Short Communication Synergic effect of salinity and light-chilling on photosystem II photochemistry of the halophyte, Sarcocornia fruticosa S. Redondo-Go ´ mez * , E. Mateos-Naranjo, M.E. Figueroa Departamento de Biologı ´a Vegetal y Ecologı ´a, Facultad de Biologı ´a, Universidad de Sevilla, Apartado 1095, 41080 Sevilla, Spain article info Article history: Received 17 September 2007 Received in revised form 4 June 2008 Accepted 18 November 2008 Available online 18 December 2008 Keywords: Chilling Chlorophyll a fluorescence Halophyte Photoinhibition Photon flux density Photosystem II Salinity Sarcocornia fruticosa abstract Laboratory experiments were conduced to assess the synergic effect of chilling and light on photosystem II photochemistry of the halophyte, Sarcocornia fruticosa, grown at different salinity concentrations (0, 170, 340, 510 and 1030mM). Chlorophyll fluorescence was measured after chilling (at 5  C in dark- ness) and light-chilling (at 5  C and 700 mmol m 2 s 1 ) treatments, and after 24 h of recovery (at 20  C and 75 mmol m 2 s 1 ). At 5  C and 700 mmol m 2 s 1 , plants grown with 0 and 170 mM NaCl showed the lowest F v /F m values, whereas quantum efficiency of PSII (F PSII ) was higher for plants grown at 170 and 340 mM NaCl, these results being consistent after two exposures to chilling treatments. Susceptibility to photoinhibition decreases when low temperature and high light are combined with high salinity. Therefore, populations of S. fruticosa that occur in arid environments with salinities c. 340 mM could show a higher tolerance to light-chilling. Ó 2008 Elsevier Ltd. All rights reserved. Salinity is major environmental problem in arid and semi-arid regions of the world, and the use of native halophytic plants to reclaim saline areas has been proposed as a solution which is both economically and ecologically relevant (Khan et al., 2000). In this regard, Sarcocornia fruticosa (L.) A.J. Scott is a succulent halophyte characterized by articular stems with carnose segments, reduced and stem-united leaves, whose growth has been reported to be stimulated by salinity (Redondo-Go ´ mez et al., 2006). This species occurs in arid and highly saline environments (Castroviejo, 1990), such as the marshes of southern Spain. Large variations in soil salinity have been measured in this zone, ranging from lower than 17 mM NaCl to extreme concentrations of more than 940 mM NaCl in the salt pans (Redondo-Go ´ mez et al., 2006). This is an area which receives sporadic rainfalls, a proportion of the salts thus tempo- rarily leaching from the soil, although this does not occur at any particular time of year (Pujol et al., 2000). Consequently, the level of salinity can stay high during the winters. On the other hand, low temperatures increase sensitivity towards photoinhibition, since photon utilization capacities in plants decrease (Hirotsu et al., 2004). Likewise, susceptibility to photoinhibition significantly increases when high light is combined with low temperatures (Powles, 1984). However, the synergic effect of chilling and light on halophytes grown at different salinity concentrations is not known. Hence, the present investigation was performed to attain a wider knowledge of the synergic effect of salinity and light-chilling on photosystem II photochemistry of S. fruticosa. Seeds of S. fruticosa were collected in December 2002 from Piedras salt marshes (37  13 0 N, 7  9 0 W; S.W. Iberian Peninsula), where minimum temperatures c. 5  C are reached approximately five times a year, between January and March (Climatic values were obtained from Punta Umbria meteorological station, n  555). Seeds were placed in a germinator (ASL Aparatos Cientı ´ficos M-92004, Spain), and subjected to an alternating diurnal regime of 10 h of light (photon flux rate, 400–700 nm, 35 mmol m 2 s 1 ) at 25  C and 14 h of darkness at 5  C, for 30 days (Redondo-Go ´ mez et al., 2006). Afterwards, seedlings were planted in plastic pots in substrate designed for salt tolerant plants (Floraska, Germany: K 2 O 210–290 mg/l; N 190–250 mg/l; P 2 O 5 130–170 mg/l, pH (CaCl 2 ) 5.4–5.9; conductivity 400–500 mSiemens), and grown in a glass- house at 20  C with 40–60% relative humidity and natural daylight. Pots were gently irrigated with tap water as necessary. When, after eleven months, seedlings had reached a height of between 10 and 15 cm, the pots were allocated to five NaCl treat- ments in shallow trays (ten pots per tray, with one tray per salinity treatment): 0,170, 340, 510 and 1030 mM, in the same glasshouse. * Corresponding author. Tel.: þ34 95 4557165; fax: þ34 95 4615780. E-mail address: susana@us.es (S. Redondo-Go ´ mez). Contents lists available at ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv 0140-1963/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2008.11.009 Journal of Arid Environments 73 (2009) 586–589