The pigment composition of the leaves of three evergreen tree species
(Laurus azorica, Myrica faya and Persea indica) belonging to the canar
ian laurel forest were determined in situ in the early morning and at
midday. The ratio variable to maximal fluorescence (Fv/Fm) decreased a
t midday in full sunlight to values of 0.7 in all species indicating p
hotoinhibition. Together with depressions in Fv/Fm the shift in the xa
nthophyll cycle was clear in all three species. No significant variati
ons between the early morning and midday were found in the xanthophyll
cycle pool. The degree in which this cycle was de-epoxidized at midda
y had a trend to be larger in Myrica faya and Persea indica than in La
urus azorica. No variation in neoxanthin and lutein content during the
day was observed. The chlorophyll a/b ratio did not show significant
differences between early morning and midday but a tendency towards ch
lorophyll losses at midday could be found in all three species. The al
pha-carotene/beta-carotene ratio did not vary along the day. The total
carotene content was lower in Myrica faya which did not contain alpha
-carotene. Studies along the year and under different stress condition
s, including the study of the antioxidative system, are needed to have
a clearer understanding of possible different patterns in these tree
species on the protection of the photosynthetic apparatus against the
excess of light.