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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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