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.