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How it works
The parameters in the Meristems section determine how meristems work, and therefore how the plant branches and develops.
Axillary meristem and leaf arrangement
Plants are often classified by how many leaves they have at each node -- one (alternate), two (opposite), or more than two (whorled). PlantStudio
simulates the first two cases, which cover most plants. Which of these arrangements
you choose determines how many axillary meristems are available for branching
and for producing inflorescences, because axillary meristems form in the angles
between leaf and stem (axils). So a plant with an opposite leaf arrangement
has twice as many axillary meristems as a plant with an alternate leaf
Meristem 3D object, scale, colors
These parameters determine how meristems appear on the plant. Normally you
will not want to see meristems, so you will keep the Meristems: Meristem 3D object scale at full size parameter set to zero. But if you want to see how the meristems work, or if
you are making some plant on which little buds would look right, you can
increase the scale.
Branching index, Apical dominance strength, Secondary branching
Branching in PlantStudio works in this way: Each day, each axillary meristem
that is not already committed to reproductive growth ponders whether it might
start a new branch. In making this decision the meristem takes three things into
First, the meristem considers the branching index for the whole plant, which runs from zero to one hundred. This gives the meristem a probabilistic limit to check -- if it draws a random number between zero and one hundred and the number falls below the branching index, the meristem can create a branch.
Second, the meristem may lower the branching index it uses based on its proximity to an apical meristem. One of the ways plants control their shape is by apical dominance. In apical dominance the apical meristem at the end of the plant stem dominates the other meristems by sending out a substance that inhibits them from branching. (This is why garden books tell you to "top" plants you want to grow branches -- you are removing the apical meristem.) PlantStudio simulates apical dominance by reducing the probability of branching in meristems close to the stem apex. You can control where the apical dominance effect starts by setting the parameter Meristems: Apical dominance strength (as node distance). For example, if a plant stem has five nodes and you set the apical dominance strength to 3.0, the first two nodes will branch normally but the last three (closest to the apical meristem) will face an increasing difficulty in branching.
Finally, the meristem may be prevented from branching if you have turned off secondary branching and it is not on the plant's main stem. Usually you will want to keep the branching index at less than 30%, because above that percentage there can be so much branching that the plant takes a very long time to draw. You can also control the amount of branching by changing how many axillary meristems are available to contemplate branching. You can reduce the number of axillary meristems by choosing alternate leaf arrangement and by increasing the minimum days needed to create new internodes and leaves. Sympodial branching Most plants have monopodial branching, in which apical meristems extend stems and axillary meristems create new branches. In sympodial branching, each apical meristem dies off after it has made one internode, and one of the axillary meristems it created takes over the main stem. You can see this type of branching in tomato plants. To specify sympodial branching, just turn this parameter on.
Updated: March 10, 1999. Questions/comments on site to email@example.com.
Copyright © 1998, 1999 Paul D. Fernhout & Cynthia F. Kurtz.