sse of photosynthetic parameters for the diagnosis of copper deficiency in <i>Pinus radiata</i> seedlings

Abstract

Six‐month‐old water cultures of Pinus radiataI D. Don seedlings showed optimal growth, and the highest CO 2 assimilation and photosystem I‐dependent ascorbate/dichlorophenolindophenol → NADP + electron flow, at 3.0 uM Cu 2+ (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 CO 2 fixation shifts to 0.3 u M Cu 2+ (normal); at that time, the 3.0 uM Cu 2+ water cultures showed toxic symptoms of foliar chlorosis. Under Cu 2+ deficient levels (0.03 uM) a clear decrease in the photosystem I‐linked electron transport and CO 2 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 Cu 2+ 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 Cu 2+ deficient and Cu 2+ 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.