Sociality
Plants sense whom they are interacting with. ~ Canadian evolutionary plant ecologist Susan Dudley
Via root interactions, plants detect if they are in the presence of a close relative and grow differently if in friendly terrain. Kin recognition and corresponding comity has been seen in cabbage, heywood, jewelweed, mustard, rice, sagebrush, searockets, and sunflowers. Only recently have botanists turned their attention to this area of study. Doubtlessly sophisticated sociality is ubiquitous among plants.
The Comity of Sunflowers
Sunflowers track the Sun, facing east before dawn and ending the day facing west. Growing close together in a field, sunflowers also keep track of each other. Sensing that their sunlight is less than optimal, a sunflower leans away from another one by about 10° to get a little better light. This creates a coordinated cascade effect among neighbors, who lean in opposite directions to get better light, but also try not to interfere too much with their neighbors.
Sunflowers also care about their bee pollinators: packing a poison into their pollen that wards off brood-parasitic wasps which otherwise afflict the bees.
Jewelweed Relations
Jewelweed is a flowering plant that lives in the forest understory, where the soil is nutrient-rich, but an abundance of light is hard to come by. With hearty soil below, the competition is aboveground for light access. Plants that gain the upper leaf not only enhance their growth potential but also put others nearby in the shade, limiting the growth of rivals.
Jewelweed aggressively competes with its neighbors: extending stems and leafing as fast as it can. But having a relative for a neighbor changes a jewelweed’s growth strategy: accommodating its kin by sharing light access. It balances its tempered leafing with more abundant root growth.
Searocket Siblings
There is little competition for sunlight on a sand dune near the seashore. The battle is below, in the sandy soil, for enough nutrients.
Searockets are a flowering annual with fleshy leaves; a member of the mustard family. A searocket rises from a long taproot.
Searockets in the presence of strangers vigorously grab all the nutrients that they can. But a searocket among family is more subdued, giving its siblings a fair share of the spoils in the soil.
All Together Now
The reason trees share food and communicate is that they need each other. It takes a forest to create a microclimate suitable for tree growth and sustenance. It’s not surprising that isolated trees have far shorter lives than those living connected together in forests. ~ Australian environmentalist Tim Flannery
Comity is not confined to kin, especially when the community is at risk. Plants inherently understand the interrelated nature of their existence as a commonwealth. We only now seem to be learning what plants have long known: that biodiversity is essential to ecosystem health.
In numbers, there is strength. Buckhorn is a weed common on cultivated land in the British Isles. Buckthorn is more resistant to a fungal pathogen, and thus less likely to be colonized by it when the plant is well connected with its siblings in the local population.
The buckhorn example highlights that plants are more vulnerable when their habitat is fragmented. As plants face stresses such as drought, they treat their neighbors kindlier, promoting survival for all rather than competing.
These findings were consistent across fitness measures, stress types, growth forms, life histories, origins, climatic zones, ecosystems, and methodologies. ~ Chinese botanist Qiang He
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With predators constantly on the prowl, it is a dangerous world, especially when one is rooted to a spot. Plants rely upon their wits and astounding alchemy to survive.
