PHOTOSYNTHETIC ACCLIMATION OF LOTUS JAPONICUS TO LOW TEMPERATURE CONDITIONS: CHANGES IN CHLOROPLAST ULTRASTRUCTURE AND IN REACTIVE OXYGEN SPECIES GENERATION.

CALZADILLA P.I; VILAS J.M.; UNREIN F.; MAIALE S.J.; RUIZ O.A.

CORRIENTES

Congreso; XXXI RAFV CORRIENTES 2016; 2016

SOCIEDAD ARGENTINA DE FISIOLOGIA VEGETAL

Photosynthesis is considered an important source of ROS in plants, and disruption of PSII activity may increase its production. This phenomena lead to photoinhibition, a process accelerated by low temperatures. With the aim to address the photosynthetic acclimation response of L. japonicus under cold stress, two ecotypes (MG-1 and MG-20) were studied. Previous data showed that photoinhibition occurs in stress and differentially between ecotypes, being MG-1 more affected than MG-20. In this study, we used flow cytometry and confocal microscopy to evaluate chloroplastic ROS generation under control and stress conditions. Our results showed that chloroplastic ROS generation was higher in the low temperature treatment compared to control, only for MG-1, and after 7 d of stress. Chloroplast ultrastructure was also evaluated by Transmission Electron Microscopy. An increased in starch granules and chloroplast swelling was observed due to chilling, and differentially between ecotypes. These effects were further enhanced with the increased time of cold exposure. Thylakoid membrane distortion and plastoglobule presence were also observed due to the stress condition.As a conclusion, data showed that the differentially photosynthetic acclimation of both L. japonicus ecotypes to cold stress could be, at least partially, explained by their chloroplastic redox imbalance and ultrastructure changes.