Plant metal content, growth responses and some photosynthetic measurements on field‐cultivated wheat growing on ore bodies enriched in Cu

Abstract

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 ug g−1) were compared to control plants growing in the same environment where the Cu concentration in the soil was 140 μg g1. 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 cm2 leaf area, 63% of that of the control plants. The ore plants were chlorotic and chlorophyll concentration was 3. 8 μg 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 μmol 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 Fm, Fv, I1/2 and Fv/Fm were lower in the ore‐grown plants than in control plants; Fm 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.

Field study of the effects of excess copper on wheat photosynthesis and productivity

“…These phenomena resulted in a decrease in the in vivo quantum yield of PSII activity. The decrease in the rate of total electron transport in stressed plants caused by excess Cu (Lanaras et al 1993) is likely to be related to the lower values of the assimilation rate (A) observed in the same Cu-stressed conditions reported herein. Productivity and stomatal conductance in the field-grown ore wheats decreased with a resultant reduction in transpiration and total water loss.…”

“…1994;Ouzounidou 1994). Lower values of CO 2 assimilation under Cu-stress were associated with a lower chlorophyll content (Table I) and parallel decreases in the concentrations of reducing carbohydrates (Lanaras et a!. 1993).…”

“…Recently Lanaras et al (1993) and Moustakas et al (1994) have studied the effect of Cu throughout the photosynthetic process of field-grown plants by analyzing some of the chlorophyll fluorescence parameters. Accordingly, excess Cu decreased the efficiency of excitation capture by the PSII reaction centers and inhibited the rate of the photochemical reactions.…”

“…Recently we have reported on the effects of excess Cu on field-grown crops by studying chlorophyll fluorescence parameters, Rubisco activity, sugar and starch contents (Lanaras et al 1993;Moustakas et al 1994). The objective of this study was to investigate further the effects of Cu on some gas exchange parameters of wheat plants combined with their productivity.…”

Fitoextração de cobre por espécies de plantas cultivadas em solução nutritiva

“…Entretanto, a presença em altas concentrações no solo afeta negativamente o crescimento e a produtividade das plantas (Sonmez et al, 2006), devido aos danos às membranas celulares por meio da peroxidação de lipídios (Bueno e Piqueras, 2002), ao comprometimento da atividade fotossintética (Lanaras et al, 1993) e aos processos de absorção e assimilação de nutrientes (Llorens et al, 2000;Devriese et al, 2001). Em solos agrícolas, um dos principais fatores relacionados ao aumento do teor de Cu em níveis fitotóxicos é a utilização intensiva de fungicidas cúpricos (Pietrzak e McPhail, 2004;Mirlean et al, 2007).…”