Variation of pigment composition and antioxidative systems along the canopy light gradient in a mixed beech/oak forest: a comparative study on deciduous tree species differing in shade tolerance

Abstract

The acclimation of leaf pigments and antioxidative systems along the vertical canopy light gradient was determined in mature European beech (Fagus sylvatica L.) and sessile oak [Quercus petraea (Matt.) Liebl.] trees in a mixed beech/oak forest in northwest Germany. The aim of the study was to investigate if the higher shade tolerance of beech, relative to oak, is correlated with characteristics of the leaf pigment composition and antioxidative systems. Both species showed a similar acclimative response to increasing light availability. Compared to shade leaves, leaves of the upper crown layer exhibited higher chlorophyll a to chlorophyll b ratios and higher contents of photoprotective carotenoids, ascorbate and glutathione per unit chlorophyll, and higher mean activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase. The comparison of beech and oak leaves sampled at crown positions with similar light environments revealed "shade-type" pigment characteristics for beech, relative to oak, whereas "sun-type" characteristics were found with respect to antioxidative systems. At a given average light availability level, leaves of F. sylvatica exhibited higher antioxidant contents and higher ascorbate peroxidase activities as compared to those of Qu. petraea. The data suggest that a higher antioxidative capacity is required in leaves of the more shade-tolerant species. The supposed higher production rate of radicals and reactive oxygen species (ROS) in beech can be explained by: (1) the lower energy utilizing capacity, as beech leaves show lower light-saturated rates of photosynthesis than oak leaves, and (2) by specific features of the photosynthetic apparatus as suggested by the pigment data. A higher ROS generation rate in beech versus oak leaves could be seen as a consequence of efficient photosynthesis under low light conditions. Therefore a high capacity of protection against oxidative stress might be a prerequisite of shade tolerance.

Do mature shade leaves of tropical tree seedlings acclimate to high sunlight and UV radiation?

“…7), while in shade leaves such reversion was shown to be extremely slow (Barth et al 2001). The level of the antioxidant AsA in tree leaves has been reported to increase with the average PAR received in the canopy (Hansen et al 2002). In the present study, shade leaves of all four species tested responded to changes in light conditions with respect to their pools of AsA + DHA (Fig.…”

Generality of relationships between leaf pigment contents and spectral vegetation indices in Mallorca (Spain)

“…Changes in chlorophyll a to b ratio can also reflect multiple adjustments in response to light quality and quantity. Ratio of two photosystems (PSI and PSII) as well as the size of light-harvesting antenna complexes modify chlorophyll a to b ratio (Hansen et al 2002;Kitajima and Hogan 2003;Fan et al 2007;Niinemets 2010a). Apart from changes in incident light availability, there is also important light gradient within the leaf, associated both with changes in carotenoid to chlorophyll ratio and chlorophyll a to b ratio (Terashima and Hikosaka 1995 for a review).…”

Effects of different irradiance levels on peroxidase activities in Quercus castaneifolia C.A. Mey. seedlings from different provenances

“…Some studies have shown that excess light enhances the production of ROS and subsequently POD activity in chloroplasts (Hansen et al 2002;Gill, Tuteja 2010).…”

“…ROS cause damage to proteins, lipids, DNA, and carbohydrates. They also control many processes like plant growth, programmed cell death, abiotic stress responses, and pathogen defence by influencing the expression of a number of genes (Hansen et al 2002;Gill, Tuteja 2010). Unfavourable conditions such as excess light (Hansen et al 2002), drought, and salt stress (Wang et al 2007) enhance the production of ROS in chloroplasts.…”

“…They also control many processes like plant growth, programmed cell death, abiotic stress responses, and pathogen defence by influencing the expression of a number of genes (Hansen et al 2002;Gill, Tuteja 2010). Unfavourable conditions such as excess light (Hansen et al 2002), drought, and salt stress (Wang et al 2007) enhance the production of ROS in chloroplasts. In contrast, plants possess protective systems against oxidative stress damage, such as enzymatic and non-enzymatic antioxidants which scavenge ROS from the cells (Foyer, Noctor 2005).…”