PLANT METAL CONTENT, GROWTH-RESPONSES AND SOME PHOTOSYNTHETIC MEASUREMENTS ON FIELD-CULTIVATED WHEAT GROWING ON ORE BODIES ENRICHED IN CU

Some elemental levels, morphological and photosynthetic characteristics and cellular metabolites of wheat plants (Triticum aestivum L. cv. Vergina) growing in the field on an ore body (Cu concentration in the soil 3050 mug g-1) were compared to control plants growing in the same environment where the Cu concentration in the soil was 140 mug g-1. The concentrations of Cu, K, Pb, Zn, Mg and Fe were higher in the ore plants but Ca was lower. Growth of the ore plants was inhibited. with decreased height (25%), weight (5%), leaf area (7%) and leaf dry weight (5%) compared to the control plants. Leaf protein concentration of the ore plants was 16.2 mg cm-2 leaf area, 63% of that of the control plants. The ore plants were chlorotic and chlorophyll concentration was 3.8 mug cm-2 leaf area, 6.4 times lower than that in the control plants. Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) activity was 13.4 mumol CO2 fixed (mg dry weight)-1 min-1, 164% of the activity in control plants. Therefore, growth inhibition did not appear to result from inhibition of the dark reactions of photosynthesis. High Rubisco activity appears to be maintained to permit maximal CO2 fixation rates whenever energy is available. Parameters of chlorophyll fluorescence F(m), F(v), t1/2 and F(v)/F(m) were lower in the ore-grown plants than in control plants; F0 was higher. These values indicate that there is a decrease in the pool size of the electron acceptors on the reducing side of photosystem II (PSII), a destruction of PSII centres and interference in the photochemistry of PSII. The nitrogen content, soluble sugars, starch and lipid content were lower in ore-grown plants. Lower carbohydrate levels appear to result from low photosynthetic activity. The fatty acid composition of lipids was similar in both groups. A lower proportion of polyunsaturated fatty acids was found in the ore-grown plants. Stress caused by high Cu concentration in the soil appears to affect the light reactions of photosynthesis leading to growth inhibition.