Plants discriminate between self and non-self

Plants discriminate between self and non-self

Montreal -- Two peas in a pod may not be so friendly when planted in the ground and even two parts of the same plant, once separated may treat the former conjoined twin as an alien "enemy," according to a Penn State researcher.

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

The question was, do plants recognize their own roots and avoid competing with them and how do they do this? Working with common garden peas, Falik worked with Ariel Novoplansky at Ben Gurion University of the Negev, Israel. The researchers used plants that had two roots and planted them in a chamber that forced them to grow a specified distance from each other and from roots of a neighboring plant.

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

The mechanism for this self/non-self discrimination could be based on either individually specific chemical recognition -- such as that known from plant reproductive systems -- or physiological coordination between roots that belong to the same plant. To test this, the researchers used plants that had two roots and two shoots and split them into two separate plants that were genetically identical, but physiologically separated. The plants acted as if their separated twin was a non-self plant, even though genetically it was identical.

"This eliminated the possibility that the mechanism was based on specific chemical recognition," said Falik. "The results prove that at least in the studied plants, self/non-self root discrimination is based on physiological coordination between roots belonging to the same plant. Such coordination might be based on internal pulsing of hormonal or electrical signals which desynchronize when the plants are separated."

Falik is currently working with David Eissenstat, professor of woody plant physiology, and Roger Koide, professor of horticultural ecology, on examining how the latitude of a plants origin affects the respiratory responses of plant roots and mycorrhizal fungi to soil temperatures.