Weeds in citrus orchars and effects of ecological factors on some plants

Weeds causing qualitative and quantitative yield reductions in citrus orchards in the TurkishRepublic of Northern Cyprus were determined. The effect of ecological and environmental factorssuch as relief, soil pH, lime contents of the soil, cation exchange capacity of the soil, and soil structureon these weeds have been studied.The survey resulted in 71 weed species representing 28 families in citrus orchards. Of these21 weed species displayed a frequency of more than 10 per cent. Only the lime content of the soil hadan major effect on the distribution of weeds, while all other ecological factors studied, showed no orlittle effects. Sonchus oleraceae L. and Silybum marianum (L.) Gaertner were more common on soilswith medium to very high lime contents and thus, are indicator plants for lime contents in soil.Furthermore, the capability of heavy metal accumulation in potted Lepidum sativum L. spp.sativum (cress), Spinacia oleraceae L. (spinach), Raphanus sativus L. var. niger (radish), and Lactucasativa L. convar. sativa (lettuce) was investigated. To do so, soils in pots were contaminated byirrigating plants with water obtained from tailing ponds (#12, 14, and 17) of a copper mine at theCyprus Mining Corporation (CMC).The results showed a linear relationship between the accumulation of heavy metals in planttissues and the concentration of heavy metals in soils. Out of the ten elements studied, Arsenic (As),Cadmium (Cd), Iron (Fe), and Lead (Pb) had been accumulated more than that of found in plantsunder normal conditions. Hyper accumulation of heavy metals had been previously reported forCadmium and Iron; however, the experimental plants did not reach reported levels. Hyperaccumulation of arsenic and Lead has not been mentioned in previous studies. Thus, the increasedaccumulation in plant tissues suggests that spinach may be used for phytoremediation of soilcontaminated with both Arsenic and Lead, cress for soil contaminated with Lead and lettuce for soilcontaminated with Arsenic.Key Words: Weeds, Indicator plant, Environment, Lime, Heavy metalsII