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1
PRESENTATION OF METABOLIC FUNCTIONS IN A 3-D MODEL OF
PLANT STRUCTURE
Risto Sievänen
Eero Nikinmaa
Jari Perttunen
http://www.metla.fi/projects/lignum
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What is a virtual plant?
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Features of a Virtual Plant
A basic unit is used for presentation of both architecture and functioning
(metabolism)
These units are combined to form different organizational levels
Local control
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metamer
barksapwood
heartwood
storage
CO2
apical meristem
axillary budH2O
CO2
H2OCHO, N
Aerial parts
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barksapwood
heartwood
differentiating fine root
root hairs
root tip
emerging fine root
Roots
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Components of model Lignum
Photosynthesis
Respiration
Shoot elongation & needle growth
Thickness growth
Root growth
Senescence
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Models dealing with metabolic processes
Vegetative and reproductive growth
Photosynthesis, respiration and carbon allocation
Mineral metabolism, especially nitrogen metabolism
Growth regulations
Intra-tree transfer of metabolites
(Dixon 1990)
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Driving variables
Solar radiation
Temperature
Wind speed
air humidity, soil moisture
CO2 concentration
etc
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Time step
• Long (year, month, day)
fast process & nonlinear function: mean value no good
consistent with structural dynamics
• short (hour, minute)
lots of data
computationally heavy
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Photosynthesis - Respiration = Growth
distribution of growth a key problem
( distribution of metabolic products )
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Distribution of growth at unit level
State of the unit
Local environmental conditions
Crown architecture
Position in the crown
growth
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Approaches to distribution of growth
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Structural rules
Allometric equations
Pipe model theory
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Pipe model theory
• Lots of data, straightforward, works well in various conditions
• Describes end result of a process, difficult to link to actual mechanisms, senescence
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Sink-Source approach
Straightforward, can be linked to experiments
Tied to one set of conditions? Relationship to actual mechanisms
Transport = (sink strength) x (source strength) x (distance factor)
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Transport/conversion approach (J.H.M. Thornley)
N, C substrates
Structure
N uptakeN, C substrates
Structure
C uptake
ConversionConversion
Root Shoot
Transport
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C concen-tration
high
low
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Transport/conversion approach
Theoretically sound, linked to mechanisms, straightforward
Transport not a diffusion process? Many compartments large model, parameter values for specific conditions
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Conclusions
Virtual plant models ideal for incorporating metabolic functions in growth models: can use appropriate structural units
Existing models of plant metabolism can be utilized in an straightforward way
Modeling the distribution of growth: a new challenge
22http://www.metla.fi/projects/lignum
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