Ratarstvo 45. hrvatski i 5. međunarodni simpozij agronoma 823 ORIGINAL SCIENTIFIC PAPER The effect of Cd-treatment on cyclic hydroxamic acid content of maize Peter Makleit University of Debrecen, Institute of Plant Science, Division of Agricultural Botany and Crop Physiology, Böszörményi u. 138. H-4032 Debrecen (pmakleit@agr.unideb.hu) Abstract The aim of this work was to examine the effect of Cd-treatment on cyclic hydroxamic acid content of maize. Application of Cd, as it is one of the toxic elements produce stress situation for the plants. As cyclic hydroxamic acids are considered stress metabolites, it was postulated that the concentration of the mentioned chemicals will change for the effect of Cd-treatment. 50, 100 and 150 μmol/litre Cd-concentrations were applied for 1, 2, or 3 hours. The maize plants were 6 days old at the time of the treatment. After one day of Cd- application the total cyclic hydroxamic acid content of roots and shoots was measured. The average cyclic hydroxamic acid content of roots was 230-350 mg/kg fresh weight. The shoots contained 490-590 mg cyclic hydroxamic acids/kg fresh weight. For the effect of Cd-treatment the cyclic hydroxamic acid content of roots and shoots decreased. The longer was the time of Cd-application and the higher was the Cd-concentration the lower was the cyclic hydroxamic acid content. It can be establish that the direction of changes in cyclic hydroxamic acid concentrations depends on many factors, like the type of stress, plant species and variety. Key words: cyclic hydoxamic acids, Cd, abiotic stress Introduction Cyclic hydroxamic acids (cHx-s) are secondary metabolites of graminaceous species (Cambier et al. 1999). Among the cHx-s‘ diverse biological roles it is very important that they play role in tolerance and resistance against pathogens and pests (Niemeyer, 1988). As in case of biotic stressors, abiotic stressors affect the level of cHx-s too. For example UV-radiation, water stress, increased light intensity, high temperature affected the level of cHx-s‘ (Epstein et al. 1986; Richardson-Bacon, 1993; Manuwoto et al. 1985; Bergvinson et al. 1994 ). Generally for the effect of biotic and abiotic stress the level of cHx-s rises. The elevated cHx-content contributes to tolerance and survival of stress situations in various ways (Hashimoto-Shudo, 1996). On the basis of these statements cHx-s are considered to be stress metabolites (Epstein et al. 1986). For proving the stress metabolite function of cHx-s I examined how an abiotic stress factor – Cd-treatment - affects the cHx-content of a selected maize variety. Material and methods The PR37D25 maize (Zea mays L.) variety was used for experimental purpose. The surface of the grains were sterilized with fivefold diluted H 2 O 2 solution. After rinsing with abundant distilled water the grains were kept in 10 mmolar CaSO 4 solution for 4 hours for the better germination. Grains were germinated between watered paper filters placed in vertical direction. The germinated plants were kept in the dark till the age of 3 days, when the roots of the plants were placed into Cd-solution with various concentration for various time (control = distilled water; Cd-solutions with 50, 100 and 150 μmol litre -1 concentrations for 1, 2 and 3 hours). Each treatment had three repetitions. After the Cd- treatment plants were placed into a greenhouse for one day where the environmental