Trees 'remember' where they come from
Jun 1, 2011
Genetically identical trees respond differently to their
environment depending on what part of the country they come from. The
surprising finding could have implications for gardeners and
foresters, and might help predict how forests will respond to climate
“The findings were really quite
stunning,” says Malcolm Campbell, professor of cell and systems
biology and vice principal, research at University of Toronto
Scarborough. “Our results show that there is a form of molecular
‘memory’ in trees where a tree’s previous personal
experience influences how it responds to the environment.”
Campbell and his colleagues were interested in
something called the “nursery effect,” which had long been
noted by foresters and gardeners. Although many plants are genetically
identical clones, it seemed that plants from different nurseries often
grew differently in identical environments.
Campbell decided to look at poplar trees. Like many plants, poplars can
reproduce themselves through their roots or through fragments of
branches. These new trees are genetically identical clones of their
Campbell’s graduate student, Sherosha Raj,
obtained three different types of genetically identical poplars from
Alberta, Saskatchewan and Manitoba. The trees were grown in identical
conditions. Then half were subjected to drought, and half continued to
In two of the three varieties, the poplars
responded differently to drought conditions depending on what part of
the country they came from. The trees seemed to “remember”
their previous environments.
Campbell’s group showed that the
differences were at the fundamental level of gene activation.
Identical plants from different parts of the country activated
different sets of genes when exposed to drought.
The results suggest that there is more diversity
in stands of seemingly identical poplar forests than previously
thought. Genetically identical stands of trees might still respond
differently to drought, disease, or pests.
The research was published in the journal Proceedings of the National
Academy of Sciences.
Campbell’s research team included co-first
author Katharina Bräutigam, Erin Hamanishi and Olivia Wilkins,
all of the University of Toronto, and researchers at the University of
British Columbia, Simon Fraser University and the University of
Alberta. The research was supported by competitive research funds from
the Natural Sciences and Engineering Research Council (NSERC) of
Canada and in kind contributions from Alberta Pacific Forest
Industries and Agriculture and Agrifood Canada.