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

Abstract

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 uM 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.