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PlantStudio Kurtz-Fernhout Software
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How plant parts grow

All of the plant parts grow either by linear growth functions (meristems, internodes, inflorescences, flowers) or S-shaped growth functions (leaves, fruits). Both linear and S-shaped growth is bounded in speed by a minimum number of days required for any plant part to reach its maximum size. This "speed limit" simulates physical limitations on the speed of growth. In addition, some of the plant parts stop demanding biomass after a number of days because they are too old to grow any more. Most leaves and other plant parts in reality will not keep growing forever but stop even if the plant is still growing. This allows the plant to concentrate its resources on newer leaves which have greater photosynthetic efficiency.

Here is a look at the growth of each type of plant part.


A meristem exists only to accumulate biomass towards creating other plant parts. In effect, what we are doing here is having the meristem "take charge of" very small internodes, leaves, and inflorescences until they are large enough to be seen. In reality you can distinguish different plant parts even when they are microscopic. Meristems demand an amount of biomass based on the amount needed to create a particular plant part or parts (an internode and one or two leaves if vegetative, or an inflorescence if reproductive). When that amount of biomass is accumulated (and the minimum number of days has passed), the meristem passes on the biomass to the new plant part, empties out its biomass, and starts accumulating again to create the next plant part.


An inflorescence is created by a vegetative meristem and begins to demand vegetative biomass for its linear growth, where it will reach its full length and width.


Leaf growth is fairly simple: the leaf demands biomass according to an S curve of growth (which is a fair description of how most leaves grow). The leaf draws its 3D object according to the ratio of its biomass to the maximum biomass expected for the leaf (
Leaves: Optimal plant biomass).


An inflorescence is created by a reproductive meristem and begins to demand reproductive biomass for its linear growth. Creation of flowers by the inflorescence has nothing to do with biomass accumulation: it just creates the flowers according to a timetable of the number of flowers expected and the number of days to create them. Like the placement of inflorescences, this is a mechanism to ensure that the plants look the way they are supposed to look.

Flowers and fruits

PlantStudio simulates flowers and fruits as the same object in different stages, which is realistic because a fruit grows out of an ovary at the base of a flower. Actually, what we generally call "flowers" can have one ovary or many, but in PlantStudio we specifically define a flower as having one ovary out of which one fruit grows. The flower/fruit object goes through three major stages. As a flower bud, the object demands biomass according to linear growth towards the optimal biomass for a flower. As an open flower, the object demands biomass according to linear growth to reach full flower size. As a fruit, the object demands biomass according to an S-curve of fruit growth. In each of these stages growth is limited in speed by a minimum number of days in each stage. Finally the fruit stops growing after some number of days even if it has not reached full size.

For plants with separate male and female flowers, only female flowers can develop into fruits. Both male and female flowers will drop off the plant after a specified number of days (
Flowers: Days until drop if fruit not set). Usually for plants with both male and female flowers the male drop-off period is short and the female drop-off period is very long. Fruits draw themselves as unripe (Fruit: Unripe section front/back face color) for a specified number of days, then draw themselves using their ripe color (Fruit: Ripe section front/back face color). Ripeness has no physiological simulation here; it is just a change in color.

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Updated: March 10, 1999. Questions/comments on site to
Copyright © 1998, 1999 Paul D. Fernhout & Cynthia F. Kurtz.