Chlorophyll fluorescence and chlorophyll content in field-grown potato as affected by nitrogen supply, genotype, and plant age

Field experiments were conducted in Sicily (south Italy) to assess chlorophyll (Chl) fluorescence parameters in response of potato crop to nitrogen dose, to variation in genotype and in plant age, and to detect relationships between Chl content, fluorescence parameter F_v/F_m, and tuber yield. The experiment included five nitrogen doses (0, 10, 20, 30, and 40 g m⁻²) and four genotypes (Spunta, Sieglinde, Daytona, and Igea). Chl fluorescence parameters (initial fluorescence, F₀, maximum fluorescence, F_m, variable fluorescence, F_v, F_v/F_m, T_max (the time required to reach F_m), and Chl content were measured weekly between the appearance of the fifth and sixth leaves and the onset of plant senescence. A positive linear relationship was established between nitrogen supply and Chl content, F₀, and T_max. Nitrogen supply up to 10 g m⁻² also had a positive effect on F_m and F_v, but above this rate it reduced F_v/F_m. Spunta had the highest Chl content, F_m, F_v, and F_v/F_m, but the lowest F₀, whereas Sieglinde had the lowest Chl content, F_v, F_v/F_m, and T_max and the highest F₀. The cvs. Igea and Daytona exhibited intermediate Chl fluorescence parameters. Chl content and T_max decreased with increasing plant age, whereas F₀, F_m, and F_v increased until complete canopy development and thereafter declined until crop maturity. Tuber and plant dry matter yield were significantly correlated with Chl content, F₀, and T_max. Thus Chl fluorescence and content detect differences in the response of potato to N supply, can discriminate between genotypes, predict plant age, and yield performance under field conditions.