Photosynthesis as a Tool for Indicating Temperature Stress Events
265
the appearance of after-effects of stress thus indicates considerable destabilization of chloroplast structure and functions.
4. Temperature limits for irreversible damage to the photosynthetic apparatus and for lethality. Lethal injuries appear as cell and tissue necrosis;
conventional thresholds are the temperatures at which visual injuries are
first recognized (L Tj), at 50% damage (L T 50) and at complete tissue death
(LTlOO)' Even before acute cell death due to freezing or lethal heat, the
integrity of the chloroplast ultrastructure may be severely disrupted. The
original photosynthetic activity can no longer be restored and this function
ceases. The occurrence of irreversible inactivation of photosynthesis has
been used as a convenient viability test in the determination of frost survival
limits of difficult objects (Lange 1965; Nash et al. 1987; Rutten and Santarius 1992).
The limiting temperatures of the range over which photosynthesis is
impaired, and the temperature limits for lethal injuries, are specific to the
individual plants and depend on species and genotype, on morphological,
Table 13.2. Temperature thresholds (0C) for apparent CO2 uptake for lichens from
different environments, in the hydrated state
Species origin
Cold limit
Photosynthetic
Heat limit
Reference
for CO2
thermal window
for CO2
uptake
uptake
Low Aso High Aso
Dictyonema glabratum
0
to
35
40
Larcher and
(syn. Cora pavonia)
Vareschi
Paramo, Venezuelan
(1988)
Andes 1770-3600m
a.s.!.
Ramalina maciformis
-6
5
32
37
Lange (1969)
Rocks, Negev desert
Cladonia alcicornis
-5
-3
18
26
Lange (1965)
Sandy terraces, Upper
Rhine
Stereocaulon alpinum
-to
-5
18
22
Lange (1965)
Moraine, Central Alps
2400m a.s.!.
Usnea aurantiaco-atra
Kappen and
Lichen tundra,
Redon
maritime Antarctic
(1987)
Erect habit
-6
0
25
29
Prostrate habit
-4
0
18
23
Usnea sphacelata
-to
0
22
28
Kappen (1989)
Continental Antarctic
Buellia sp.
-6
-1
12
16
Kappen and
Endolithic in rocks
Friedman
Dry valleys, Antarctic
(1983)
265
the appearance of after-effects of stress thus indicates considerable destabilization of chloroplast structure and functions.
4. Temperature limits for irreversible damage to the photosynthetic apparatus and for lethality. Lethal injuries appear as cell and tissue necrosis;
conventional thresholds are the temperatures at which visual injuries are
first recognized (L Tj), at 50% damage (L T 50) and at complete tissue death
(LTlOO)' Even before acute cell death due to freezing or lethal heat, the
integrity of the chloroplast ultrastructure may be severely disrupted. The
original photosynthetic activity can no longer be restored and this function
ceases. The occurrence of irreversible inactivation of photosynthesis has
been used as a convenient viability test in the determination of frost survival
limits of difficult objects (Lange 1965; Nash et al. 1987; Rutten and Santarius 1992).
The limiting temperatures of the range over which photosynthesis is
impaired, and the temperature limits for lethal injuries, are specific to the
individual plants and depend on species and genotype, on morphological,
Table 13.2. Temperature thresholds (0C) for apparent CO2 uptake for lichens from
different environments, in the hydrated state
Species origin
Cold limit
Photosynthetic
Heat limit
Reference
for CO2
thermal window
for CO2
uptake
uptake
Low Aso High Aso
Dictyonema glabratum
0
to
35
40
Larcher and
(syn. Cora pavonia)
Vareschi
Paramo, Venezuelan
(1988)
Andes 1770-3600m
a.s.!.
Ramalina maciformis
-6
5
32
37
Lange (1969)
Rocks, Negev desert
Cladonia alcicornis
-5
-3
18
26
Lange (1965)
Sandy terraces, Upper
Rhine
Stereocaulon alpinum
-to
-5
18
22
Lange (1965)
Moraine, Central Alps
2400m a.s.!.
Usnea aurantiaco-atra
Kappen and
Lichen tundra,
Redon
maritime Antarctic
(1987)
Erect habit
-6
0
25
29
Prostrate habit
-4
0
18
23
Usnea sphacelata
-to
0
22
28
Kappen (1989)
Continental Antarctic
Buellia sp.
-6
-1
12
16
Kappen and
Endolithic in rocks
Friedman
Dry valleys, Antarctic
(1983)