The pollen grain of pollen is generally made of only 2 haploid cells: – The tube cell, responsible for the elongation of the pollen tube, – The generative cell that will give 2 male gametes or sperm cells. The pollen grain is surrounded with 2 walls: – The exine, thick, ornamented or smooth, – And the intine, fine and doubling inside the exine. In certain places called apertures, exine is thinner and intine thicker. In the pollen of Monocots or Basal Dicots, there is normally only one aperture, circular or furrowed. Sometimes, this aperture stretches, being thinned by places it then gives several pores. In the pollen of true Dicots (Eudicots), there are normally 3 apertures. However, this number can vary and be multiplied. 
Pollen germination and pollen tube
Germination of pollen begins when the grain swells because of the absorption of the water at stigma surface. Turgescent vacuoles push the intine and the cytoplasm towards an aperture of the pollen grain of pollen: it is the beginning of the growth of the pollen tube. When the pollen tube gets longer, the 2 cells (generative cell and tube cell) and the cytoplasm are confined at its extremity, the generative cell being slightly behind the tube cell. Phenomena of cellular strain are limited at the end of the tube. The pollen tube crosses the style without ever penetrating into cells; cells of the conducting tissue act as rails for the pollen tube that finishes its growth at the level of the micropyle into the ovule.
Curriculum vitae
LAURENT BRAY E-mail: [->contact@botanique.org] PROFESSIONAL EXPERIENCE ——- 1995-2005 City of Paris, Green Spaces Department, Curator and scientific Head of Plant Collections: – Established the Botanic Garden of the city of Paris by applying business and administrative methods: strategic planning, cost analysis, benchmarking, SWOT and developed a data base following the International Transfer Format, – Developed Biodiversity Conservation activities and created plant collections, – Developed Education activities (botanic courses, research activities, science for pupils) and links with universities (plant material donation for research, trainees, excursions for students). Wild and cultivated green spaces assessment: – Impact studies: phytosociological analysis, protected plant species, – Management propositions following the national and international laws on biodiversity conservation especially the European directive Natura2000. 1995 Cirad, International Center of Agronomy for Development, Paris: Authored the project for Biodiversity Conservation and Sustainable Development of Djibouti accepted by the Global Environment Facility (1-month contract). 1992-1994 French Technical Assistance, Head of Life Sciences Department at the Institute of Higher and Technical Studies (ISERST) in Djibouti: – Sale of goods and services: technical assistance, soil analysis, seedling production…, fund raising (USA, EEC, France, UN…), – Lead (a) Plant genetic resources in arid zones funded by the French cooperation, (b) Agro-pastoralism resources funded by the Italian cooperation, – Managed and trained 12 people from several countries. 1991 Cabinet Mazars, Auditor, Paris: Financial and organizational audit of firms, banks and mutual funds. EDUCATION AND DIPLOMAS —— 2001 MBA. Conservatoire National des Arts & Métiers, Paris. 1990 Ph.D. in Biology and Physiology of Plants. University P. & M. Curie, Paris. Graduated with the highest honors. 1990 Training course in Financial auditing, HEC (1 month). 1988 Master in Plant Biology. Passed with distinction. University P. & M. Curie, Paris. SKILLS AND MISCELLANEOUS ——- Languages Fluency in English and Italian. Computer Office Professional (Word, Excel, Access, PowerPoint), MS Project. Associations Member of the French Association of Experts in Technical Assistance, board member of the French speaking botanic gardens association and different botanic gardens in France: University Paris XI, Savigny-le-Temple and veterinary college of Maisons-Alfort.
