Abstract: [Objective] In this study, transgenic Populus alba×P. berolinensis line (ABJ01) and non-transgenic line (9#) were used to test effects of drought stress. To provide a new reference for drought assessment and scientific basis for promotion and application of transgenic poplars, seedling height, morphological and anatomical structure of leaves, and photosynthetic characteristics of transgenic poplar and non-transgenic poplar under drought stress were measured. [Method] At the end of June 2015, a soil drought stress experiment was conducted with seedlings of transgenic poplar and non-transgenic poplar at the average height around 45 cm. The seedlings were subjected to three regimes of water (control, moderate stress, and severe stress), and the soil moisture was controlled at 60%-80%, 40%-60%, 20%-40% of the field water capacity, respectively for 30 days. [Result] Seedling height growth of the two lines was inhibited to a certain degree by drought stress, and the inhibition was increasing severe with the stress level increased. The seedling height of transgenic line ABJ01 was 9.38% higher than non-transgenic line 9# under severe drought stress. Single leaf area of the two lines was significantly reduced under drought stress, indicating that drought stress suppressed growth of poplar leaves. Single leaf area of 9# was significantly lower than ABJ01, accounting for 10.82% and 13.79% of the control, respectively, indicating limitation of leaf growth in ABJ01 was lower under drought stress. Anatomical structure of leaves showed that growth of leaf epidermal cells and mesophyll cells in ABJ01 and 9# were inhibited by drought stress, however the inhibited degree of ABJ01 was lower. Under moderate drought stress, leaf upper epidermal thickness and lower epidermal thickness of ABJ01 were 5.55% and 4.70% significantly greater than that of 9#, respectively. Thickness of palisade tissue of ABJ01 was 6.17% significant greater than 9#. In contrast, sponge tissue thickness and SR were 12.35% and 12.38% significantly lower than those of 9#, respectively. Under severe drought stress condition, leaf upper epidermal thickness and lower epidermal thickness of ABJ01 were 16.27% and 10.05% significantly higher than 9#, respectively, but sponge tissue thickness and SR were 11.71% and 11.58% significant lower than those of 9#, respectively. The more developed palisade tissue and relatively reduced spongy tissue may facilitate the conduction of CO₂, and maintain the higher P_n in leaf of ABJ01, which would contribute to adaptation to drought stress. Photosynthetic physiological data suggested that P_n of 9# was 2.8 times lower than that of ABJ01, and ABJ01 P_n was significantly higher than non-transgenic lines 9# (10.50%-18.97%), indicating ABJ01 had a greater photosynthetic capacity. Under control treatment, there were no significant differences in G_s, F_v/F_m between the two lines. However under drought stress, the decreased trend in transgenic line was relatively smaller compared with non-transgenic line under drought stress, indicating that ABJ01 indexes was less affected by drought stress. In addition, ABJ01 Tr was less than 9#, suggesting that ABJ01 had stronger capacity in water holding under drought conditions. The chlorophyll a, chlorophyll b and total chlorophyll content in ABJ01 were higher than those of 9#. ABJ01 F_v/F_m was higher than 9#, indicating that the ability of maintaining the stability of chlorophyll content was stronger and the damage of PSⅡ was less in transgenic line. [Conclusion] The study suggests that exogenous gene JERF36 may improve the gas exchange capacity and water-holding capacity of transgenic Populus alba×P. berolinensis under drought stress by impacting the leaf structural of transgenic poplar, finally enhance drought tolerance of transgenic Populus alba×P. berolinensis.

Key words: drought stress, transgenic poplar, leaf anatomical structure, photosynthetic characteristics