Gas Exchange, Xylem Ions and Abscisic Acid Response to Na^+-Salts and Cl^--Salts in Populus euphratica

钠盐和氯盐胁迫下胡杨木质部汁液ABA、离子浓度和叶片气体交换的变化(英文)

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 (NaNO3 : NaHCO3 : NaH2PO4 = 5 : 4 : 1, pH 6.8, osmotic potential = -0.24 MPa) or by 50 mmol/L Cl--salts (KCl : NH4Cl = 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 Ca2+ 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+, Ca2+ and Mg2+ 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.

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?