sie abstammen. Bei Kreuzung spaltet die Nachkommenschaft in rot und weiß blühende Pflanzen auf. Aufgrund der Instabilität des transferierten A1-Gens ergibt sich kein Mendelsches Aufspaltungsverhältnis für die Blütenfarbe, wie das dem heterozygotem Zustand entsprechen würde. Auch existieren (wie bei den Entmischungsprodukten) gesprenkelte Blütentypen. Die Instabilität konnte als lich

Am "Max-Planck-Institut für Züchtungsforschung Köln-Vogelsang" wurde Mitte der achtziger Jahre in eine weißblühende Linie von Petunia hybrida Hort. (Vilm.) ein Anthocyansynthese-Gen von Zea mays L. transferiert. Unter den nach diesem Gentransfer entstandenen ziegelrot blühenden Pflanzen befand sich auch ein Typ, der ein Sternmuster in der Blüte zeigt. In der vorliegenden Arbeit konnte diese Musterbildung auf eine chimärische Konstitution zurückgeführt werden: Die Instabilität des A1-Gens in der Petunie resultiert in einen Farbstoffausfall in der alleinig farbstofführenden Epidermis, die von der ersten Scheitelschicht (L1) des Sproßscheitels gebildet wird. Subepidermale Gewebe können als genetisch intakt im Sinne einer potentiellen Fähigkeit zur Farbstoffsynthese charakterisiert werden. Deutlich wird das unter anderem an den partnerinduktiven Wirkungen, die von subepidermalem, L2-bürtigen Gewebe ausgehen und die Anthocyanbildung in der benachbarten, farbstoffdefekten Epidermis veranlaßt. Da die L1 am Kronblattrand alle Gewebe, also auch das Mesophyll bildet, bleiben diese Bereiche weiß gefärbt. Nur im Binnenfeld der Petalen, wo L2-bürtiges, intaktes Gewebe an die Epidermen anschließt, treten diese partnerinduktiven Wirkungen auf. Das Resultat ist ein Sternmuster der aus fünf Petalen zusammengewachsenen Kronröhre. Spontan und nach in-vitro-Kalluskultur entmischen die Pflanzen in ihre einzelnen Komponenten, so daß rot und weiß blühende Typen entstehen, die mit ihrer Blütenfarbe und ihrem Ploidiegrad (unterscheidbar bei Ploidiemarkierung) die jeweilige Scheitelschicht repräsentieren, von der sie abstammen. Bei Kreuzung spaltet die Nachkommenschaft in rot und weiß blühende Pflanzen auf. Aufgrund der Instabilität des transferierten A1-Gens ergibt sich kein Mendelsches Aufspaltungsverhältnis für die Blütenfarbe, wie das dem heterozygotem Zustand entsprechen würde. Auch existieren (wie bei den Entmischungsprodukten) gesprenkelte Blütentypen. Die Instabilität konnte als lich

This thesis presents an analysis of the structural and histochemical aspects of cytoplasmic male sterility (cms) in Petuniahybrida . In petunia and in other crops, cms is the most commonly used tool for hybrid seed production. Application of the trait makes hybrid seed production possible without the need of emasculation of the maternal line. However, in spite of its economic importance, little is known on the primary causative factor and the initial step of pollen abortion in cms plants. Insights in the initial effects of cms may lead to a more comprehensive understanding of the regulation and expression of male sterility controlling genes, and, additionally, may possibly provide strategies for the introduction or induction of male sterility in crops in which cms systems are not available.In the first Chapter, some molecular aspects of cms are evaluated. Several lines of evidence indicate that the genetic determinants responsible for cms are carried by the mitochondrial genome. The mitochondrial involvement is found in a variety of plant species, including Petuniahybrida . Most of the mitochondrial encoded polypeptides are components of complexes which are responsible for key steps in the process of oxidative phosphorylation and the generation of ATP. Correspondingly, mitochondria isolated from tissues of cms plants, may code for an aberrant polypeptide composition of components of one of these complexes. Nevertheless, more information on the expression of mitochondrial genes in different anther tissues at various stages of development is necessary before we can conclude whether or not the deviations in mitochondrial DNA are functionally associated with the non-formation of viable pollen.The initial abnormalities in anther development of cms plants are generally found in the tapetal tissue. Also in the cms form of Petuniahybrida cv. Blue Bedder (BBS), the first symptoms of deviation are found in the tapetum (Chapter 2). Light microscopical analysis shows, that in B

Styles, ovaries, anthers and pollen of Petunia hybrida and pollen of Liliun longiflorum were analysed for the presence of abscisic acid (ABA) by means of high performance liquid chromatography (HPLC) combined with UV and fluorometric detection. All these reproductive organs were shown to contain endogenous ABA. However, styles have a particular high content in comparison with that of ovaries, anthers and pollen. In addition the ABA content of styles increased rapidly during flower development prior to anthesis, while in ovaries and anthers after an initial decrease the ABA content remained constant at a comparatively low level. After compatible cross-pollination the ABA content of styles in particular, but also of ovaries, was significantly reduced compared with incompatible self-pollination. Lilium longiflorum pollen also contained ABA. Upon germination in vitro the ABA content of Lilium pollen decreased rapidly, while at the same time a large amount ABA was released into the germination medium, possibly due to enzymic hydrolysis of ABA conjugates present in pollen.

Siphonogamy, or the fact that fertilization is mediated through a pollen tube, is emerging as a uniquely adapted system for male-female interaction (Heslop-Harrison, 1983) and for male gametophyte selection (Mulcahy, 1979). However, we still know very little on the physiological mechani sms that control such selection. A better understanding of male-female interaction from pollination to fertilization may enlighten this process. In this respect most of the work has been done regardi ng poll en germination at the stigma (Heslop-Harrison and Heslop-Harrison, 1985) or concerning pollen tube growth in the style (van Went and Willemsen, 1984). However, there is a paucity of data regarding pollen tube growth in the ovary region (Knox, 1984).