Geoscience Reference
In-Depth Information
processes can be detected very soon after the onset of a stress,
their activities also disappear rather rapidly. As a consequence,
the lifetime of these processes is rather short. An example of a
short-term response is a change in light, water availability or
temperature that are part of the acclimation process.
14.3
effect of temperature on plant and its
environment
Mesophytic plants (terrestrial plants adapted to temperate environ-
ments that are neither excessively wet nor dry) have a relatively
narrow temperature range of about 10°C for optimal growth and
development. Outside of this range, varying amounts of damage
occur, depending on the magnitude and duration of the temper-
ature fluctuation. In this section, we will discuss three types of
temperature stress: high temperatures, low temperatures above
freezing and temperatures below freezing. Most actively growing
tissues of higher plants are tillable to survive extended exposure to
temperatures above 45°C or even short exposure to temperatures
of 55°C or above. However, non-growing cells or dehydrated tis-
sues (e.g. seeds and pollen) remain viable at much higher temper-
atures. Pollen grains of some species can survive 70°C and some
dry seeds can tolerate temperatures as high as 120°C.
Plants and related organisms may be broadly classified
according to their ability to withstand temperature. Those
that grow optimally at lower temperatures (between 0°C and
10°C) are called psychrophiles. The psychrophiles include pri-
marily algae, fungi and bacteria. Higher plants generally fall
into the category of mesophiles, whose optimum temperature
lies roughly between 10°C and 30°C. Thermophiles will grow
unhindered at temperatures between 30°C and 65°C (Oosterhuis
2002; Zrobek-Sokolnik 2012), although there are reports of
cyanobacteria growing at temperature as high as 85°C, these
temperature ranges apply
t
hydrated, actively growing organ-
isms. Dehydrated organisms and organs, such as resurrection
plants (
Selaginella lepidophylla
) and dry seeds with moisture
contents as low as 5%, are able to withstand a much broader
range of temperatures for extended periods of time.
temperature
effects on
membrane and
its enzyme
Plant membranes consist of a lipid bilayer interspersed with
proteins and sterols, and any abiotic factor that alters mem-
brane properties can disrupt cellular processes. The physical
properties of the lipids greatly influence the activities of the
integral membrane proteins, including H
+
-pumping ATPases,
