S05 - Session O2 - Facing the dynamic environment: a systemic perspective on the physiology of leafy cuttings

Authors: Uwe Druege *

Leafy, in particular shoot tip but also nodal cuttings, are the starting material for vegetative propagation of many ornamental plant species. The optimization of the propagation process is challenged by 1) highly complex propagation chains that often involve production of cuttings in tropical regions and their subsequent storage and transport, 2) a continuous change of the chains because of new demands from the society and developing new technologies and 3) the great genetic diversity of propagated plants. Better understanding of the crucial physiological principles that underly the vitality and root development in cuttings in the complex environment would provide a roadmap how to reach the ultimate goal, an intensively rooted cutting with intact green leaves with the lowest possible input of resources and time. Majorly based on own research on cuttings of several ornamental species including chrysanthemum, pelargonium, petunia and rose, a model will be presented that integrates important physiological functions of distinct cutting parts which are decisive for successful propagation and further highly responsive to environmental factors. Depending on the type of cutting, the rooting zone, differently developed leaves, the shoot apex and outgrowing axillary buds are considered as important physiological units of a cutting. Homeostasis and signal transduction of distinct plant hormones at whole cutting level are considered as important factors that control the functional integrity of the cutting and the reprogramming of cells in the stem base towards the initiation and further development of roots. The carbon-nitrogen source-sink balance in cuttings is considered as important bottleneck for the supply of the developing roots with building blocks and is further linked to the hormone system. Distinct physiological outputs may be used to monitor the rooting capacity of cuttings and to optimize the cutting environment. Characterization of bottleneck-specific plant groups may help to face the great genetic diversity.