Lifeboat Foundation

The sun moves around in the sky, in many places casting its life-giving rays on different spots throughout the day. A plant that could move to the nearest sunny spot would have an advantage over ordinary plants that are stuck in one place. But plants have it rough. Unlike people, they can’t pull up roots and relocate somewhere else.

Ambulatory plants that simply walk over to the nearest sunny spot would outcomplete regular plants, eventually becoming rulers of the plant kingdom. Unfortunately, it all seems a bit unlikely. Except for some interesting exceptions like species of Tillandsia (the so-called “air plants,” which are discussed below), plants need their roots. And roots are, well, rooted in place. However, while the vast majority of plants do need roots, they don’t need them every minute. As everyone who has experienced the concept of cut flowers in a vase of water knows, plants can go for quite some time without roots. And roots can do fine without the rest of the plant for a considerable time as well — just check your fridge, pantry, or grocery store for an assortment of potatos, carrots, etc., which do just that. In nature, in fact, many plants over-winter with just the underground roots alive all winter long, then grow new above-ground parts come Spring. The trick, then, is to build a plant that can separate temporarily at the base. The above-ground part then wanders off in search of maximum sunlight. As evening approaches, the plant literally returns to its roots, reattaches, and spends the night with its above-ground and below-ground sections in metabolic union.

It is unclear if such a plant variety would ever evolve spontaneously. However, genetic engineering should be able to do it at some point. Moving short distances would be feasible for plants based on their current capabilities — many plants can and do change in shape fast enough over the course of a day already. Flowers open and close, leaves move around, etc. For example the immature flower heads of the sunflower face the sun, tracking it as it crosses the sky over the course of the day. Engineering a plant that can detach at the base, walk off looking for sun, return in the evening and reattach until morning presents a number of varied challenges, all of which must be solved before it can work, including a detachment and reattachment mechanism, a slow but real walking capability, and the sensory capacity to find its way back to its roots. Yet there seems no fundamental reason why it could not be done.

Once such plants are on the march, additional genetic changes will be possible. Plants need not return to their own roots, but could instead return to the roots of another plant, perhaps even of a different species. Animals looking for a nutritious drink might try to suck juice from the exposed detachment point of the roots after the top of the plant has wandered off for the day in search of sun. Plants could evolve or be further engineered to allow animals to suck for juice only if they fertilize the plant as a down payment, by urinating at the base! Plants that can walk around would be strongly motivated (in an evolutionary sense) to develop better sensory systems and faster movements to compete with other plants. Such capabilities are normally associated with animals, not plants, so these plants of the future, as they evolve, would tend to increasingly blur the line between plants and animals. A world with walking plants would be different indeed!

Another strategy for adding walking plants to the biosphere would start with plants like Tillandsia, the air plants, which either do not have roots at all or have small ones used only to hold them in place. The genetic engineering complexities of a detachment/reattachment mechanism and a homing mechanism for finding roots earlier left behind would be unnecessary, simplifying the problem greatly. However as for soil-rooted plants. creating the capacity for locomotion would still be a challenge. Tillandsia plants absorb water and nutrients through their leaves, so an ambulatory version would have considerable advantages. They could walk around (and climb around, since they typically live on trees), looking for sun, taking a dip when thirsty, and loading up on compost (or, predator-like, trimming leaves off of other plants) to absorb nutrients from. Perhaps ambulatory descendants of the Tillandsia genus will one day rule the Earth.

Next time: Plants with Mirror Molecules