Abstract: Photosynthesis characteristics of Lonicera tragophylla Hemsl. and its hybrid L. ×tellmanniana Hort. Spoth seedlings were investigated in summer under field condition. Compared with Lonicera tragophylla Hemsl. , L. ×tellmanniana Hort. Spoth seedlings had relatively larger single leaf area, but lower specific leaf weight ( SLW) and pigments content on leaf area basis. The light saturated photosynthetic rate ( Pn) and stomatal conductance (Gs) in L. ×tellmanniana Hort. Spoth leaveswere significantly higher than that in Lonicera tragophylla Hemsl. leaves. The light saturated intensities were 400 μmol·m^{- 2} · s^{- 1} for Lonicera tragophylla Hemsl. and 1 200μmol·m^{- 2} ·s^{- 1} for L. ×tellmanniana Hort. Spoth. During daily courses, the daily maximum photosynthetic rate in Lonicera tragophylla Hemsl. and L. ×tellmanniana Hort. Spoth leaves reached at 8: 00 am and 10: 00 am, respectively. In this study, the maximum quantum yield of photosystem Ⅱ exhibited little difference between Lonicera tragophylla Hemsl. and L. ×tellmanniana Hort. Spoth leaves. However, higher actual photosystem Ⅱ efficiency (ΦPSⅡ) and lower non2photochemical quenching (NPQ) in L. ×tellmanniana Hort. Spoth leaves were clearly observed when exposured to moderate and high irradiance. According to these results, it is easily deduced that Lonicera tragophylla Hemsl. seedlings are more sensitive to high irradiance than L. ×tellm anniana Hort. Spoth seedlings. Therefore, we suggest that Lonicera tragophylla Hemsl. seedlings should be planted in shade, and L. ×tellmanniana Hort. Spoth seedlings can be grown under full sunlight.

Key words: Climbing honeysuckle, Cultivation, Photosynthesis, Chlorphyll fluorescence