Using the identification of several morphological criteria and considering the plant as a whole, from germination to death, architectural analysis is essentially a detailed, multilevel, comprehensive and dynamic approach to plant development. Despite their recent origin, architectural concepts and analysis methods provide a powerful tool for studying plant form and ontogeny. Completed by precise morphological observations and appropriated quantitative methods of analysis, recent researches in this field have greatly increased our understanding of plant structure and development and have led to the establishment of a real conceptual and methodological framework for plant form and structure analysis and representation. This paper is a summarized update of current knowledge on plant architecture and morphology; its implication and possible role in various aspects of modern plant biology is also discussed.

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Abstract. The ImageCLEF's plant identification task provides a testbed for the system-oriented evaluation of plant identification, more precisely on the 126 tree species identification based on leaf images. Three types of image content are considered: Scan, Scan-like (leaf photographs with a white uniform background), and Photograph (unconstrained leaf with natural background). The main originality of this data is that it was specifically built through a citizen sciences initiative conducted by Tela Botanica, a French social network of amateur and expert botanists. This makes the task closer to the conditions of a real-world application. This overview presents more precisely the resources and assessments of task, summarizes the retrieval approaches employed by the participating groups, and provides an analysis of the main evaluation results. With a total of eleven groups from eight countries and with a total of 30 runs submitted, involving distinct and original methods, this second year pilot task confirms Image Retrieval community interest for biodiversity and botany, and highlights further challenging studies in plant identification.

The modelling framework serves as a tool for theoretical botany to explore the emergence of specific morphological and architectural patterns and can help to understand plant phenotypic plasticity and its strategy in response to environmental changes.

During the growing seasons 1994-1995 and 1995-1996, weekly measures of length and number of internodes and morphological observations were made on annual shoots of 11- to 21-year-old Nothofagus dombeyi (Mirb.) Blume trees growing in northern Patagonia, Argentina. Growth period and shoot size at the end of the extension period were highly variable. Four main types of annual shoots could be identified according to the death or persistence of the apical meristem and the development or not of axillary branches during the growth season of main stem extension. For all shoots the maximum growth rate took place in late November and was followed by a slower growth rate or cessation of growth in early December to early January. For those shoots with a long growth period, a second growth peak took place in late January-February, and only those shoots with a growth rate higher than 35-40 mm/week developed axillary branches as they elongated. Results from bud dissections suggest that the early growth rate peak corresponded to the development of those structures preformed at the time of bud break. The death of the apical meristem of a shoot affected both the position and the relative size of axillary branching on that shoot.Key words: Nothofagus, annual shoot, growth dynamics, branching pattern.

A new approach for modelling plant growth using the software AMAPpara is presented. This software takes into consideration knowledge about plant architecture which has been accumulated at the Plant Modelling Unit of CIRAD for several years, and introduces physiological concepts in order to simulate the dynamic functioning of trees. The plant is considered as a serial connection of vegetative organs which conduct water from the roots to the leaves. Another simple description of the plant as a network of parallel pipes is also presented which allows an analytical formulation of growth to be written. This recurring formula is used for very simple architectures and is useful to understand the role of each organ in water transport and assimilate production. Growth simulations are presented which show the influence of modifications in architecture on plant development.

The model is applied to mono-specific field crops and forest stands. For high-density crops at full cover, the model is shown to be equivalent to the classical equation of field crop production (Howell and Musick, 1985, in Les besoins en eau des cultures; Paris: INRA Editions). However, our method is more accurate at the early stages of growth (before cover) or in the case of intermediate densities. It may potentially account for local effects, such as uneven spacing, variation in the time of plant emergence or variation in seed biomass. The application of the model to trees illustrates the expression of plant plasticity in response to competition for light. Density strongly impacts on tree architectural development through interactions with the source-sink balances during growth. The effects of density on tree height and radial growth that are commonly observed in real stands appear as emerging properties of the model.