Plants capture photons of energy from sunlight with some sophisticated photosynthetic chemistry. But to maximize that energy gain, they have to position their leafy photo-capture surfaces in particular ways.
I have always been fascinated by the bizarre geometry of oak trees, especially the California Live Oak whose thick horizontal branches seem to defy gravity as they grow outward from the central trunk dozens of feet without any vertical supports.
Lateral spread accomplishes at least two important things for oak trees: it shades out potential competitors, and it avoids the problem of upper leaves shading lower leaves, thus maximizing the photosynthetic surface area.
A different strategy is to grow above the canopy of your neighbor to avoid being shaded out — so well illustrated by the giant Redwoods.
Normally, branch stem, and root growth are controlled by gravity sensors (statocytes) that stimulate elongation of cells on one side of a stem relative to the other, bending the growth tip. This gravitropic response allows roots to grow downward and shoots to grow upward regardless of their lateral or vertical (e.g., upside down) placement, but it doesn’t explain why oaks preferentially branch out horizontally or maple tree branches grow in a V-shape.
Recently, researchers at Leeds University have identified an “anti-gravitropic” response opposing the gravitropic one on the other side of the stem, such that branches and stems are maintained at a pre-set angle from the main trunk. The particular angle of growth is adaptive to a set of environmental conditions: best angle for shedding heavy snow, best angle for resisting strong horizontal winds, etc.
Isn’t nature amazing?