Alkaline-salt tolerance indices of Ulmus pumila L. seedling and family evaluation on alkaline-salt tolerance

To evaluate alkaline-salt tolerance of one-year-old Ulmus pumila seedlings, ten physiological indices and three adaptability indices were investigated under simulation control test with different alkaline-salt content levels. Results showed that among these physiological indices, the photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), optimal photochemical efficiency(Fv/Fm) and potential activity (Fv/F0) of photosystem II were sensitively response to alkaline-salt stress in soil for seedlings, and there were significant variations between tested families. These five indices are valuable for family evaluation. Two indices, Fv/Fm and Fv/F0, have no significant interaction effects between family and soil alkaline-salt content level, which means that they can better reflect the tolerance response for all tested families and are the first choice. While water use efficiency (WUE) only acts as a referenced index. The results of family evaluation based on the effective photosynthesis and fluorescence indices and damaged symptom conditions were similar, the integrated evaluation with three types of indices showed that: the families 2, 6 and 9 were among the most tolerant ones; while families 1, 4 and 5 were weaker and the families 3, 7 and 8 were sensitive to alkaline-salt stress, but were tolerant at certain degree to slight and moderate stress. The 0.6% of alkaline-salt content in soil should be the point to limit seedling growth and adaptation in most tested families of U. pumila. The significant positive correlative coefficients among the five indices mentioned above have suggested that one index could be referenced to others. In conclusion, selection of family for higher tolerance to alkaline-salt stress in seedlings by physiological indices is feasible.