Differential Photosynthetic Response of Tomato Plants—Ailsa Craig and Carotenoid Mutant tangerine—To Low Light Intensity and Low Temperature Treatment

The response of tomato plants, Ailsa Craig and the carotenoid mutant tangerine, to five days of treatment by low light intensity at normal and low temperature with respect to the photosynthetic performance as well as their capacity to recover after three days under normal conditions was evaluated. Tangerine plants are characterized by defective prolycopene isomerase (CRTISO) and accumulate tetra-cis lycopene instead of all-trans lycopene. The gas exchange parameters were evaluated on intact plants and the pigment content in leaves was estimated. The photosynthetic competence of photosystem II (PSII) and photosystem I (PSI) and the effectiveness of the energy dissipation were assessed by pulse-amplitude-modulated (PAM) fluorometry. The abundance of reaction center proteins of PSII and PSI was estimated by immunoblotting. The application of low light alone or low light and low temperature reduced the chlorophyll content in both types of plants, which was more strongly expressed in Ailsa Craig. The net photosynthetic rate and photochemical activities of PSII and PSI were negatively affected by low light and much more strongly decreased when low light was applied at low temperature. The low-light-induced increase in excitation pressure on PSII and the effectiveness of non-photochemical quenching were not temperature-dependent. The negative effect of the combined treatment in tangerine was more strongly expressed in comparison with Ailsa Craig with respect to the abundance of reaction center proteins of both photosystems. Most probably, the differential photosynthetic response of the carotenoid mutant tangerine and Ailsa Craig to the combined treatment by low light and low temperature is related to the accumulation of tetra-cis-lycopene instead of all-trans-lycopene.