The Effect of EDTA on Maize Seedlings Response to Cd-Induced Stress

The possibility of utilizing plants for soil decon­ tamination of heavy metals received more and more interest in recent years. Plants useful for phytoremediation should be characterized by a high biomass production and by accumulation of high amounts of metals in easily harvested shoots (Blaylock et al., 1997). These conditions are ful­ filled by some cultivars of Indian mustard (Bras­ sica juncea), but other agronomic crops, such as maize, in combination with soil amendments, can also be useful. Maize is characterized by a fast growth and high production of the biomass of shoots (25000 kg/ha x crop) (Huang and Cunning­ ham, 1996), but it does not belong to species effi­ ciently accumulating heavy metals. However, re­ cent studies have shown that chelates added to the soil, among which EDTA is the most effective, can considerably increase Pb accumulation in maize shoots (Huang and Cunningham, 1996; Huang et al., 1997). A similar effect was obtained in the case of lead (Blaylock et al., 1997; Vassil et al., 1998) and cadmium accumulation (Blaylock et al., 1997) by Brassica juncea. It was found that the PbEDTA complex is taken up more easily by plants and transported through the xylem to shoots. Higher metal accumulation in shoots after add­ ing chelates to the growth medium can result from increase in their availability for plant roots or from increased/facilitated metal transport to shoots. Metal transport can be easily demonstrated in hy­ droponic cultures in which almost the whole metal pool is available for plants. The results of such studies can be valuable because it was shown that differences in Cd accumulation in shoots of 19 maize inbred lines did not depend on the kind of cultivation (hydroponic culture or soil), but they were rather of genetic origin (Florijn and Van Beusichem, 1993). Hydroponic cultures are used more and more frequently for fast classification of species able to tolerate and accumulate metals (Cd, Cu, Pb, Zn) in plant shoots (Huang and Cun­ ningham, 1996; Ebbs and Kochian, 1998). The aim of these studies was to investigate whether EDTA increases Cd accumulation in hydroponically cultivated maize seedlings, and in what way such a modification of the medium af­ fects plant growth.