Geoscience Reference
In-Depth Information
Stress
removed
Homeostatic
Stress
state C
Homeostatic
Homeostatic
state A
Acclimation
state A
Homeostatic
state B
Stress
removed
Time
FIGURe 14.1
Schematic relationship between stress and
acclimation. (Adapted from Hopkins, W. G., Hüner, N. P. A.
2009.
Introduction to Plant Physiology
, 4th ed., John Wiley
Sons, Inc., Hoboken, USA.)
these physiological processes over a short-term as well as a
long-term basis. Short-term acclimations involve responses
occurring within minutes of environmental change and typi-
cally involve pre-existing components within a biochemical
pathway; these responses are easily reversible, for example,
increases in enzyme activity (i.e. Calvin cycle) in response to
increases in temperature. Long-term acclimation, on the other
hand, may begin within minutes, but is pronounced within days
or weeks following an environmental change. These responses
typically involve altered patterns of gene expression, realloca-
tion of resources between the component processes of photo-
synthesis, and morphological change. The responses are not
immediately reversible and often lead to the development of
a visually different phenotype. Long-term responses represent
acclimation if they improve performance in the altered environ-
ment. Acclimation usually involves the differential expression
of specific sets of genes associated with exposure to a particular
stress. The remarkable capacity to
regulate gene expression
in
response to environmental change in a time-nested manner is
the basis of plant plasticity. A good example is plants growing
in shade develop larger leaves and an enhanced photosynthetic
apparatus for improved light capture.
The short-term processes involved in acclimation can be ini-
tiated within seconds or minutes but long-term processes are
less transient and, thus, usually exhibit a longer lifetime.
