Effects Of Exogenous Polyamines On Photosynthetic Characteristics In Leaves Of Gala Apple

Photosynthesis is the basis of crop yield .But the photosynthesis is not efficiency because of many internal and external factors in nature.Polyamines have significantly physiological and regulatory effects on the plant growth. In order to guide chemical control technique for improving fruit trees photosynthesis, it is necessary to clarify the regular and mechanism of photosynthesis under polyamines treatments. One-year old Gala apple tissue culture seedings were used as materials in the study .The seedings were sprayed with different concentrations(1×10-4mol/L, 1×10-5mol/L, 1×10-6mol/L)Put and different concentrations(1× 10-4mol/L, 1 × 10-5mol/L, 1 × 10-6mol/L) Spd respectively under well-watered condition and sprayed with different concentrations(1 × 10-4 mol/L, 1× 10-5mol/L)Put under water stress on the leaves.The treatment with spraying water was the control.The purpose of the study was to analyze the effects of exogenous polyamines on photosynthesis characteristics under well-watered condition and water stress by measurement of photosynthetic gas exchange, chlorophyll fluorescence, chlorophyll,protein and SOD activity under stress .The results were summarized as follows:1. The daily variation of photosynthetic rate in leaves of Gala apple presented a double-peak curve and an obvious 'midday depression' phenomenon occurred when the water condition was well and relative soil water content was 55%(SRWC=55%).The peak values occurred at about 9:00 and 15:00 respectively.The first peak value was higher than the second peak value. The daily variation of net photosynthetic rate presented a single-peak curve when relative soil water content was 35%(SRWC=35%).The peak value occurred at about 9:00. Under the well-watered condition.the main reasons for the midday depression were stomatal and non-stomatal factors,while under water stress , the main reason was non-stomatal factors. Exogenous polyamines treatments have little effect on the daily variation of photosynthetic rate.2. The improvement of photosynthesis resulted from stomatal conductance ascending and intercellular concentration descending under the well-watered condition with Put or Spd treatments. Photosynthetic rates of 1×10-4 mol/L Put and Spd treatments increased 21% and 17% at about 9:00,which were higher than that of the control.Photosynthesis declined under water stress.Photosynthesis,stomatal conductance and water use efficiency ascended and intercellular concentration descended with Put treatments.The main reasons for polyamines improving photosynthesis of Gala apple were stomatal and non-stomatal factors.3. Light saturation point(LSP),CO2 saturation point(CSP),carboxylation efficiency(CE),maximum regeneration rate of RuBp and chlorophyll activity declined under water stress.With water stress time...