Effects of photoperiod and exogenous iron on photosynthetic characteristics, fruit quality and mineral elements of tomato.

[Objective] This study explored the effects of different concentrations of exogenous iron (EDTA-Fe, Fe) on photosynthetic characteristics, fruit quality and mineral elements of tomato under different photoperiod conditions to provide basis for the improvement of tomato nutritional quality based on coordinated regulation of photoperiod and Fe nutrient. [Method] In this experiment, strawberry tomato was planted under two photoperiods (12 h/12 h and 16 h/8 h) to study the effects of photoperiods and exogenous Fe fertilizer (0 (CK), 100, 150 and 200 µmol/L) on photosynthetic characteristics, fruit quality and mineral elements contents of tomato. [Result] Under different photoperiods, with the increase of exogenous Fe concentration, contents of tomato leaf chlorophyll a and chlorophyll b, carotenoids and chlorophyll (a+b) as well as net photosynthetic rate increased to peaks at 150 µmol/L before decreases. Compared with CK, stomatal conductance, intercellular CO₂ concentration and transpiration rate of tomato leaves treated with Fe fertilizers were significantly increased. Contents of soluble sugar, Vc, free amino acid, soluble protein and lycopene in tomato fruits increased firstly and then decreased with the increase of exogenous Fe concentration, and high values were obtained when Fe concentration was 100 -150 µmol/L. The titratable acid content showed a trend of decreasing first followed by increasing. Compared with the same treatment under 12 h/12 h photoperiod, contents of chlorophyll a, chlorophyll b, carotenoids, chlorophyll (a + b) and net photosynthetic rate as well as contents of soluble sugar, free amino acids, soluble protein and lycopene in tomato fruits were increased differently under 16 h/8 h photoperiod. There were significant differences in contents of K, Ca, Mg, Zn, Fe and Mn in tomato fruits at mature stage under the two photoperiods. [Conclusion] Exogenous Fe could effectively promote photosynthesis and fruit quality of tomato under different photoperiods,and spraying 100 - 150 µmol/L Fe fertilizer on leaf surface under 16 h/8 h photoperiod was the best. [ABSTRACT FROM AUTHOR]