Seasonal Eco-Physiology Characteristics of Four Evergreen Rhododendron Species to the Subalpine Habitats

Four evergreen broadleaf Rhododendron spp. (Rhododendrons), namely, aganniphum, R. nyingchiense, wardii, and triflorum, occur in harsh subalpine habitats the southwest Qinghai-Tibet Plateau (QTP), China. Considering that four Rhododendrons cannot escape their unique environment, they must evolve a set of adaptations to survive, but information is lacking. To uncover physiological adaptation characteristics, present study, we monitored characteristics by determination seasonal variation antioxidant enzyme activity, osmotic adjustment substrates, carbohydrate contents, pigment content photosynthetic efficiency. The results showed superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activities proline had significant difference autumn were insignificant summer. Specifically, aganniphum maximum protective activity winter as well chl a, b, car contents. values maximal quantum yield (Fv/Fm), photochemical efficiency (ΦPSII), non-photochemical quenching (NPQ) significantly higher summer than other seasons. lower qP indicated susceptible photoinhibition. Overall, similar physical habitats. parameters photosystem II (PSII), actual PSII, chlorophyll fluorescence quenching, increased Meanwhile, total soluble sugar content, carotenoid spring, autumn, winter. These suggested can adapt heat dissipation avoid damage excessive radiation during warm season while scavenging reactive oxygen increasing intracellular fluid concentration caused chilling temperatures cold findings would provide reference for conservation application these valuable ornamental Rhododendrons, enrich theory plant eco-physiology high altitudes QTP.