Study On The Relationship Between Lignin Metabolism And Mastication Of Nanfeng Tangerine

Nanfeng tangerine(Citrus reticulata Blanco ‘Kinokuni') is China's Citrus varieties. It is famous at all times and in all countries for its golden color, thin skin, little nuclear, rich nutrition, juiciness, mastication and good taste. However, consumers nowadays generally believe that Nanfeng tangerine fruit quality is not good as before, especially in slag pulp,seriously affecting the Nanfeng tangerine's commodity performance and economic value.This study, compared with the melting Shatangju, study lignin, monolignol content and their related metabolic enzymes in fruit membrane and juice sac of the small-fruit Nanfeng tangerine 97-2 during the development of fruit. It designs to ascertain the correlation on lignin metabolism and mastication of Nanfeng tangerine fruit, and to provide a theoretical basis for improving the quality of Nanfeng tangerine fruit. The results are as follows:(1)During the development of fruit, with a declining trend, the membrane/pulp, of small-fruit Nanfeng tangerine 97-2 is significantly higher than shatangju. It can be seen from the graph of lignin staining pattern that lignin were concentrated primarily around the kernel, tangerine pith, peel, seed and a small number of membrane.The staining pattern of the fruit sections is darker red and larger area in small-fruit Nanfeng tangerine than shatangju. Moreover, in the membrane, lignin in small-fruit Nanfeng tangerine is greater than shatangju. Lignin contents tended to reduce during the development of fruit. In the first four periods, lignin content of shatangju membrane is higher than small-fruit Nanfeng tangerine 97-2, however, in mature period, it presents the opposite result,lignin content of small-fruit Nanfeng tangerine 97-2 is significant higher than shatangju. Lignin in juice sac is generally lower than membrane. In the before fruit enlargement period, colored period and mature period, lignin content of small-fruit Nanfeng tangerine 97-2 is all significant higher than shatangju.(2) Monolignol presented declining trend during the development of fruit. In the same period, monolignol of small-fruit Nanfeng tangerine 97-2 is always significant higher than shatangju, except for the membrane coniferyl alcohol in middle fruit enlargement period.The analysis showed, the monolignol content in membrane is much higher than juice sac,and coniferyl alcohol content is much higher than sinapyl alcohol content, so coniferyl alcohol content is the main monolignol of nanfeng tangerine 97-2 and Shatangju.(3) PAL, PPO, 4CL, CAD and POD is key enzymes in lignin biosynthetic pathway,and they almost showed a decreasing trend as lignin content during the development of fruit. In mature period, except that PAL enzyme activity of shatangju juice sac is greater than Nanfeng tangerine 97-2, four other enzyme activity of Nanfeng tangerine are higher than Shatangju. Correlation analysis showes that PPO is the key enzyme of the synthesis pathway of lignin and sinapyl alcohol in membrane, while the POD and PPO is a key enzyme in determining the coniferyl alcohol content.In summary, the mastication of Nanfeng tangerine is closely related to the content of lignin in membrane, in other words,the higher lignin content lead to the worse mastication.The lignin of Nanfeng tangerine pulp consists of two monomer, coniferyl and Sinapyl alcohol. Free state coniferyl alcohol content is higher than free state Sinapyl alcohol content. PPO is key enzyme oflignin biosynthes in Nanfeng tangerine membrane.