Abstract:

To interpret the patterns of genetic variation of photosynthesis and the relationships with growth traits within gene resources of Populus nigra，gas exchange and chlorophyll fluorescence parameters of 108 genotypes originated from different areas of Europe and China were measured. The results showed that there was abundant genetic variation for traits of gas exchange and chlorophyll fluorescence in P. nigra. The genotypes originated from China and the U.K. had relatively higher photosynthesis rate (P_n)，while genotypes introduced from Hungary had the highest quantum efficiency of photosystem II centers (F_v/F_m). The measured traits were found to have generally high broad sense heritability (H²) with considerable variation coefficient. Stomatal conductance (G_s) and electron transport rate (ETR) might be the crucial factors that influence photosynthetic ability of P. nigra. Parameters including P_n，intercellular concentration of carbon dioxide (CO₂) (C_i)，G_s and ETR were expected to be potentially applicable for the evaluation of photosynthetic efficiency in P. nigra. Emphasis should be put on the genotypes introduced from Serbia and other countries of Southern and Eastern Europe in further breeding research that aims at high photosynthetic efficiency in poplar.

Key words: Populus nigra, gas exchange, chlorophyll fluorescence parameter, genetic variation, photosynthetic efficiency