Abstract
Summary The effects of copper deficiency on chlorophyll concentration, photochemical activity, polypeptide composition and ultrastructure of chloroplasts from sugar beet (Beta vulgaris L.) leaves were investigated. The chlorophyll content of copper-deficient leaves was reduced to less than half of the control. The chlorophyll a/b ratio was increased, averaging 3.4 against 3.1 in the controls. Photosystem I- and II-dependent electron transport activities were differently affected by copper deficiency, the photosystem I-mediated methyl viologen reduction being more drastically decreased than the photosystem II-mediated p-benzoquinone reduction (80 and 65 % inhibition, respectively). The polypeptide pattern of chloroplast internal membranes was qualitatively similar in control and deficient leaves. Quantitative differences appeared in the 70, 55, 25 and 15 kdalton regions. Chloroplasts from copper-deficient leaves exhibited significant changes in their ultrastructure dependent on the strength of the copper deficiency. In such chloroplasts the internal membrane system was greatly reduced. It is our contention that the changes in internal organization account for some of the observed reductions in pigment and photochemical capability shown by chloroplasts from copper-deficient leaves.
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