Effects of Long-term Chilling under Excessive Light on Xanthophyll Cycle Activity and Non-photochemical Fluorescence Quenching in Lycopersicon Genotypes

Plants of three Lycopersicon genotypes, the chilling-sensitive cultivated tomato, L. esculentum cv. Abunda, and two relatively chilling-tolerant lines of L. peruvianum (LA 2172 and LA 385) were grown at 20–27°C (control plants) and subjected to a temperature shift to 10° under 300 µmol photons m−2 s−1 (12-h light periods). Two weeks after the temperature shift, the effects of chilling and light stress on photosynthetic pigment composition, xanthophyll cycle activity and non-photochemical chlorophyll fluorescence quenching were studied. In leaves of all three genotypes, the chilling treatment caused substantial increases in contents of xanthophyll cycle pigments (sum of viola-, anthera- and zeaxanthin), lutein and neoxanthin, based on chlorophyll. In the chilling-treated plants, particularly in L. esculentum and L. peruvianum LA 385, higher fractions of zeaxanthin and antheraxanthin and higher zeaxanthin/chlorophyll ratios were built up in excessive light at temperatures between 0° and 40 °C. The chilling-treated plants exhibited increased non-photochemical quenching, indicating enhanced thermal dissipation of excessively absorbed light energy. The data show that leaves of the chilling-sensitive tomato as well as of its less sensitive relatives, which have developed at warm temperatures, are capable of responding to a shift to conditions of chilling and excessive light by acclimating the thylakoid membrane with respect to pigment content and xanthophyll cycle activity. The enhanced thermal energy conversion associated with increased zeaxanthin (and antheraxanthin) levels is assumed to provide protection of the leaves from severe photodestruction during events of light stress at low temperatures.