By CAROL KAESUK YOON

From its diminutive lavender flowers to its straggly windblown stalks, there is nothing about the beach weed known as the Great Lakes sea rocket to suggest that it might be any sort of a botanical wonder.
Yet scientists have found evidence that the sea rocket is able to do something that no other plant has ever been shown to do. The sea rocket, researchers report, can distinguish between plants that are related to it and those that are not. And not only does this plant recognize its kin, but it also gives them preferential treatment.
If the sea rocket detects unrelated plants growing in the ground with it, the plant aggressively sprouts nutrient-grabbing roots. But if it detects family, it politely restrains itself.
The finding is a surprise, even a bit of a shock, in part because most animals have not even been shown to have the ability to recognize relatives, despite the huge advantages in doing so.
“I’m just amazed at what we’ve found,” said Susan A. Dudley, an evolutionary plant ecologist at McMaster University in Hamilton, Ontario, who carried out the study .
“Plants,” Dr. Dudley said, “have a secret social life.” Since that research was published in August in Biology Letters, a journal of the United Kingdom’s national academy of science, Dr. Dudley and colleagues have found evidence that three other plant species can also recognize relatives.
The studies are part of an emerging picture of life among plants, one in which these organisms, long viewed as immobile, passive greenery, can be seen to sense all sorts of things about the plants around them and use that information to interact with them.
Plants’ social life may have remained mysterious for so long because, as researchers have seen in species like sagebrush and thornapples, the ways plants sense can be quite different from the ways animals do. Some plants, for example, sense potentially competing plants by subtle changes in light. That is because plants absorb and reflect particular wavelengths of sunlight, creating signature shifts that other plants can detect.
Scientists also find plants gathering information on other plants with chemicals released into the soil and air. A parasitic weed, dodder, has been found to be particularly keen at sensing such chemicals.
Dodder is unable to grow roots or make sugars using photosynthesis, the process used by nearly all other plants. As a result, scientists knew that after sprouting from seed, the plant would quickly need to begin growing on and into another plant to extract the nutrients needed to survive.
But even the scientists studying the plant were surprised at the speed and precision with which a dodder seedling could sense and hunt its victim. In time-lapse movies, scientists saw dodder sprouts moving in a circular fashion, in what they discovered was a sampling of the airborne chemicals released by nearby plants .
Then, using just the hint of the smells and without having touched another plant, the dodder grew toward its preferred victim. That is, the dodder reliably sensed and attacked the species of plant on which it would grow best.
“When you see the movies, you very much have this impression of it being like behavior, animal behavior,” said Dr. Consuelo M. De Moraes, a chemical ecologist at Pennsylvania State University who was on the team studying the plant. “It’s like a little worm moving toward this other plant.”
Although a view of plants as sensing organisms is beginning to emerge, scientists have been finding hints of such interactions for 20 years. But discoveries have continued to surprise scientists because of what some describe as an entrenched disbelief that plants, without benefit of eyes, ears, nose, mouth or brain, can do all they are seen to do.
“A lot of the examples of plant behavior are examples in which the phenomena are pretty easy to observe,” said Dr. Richard Karban, a plant ecologist at the University of California, Davis.
The problem, for many scientists, is that as obvious as the behaviors sometimes are, they can seem just too complex and animal-like for a plant. “Maybe if we understood more mechanistically how it’s happening,” Dr. Karban added, “we’d feel more comfortable about accepting the results that we’re finding.”