Plant Science 135 (1998) 115–124
Nitrogen dependent changes in antioxidant system and in fatty
acid composition of chloroplast membranes from Coffea arabica
L. plants submitted to high irradiance
Jose ´ C. Ramalho
a
, Paula S. Campos
b
, Miguel Teixeira
c
, M. Antonieta Nunes
a,
*
a
Instituto Inestigac ¸a ˜o Cientı ´fica Tropical —CEPTA, Tapada da Ajuda, Ap. 3014, P-1301 Lisboa Codex, Portugal
b
Deptartamento de Fisiologia Vegetal, EAN, P-2780 Oeiras, Portugal
c
ITQB, Uniersidade Noa de Lisboa, Ap. 127, P-2780 Oeiras, Portugal
Received 2 February 1998; received in revised form 16 March 1998; accepted 8 April 1998
Abstract
In the present work we investigated the contribution of N availability to the changes in some antioxidant systems
and in fatty acid composition of chloroplast membranes, in order to evaluate their role in the high light acclimation
in coffee plants. Young coffee (Coffea arabica L. cv. Catuaı ´) plants, grown under low irradiance (up to 150 mol m
-2
s
-1
) with high (2N), medium (1N) and low (0N) N availability, were exposed to high irradiance (up to 1500 mol
m
-2
s
-1
) for a maximal period of 15 days. Changes in several parameters were monitored during that period in the
two top pairs of mature leaves. The formation rate of superoxide (O
2
-
) estimated by ESR (K
f
) did not differ among
N-treatments before the onset of high light, but increased 70 and 30% in 0N and 1N plants, respectively, and
decreased 33% in 2N plants by the end of the stress. By this time, the chloroplastic activities of Cu,Zn-superoxide
dismutase (Cu,Zn-SOD), ascorbate peroxidase (APer) and glutathione reductase (GRed) increased, respectively, 18,
225 and 138% in 2N plants. The 0N plants presented a 120% increase in Cu,Zn-SOD activity (which agrees with the
higher K
f
of O
2
-
) and a 68% decrease in APer activity, suggesting an increase in H
2
O
2
levels, while GRed activity
decreased 20%. The total carotenoid content was higher in 2N plants and increased (about 20%) only in these plants
by the end of stress. After 12 days of high irradiance, the total fatty acid (TFA) content increased about 30% in 2N
and 1N plants, but did not significantly change in 0N plants. In 2N and 1N plants a preferential synthesis of palmitic
acid (16:0) and a decrease in the linolenic acid (18:3) percentage caused a decrease in the unsaturation level, which
Abbreiations: APer, Ascorbate peroxidase; chl, chlorophyll;
3
chl*, triplet state of chl; Cu,Zn-SOD, Cu,Zn-superoxide dismutase;
cyt, cytochrome; ESR, electron spin resonance; GRed, glutathione reductase; GSH and GSSG, reduced and oxidised glutathione;
H
2
O
2
, hydrogen peroxide; K
f
, rate constant of O
2
-
formation;
1
O
2
, singlet oxygen; O
2
-
, superoxide anion radical;
OH, hydroxyl
radical; P
680
, PSII reaction center; PG, phosphatidylglycerol; PPFD, photosynthetic photon flux density; PSI and II, photosystems
I and II; rubisco, ribulose-1,5-bisphosphate carboxylase – oxygenase; TFA, total fatty acids; Tiron, 4,5-dihydroxy-1,3-benzene-disul-
fonic acid.
* Corresponding author. Tel.: + 351 1 4416855; fax: +351 1 3631085.
0168-9452/98/$19.00 © 1998 Elsevier Science Ireland Ltd. All rights reserved.
PII S0168-9452(98)00073-9