Abstract:

A pot experiment was conducted to determine the impacts of the low，middle and high concentrations of 4-hydroxybenzoic acid on the chlorophyll content，photosynthesis gas exchange parameters and chlorophyll fluorescence parameters of the different strawberry（Fragaria × ananassa Duch.） cultivars（‘Tutela’，‘Toyonoka’and‘All Star’）. The results showed that the content of chlorophyll a，chlorophyll b and carotenoids of three strawberry cultivars were reduced under the 4-hydroxybenzoic acid stress with the largest decline of‘All Star’. The net photosynthetic rate and transpiration rate of‘Toyonoka’with a little increase under the lowest concentration of 4-hydroxybenzoic acid，while the net photosynthetic rate，stomatal conductance and transpiration rate of‘Toyonoka’，‘Tutela’and‘All Star’Were all decreased under the 4-hydroxybenzoic acid stress，and the greater decline the higher concentration. The initial fluorescence（F_o）and non-photochemical quenching coefficient（q_N）were significantly increased under 100 mg · kg^-1 and 200 mg · kg^-1 4-hydroxybenzoic acid stress. Under the highest concentration of 4-hydroxybenzoic acid stress，the initial fluorescences（F_o）of‘All Star’，‘Toyonoka’and‘Tutela’were increased by 15.1%，21.5% and 9.3%，respectively，and non-photochemical quenching coefficient of the three strawberry cultivars were increased by 131.3%，190.5% and 26.6%，respectively. The maximum fluorescence（F_m），maximal photochemical efficiency（F_v/F_m），efficiency of excitation capture of open PSⅡ center（F_v′/F_m′）and effective quantum efficiency of PSⅡ（Φ_PSII）of three strawberry cultivars were firstly increased with the increasing concentration of 4-hydroxybenzoic acid and then decreased. The comprehensive advantage of chlorophyll fluorescence parameters of three strawberry cultivars was‘Tutela’>‘Toyonoka’>‘All Star’. Low 4-hydroxybenzoic acid concentration（50 mg · kg^-1） didn’t affect significantly the dry matter accumulation of‘Tutela’and‘Toyonoka’，but the aboveground and underground dry quality，and ratio of root/shoot per plant of three strawberry cultivars were significantly decreased in other treatments. The photosynthetic pigments，photosynthesis and chlorophyll fluorescence characteristics of‘Tutela’were less influenced by 4-hydroxybenzoic acid stress than‘All Star’and‘Toyonoka’. So a higher photosynthetic performance might be an important physiological trait of resistant cultivars in the adaptability to replant disease.

Key words: strawberry, 4-hydroxybenzoic acid, autotoxin, photosynthesis, fluorescence characteristic