Photosynthetic pigment concentration, organization and interconversions in a pale green Syrian landrace of barley (Hordeum vulgare L., Tadmor) adapted to harsh climatic conditions

Abstract

Tadmor is a Syrian barley landrace that has adapted to semi-arid environments. Its leaves are pale green because of a 30% decrease in the chlorophyll and the carotenoid content of the chloroplasts (leading to a 7·5% decrease in light absorption) compared with barley genotypes that are not adapted to harsh Mediterranean climatic conditions (e.g. Plaisant). This difference in pigment content was attenuated during growth of the plants in strong light, but was strongly amplified when strong light was combined with a high growth temperature. The low pigment content of Tadmor leaves was not associated with significant changes in the pigment distribution between the photosystems or between the reaction centres of the photosystems and their associated chlorophyll antennae. No significant difference in the photosynthetic activity (O 2 production per unit absorbed light) was observed between Tadmor and Plaisant. The conversion of violaxanthin to zeaxanthin in strong light and its reversal in darkness were much faster and operated at a higher capacity in Tadmor leaves compared with Plaisant leaves, resulting in an increased photostability of photosystem II in the former leaves. The accelerated xanthophylls interconversion in the Syrian landrace was associated with, and possibly related to, an increased fluidity of the thylakoid membranes. The lipid peroxide level was lower in Tadmor compared with Plaisant. In contrast, no difference was found in the non-photochemical quenching of chlorophyll fluorescence between the two barley genotypes. The data indicate that the pale green Syrian landrace is equipped to survive excessive irradiance through a passive reduction of the light absorptance of its leaves, which mitigates the heating effects of strong light, and through the active protection of its photochemical apparatus by a rapid xanthophyll cycling.

Global Scale Transcriptional Profiling of Two Contrasting Barley Genotypes Exposed to Moderate Drought Conditions: Contribution of Leaves and Crowns to Water Shortage Coping Strategies

“…This is true also for our results. Repression of such genes may also resulted from photosynthetic accommodation strategies of Tad, such as reduced chlorophyll content (Tardy et al, 1998; Havaux and Tardy, 1999). …”

Cold-induced photoinhibition affects establishment of Eucalyptus nitens (Deane and Maiden) Maiden and Eucalyptus globulus Labill

“…Demmig- Adams and Adams 1992). Low chlorophyll levels have been proposed as an adaptation to excess irradiance through passive reduction in light absorption (Tardy et al 1998). Seedlings in all treatments had significantly lower chlorophyll levels than E. nitens saplings.…”

Comparison of violaxanthin de-epoxidation from the stroma and lumen sides of isolated thylakoid membranes from Arabidopsis : implications for the mechanism of de-epoxidation

“…Moreover, differences in the convertibility of Vx among different species or sun and shade leaves (e.g. Demmig-Adams 1998) could be explained not only by differences in the pool size of nonprotein-bound xanthophylls, but also by different membrane properties (fluidity, size of grana) that effect xanthophyll diffusion, as has been proposed in a study with two barley genotypes adapted to different climatic environments (Tardy et al 1998). It is further worth noting that addition of exoVxDE to WT thylakoids did not accelerate Vx conversion although (i) exoVxDE itself was sufficient to catalyze Vx de-epoxidation at high rates and (ii) the amount of endoVxDE is assumed to be very low.…”