Eco-physiological studies on reforestation in barren lands

(1)研究了水分胁迫对牛皮桦（pittosporum Tobira）和桦树（Betula grossa）幼苗生理适应的影响。在培养基中缺水2个月后，Pittosporum幼苗的耐旱性提高。在-0.42 MPa培养基中，当培养基水势降至-0.69 MPa时，胁迫预处理的Pittosporum幼苗的蒸腾速率迅速下降，而未处理的幼苗蒸腾速率则没有变化。长期缺水不影响白桦幼苗的耐旱性。阿拉伯半岛干旱地区的旱生植物在长期缺水后没有表现出任何生理适应，而中生植物刺槐则表现出胁迫适应。(2)中国干旱区旱生植物叶片背面和正面均有大量气孔、毛和角质层蜡。日本中生植物叶片正面气孔很少。(3)接种菌根后的红松幼苗生物量增量大于无菌苗。去除菌根状菌会降低菌根的光合活性。(4)速生品种日木（Chamaecyparis obtusa）扦插在干旱胁迫下表现出较强的脱水耐受性和快速的ABA生成能力。

(1) The effect of water stress on the physiological acclimation of pittosporum Tobira and Betula grossa seedlings was investigated. Water deficiency in a culture medium for 2 months raised the drought tolerance of the Pittosporum seedlings. The transpiration rate of the stress-preconditioned Pittosporum seedlings cultured in the -0.42 MPa medium rapidly decreased when the water potential of the medium was lowered to -0.69 MPa, whereas the transpiration rate of unconditioned plants did not. Prolonged water deficiency did not affect the drought tolerance of the Betula seedlings.Xerophytes living in the arid area of Arabian peninsula did not indicate any physiological acclimation after a long-period water deficiency, whereas Pseudoacacia, a mesophyte, indicated stress acclimation.(2) A large number of stomata, hairs, and cuticle wax were observed on both abaxial and adaxial sides of leaves of xerophytes living in arid areas of China. Very few stomata were observed on the adaxial side of leaves of Japanese mesophytes.(3) Biomass increment of Pinus Thunbergii seedlings inoculated with mychorrhiza was greater than that of aseptic seedlings. Removal of rhizomorph of mychorriza decreased photosynthetic activity of them.(4) Cuttings of fast-growing cultivars of Hinoki (Chamaecyparis obtusa) indicated high dehydration tolerance and rapid ABA production under drought stress.