Using the pressure-volume technique, tissue water relations characteristics of three tree species, Salix matsudana, Pinus sylvestris var. mongolica and Sabina vulgaris, living in Mu Us desert in Inner Mongoria, China, were examined during summer season to facilitate an understanding of the physiological basis of inter-specific differences in drought resistance. As both osmotic potential at full tissue hydration (ψ_s^sat) and at the turgor loss point (ψ_w^tlp) for S. matsudana decreased as the season progressed and soil water condition became wet, seasonal osmotic adjustment did not occured for this rather mesophytic species. However, with higher value of bulk modulus of elasticity (ε), S. matsudana could maintain high water concentration under dry condition. All of the tree species treated in this experiment showed structural adaptation to arid condition with high rate of apopulast water in cell wall (V_a). Chronic water stress resulted active osmotic adjustment in S. matsudana with decreases of 0.2 MPa in ψ_s^sat and increases in ε along sand dune slope.

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In order to study the specific characteristics of the shade tolerance in relation to photosynthetic potentials, light-photosynthesis curve were analyzed for 1-year old saplings of Quercus acutissima Carr., Zelkova serrata Mak., Quercus glauca Thunb., Lithocarpus edulis Rehd., and 8-year old trees of Abies firma S&Z. grown under different light condition. The experiment was conducted at Ehime University Forest Nursery, Higashino, Matsuyama, and the relative light intensities assigned were 100%, 50%, 25%, 12.5% and 5%, respectively. The coefficients “b” and “b/a” of the parabolic light-photosynthesis curve were analysed to examine the light response species characteristics. The initial gradient “b” of the light-photosynthesis curve rose under low relative light intensity in three species, Z. serrata, A. firma and Q. glauca, but the changes of the photosynthetic rate at light saturation “b/a” were less remarkable. In the case of Q. acutissima, “b” was kept unchanged, while “b/a” declined remarkably under low relative light intensity. In the case of L. edulis, “b” rose and “b/a” declined under low relative light intensity. Z. serrata, A. firma and Q. glauca raised the low light adaptability and didn't lose the high light adaptability when grown under low relative light intensity, were concluded to have high shade tolerance. L. edulis increased low light adaptability while it lost the high light adaptability. Q. acutissima couldn't raise the low light adaptability and lost the high light adaptability under low relative light intensity, was discussed to be less shade tolerant.

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We discussed about the new judging method, on the tree vitality based on the stem surface temperature. In a model experiment with artificial sap flow, the stem surface temperature related to the transpiration of a tree. In the field condition, the stem surface temperature of planting trees had a good correlation with diameter growth and the tree vitality judged with the four-ranking method by the Science and Technology Agency. And on any fine day in summer, we could get nearly same correlation between the stem surface temperature and the tree vitality judged with the four-ranking method. Then, we named the tree vitality based on the stem surface temperature “plant activity”, and defined it as the tree vitality related to the transpiration of tree.

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