Chlorophyll distribution pattern in inner stem tissues: evidence from epifluorescence microscopy and reflectance measurements in 20 woody species

Abstract

The occurrence of functional chloroplasts in internal stem tissues and their distribution profiles in 20 woody species have been investigated. Chloroplasts were identified from the red chlorophyll auto-fluorescence using epi-fluorescence microscopy. Chloroplasts were detected in the cortex of all species examined, in the xylem rays of 19 and in the perimedullar and the pith cells of 16 out of the 20 investigated species. Chloroplast containing cell clusters in the pith were identified in some species. In addition, we report on the semi-quantitative distribution of chlorophylls in various internal stem tissues. Chlorophyll level was estimated by reflectance measurements at specific wave bands. Although decreasing chlorophyll gradients from cortex to pith were observed in half of the species, chlorophyll distribution in the remaining species was irregular with occasionally high levels in the pith. According to our data, chlorophyll occurrence in stem internal tissues is quite widespread, even in the light remote, deeply shaded central compartments like pith, provided that corresponding cells are viable. The species-specific tissue distribution of chlorophyll levels may be used to select suitable plants to investigate further this neglected area of photosynthesis research.

Sinks for photosynthetic electron flow in green petioles and pedicels of Zantedeschia aethiopica: evidence for innately high photorespiration and cyclic electron flow rates

“…1a; Table 1). Equal absorptance in the presence of unequal chlorophyll concentrations (see Table 1) are not contradictory since the dependence of absorptance on chlorophyll concentration is very weak, at least for the range of concentrations found in our test organs (Dima et al 2006). The second proposed function for cyclic electron flow is linked to photorespiration.…”

Evidence for light-independent and steeply decreasing PSII efficiency along twig depth in four tree species

“…Plants and sampling: Plant material was selected on the basis of previous reports for the presence of chloroplasts in internal stem tissues including xylem rays and pith (Dima et al 2006). An additional criterion was the easiness of isolation of intact periderm and bark strips for optical measurements.…”

“…In stems with a well developed periderm, for example, chloroplasts are hidden in inner tissues not only adjacent to periderm (i.e. cortex) but in light remote sites like xylem rays and pith as well (Pfanz et al 2002, Dima et al 2006. Photosynthesis in such stems is believed to re-cycle internal CO 2 and participate in the total tree carbon balance (Pfanz et al 2002).…”

Maximum and effective PSII yields in the cortex of the main stem of young Prunus cerasus trees: effects of seasons and exposure

“…The trunk, stem or twig cortex of many trees contain chloroplasts (Scott 1907;Pfanz et al 2002;Dima et al 2006) displaying light-dependent CO 2 assimilation (Pfanz et al 2002) and chlorophyll fluorescence transients (Larcher 1988) indicative of an active photosynthetic system. The so-called corticular photosynthesis, however, is a neglected area of photosynthesis research.…”