Tree crowns grow into self-similar shapes controlled by gravity and light sensing

Area of Science:

• Plant biology
• Mathematical modeling
• Biomechanics

Background:

• Plants exhibit tropisms, directional growth responses to stimuli like light (phototropism) and gravity (gravitropism).
• The influence of these tropisms on the overall architecture of tree crowns remains poorly understood.
• Understanding tree crown morphology is crucial for ecology and forestry.

Purpose of the Study:

• To investigate how phototropism and gravitropism collectively shape tree crowns.
• To develop a predictive model for tree crown development based on tropism dynamics.
• To explore the relationship between tropism balance and observed tree species morphology.

Main Methods:

• Development of a novel propagating front model for tree growth.
• Analysis of self-similar solutions emerging from the model over extended time scales.
• Systematic variation of phototropism and gravitropism intensities to observe resulting crown shapes.

Main Results:

• The model generates diverse, self-similar tree crown shapes independent of initial conditions.
• Specific balances of phototropism and gravitropism lead to distinct and sometimes singular crown forms.
• Emergent shapes show notable resemblance to morphologies of various extant tree species.

Conclusions:

• The balance between phototropism and gravitropism is a fundamental determinant of tree crown shape.
• Mathematical modeling provides a powerful framework for understanding plant architectural development.
• This research offers insights into the evolutionary and developmental basis of tree diversity.