Publications
– Bray L., 2003. L’orangerie de l’hôtel Le Peletier de Saint-Fargeau – Plantes d’introductions récentes pour le prestige et plantes indigènes médicinales. Bulletin de la société de l’histoire de Paris et de l’Ile-de-France, 130 : 103-107. – Bray L., 2002. L’espèce : discussion d’une notion intuitive. Hommes & Plantes, 43 : 32-35. – Bray L., 2001. Achievement of new botanic gardens through analysis of existing parts and integration of key assets to fulfill the French-speaking botanic garden charter. In Plants, People and Planet Earth – the role of botanic gardens in sustainable living. Proceedings of the Fifth International Botanic Gardens Conservation Congress Davis, G. & Scott, A. ed. : CD-ROM. – Bray L., 2000. Plantes à fleurs d’Europe occidentale. Systématique évolutive. Ed. Diderot Multimédia / Diffusion Le Seuil : 272 p. – Bray L., 2000. Du jardin de ville au jardin botanique : le management appliqué à la conservation de la biodiversité. European Master of Business and Administration, Ceprim-Conservatoire National des Arts & Métiers : 71 p. – Bray L. Duru J., Charrier C., Loriot S., 2000. Les nouvelles missions éducatives du jardin botanique de la ville de Paris. Compte-rendus du congrès sur l’éducation dans les jardins botaniques de la Gacilly (9-11 juin 1999) : 7-11. Haïcour R., Bray L., Ducreux G., 1999. Abrégé de systématique des plantes à fleurs communes de France. Edition de l’Université Paris-Sud : 58 p. – Bray L., Pertuzon C., 1999. Systématique des Palmiers ou Arecaceae. Hommes & Plantes (n° spécial) : 15-16. – Bray G., Bray L., 1998. Gestion informatisée des collections végétales vivantes ou mortes selon la 2ème norme ITF définie par le Botanical Garden Conservation International. Base de données relationnelles fonctionnant en réseau avec une gestion des groupes d’utilisateurs. – Bray L., Bonnet S., Couette F., 1997. Conservation des ressources phytogénétiques par le jardin botanique de la Ville de Paris. Actes du Séminaire Agrogène 1997 : 104-116. – Di Michele M.N., Bray L., Mounir S., Ali A., Nasser M., 1995. Faisabilité du semis direct d’arbres à usages multiples. In : Quel avenir pour l’amélioration des plantes ? Dubois J. & Demarly Y. éd., John Libbey Eurotext, Paris : 448-459. – Bray L., Lecouturier V., Di Michele M.N., 1995. Sensibilité d’Acacia flava et d’Acacia nilotica à Agrobacterium tumefaciens. In : Quel avenir pour l’amélioration des plantes ? Dubois J. & Demarly Y., John Libbey Eurotext, Paris : 195-204. – Di Michele M.N., Bray L., 1995. Multiplication végétative in vitro d’Acacia flava syn. erhenbergiana. In : Quel avenir pour l’amélioration des plantes ? Dubois J. & Demarly Y., John Libbey Eurotext, Paris : 97-108. – Bray L., Mounir S., Di Michele M.N., Mohamed C., 1994. Comparaison de deux provenances djiboutiennes (Ruelli et Ribta) d’arbre à encens (Boswellia papyrifera), espèce d’intérêt économique pour Djibouti et la Corne de l’Afrique. Sciences et Environnement, 9 : 29-32. – Bray L., Di Michele M.N., Nima A., Mahamoud H., 1994. Les recherches en Biotechnologies à Djibouti. Sciences et Environnement, 9 : 63-67. – Jalludin M., Bray L., Atasi M., Gafaneh A., Zotskina E., Hirsch J., Houdart X., Weight D., Ali A., 1993. Evaluation des ressources en eau et terre du site expérimental du cône de déjection de l’oued Atar. Revue de l’ISERST, 8 : 23-26. – Bray L., Di Michele M.N., 1993. Réflexions sur la désertification et l’environnement. Revue de l’ISERST, 8 : 9-17. – Di Michele M.N., L. Bray, 1992. La culture in vitro à Djibouti : un outil de la lutte contre la désertification. Rivista di Agricoltura Subtropicale e Tropicale, 87 : 85-96. – Bray L., D. Chriqui, K. Gloux, M. Meyer, J. Peduzzi, 1992. Teneurs en trigonelline et en acides aminés de vitro-plants de