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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Aerial parts
apical meristem
CO2
CO2
H2O
axillary bud
CHO, N
H2O
storage
bark
sapwood
heartwood
 metamer
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Roots
differentiating fine root
root hairs
bark
sapwood
heartwood
root
tip
emerging fine root
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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
growth
State of the unit
Local environmental
conditions
Crown architecture
Position in the crown
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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
Transport = (sink strength) x (source strength) x
(distance factor)
Straightforward, can be linked
to experiments
Tied to one set of conditions?
Relationship to actual
mechanisms
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Transport/conversion approach
(J.H.M. Thornley)
Root
N uptake
N, C
substrates
Conversion
Structure
Shoot
Transport
N, C
substrates
C uptake
Conversion
Structure
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C concentration
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
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http://www.metla.fi/projects/lignum
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