Why do plants have a spiral of life?

Everything is NOT a spiral in nature.

Actually, Spiral Forms are rarely associated with mineral molecular arrangements but they ARE associated with animal, vegetable and fungal lifeforms (which all require operation of DNA.)

The spiral growth form follows the path of a mathematical formula called a Fibonacci Series which gives a progression of numbers in which the next number is produced as the sum of the previous two numbers. So the series can be 0,1,1,2,3,5,8,13, etc.

Everything new seems to be based on what has gone before and I think that you will find that Sunflower seeds and snailshells follow this growth principle. It has no theoretical limit and therefore the series is cut off at the point of death.

Continuation

In dynamic situations, an object or particle will travel along a straight path at constant velocity until compelled to change this by an external force. If it encounters such a force and the distance between the particle and the source of the force becomes reduced to a critical value, the particle will enter a spiral path in which its acceleration vector rotates and increases as it passes around the centre of the force. This effect is seen in a fluid vortex ("whirlpool") or in a Galaxy where it is the mechanism of galactic accretion or dispersal and black hole operation.

The general situation of catastrophic detachment of a particle from a rotating body is for it to cease to be influenced by the rotating acceleration vector of the attachment and hence to travel outward radially straight from the point of release. ie NOT in a Spiral.

The kid lets go of the roundabout and releases the [mvSquared /r] force holding him so that he flies off in a path determined by his circumferential velocity at the time of release. The appearance of a spiral of sparks from a Catherine Wheel firework is formed by a succession of emergent glowing particles each travelling radially outward from a point progressively further around the centre. The spiral seen is a composite appearance and not the path of a singular particle.

When a particle travels in a spiral path, this is instantaneously circular but with the radius progressively changing as a function of the angular position of the particle about the centre. The sign of the function determines if the spiral is increasing or decreasing. eg It is the path of a mass spinning around on the end of a tight cord which is winding or unwinding around a fixed cylinder.

The force of gravity between masses allows understanding of one cosmic body being stripped of matter in a stream of particles by and to another, in a pair of expanding and contracting spirals.