Populus trichocarpa x Populus deltoides soumis à un stress de salinité. In : Biotechnologies appliquées aux arbres forestiers, 1991. Réseau AFOCEL-Ministère de la Recherche et de l’Espace, AFOCEL, Paris : 111-126. – Bray L., D. Chriqui, K. Gloux, D. Meyer, J. Peduzzi, 1991. Betaines and free amino acids in salt stressed vitroplants and resting buds of Populus trichocarpa x deltoides. Physiol. Plant., 83 : 136-143. – Bray L., 1990. Conséquences métaboliques et cellulaires du stress de salinité chez les vitroplants de Populus trichocarpa x deltoides cv Hunnegem. Thèse de Doctorat de l’Univ. P. & M. Curie, Paris : 138 pp. – Bray L., D. Chriqui, K. Gloux, D. Le Rudulier , 1990. Trigonelline accumulation in Populus trichocarpa x deltoides during winter dormancy or after in vitro culture under salt stress. In : Cinquantenaire de la culture in vitro chez les végétaux, Colloques de l’INRA, 51, C. Doré, INRA pub. : 253-254. – Bray L., D. Chriqui, K. Gloux, D. Le Rudulier, 1989. Variations de la teneur en trigonelline associées au stress salin et à la dormance hivernale chez Populus trichocarpa x deltoides. Annales de recherches sylvicoles AFOCEL : 133-137. – Bray L., 1988. Recherches préliminaires sur la résistance au stress salin chez Populus trichocarpa x deltoides cv Hunnegem. Diplôme d’Etudes Approfondies, Univ. P. & M. Curie, Paris : 60 pp. YEARLY PUBLICATIONS ——- – Editor of the Index seminum of the botanic garden of the city of Paris from 1997 to 2000. The objective of this list of seeds, freely distributed to other botanic gardens, is to promote our biodiversity conservation activities, especially of genetic resources of plants of wild origin.
Participations at conventions
– Bray L., 2004. Les adventices allergisantes – Dissémination : reproduction sexuée ou végétative. Troisième séminaire national Botanique et Allergie, 29-30 May, Vienne-le-Château (France), oral communication. – Bray L., Delmas M., 2004. Botanic gardens must promote holistic knowledge of plants. Session : Environmental Reconciliation – a vision for botanic gardens. Second World Botanic Congress, 17-23 April, Barcelona (Spain), oral communication. – Bray L., 2003. Pollen des phanérophytes : morphologie, transport, dispersion géographique. Deuxième séminaire national Botanique et Allergie, 2-3 May, Sorèze (France), oral communication. – Gourlet J., Joly E., Bray L., 2000. The strategy of the botanical garden of the city of Paris: objectives, actions and achievements. First World Botanic Gardens Congress, Partnership Within and Beyond the Garden, 25-30 April, Asheville (USA), oral communication. – Bray L., 2000. Business and administration methods applied to science education in the botanical garden of the city of Paris. “Eurogard 2000” The Second European Botanic Garden Conference, 10-16 April, Las Palmas-Canary Islands (Spain), oral communication. – Charrier C., Bray L., Joly E., 2000. Cultivated-origin seeds for improving conservation of wild-origin seeds of endangered species. “Eurogard 2000” The Second European Botanic Garden Conference, 10-16 April, Las Palmas-Canary Islands (Spain), oral communication. – Bray L., 1999. The strategic importance of science education in the botanical garden of the city of Paris. Fourth International Congress on Education in Botanic Garden, 6-11 November, Trivandrum (India), oral communication. – Bray L., Pierre E., 1999. Les actions éducatives du jardin botanique de la ville de Paris. Congress on Environmental education organised by the French Speaking Botanic Gardens Association. La Gacilly (France), 9-11 June, oral communication. – Bray L., 1998. How a green spaces department can reach the commitments of a botanical garden : the example of the city of Paris. Fifth International Botanic Gardens