Effects Of Leaf Structure And Pigment Content On Photosynthetic Capacity Maintenance And Photoprotection In Variegated Leaves Of Actinidia Kolomikta(Maxim & Rupr.) Maxim.

Actinidia kolomikta（Maxim&Rupr.）Maxim.is one specie of deciduous woody vine of the genus Actinidia.It is distributed in the Northeast China.The fruit of A.kolomikta has high nutritional value and broad market prospects.The significant feature of A.kolomikta is that the leaf exhibit striking color during growth and development process,forming unique white and pink patchy color.Our previous study showed that variegated leaves have higher photosynthetic rate,but how it can maintain photosynthetic function is still unclear.In order to explore this problem,the white leaves,green leaves and red leaves of A.kolomikta were taken as the main research objects.The leaf structure,pigment content,spectral characteristics,photosystemⅡactivity,photosynthetic assimilation ability and photoprotective ability were measured and analyzed.The effects of leaf structure and pigment composition on spectral characteristics,photosynthetic apparatus activity and photosynthetic capacity were clarified,which will provide theoretical basis for elucidating the maintenance mechanism of photosynthetic capacity and photoprotective mechanism of variegated leaves of A.kolomikta.These results were as follows:1.The reasons for the formation of the variegated leaves of A.kolomikta were determined by the structure and pigment,resulting in differences in the spectral characteristics of the colored leaves and green leaves.The photosynthetic pigment content of white leaves was lower than green and red leaves.Because of the existence of air chamber in the palisade tissue,the incident light reflectance was the highest in white leaves,followed by red leaves,and the lowest in green leaves at 450～700 nm.The change trend of light absorption rate of different leaves was opposite to that of reflected light.Although gas chambers were observed in red leaves,their anthocyanin content is higher.Therefore,there was no significant difference in reflectance and absorption rate between red leaves and green leaves at 450～560 nm.2.Due to the special structure of the white leaves of A.kolomikta,the absorption coefficient of the incident light irradiated from the adaxial side is significantly lower than that of the green leaves.Under the same excitation light,the adaxial fluorescence parameters may not accurately evaluate the activity of the photosystem.Therefore,chlorophyll fluorescence parameters were measured by designing different excitation light intensity,some fluorescence parameters reflecting the activity of the photosystem exist obvious difference when the excitation light was corrected,and some fluorescence parameters even showed the opposite change trend.3.The sponge tissue of white leaves of A.kolomikta has strong photosynthetic capacity.The photosynthetic rate of the white leaves of A.kolomikta reached 83%of that of the green leaves,the stomatal conductance was smaller than that of the green leaves,and the intercellular CO₂concentration was higher than that of the green leaves,indicating that the photosynthetic rate of the white leaves of A.kolomikta decreased was due to non-stomatal limitation.There was no significant difference in net photosynthetic rate between the abaxial side of white leaves and the abaxial side of green leaves.The CE value and maximum photochemical efficiency of the abaxial side of white leaves were higher than those of the adaxial side of white leaves.It is speculated that the sponge tissue of white leaves has higher light energy utilization rate;through chlorophyll fluorescence imaging,it was proved that the chlorophyll fluorescence of white leaf sponge tissue was strong.RNA in situ hybridization was used to locate Rubisco BPαgene,and it was found that there was a high expression of Rubisco BPα gene in white leaf sponge tissue.It shows that sponge tissue,as the main photosynthetic tissue of white leaves,compensates for the low photosynthetic capacity of white leaf palisade tissue,thus maintaining the overall photosynthetic capacity of white leaves.4.Photoprotection ability in the white leaves of A.kolomikta was lower than red leaves.After strong light stress,the F_v/F_mof color leaves and green leaves of A.kolomikta decreased,but the degree of photoinhibition of white leaves was the largest compared to green and pink leaves.With the treatment time,the non-photochemical quenching of white leaves increased slightly,and the total antioxidant capacity was the weakest.The decrease of photochemical quenching in red leaves was significantly lower than that in white leaves,and the xanthophyll cycle and total antioxidant capacity were higher than those in white and green leaves.