J. Plant Physiol. 161. 25 – 33 (2004) http://www.elsevier-deutschland.de/jplhp Osmotic adjustment, gas exchanges and chlorophyll fluorescence of a hexaploid triticale and its parental species under salt stress Annick Morant-Manceau*, Elisabeth Pradier, GérardTremblin Laboratoire de Physiologie et Biochimie Végétales, Faculté des Sciences et Techniques, Université du Maine,Avenue Olivier Messiaen, 72085 Le Mans cedex 9, France Received October 28, 2002 · Accepted March 24, 2003 Summary The effect of salt stress (NaCl 85.7 or 110 mmol/L) was investigated in the triticale T300 and its parental species, Triticum dicoccum farrum (Triticum df ) and Secale cereale cv. Petkus. Triticum df and T300 were more salt-tolerant than the rye (110mmol/L NaCl was the highest concentration allow- ing rye growth to the three-leaf stage). Na + ,K + and Cl – ions accounted for almost half of the osmotic adjustment in Triticum df and T300, and up to 90 % in rye. Salinity decreased the net photosynthesis and transpiration rates of the three cereals as compared to control plants, but induced no significant change in chlorophyll a fluorescence parameters. Water-use efficiency (WUE) increased with salinity. In the presence of 110mmol/L NaCl, the K + /Na + ratio decreased markedly in rye as compared to the other two cereals. Proline concentration, which increased in Triticum df and T300, could have pro- tected membrane selectivity in favour of K + . Proline content remained low in rye, and increasing solu- ble sugar content did not appear to prevent competition between Na + and K + . The salt sensitivity of rye could be due to low K + uptake in the presence of a high NaCl concentration. Key words: chlorophyll fluorescence – NaCl – osmotic potential – photosynthesis – proline – Secale cereale cv. Petkus – soluble sugars – transpiration – triticale – Triticum dicoccum farrum – water-use efficiency Abbreviations: chl a = chlorophyll a. – cv. = cultivar. – π= osmotic potential. – PS II = photosystem II. – RETR = relative electron transport rate. – RWC = relative water content. – Triticum df = Triticum dicoc- cum farrum. – TSS = total soluble sugars. – WUE = water-use efficiency Introduction Hexaploid triticale is regarded as a cereal with considerable potential, particularly in marginal agricultural areas (Vermorel and Bernard1979). Trials have shown that some triticales per- * E-mail corresponding author: Annick.Manceau@univ-lemans.fr form well compared to their parental species, but many hybrids have failed to give the expected results (Lelley 1992). Except in Poland, no net increase of growing area has occur- red since 1986. The basic genetic potential of the wheat/rye hybrid may have been overestimated. An amphidiploid hybrid such as triticale T300 represents a simple addition of the two parental genotypes. The performance of the hybrid may 0176-1617/04/161/01-25 $ 30.00/0