Studies On The Photosynthetic And Florescent Characteristics Of Seasonal Strawberry

Based on the production practice of strawberry in north China, the research had been carried out in the demonstration of college of horticultural science and engineering of Shandong Agricultural University with strawberry cultivars Fragaria vesca L.cvs.Selva, Midlight and Fragaria ananassa.Toyonoka, Houkouwase.We studied the photosynthetic characteristics, enzyme activity, the relationship between endogenous hormone and flowering mechanism. The main results were as follows:1. During the different seasons, the net photosynthetic rate of different strawberry cultivars showed a "bimodal" curve. The first peak value were at around 9:00 am and the second peak were from 12 to 15, the latter were lower than the fronter. There were transitory middaydepression phenomenon and higher photosynthetic peak value of in winter. The durative time was different during different seasons.2. The diurnal changes of the chlorophyll fluorescence parameters (Fv/Fm,ΦPSII)showed"V"shaped curve during different seasons.These parameters were higher in moring or afternoon, which depressed at noon or afternoon. The bottom of these parameters showed at different times during different seasons. The level of 18:00 was basic restoration or more than that of 8:00 and 10:00. The diurnal changes of the chlorophyll fluorescence parameters of ETR showed a "bimodal" curve.3. When the CO2 concentration was between 900¹000μmol·mol-1 under different light intensity, the net photosynthetic rate of different strawberry cultivars leaves was higher. When the light intensity was 1000¹600μmol·m^-2·s^-1 under different CO2 concentration, which was suitable for the photosynthesis in different strawberry cultivars. As the CO2 concentration increased, the light compensation point of different strawberry cultivars decreased, which were 20μmol·m^-2·s^-1～100μmol·m^-2·s^-1. The light saturation point of them were about 1000μmol·m^-2·s^-1. Under different light intensities, the CO2 compensation point of four cultivars of strawberry leaves were 150μmol·mol^-1. The CO₂ saturation point of that were higher than 1000μmol·mol-1. CO₂ fertilizer application will be conducive to the photosynthetic substance accumulation and strawberry growth.4. The stomata conductance of the Selva leaf was affected by light intensity obviously, which showed different trend in different conditions. But light intensity had little influence on the stomata conductance of Midlight, Toyonoka and Houkouwase leaves . Whether the temperature was lower (5℃) or higher (30℃), strawberry can carry on photosynthesis. But the net photosynthetic rate of Selva and Midlight were higher than that of Toyonoka and Houkouwase.5. The chlorophyll content and photosynthetic capacity of the strawberry cultivars had been about 25 days to the highest during the development process of strawberry leaves. The senescence periods of Selva and Midlight leaves were 67 days. The senescence periods of Toyonoka was 60 days. The senescence periods of Houkouwase was 53 days.The senescence periods was regarded as one of the basis for selecting leaves in production. 6. During the development process of strawberry leaves, the activity of superoxide dismutase first increased and then decreased. The activity of Peroxidase has been always increased, which rose quickly and gradually increased lately. When the strawberry leaves started 53d, the malondialdehyde content changed very small and declined slightly, which was significantly increased 53d later.7. The content of ZT, KT and 6-BA of Selva roots were highest for strawberry growth in spring. The content of ZT and 6-BA of Midlight roots were highest in spring, the highest content of KT of Midlight were in winter. The content of ZT, KT and 6-BA of Toyonoka roots were highest in winter. The anniversary content of the ABA was not high. The highest content of ABA of Selva leaves was 0.065μg·g^-1 in spring. The highest content of ABA of Midlight leaves was 0.069μg·g^-1in winter. The highest content of ABA of of Toyonoka leaves was 0.085μg·g^-1 in summer. The highest content of GA of Selva roots was in summer, which of Selva leaves was in winter. The highest content of GA of Midlight and Toyonoka roots and leaves were in summer. The highest content of IAA of Selva and Midlight roots were in summer, which of Toyonoka roots was in winter. The highest content of IAA of different strawberry cultivars roots and leaves all were in summer. The endogenesis hormone levels of roots and leaves of different strawberry cultivars were different under different Seasons. The specific mechanism of endogenesis hormones of strawberry in the four seasons need further study.8. Summer shade can reduce the photosynthesis of strawberry leaves under a bright light treatment. CO2 fertilizer application will be conducive to the photosynthetic substance accumulation and strawberry growth.