Mycorrhizal micropropagated Castanea sativa plants were studied in terms of growth and physiological parameters following in vitro mycorrhization with Pisolithus tinctorius. Mycorrhization enhanced growth of micropropagated chestnut plants, increased their protein content and photosynthetic rates, decreased the respiratory rates and CO 2 compensation point. RuBisCO activity was not significantly different in mycorrhizal and control plants, although there was an increase in the amount of RuBisCO in the former. Mycorrhization increased plant biomass and improved plants physiological status, thus enhancing the acclimatization process.

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Highly purified, intact chloroplasts were prepared from pea (Pisum sativum L.) and spinach (Spinacia oleracea L.) following an identical procedure, and were used to investigate the cupric cation inhibition on the photosynthetic activity. In both species, copper inhibition showed a similar inhibitor concentration that decreases the enzyme activity by 50% (IC(50) approximately 1.8 microM) and did not depend on the internal or external phosphate (Pi) concentration, indicating that copper did not interact with the Pi translocator. Fluorescence analysis suggested that the presence of copper did not facilitate photoinhibition, because there were no changes in maximal fluorescence (F(m)) nor in basal fluorescence (F(o)) of copper-treated samples. The electron transport through the photosystem II (PSII) was also not affected (operating efficiency of PSII-F'v/F'm similar in all conditions). Yet, under Cu(2+) stress, the proportion of open PSII reaction centers was dramatically decreased, and the first quinone acceptor (Q(A)) reoxidation was fully inhibited, as demonstrated by the constant photochemical quenching (q(P)) along experiment time. The quantum yield of PSII electron transport (Phi(PSII)) was also clearly affected by copper, and therefore reduced the photochemistry efficiency. Manganese, when added simultaneously with copper, delayed the inhibition, as measured by oxygen evolution and chlorophyll fluorescence, but neither reversed the copper effect when added to copper-inhibited plastids, nor prevented the inhibition of the Hill activity of isolated copper-treated thylakoids. Our results suggest that manganese competed with copper to penetrate the chloroplast envelope. This competition seems to be specific because other divalent cations e.g. magnesium and calcium, did not interfere with the copper action in intact chloroplasts. All results do suggest that, under these conditions, the stroma proteins, such as the Calvin-Benson cycle enzymes or others are the most probable first target for the Cu(2+) action, resulting in the total inhibition of chloroplast photosynthesis and in the consequent unbalanced rate of production and consumption of the reducing power.

Sycamore suspension cells (Acer pseudoplatanus L.) were grown in the presence of sublethal concentrations of copper (50 BM). During the first 5-6 days of treatment, growth was not affected, but cell respiration (coupled and uncoupled) declined to 60% of its normal value. This decline of respiration was attributed to a progressive diminution of the number of mitochondria in copper-treated cells, based on the demonstration of the concomitant decline of (1) cardiolipin (diphosphatidylglycerol) and cytochrome aa3 (cytochrome oxidase), two specific markers of mitochondrial inner membrane, and (2) fumarase activity, a specific marker of mitochondrial matrix space. In addition, the mitochondria extracted from copper-treated cells presented the same properties as those from control cells, concerning substrate oxidation, cardiolipin and cytochrome aa3 contents, and fumarase activity. These results strongly suggest that copper triggered an arrest of mitochondrial biogenesis, which preceded cell division arrest.

Copper deficiency in wheat (Triticum aestivum L. cv. Nazareno Stramppeli) markedly affects photosynthetic activity. Flag leaves of copper‐deficient plants showed a 50% reduction of the photosynthetic rate expressed as mg CO2 dm−2h−1. The activities of PSI and PSII, determined for isolated chloroplasts, as well as fluorescence measurements on intact leaves of copper‐deficient plants, indicated a low activity of photosynthetic electron transport. Ribulose bisphosphate carboxylase/oxygenase (Rubisco) activity was not affected by copper deficiency but copper deficiency affected the chloroplast ultrastructure, especially at the level of grana, where a disorganization of thylakoids is evident.