ALO docView - Antioxidant composition of selected high alpine plant species from different altitudes (1996)

Plant, Cell and Environment (1996) 19,138-146

Antioxidant composition of selected high alpine

from different altitudes

species

B. WILDI & C. LUTZ

GSF-Forschungszentrum für Umwelt und Gesundheit, Expositionskammern, Ingolstädter Landstr. 1, D-85764 Oberschleißheim,

Germany

ABSTRACT

Selected high alpine plant species were collected from dif¬

ferent elevations in the Obergurgl/Ötztal subnival and

nival regions in Austria to investigate the content of

antioxidants in plants growing under the particular in vivo

conditions experienced in this area (e.g. chilling stress,

short Vegetation period and high irradiation). The con-

tents of antioxidants (ascorbic acid, tocopherol and glu-

tathione) and photosynthetic pigments were measured

throughout the day. The Contents of most compounds were

found to follow a diurnal rhythm, with the maximum

occurring at midday and the minimum during the night. It

was not clear whether these fluctuations were tempera-

ture-dependent or light-dependent.

Analyses of the antioxidant spectrum in the same plant

species at different altitudes (and thus under different envi-

ronmental conditions: as altitude increases, for example,

day temperature decreases and light intensity increases)

revealed that the total amount of antioxidants increases as

altitude increases. This enhancement was mainly due to

ascorbic acid Contents. Each plant species displayed a spe-

cific reaction to the increase in stress that accompanies an

increase in altitude, resulting in a broad adaptation spec¬

trum for these plants. The present study suggests that the

combined effect of Iower temperature and higher light

intensity induces higher antioxidant Contents.

Key-words: alpine plants; altitude effects; antioxidants;

pigments; stress avoidance.

INTRODUCTION

Alpine environments are characterized by short, often cold

and unpredictable growing seasons. At increasing altitudes

(here above the timber line), plants are exposed to decreas-

ing mean temperatures and increasing light intensities

(Larcher 1983, 1994a). Photosynthesis in high alpine plants

seems to be adapted to these conditions, as has been found

in the field by Moser (1973), Larcher & Wagner (1976),

Bergweiler (1987), Bergweiler & Lutz (manuscript in

preparation) and Körner & Diemer (1987, 1994). In a study

Correspondence: Cornelius Lutz, GSF-Forschungszentrum für

Umwelt und Gesundheit, Expositionskammern, Ingolstädter

Landstr. 1, D-85764 Oberschleißheim, Germany.

138

on Carex curvula, Körner (1982) described the light envi-

ronment in a canopy as being more important than tempera¬

ture for CO 2 -dependent photosynthetic yield. There nor-

mally seems to be no impairment of photosynthesis by high

light and low temperature under field conditions, which

indicates a very well regulated system of carbohydrate

turnover together with a functional system of antioxidants.

Intense irradiation may generate oxygen radicals, such as

singlet oxygen, in chloroplasts, which activate a defence

system (Knox & Dodge 1985). In lowland plants, only

species adapted to winter show similar protection of photo¬

synthesis (Somersalo & Krause 1990). Such protection is

probably mediated by an increase in photosynthetic elec-

tron transport (Huner 1985). This hypothesis is supported

by our studies on different high alpine species, including

green Soldanella alpina leaves taken from the snow, where

the rate of electron transport in photosystem II is up to 30%

higher than in lowland species (Bergweiler 1987).

Numerous studies describe regeneration of metabolism

and photosynthetic activities after climatic extremes, which

seems to occur much faster in alpine Vegetation than in cold-

exposed and photoinhibited species such as Hordeum

vulgäre or Spinacia oleracea. In addition to an effective elec¬

tron transport system, the unavoidable formation of radicals,

mainly in photosynthesis, requires a scavenging system.

To add a new dimension to the excellent ecophysiologi-

cal work already carried out on high alpine plant photo¬

synthesis, it is of interest to pose the following question:

what role does the antioxidative system play in plants from

higher altitudes in protecting leaves from climatic stress?

Ascorbic acid, a-tocopherol, glutathione, ß-carotene and

additional photosynthetic pigments were analysed. It has

been demonstrated in many experiments that the first three

compounds protect against oxidative damage by inhibiting or

quenching free radicals and reactive oxygen species (Ong &

Packer 1992). The antioxidant compositions of typical high

mountain plants are compared in relation to growth sites and

local light and temperature conditions. The antioxidant com¬

positions of high alpine plant species have not, to our know-

ledge, been examined before. This is also the first field study

on diurnal changes of antioxidants in alpine plants.

MATERIALS AND METHODS

Plants and study Sites

We investigated nine different plant species (shown in