Larry Niven used his previously created Known Space universe as the backdrop for the Ringworld story. It was a rich backdrop. Included in those previously published stories were Slaver sunflowers, genetically engineered by an alien race called the Tnuctipun. The Tnuctipun were telepathically controlled by the Thrintin (aka Slavers). Both species died off in a rebellion a billion and a half years ago, but a number of the genetically engineered life forms survived into the present day.
Slaver sunflowers are plants with a single silvered blossom that focuses light onto a photosynthetic node in the middle of the flower making food for the plant. The silvered blossoms can concentrate light elsewhere too. Ostensibly, the Tnuctipun genetically engineered sunflowers to protect the boundaries of Slaver estates. Individually, sunflowers wouldn’t give anyone more than a bad sunburn, but a hedge or field of them concentrating sunlight in unison would burn an invader to ash (at least during the day). This makes them very dangerous and, opens up a lot of possibilities because Louis and Speaker discover a huge field of sunflowers on the Ringworld.
The question is, given how dangerous they are, why would anyone bring sunflowers to the Ringworld? There are two possibilities: either the City Builders brought them from another world, or the Ringworld Engineers did. If the City Builders brought them back from one of their interstellar expeditions then they probably got loose when the cities fell. However, if the Ringworld Engineers brought them there is a more interesting possibility.
In order to burn an invader, the sunflowers must have been controlled in some way (to know who to aim at). We know that the Slavers didn’t control the sunflowers so the remaining possibility is the Tnuctipun. In order to control the sunflowers the Tnuctipun must have been able to communicate with them, at least at the field level. This communication probably used the Tnuctipun science language which we know the Tnuctipun built into the Bandersnatchi (another of their engineered life forms). Also, we know from previous Known Space stories that the Tnuctipun liked elegant designs. Their designs served multiple purposes in both their technological and biological constructs.
Do sunflowers potentially have multiple purposes? The answer is yes. Not only can sunflowers destroy objects by focusing sunlight on them, but a field of them would also make an ultra high resolution optical interferometer (a type of telescope). Sunflower fields then, acting as enormous optical interferometers, would be able to collect intelligence on ships and facilities in orbit as well as on other bodies in any given solar system. Therefore, the Tnuctipun probably would have designed sunflowers with both offensive and intelligence gathering capabilities.
We don’t know if the Tnuctipun designed sunflower fields to be sentient. We do know that they would have focused their efforts on image processing, as interferometers require enormous amounts of computer processing. Sentience may have been added in a supervisory role. Or, perhaps sentience developed as an emergent property. In either case one gets an image of an ethereal, almost ghostly, presence as the sunflower mind. If sunflower fields are sentient then different sized fields could have different levels of intelligence. However, the Tnuctipun might have placed limits on the amount of processing power which any individual sunflower field could attain (by limiting root connectivity). They would have done this to address the tendency for AIs in the Known Space universe to go rogue. In any case, whether designed or emergent, sunflower fields could be sentient.
How could individual plants communicate with their neighbors and form the necessary processing networks? Each sunflower might have a bulb with roots extending out from it. The bulb would contain a very small amount of optical neural tissue (probably less neural tissue than a fruit fly) that would control the pointing of the sunflower and provide some limited amount of memory. This bulb would be connected to several nearby sunflower bulbs using optical fibers in the sunflower’s roots. This connective topology would make a sunflower field a massively parallel optical computer. A sunflower would create light used in its optical neural tissue and fiber optic root system by using light emitting molecules which in turn would be powered by sugars (or their analogues).
The sunflowers might lack long term memory. The Tnuctipun would have designed them to process the data they collect but only retain the processed images long term (until the images were accessed by the Tnuctipun). Image collection would occur at night while image processing would be more likely to go on during the day (when the plants are continuously turning sunlight into sugars). For security purposes, the sunflowers would forget most things not hardwired into them. Think of a huge intellect that can’t remember anything for more than a day (or at least not much). Treaties would be difficult to negotiate unless the sunflowers burned their contents into a nearby mountain side (writing in the Tnuctipun science language).
We know that the Slavers couldn’t read the minds of their computers. In addition to having a computer-like mind, the use of optical neural tissue alone might have made the sunflowers immune to the Slavers’ Power. Also, the Slavers typically focused their Power on a single individual mind, not a vast field of plants; a single sunflower would not even nudge the sentience meter (it would be like commanding a single neuron). But, the question remains, why weren’t sunflowers destroyed along with all the other sentient species in the galaxy at the end of the Slaver War? As suggested, sunflowers may have been designed to be immune to the Slavers’ Power. However, even if sunflowers weren’t immune from the Slaver telepathic amplifier that ended all intelligent life in the galaxy, their seeds would still germinate and grow into adults after the suicide command was given.
Sunflowers would be a prime customer for Garvey Limited (“The Handicapped”). Garvey would first sell them permanent memory storage devices. Next, they’d sell them something analogous to Dolphins’ Hands to give them a way to manipulate their environment (probably closer to robots without brains). One way the sunflowers might pay for these devices is by solving math problems or by doing massive simulations.
If the sunflower fields can dynamically reconfigure their networks to add and subtract portions of a field (by connecting or disconnecting root connections) then it would change their intelligence and might change their personality. If that happens, the Known Space definition of Legal Entity (LE) might have to become more dynamic (and perhaps it already is, given that Jotoki can apparently perform an analogous reconfiguration). In their natural state, sunflower fields would probably find it easier to talk to computers than to biological LEs.
Back to the Ringworld and how all this relates to it: Sunflower field sentience would not be discovered until after the Second Ringworld expedition in 2878. Otherwise the expedition would know that sunflower fields are sentient. We know from Ringworld sequels that the Ringworld Engineers created reproductions of nearby worlds with the potential for intelligence, or on which intelligence had arisen, in one of the Great Oceans. If the sunflower fields are sentient, then this explains why the Ringworld Engineers brought them to the Ringworld. They were just another alien race the Engineers wanted to keep an eye on. Then, someone (probably a City Builder) innocently transplanted a few from their island environment, and the sunflowers started taking over the Ringworld (a very slow process).
Even so, sunflowers will never take over the entire structure’s land area. Sunflowers need carbon dioxide to live and this comes from microbes and animals. There are no geological processes on the Ringworld to hold and recycle carbon dioxide, except the Spill Mountains. So, while sunflowers can eventually take over much of the Ringworld they need to let at least microbes survive. This doesn’t mean that there wouldn’t be animals, and that they wouldn’t be sentient. After all, since the sunflowers don’t have any way to maintain the Ringworld, they need to leave some sentients around who can maintain the place.
As you can see, the Ringworld is a fun playground.
Doug McElwain has been a science fiction fan for over forty years. As a fan, he has corresponded with Larry Niven and Ed Lerner about the implications inherent in the Fleet of Worlds, Ringworld, and Known Space stories.