99 INTRODUCTION Iron chlorosis of plants is very common on calcareous or alkaline soils or in potting media. Although Fe is abundant in all soils, it is not readily available to all plant species grown under conditions of Fe deficien- cy. Iron chlorosis affects both growth / flowering and quality of gardenia plants. About 25% of the world population lives in arid areas where drought and salt accumulation are major limiting factors. Such condi- tions reduce Fe absorption. Under these conditions the quality of irrigation water is deteriorated and water content in salts increases affecting the growth of gardenia plants and leading to salt toxicity symp- toms. It is well known that soil salinity causes injury symptoms to plants. The main salts involved are chlo- rides, sulfates and nitrates. The possible factors con- tributing to salinization include the supply of animal manure or compost with a high salt content, the ex- cessive application of chemical fertilizers, the use of brackish water for irrigation, the high water table, and the exposure to salt spray near the sea. The first symp- toms of salinity are small, chlorotic or bluish-green leaves and stems with short internodes. The advanced symptoms of salinity in plants include browning and necrosis of leaf edges or other leaf tissues. Salinity tolerance of ornamental plants on gradu- ally increased salt concentration in nutrient solution is an important factor, particularly for planning of a fertilizer program and for the evaluation of the suit- ability of the irrigation water. Usually, chlorosis is ini- tially observed and later necrosis on the tips and mar- Effects of NaCl and Fe-EDDHA concentration on salt toxicity and chemical composition of gardenia (Gardenia jasminoides Ellis) plants EFROSSINI AVRAMAKI 1* , CHRISTOS CHATZISSAVVIDIS 2 and IOANNIS PAPADAKIS 1 1 Department of Horticulture, School of Agriculture, Aristotle University, 54 124 Thessaloniki, Greece 2 Department of Agricultural Development, Democritus University of Thrace, 68 200 Orestiada, Greece Received: 18 April 2006 Accepted after revision: 29 August 2006 Young gardenia (Gardenia jasminoides Ellis) plants rooted under a fog system were grown in black plastic bags containing a sand / perlite (1:1) mixture. The plants were irrigated with Hoagland No2 nutrient solution modified to contain three Fe concentrations (0.5, 1 and 2 mg l –1 ) in the form of Fe-EDDHA and four concentrations of NaCl (0, 10, 20 and 40 mM). After three months, severe toxicity symptoms were observed on the older leaves (chlorosis of tips and margins) mainly of the plants treated with 40 mM NaCl. Salinity had little effect on leaf P, whereas P concentration of roots increased in the treatments containing 20 or 40 mM NaCl plus 0.5 mg l –1 Fe. Generally, K and Ca concentrations of leaves and roots were not affected by the increase of NaCl concentration in the nutrient solution. In the roots, the lowest Mg concentra- tion was observed in the treatments containing 2 mg l –1 Fe, whereas in the leaves, no significant differences were recorded. Regarding Mn concentration, it was not affected in the leaves but it increased in the roots of the treatments containing 20 and 40 mM NaCl plus 0.5 mg l –1 Fe. Final- ly, Fe concentration was increased in the roots of the plants treated with 0.5 mg l –1 Fe plus 20 or 40 mM NaCl. Concerning Na concentration, generally, it was increased in the leaves and de- creased in the roots of the treatments containing high NaCl plus low or medium Fe concentration. Key words: gardenia, iron, salinity. * Corresponding author: tel.: +30 25520 27960, fax: +30 25520 22229, e-mail: glimper@otenet.gr Journal of Biological Research 7: 99 – 104, 2007 J. Biol. Res. is available online at http://www.jbr.gr Indexed in: CAS (Chemical Abstracts Service) and DOAJ (Directory of Open Access Journals)