Coordinated development of the architecture of the primary shoot in bush rose S. Demotes-Mainard*, G. Guéritaine*, R. Boumaza*, P. Favre*, V. Guérin*, L. Huché-Thélier*, B. Andrieu** *UMR SAGAH, Angers, France ** UMR EGC, Grignon, France D I E T A G R I C U L T U R E E N V I R O N M E N T

In ornamental plants, the architecture is important for both plant functions and plant visual quality Creeping or erect stature Symmetry Foliage density Development, Organ extension, Resources allocation Perception of environment Acquisition of resources Architecture Plant- Environment interface Yield and nutritive quality Visual quality Food & fodder crops Ornamental crops Not mentioning other users

Growing roses in a glasshouse enables to modulate the environmental conditions Temperature, CO2, radiation, humidity, water and nutrient supply can be manipulated Growing roses in a glasshouse implies: the possibility to manipulate plant environment the requirement to optimize the costs linked to the glasshouse and to control the diseases and insects => need tools to define the best compromizes

In roses, architecture is strongly modified by environmental conditions Sensitivity to global environmental conditions Girault et al. (2008) Plant Cell Env. 31: Sensitivity to local environmental conditions For growers: Knowledge on how to manipulate plant architecture to match needs for: - innovative shapes - stable, reproductible shapes References on how new varieties are going to behave Methods to manipulate plant shape cheaper than pruning For research : Rose bush as a model to investigate G*E interactions on formation of plant architecture

Objectives Objective of the project To develop a functional structural model of bush rose in order to explore the plant response to genotype × environment interactions Objective of the work presented here To produce an organized description of the kinetics of development and final dimensions of the organs forming the primary shoot of the rosebush and of their relationships Expected outcomes of this work: –Identification of pattern that may be stable enough to be incorporated into a functional structural model –A parametric 3D rose model that can be used to investigate light distribution on the plant –A grid for analyzing rose architecture in response to genotype × environment interactions

Material and methods Roses (Rosa hybrida) of the ‘Radrazz’ cultivar - Plant developmental stages - Number of phytomers on main shoot - Leaf shape measurements at various stages - Detailed kinetics of extension for terminal leaflets and for internodes 2 glasshouse experiments with destructive and non-destructive measurements Bud break from a cutting Flowering of primary axis

Simple relationships allowed to describe the sequence of leaves along the stem Allometric relationships related all leaflet dimensions to length of terminal-leaflet This was true when comparing mature leaves and was quite accurate for a leaf at different stages of growth Mean leaflet number per leaf BaseTo p Main stem consisted of between 8 and 12 phytomers at flowering The number of leaflets per leaf varied according to position along the stem, following a well defined pattern

Extension of terminal leaflets and internodes were fitted by linear relations with thermal time A phytomer : Term. leaflet (A) ___ : Internode (I) Within plants : - Leaflets of successive phytomers had very similar durations of extension: the variability in final size resulted only from variability in extension rates - Internodes of successive phytomers show some variability in the duration of extension: the variability in final sizes resulted mainly from variability in extension rates and slightly from variability in duration of extension Between plants: For plants having a same number of phytomers, variability of size resulted from variation in extension rates A I

Extension of terminal leaflets and internodes are coordinated The beginning of linear growth: terminal leaflet was synchronous with the internode of the same phytomer End of growth: terminal leaflet was synchronous with the internode of the next phytomer ° Cd since peduncle is 1 cm Beginning of extension ° Cd since peduncle is 1 cm End of extension

First L-system implementation, using L-studio

First implementation of a dynamic rose tree First L-system implementation, using L-studio

Implications This works provides a framework for studying the development of rosebushes architecture The stability of the relationships will be evaluated over a range of genotypes and growth conditions Two main types of application : –A grid for analyzing the response of rose phenotypic development genotype × environment interactions –A dynamic, plant model that can be fitted to experimental data and coupled with a radiative transfer model to test hypotheses on plant responses to global and local light environment –Depending on their stability, some or all of observed patterns willl be re-used in the development of a functional plant model