Plants Discriminate Between Self And Non Self

"We were looking at how plants determine who is a competitor whencompeting with other roots for limited resources," says Dr. Omer Falik,postdoctoral researcher in plant ecology. "There is no reason for rootsto fight if they belong to the same plant."

The question was, do plants recognize their own roots and avoidcompeting with them and how do they do this? Working with common gardenpeas, Falik worked with Dr. Ariel Novoplansky at Ben Gurion Universityof the Negev, Israel. The researchers used plants that had two rootsand planted them in a chamber that forced them to grow a specifieddistance from each other and from roots of a neighboring plant.

"We found that the roots grew significantly more and longer secondaryroots on the non-self side," Falik told attendees at the 90th AnnualMeeting of the Ecological Society of America today (Aug 8) in Montreal,Canada.

The mechanism for this self/non-self discrimination could be based oneither individually specific chemical recognition -- such as that knownfrom plant reproductive systems -- or physiological coordinationbetween roots that belong to the same plant. To test this, theresearchers used plants that had two roots and two shoots and splitthem into two separate plants that were genetically identical, butphysiologically separated. The plants acted as if their separated twinwas a non-self plant, even though genetically it was identical. "Thiseliminated the possibility that the mechanism was based on specificchemical recognition," says Falik. "The results prove that at least inthe studied plants, self/non-self root discrimination is based onphysiological coordination between roots belonging to the same plant.Such coordination might be based on internal pulsing of hormonal orelectrical signals which desynchronize when the plants are separated."

Falik is currently working with Dr. David Eissenstat, professor ofwoody plant physiology and Dr. Roger Koide, professor of horticulturalecology on examining how the latitude of a plants origin affects therespiratory responses of plant roots and mycorrhizal fungi to soiltemperatures.