Sur l'étude, la modélisation et la simulation du transport de sucrose dans le phloème des arbres
Dans le cadre d'une réunion d'un projet PHC "Dumont D'Urville" entre la France et la Nouvelle Zélande, sur "la modélisation et la simulation du transport de sucrose dans le phloème des arbres", auquel participent Emilie PEYNAUD et Yves DUMONT, et qui se déroulera du 6 au 8 septembre, l'Umr AMAP un séminaire ouvert Í tous, le jeudi 7 septembre de 10h Í 12h en salle 201 du PS2, avec les deux exposés suivants:
de 10h Í 11h:
Youcef Mammeri (U. de Picardie, Amiens) et Damien Sellier (Scion Research Institut, New Zealand)
A SURFACE MODEL OF NONLINEAR, NON-STEADY-STATE PHLOEM TRANSPORT
Abstract Phloem transport is the process by which carbohydrates produced by photosynthesis in the leaves get distributed in a plant. According to Mͼnch, the osmotically generated hydrostatic phloem pressure is the force driving the long-distance transport of photoassimilates. We will present our model of coupled water- carbohydrate transport following Thompson and Holbrook's approach. Then we will explain how the model is applied to simulate the flow of phloem sap for an organic tree shape, on a 3D surface and in a channel with orthotropic hydraulic properties.
de 11h Í 12h:
Sebastian Leuzinger (Auckland University of Technology, Auckland, New Zealand)
OF MANGROVES AND KAURI TREES: SOME SECRETS LEFT!
This is a status report of a small New Zealand research group using state-of-the-art ecophysiological sensors (point dendrometers, heat-ratio sap flow meters, stem psychrometers, leaf water potential, and leaf growth meters). I will focus on a few recent, ongoing projects: first, I will illustrate the complexity of stem radius changes in mangroves, which is due to their peculiar secondary phloem strands. We find a counter-intuitive reversal of stem diameter changes, whereby, as transpiration starts in the morning, trees show shrinkage at the bottom of the stem first, but only later at the upper stem. The pattern can only be explained with substantial changes in osmolyte concentration in the phloem. Second, I will show some first results of an in situ 'leaf growth meter' that we built for usage in the field, to answer the seemingly simple question of 'when do leaves grow'? I will further give an outlook on a project idea on a novel way of measuring phloem flow using electrokinetic signals. Lastly, I will give some insight on sap flow measurements of a living kauri stump, which seems to be kept alive by it's photosynthesising conspecifics. We find that this kauri 'methusalem' is consuming carbohydrates at night, when the surrounding trees' water potential is high, which proves its dependency on the 'working' generation of trees.
de 10h � 11h:
Youcef Mammeri (U. de Picardie, Amiens) et Damien Sellier (Scion Research Institut, New Zealand)
A SURFACE MODEL OF NONLINEAR, NON-STEADY-STATE PHLOEM TRANSPORT
Abstract Phloem transport is the process by which carbohydrates produced by photosynthesis in the leaves get distributed in a plant. According to M�nch, the osmotically generated hydrostatic phloem pressure is the force driving the long-distance transport of photoassimilates. We will present our model of coupled water- carbohydrate transport following Thompson and Holbrook's approach. Then we will explain how the model is applied to simulate the flow of phloem sap for an organic tree shape, on a 3D surface and in a channel with orthotropic hydraulic properties.
de 11h � 12h:
Sebastian Leuzinger (Auckland University of Technology, Auckland, New Zealand)
OF MANGROVES AND KAURI TREES: SOME SECRETS LEFT!
This is a status report of a small New Zealand research group using state-of-the-art ecophysiological sensors (point dendrometers, heat-ratio sap flow meters, stem psychrometers, leaf water potential, and leaf growth meters). I will focus on a few recent, ongoing projects: first, I will illustrate the complexity of stem radius changes in mangroves, which is due to their peculiar secondary phloem strands. We find a counter-intuitive reversal of stem diameter changes, whereby, as transpiration starts in the morning, trees show shrinkage at the bottom of the stem first, but only later at the upper stem. The pattern can only be explained with substantial changes in osmolyte concentration in the phloem. Second, I will show some first results of an in situ 'leaf growth meter' that we built for usage in the field, to answer the seemingly simple question of 'when do leaves grow'? I will further give an outlook on a project idea on a novel way of measuring phloem flow using electrokinetic signals. Lastly, I will give some insight on sap flow measurements of a living kauri stump, which seems to be kept alive by it's photosynthesising conspecifics. We find that this kauri 'methusalem' is consuming carbohydrates at night, when the surrounding trees' water potential is high, which proves its dependency on the 'working' generation of trees.