Fight against cold: photosynthetic and antioxidant responses of different bell pepper cultivars (Capsicum annuum L.) to cold stress

The special metabolites of bell pepper (Capsicum annuum L.) leaves can protect the plant under possibly damaging circum- stances, such as high light, UV, unfavorable temperatures, or other environmental effects. In this study, we examined the cold stress tolerance of three different Hungarian pepper varieties (Darina, Édesalma, Rekord), focusing on the antioxidant and photosynthetic responses. The plants were developed in growth chambers under optimal temperature conditions (day/night 25 °C/20 °C) until the leaves on the fourth node became fully developed, then half of the plants received a cold treatment (day/ night 15 °C/10 °C). Via a detailed pigment analysis, the PS II chlorophyll fluorescence responses, gas exchange parameters and total antioxidant capacities, leaf acclimation to low temperatures has been characterized. Our results display some of the developing physiological and antioxidant properties, which are among the main factors in monitoring the damaging effects of cold temperatures. Nevertheless, despite their differences, the tested pepper varieties did not show different cold responses

Assessing the Applicability of Singlet Oxygen Photosensitizers in Leaf Studies.

Singlet oxygen (1 O2 ) is of special interest in plant stress physiology. Studies focused on internal, chlorophyll mediated production are often complemented with the use of artificial 1 O2 photosensitizers. Here we report a comparative study on the effects of Rose Bengal (RB), Methylene Violet (MVI), Neutral Red (NR) and Indigo Carmine (IC). These were infiltrated into tobacco leaves at concentrations generating the same fluxes of 1 O2 in solution. Following green light induced 1 O2 production from these dyes, leaf photosynthesis was characterized by Photosystem (PS) II and PS I electron transport and oxidative damage was monitored as degradation of D1, a PS II core protein. Cellular localizations were identified on the basis of the dyes' fluorescence using confocal laser scanning microscopy. We found that RB and NR were both localized in chloroplasts but the latter had very little effect, probably due to its pH-dependent photosensitizing. Both RB and intracellular, non-plastid MVI decreased PS II electron transport but the effect of RB was stronger than that of MVI and only RB was capable of damaging the D1 protein. Intercellularly localized IC had no significant effect. Our results also suggest caution when using RB as photosensitizer because it affects PS II electron transport. This article is protected by copyright. All rights reserved