481 Effect of Foliar and Root Applications of Amino Acids on Iron Uptake by Tomato Plants M. Cerdán a , A. Sánchez-Sánchez, M. Oliver, M. Juárez and J.J. Sánchez-Andreu Universidad de Alicante Facultad de Ciencias Departamento de Agroquímica y Bioquímica 03080 Alicante Spain Keywords: Fe deficiency, Lycopersicon esculentum Mill., lime-induced iron chlorosis, biostimulant substances, nutrient uptake Abstract Tomato seedlings grown in lime nutrient solution were treated with foliar and root applications of two commercial amino acids products from plant and animal origin. Each product was sprayed 2, 7, 12 and 17 days after transplanting at two different concentrations (1 and 2 ml L -1 ). For root applications, 0.1 and 0.5 ml L -1 amino acids products were added to lime nutrient solution. Control, untreated plants grown in Fe-sufficient nutrient solution, and untreated lime supplied plants were present as well. Foliar and root application of commercial amino acids product from animal origin led to a severe plant growth depression. On the contrary, shoot and root fresh weights were no affected by addition of plant origin amino acids product for any doses applied. This effect suggests that animal origin product may be phytotoxic at doses used. On the other hand, foliar application of both amino acids products significantly inhibited root Fe(III)-chelate reductase (FCR) activity. As a result of that an important decrease of total Fe concentration and Fe(II) and chlorophyll content was observed in leaves of lime supplied plants. However, the high ratio Fe(II)/Total Fe in plants sprayed with plant origin amino acids product suggests that this treatment increased leaf Fe(III)-chelate reductase activity, specially at the low dose. Statistically differences in total Fe, Fe(II) and chlorophyll contents among untreated lime supplied plants and plants treated with root application of both amino acids products were not found, except to the low dose of plant origin product. That treatment enhanced root FCR activity and leaf total Fe concentration in lime supplied plants. According to these results, neither foliar nor root applications of amino acids were able to counteract lime Fe- deficiency symptoms in plants. INTRODUCTION Iron deficiency is a common nutritional disorder affecting plants grown in alkaline and/or calcareous soils. Soil application of synthetic iron chelates derivates from polyamine-carboxylic acids is the most common and efficient agricultural practice to relieve and/or avoid lime-induced iron deficiency (Álvarez-Fernández et al., 2005), but these products are very expensive and they can only be applied to high economic value crops. Also, the use of synthetic iron chelates involves an environmental risks associated with their mobility along the soil profile (Rombolá et al., 2002). Therefore, it is essential to find more economical and environmental-friendly alternatives to avoid Fe deficiency in plants. The commercial products based on amino acids have been used by farmers since more than 30 year due to the numerous beneficial effects found on several crops. These results can no be explained by the simple fertilizing action due to the organic nitrogen content of amino acids. Several studies have shown that these effects are essentially linked to the biostimulant action of amino acids in plants grown under different biotic a mar.cerdan@ua.es Proc. IV th Balkan Symp. on Vegetables and Potatoes Eds.: L. Krasteva and N. Panayotov Acta Hort. 830, ISHS 2009