The analysis of stable isotope value, chlorophyll and nutritional quality of Leymus chinensis

The stable isotope value (13C), chlorophyll (SPAD) value and main nutrients of different varieties of Leymus chinensis which were planted in 3 different types of soils were determined and the correlation and regressions between these indices were explored and discussed. The results showed that the effects of the soil on 13C and SPAD values of L. chinensis varieties BG2 and B were high significant (P0.01), while the effect on the SPAD value of the varieties Y1 were not significant. The correlations between the 13C values of L. chinensis and the soil organic matter(SOM), available nitrogen (AN), total salt content (TS) and water content (WC) ranged from 0.737 to 0.800 (P＜0.01). In addition to that the regression relationship of the 13C value of L. chinensis with the total salt content of the soil was significant（P＜0.05）, its regression relationships with the other measured soil factors were all high significant（P＜0.01）. The correlations indices between the 13C values （-28.613～-27.383）and the crude protein(CP), crude fiber(CF) and lysine were 0.533, 0.591 and 0.401 respectively and the regression relationships were significant. The correlations with the indispensable amino acid (IAC) and energy content were 0.469 and 0.649, respectively and the regression relationships were significant. The correlations between the SPAD values of L. chinensis and the CP, neutral detergent fiber, phosphorus, crude ash and dry matter (DM) content were relatively high with the correlation indices ranging from 0.596 to 0.783. The correlation between the SPAD values（37.075~42.893） and the proline was the highest (R2=0.902, P＜0.01). The correlations between the SPAD values and the total amino acid (TAA) content and IAC content ranged from 0.833 to 0.887 and the regression relationships were both high significant. These tested indices performed significant regression relationship. In conclusion, the SPAD value was the best index to suggest the nutrition quality of L. chinensis. The Y1 and Y3 varieties of L. chinensis should be widely cultivated as they had relatively high SPAD value, DM, CP, energy content, the proportion of TAA and IAC and relatively low CF content.