Conservation Congress, 14-18 September, Cape Town (South Africa), oral communication. – Bray L., Dagneau C., Jamet V., 1998. La biodiversité méditerranéenne exprimée dans les activités du jardin botanique de la Ville de Paris (The mediterranean biodiversity in the activities of the botanical garden of the City of Paris). IXème Colloque d’OPTIMA, National Natural History Museum, Paris (France), 11-17 May, poster. – Bray L., 1998. Conservation policy in the botanical garden of the city of Paris. Kew Mutual Improvement Society, 19 January, Kew (Great Britain), oral communication. – Beaufils J.-B., Bray L., 1997. Conservation of endemic and/or endangered plant species of New-Caledonia. “Eurogard 97” The First European Botanic Garden Conference, 2-5 April, Edinburgh (Great Britain ), poster. – Bray L., 1997. Plant genetic resources conservation by the botanical garden of the city of Paris. “Eurogard 97” The First European Botanic Garden Conference, 2-5 April, Edinburgh (Great Britain ), poster. – Bray L., 1997. L’accès aux ressources génétiques dans les jardins botaniques. Congress organised by Agrogene, 30-31 January, Paris (France), oral communication. – Bray L., 1996. The new millenium challenge for the botanic gardens of Paris. Third international congress on education in botanic gardens, 7-11 Spetember, New-York (USA), oral communication. – Bray L., Di Michele M. N., 1996. Influence of trigonelline applied on salt-stressed vitroplants and seedlings of Acacia ehrenbergiana. Congress organised by EUCARPIA, 11-15 March, Montpellier (France), poster. – Bray L., Di Michele M.N., 1995. Biotechnologies et ressources génétiques. Cinquièmes journées scientifiques du réseau Biotechnologies – Génie génétique des plantes de l’UREF & ISRA, 13-15 December, Dakar (Senegal), oral communication. – Bray L., Bray M.N., Lecouturier V., 1993. Amélioration de la résistance à la salinité chez Acacia sp. Quatrièmes journées scientifiques du réseau Biotechnologies – Génie génétique des plantes de l’UREF & CRA/FSA, 18-21 October, Gembloux (Belgium), oral communication. – Bray L., 1993. International workshop on halophytes for reclamation of saline wastelands and as a resource for livestock. PNUE, 22-27 November, mission report, Nairobi (Kenya): 11 pp. – Bray L., 1992. Symposium UIFRO Production de variétés génétiquement améliorées d’espèces forestières à croissance rapide. AFOCEL-UIFRO, Bordeaux (France), 14-18 September. – Bray L., D. Chriqui, K. Gloux, D. Le Rudulier, M. Meyer, J. Peduzzi, 1991. Variations des teneurs en acides aminés et en bétaïnes chez Populus trichocarpa x P. deltoides durant un stress de salinité ou durant la dormance hivernale. Réunion du Groupe d’Etudes de l’Arbre, INRA, 27-28 March, Nancy (France), oral communication. – Bray L., D. Chriqui, K. Gloux, D. Le Rudulier, 1989. Accumulation de trigonelline chez Populus trichocarpa x deltoides durant la dormance hivernale ou après un stress salin. XIème colloque de la section française de l’IAPTC, 24-25 October, Versailles (France), poster. – Jehan H., L. Bray, J.C. Caissard, D. Chriqui, 1989. Modulations des réponses de régénération in vitro et de transformation génétique chez Populus trichocarpa x deltoides. XIème colloque de la section française de l’IAPTC, 24-25 October, Versailles (France), poster.. – Bray L., H. Jehan, J.C. Caissard, D. Chriqui, 1989. Recherches de bases sur l’obtention de régénérants transformés chez Populus trichocarpa x deltoides. International conference on biotechnologies, Amiens (France), 10-12 July, poster. – Bray L., D. Chriqui, K. Gloux, D. Le Rudulier, 1989. Trigonelline accumulation in salt-stressed vitroplants of Populus trichocarpa x deltoides. International conference on biotechnologies, Amiens (France),10-12 July, poster.