【摘要】 研究了渗透胁迫和盐胁迫下一年生胡杨 (PopuluseuphraticaOliv.)幼苗的木质部汁液脱落酸 (ABA)、离子浓度及叶片气体交换的变化。PEG 6 0 0 0 (溶液渗透势 - 0 .2 4MPa)、5 0mmol/L含钠离子的盐溶液 (NaNO3 ∶NaHCO3 ∶NaH2 PO4=5∶4∶1,pH 6 .8,渗透势 - 0 .2 4MPa)和 5 0mmol/L含氯离子的盐溶液 (KCl∶NH4Cl=1∶1,渗透势 - 0 .2 4MPa) 3种处理都显著降低了苗木的净光合速率 (Pn)和蒸腾速率 (TRN) ,但盐处理植株的TRN高于PEG处理的苗木。木质部汁液ABA的浓度在PEG处理后 1h达到峰值 ,之后开始下降 ,降到对照水平后又逐渐回升。盐处理苗木的ABA也是在处理开始后就迅速升高 ,但之后ABA水平明显高于PEG处理的植株。结果显示 ,渗透胁迫和离子胁迫都能提高胡杨木质部汁液ABA的浓度 :盐处理开始后ABA的迅速升高主要是渗透胁迫的作用 ,而此后离子胁迫 (Na+ 和Cl-)对ABA水平的提高具有重要作用。钠盐处理对胡杨净光合速率和蒸腾速率的抑制作用高于氯盐处理 ,其木质部汁液中较高水平的ABA和盐离子 (Na+ 和Cl-)是可能的原因。钠盐处理苗木的盐离子 (Na+ 和Cl-)水平高于氯盐处理 ,主要是由以下两方面的原因所致 :(1)细胞膜上的Ca2 + 被Na+ 所取代 ,增加了膜的透性 ;(2 )胡杨根细胞液泡对Na+ 的区隔化能力较弱 (与?更多还原

【Abstract】 We investigated the osmotic stress and ion_specific effects on xylem abscisic acid (ABA), ion uptake and transport and gas exchange in one_year_old seedlings of Populus euphratica Oliv. Net photosynthetic rates ( P n ) and unit transpiration rates ( TRN ) were both significantly decreased upon an osmotic shock caused by PEG 6000 solution (osmotic potential=-0.24 MPa) or a saline, which was applied by 50 mmol/L Na +_salts (NaNO 3∶NaHCO 3∶NaH 2PO 4=5∶4∶1, pH 6.8, osmotic potential=-0.24 MPa) or by 50 mmol/L Cl -_salts (KCl∶NH 4Cl=1∶1, osmotic potential=-0.24 MPa). However, salt_treated P. euphratica plants maintained typically higher TRN than those exposed to PEG. Xylem ABA concentrations increased rapidly following the PEG treatment, exhibiting peaking values at 1 h, then returning to pre_stress levels, followed by a gradual increase. Similarly, both Na +_treated and Cl -_treated trees exhibited a rapid rise of ABA after salt stress was initiated. Notably, salt_treated plants maintained a relatively higher ABA than PEG_treated plants in a longer term. Collectively, results suggest that osmotic stress and ion_specific effects were both responsible for salt_induced ABA in P. euphratica: the initial rapid increase of xylem ABA appears to be a consequence of an osmotic shock, whereas specific salt effects seem to be responsible for ABA accumulation later on. Compared with Cl -_treated trees, a higher inhibitory effect on gas exchange ( P n and TRN ) was observed in Na +_salt plants, resulting from its long_sustained ABA and higher salt concentrations in the xylem. Displacement of membrane_associated Ca 2+ by Na + and the lesser capacity in Na + compartmentation in root vacuoles likely contribute to the high influx of Na + and Cl - in Na +_treated plants. Xylem K +, Ca 2+ and Mg 2+ concentrations were elevated by external Na +_salts and Cl -_salts, suggesting that P. euphratica maintained a higher capacity in nutrient uptake under saline conditions, which makes a contribution to its salinity tolerance.更多还原