TOMATO PLANT NUTRITION AS AFFECTED BY ARSENITE CONCENTRATION

As a part of a general study of environmental contamination by arsenic (As), the effects caused by arsenite on the processes of uptake and a ccumulation of macronutrient elements calcium (Ca), potassium (K), mag nesium (Mg), nitrogen (N), and phosphorus (P) in tomato plants (Lycope rsicum esculentum Mill, cultivar Marmande) were studied. Tomato plants were grown in nutrient solution (hydroponic growing system) containin g three levels of As (added as sodium arsenite, NaAsO2): 2, 5, and 10 mg As L-1. One control, with no As addition, was also included. Vegeta tive growth and fruit yield were affected by As level in the nutrient solution. Plant growth, expressed as dry and fresh weights of leaves a nd roots, were significantly restricted by As. Fresh fruit production decreased to 60.7, 47.3, and 23.3% at 2, 5, and 10 mg As L-1, respecti vely, compared to control. Contamination by As caused changes in both concentration and uptake of all the macronutrients studied. A reductio n in the root concentration of P, Ca, and Na was observed while there was a statistically significant increase in root N and K. Arsenic trea tments changed the foliar concentrations of P, K, and Ca from sufficie ncy to deficiency levels. These biologically significant reductions in leaf P, K, and Ca, however, were not important enough to justify the toxic effects of arsenite on tomato plants as a simple nutritional dis order.