Photosynthetic Characteristics Of White Leaves Regreenging In Pseudosasa Japonica F. Akebonosuji H. Okamura Under Different Light Qualities

Pseudosasa japonica f.akebonosuji H.Okamura is a rare ornamental bamboo introduced from Japan belongs to Pseudosasa japonica which leaves are green,white and striped.Its white leaves can be restored to green.In order to explore the relationship between light qualities and leaves turning green ability,white and different degrees of greening leaves were treated with blue,red and white light.Photosynthetic pigments,light system characteristics,photosynthetic efficiency and chloroplast ultrastructur in leaves were measured at 0,5,10,15,20 and 25 d.The results showed that:?1?During the process of white leaf turning green,the content of photosynthetic pigments increased gradually,and the daily accumulation of blue light was the highest.At 25 d,chlorophyll a(1.025 mg·g^-1)and chlorophyll b(5.400 mg·g^-1)contents were higher than red and white light under blue light,while carotenoid content under red light reached the highest value at 25 d,which was 0.726mg·g^-1.?2?The PSII,PS I,and the ability for electron transfer are both greater than red and white.The maximum photochemical efficiency Fv/Fm?0.58?and the blade performance index PI_ABS?0.33?of blue light treatment were significantly higher than that of red and white light?P<0.05?.The absorbed light energy was used for electron transfer quantum yield?Eo in blue light treatment.The 10 d was significantly increased by 26%,but the red and white light recovered lagging,and increased significantly at 20 d;the maximum redox capacity of PSI was?I/I₀ and at 25 d,blue light>red light>white light.?3?The net photosynthetic rate increased rapidly during the process of white leaf turning green,and the difference between blue light and other light treatment was significantly higher.The net photosynthetic rate of the leaves under blue light was significantly higher than that of red and white at 5time points.It was 1.25 times of red light and 1.11 times of white light at 25 d.The change of intercellular CO₂ concentration was opposite to the change of net photosynthetic rate.The transpiration rate and the increase of greening degree gradually increased to 2.26 mmol H₂O m^-2s^-1 at 25 d,and the activity of key enzymes of carbon assimilation rate was significantly higher than that of red light by 52%and 41%higher than white light.?4?During the process of white leaf turning green,the granule layer is tightly fragmented to fold,and the time of initiation under blue light is earlier than that of red light and white light.The structure was complete at 5 d under blue light,and there was mature chloroplast at 10 d,while there were still a large number of vesicles under red and white light at 10 d;the average number of chloroplasts in single cell at 25 d under blue light treatment Higher than red and white.In summary,the re-assembly of the thylakoids under blue light,the increase of the number of photoreaction centers,and the improvement of the photochemical energy conversion efficiency unanimously reveal that the blue light is relatively red and white,and promotes the early repair of the damaged plastids to accelerate the turn of the white leaves.