sse of photosynthetic parameters for the diagnosis of copper deficiency in Pinus radiata seedlings

Six-month-old water cultures of Pinus radiataI D. Don seedlings showed optimal growth, and the highest CO₂ assimilation and photosystem I-dependent ascorbate/dichlorophenolindophenol → NADP⁺ electron flow, at 3.0 uM Cu²⁺ (excess) in the hydroponic media. In the nine-month-old water cultures, when the early Cu deprivation has been overcome, the optimum for plant growth and CO₂ fixation shifts to 0.3 u M Cu²⁺ (normal); at that time, the 3.0 uM Cu²⁺ water cultures showed toxic symptoms of foliar chlorosis. Under Cu²⁺ deficient levels (0.03 uM) a clear decrease in the photosystem I-linked electron transport and CO₂ assimilation rates, as well as in the whole plant development, could be observed. Both six- and nine-month-old water cultures showed a close relationship between the Cu²⁺ concentration of the media and the foliar Cu content. However, leaf chlorophyll and the Cu content of thylakoid lamellae showed such a correlation only in the Cu²⁺ deficient and Cu²⁺ normal water cultures. The conclusion from these results is that the electron transport rate ascorbate/dicblorophenolindophenol → NADP⁺, and the Cu content of the photosynthetic membranes, can be used to diagnose a Cu deficiency in Pinus radiata plants.