The Study Of The Stone Cell Distribution And Lignin Structure In Different Pear Varieties

The quality of fresh pear is low in our country, it has a high content of stone cell、thick skin、the fresh is hardened and poor taste、the sugar content is also low. Combinedwith the extensive management，lack of breeding technology and so on，resulting in adecline in the quality and variety degeneration. Stone cell content is a key determinant of pearfruit quality. Stone cells are formed by the deposition of lignin on primary cell walls,followed by the secondary thickening of cell walls. Studies of the structural features anddeposition of pear lignin are rare. The content, size and density of stone cell of Pyruspyrifolia (Burm F) Nakai， Pyrus bretschneideri Rehd., Pyrus communis L. andPyrusussuriensisMaxim is different. We investigated the relationship between the ligninstructure characteristics and the content and distribution of stone cell by the comparison ofstone cell content, distribution and the lignin content, lignin structure characteristicanalysis of spectroscopy in pears.1) The stone cell content was higher, the lignin content was higher accordingly indifferent pears.The sequence of stone cell content and lignin content were Jingbai>Dangshansu> Bali> Yali> Wonhwang.2) The sequence of the polymerization degree and distribution of stone cell wasDangshansu> Jingbai> Bali> Yali> Wonhwang which was agree to the result ofultramicroscopic observation.This was different from the results of stone cell and lignincontent. Though the lingnin and stone cell content of Dangshansu was lower than Jingbai,the aggregation degree of stone cell was higher than Jingbai.Therefore, the stone cellcontent was lower, but the taste was relatively poor.3) The characteristics of the infrared absorption peak and the content and constitutionof lignin functional groups were substantially alike by the comparison of the FTIRspectrum of lignin in pears. Aromatic C-O stretching(S units) was detected in1217cm-1/1228cm-1and G ring plus C=O stretching was detected in1267cm-1/1274cm-1. Itdescription that the lignin of the pear fruits is the G-S-type. But the relative content ofdifferent varieties of pears in the G/S is varied, the ratio is higher than the timber in the G/S and close to the Gramineae,s G/S.So the Pear stone cells was not as hard as wood, itstill edible.4) The1H-NMR spectral peaks of lignin were basically the same by analyzing the1H-NMR spectra of different pears, while the proton content of each corresponding peakrepresents was different. There was an obvious absorption peak at3.79, which represents methoxyprotons and H insome structures. The peak at7.0and6.6was guaiacylaromaticring protons and lilac aromatic ring protons respectively. G/S ratio between the differentvarieties of pears is Dangshansu> Wonhwang> Jingbai> Bali> Yali,they are2.15、1.62、1.47、1.42and1.24. It explained that Dangshan pear G-lignin content is higherthan the S-lignin,the ratio of G/S is higher than Jingbai, it caused Dangshan pear stonecells polymerization much greater than Jingbaili, so the impact of the stone cells wassignificantly greater than Jingbaili while edible.5) The sequence of carbon element content of lignin was Jingbai>Yali>Bali>Wonhwang>Dangshansu, the sequence of hydrogen element content wasWonhwang>Jingbai> Bali>Yali> Dangshansu and the sequence of oxygen elementcontent was Wonhwang> Bali>Yali> Dangshansu>Jingbai according to the analysis oforganic element content of lignin in different varieties of pear. The oxygen element contentof lignin in Dangshansu was higher than carbon element which was up to1.987percentagepoints. But the carbon element content of lignin was higher than oxygen element in theremaining species. This may lead to the degree of polymerization of stone cells inDangshan pear is higher than the other four species.