Effect of different light quality on growth and photosynthetic characteristics of Populus szechuanica var.tibetica seedlings
[Objective]The effects of different light qualities on the growth and photosynthetic characteristics of Populus szechuanica var.tibeti-ca seedlings were studied,and the response of P.szechuanica var.tibetica to the strong light environment in the plateau area was further ex-plored,which provided a theoretical basis for the screening of poplars with high luminous efficiency.[Method]Three color films of white,blue and green were set up with the seedlings of the P.szechuanica var.tibetica cuttings of current-year,and the white film was used as the control to determine and analyze the growth and physiological indicators,chlorophyll fluorescence and photosynthetic parameters.[Result]Both blue and green film significantly improved the plant height of P.szechuanica var.tibetica seedlings by 28.1％and 38.5％,respectively,while the leaf width of seedlings under blue film decreased significantly by 33.3％.Blue film significantly increased the contents of photosynthetic pig-ment(31.74％),soluble total sugar(55.57％)and sucrose(78.58％)in seedling leaves,while green film reduced the accumulation of soluble total sugar and starch in seedling leaves.The blue film could increase PS Ⅱ electron transport quantum yield under light(ΦPSⅡ)and decrease non-photochemical quenching coefficient(NPQ),while green film significantly reduced electron transfer rate(ETR)and ΦPSⅡ and increased NPQ.The diurnal variation curves of net photosynthetic rate(Pn)of P.szechuanica var.tibetica leaves with the three color films were all'bimodal type',and the order of overall Pn values were blue film＞white film＞green film,and the photosynthetic lunch break oc-curred at 12:00 with different color film treatment.The overall trend of stomatal conductance(Gs)and transpiration rate(Tr)was similar to that of Pn,while the intercellular CO2 concentration(Ci)showed a'W-shaped'curve.The blue film significantly increased the maximum net photosynthetic rate(Pn max),light compensation point(LCP)and CO2 saturation point(CCP)of P.szechuanica var.tibetica leaves,while the green film reduced the maximum net photosynthetic rate(Pn max),dark respiration rate(Rd),and light compensation point(LCP),and significantly increased the photorespiration rate(Rp)and CO2 compensation point(CCP).[Conclusion]Covering the blue film could enhance the photosynthetic pigment content of P.szechuanica var.tibetica seedlings,improve the utilization rate of weak light and CO2,improve photosynthetic efficiency,enhance the accumulation of photosynthetic products,and promote plant growth.
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