1 PRESENTATION OF METABOLIC FUNCTIONS IN A 3-D MODEL OF PLANT STRUCTURE Risto Sievänen Eero Nikinmaa Jari Perttunen

2 What is a virtual plant?

3

4 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

5  metamer bark sapwood heartwood storage CO 2 apical meristem axillary bud H2OH2O CO 2 H2OH2O CHO, N Aerial parts

6 bark sapwood heartwood differentiating fine root root hairs root tip emerging fine root Roots

7 Components of model Lignum Photosynthesis Respiration Shoot elongation & needle growth Thickness growth Root growth Senescence

8 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)

9 Driving variables Solar radiation Temperature Wind speed air humidity, soil moisture CO 2 concentration etc

10 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

11 Photosynthesis - Respiration = Growth  distribution of growth a key problem (  distribution of metabolic products )

12 Distribution of growth at unit level State of the unit Local environmental conditions Crown architecture Position in the crown growth

13 Approaches to distribution of growth

14 Structural rules Allometric equations Pipe model theory

15 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

16 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)

17 Transport/conversion approach (J.H.M. Thornley) N, C substrates Structure N uptake N, C substrates Structure C uptake Conversion RootShoot Transport

18 C concen- tration high low

19

20 Transport/conversion approach Theoretically sound, linked to mechanisms, straightforward Transport not a diffusion process? Many compartments  large model, parameter values for specific conditions

21 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

22

23

24