| Citrus 'Huangguogan' form shimian was used as the material.The effects of different planting densities on orchard environmental factors,leaf morphology and physiology,leaf photosynthetic parameters,fruit quality,and proteomics property were analyzed.In order to determine the optimum density for 'Huangguogan,,meanwhile explored the photosynthetic response regularity and regulation mechanism of 'Huangguogan,.This study is expected to provide theoretical and practical support for production management.The results are as follows.(1)With the decreasing of planting density,orchard environmental factors,including light,daily average temperature and soil moisture,were increased.Compared with the density of 2x3m,the PAR,air temperature,soil temperature and soil moisture of density 4x5m on average were increased by 423.7%,5.5%,2.18%and 4.9%.Air CO2 concentration and air humidity on average decreased by 1.8%and 4%.The daily range of PAR,air temperature,air humidity,soil temperature and soil humidity increased,and the daily range of air C02 concentration decreased.(2)With the decreasing of planting density,LAI of 'Huangguogan' leaf canopy decreased,chlorophyll content decreased,photosynthetic key enzyme activity increased,and Leaf shape changed to morphological character of sun-exposed leaves.Compared with the density of 2×3m,LAI of density 4×5m decreased 51.5%,DIFN increased 4.33 times,and the MTA increased 7°.Leaf area,Leaf thickness,leaf water content and SLA respectively decreased by 13.2%,27.6%,6.22%and 29.2%.The shape of stomata changed from small to large.The content of Chla,Chlb and TChl respectively decreased by 3.24%,25.92%and 9.99%,but the ratio of chlorophyll a/b increased 30.05%.The activity of RubisCO,RCA and PEPC were increased by 19.5%,29.6%and 22.2%,and the ratio of RubisCO/PEPC had no significant difference.(3)With the decreasing of planting density,the photosynthetic physiological indexes of Huangguogan showed an upward trend.Compared with the density of 2x3m,Photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)of density 4x5m were increased by 115.8%,62.4%and 52.7%,and intercellular C02 concentration(Ci)decreased by 13.1%.There were different degrees of recoverable photosynthetic inhibition in about 14:00 at the young fruit stage and mature stage.LSPn and CSPn were increased by 53%and 24%.The FO,Fm,FO/Fm were increased by 17%,35.2%and 20.6%,and Fv/Fm increased slightly without significant difference.(4)With the decreasing of density,the quality of 'Huangguogan' fruit was improved significantly.Compared with the density of 2×3m,fruit weight,transverse diameter and longitudinal diameter of density 4x5m were increased by 70.9%,20.2%and 17.2%,and the fruit shape index had no significant difference.The total soluble solids(TSS),total sugar content,the ratio of sugar and acid were increased by 1.9%,16.9%and 47%,TA decreased 21.9%,and Vc content showed no significant difference.The yield per mu increased first and then down,the number of fruit per plant and the yield per plant increased by 1.01 and 2.53 times,the income and benefit increased by 70.6%and 319.1%.(5)The results of differential protein expression of 'Huangguogan' leaf were show as follows.Compared with the density of 2 x3m,the leaf proteins of density 4×5m had 395 down-regulated proteins which mainly located in ribosomes and macromolecular complexes and involved in the biological process of gene,ribosome and proteasome expression,and it had 485 up-regulated proteins which located in the plastid and chloroplast and involved in the biological process of precursor metabolites and energy production and photosynthesis.Among them,photosynthesis related proteins are mainly concentrated in PSI,PS II,electron transfer,photosynthetic phosphorylation and carbon assimilation.(6)The mechanisms of photosynthetic regulation of 'Huangguogan' caused by density changing were mainly as follows.Increase the absorption of more long wavelength light in Huangguogan leaf via increasing chlorophyll a/b and the expression of PS I reaction center protein.Accelerate its light energy conversion,light energy distribution and electron transport rate via increasing chlorophyll a/b binding protein and cytochrome b6f complex protein expression in PS ?.Accelerate its photosynthetic phosphorylation rate via increasing ATPase expression.Enhance its carbon assimilation ability to cope with the increased rate of light response via improving the photosynthetic enzyme activity,improving the Kalvin cycle and C4 pathway key enzyme protein expression.Enhance the light protection mechanism of its leaves to avoid light damage via adjusting the leaf morphology to the sun-exposed leaves state and increasing the expression of Psb family protein and heat shock protein of PS ?. |
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