不同浓度NaCl和Na2CO3处理对菊芋幼苗光合及叶绿素荧光的影响

 以砂培菊芋(Helianthus tuberosus)幼苗作为试验材料,分别进行不同浓度NaCl (50、 100、150、200、250 mmol&;#8226;L^－1)和Na₂CO₃ (25、50、 75、100、125 mmol&;#8226;L^－1)胁迫处理,以1/2全营养液作为对照,处理7 d后研究NaCl和Na₂CO₃胁迫处理对菊芋幼苗叶片光合作用及叶绿素动力学 参数的影响。结果表明：1)在NaCl处理下,当浓度小于150 mmol&;#8226;L^－1时,增加了菊芋的叶绿素含量、净光合速率(Net photosynthetic rate, P_n)和气孔导度(Stomatal conductivity, G_s),对荧光参数PSⅡ的电子传递情况( F_m/F_o)、PSⅡ原初光能转换效率(F_v/F_m)、PSⅡ量子效率 (Actual quantum yield of PSⅡ under actinic irradiation,φPSⅡ)和光化学猝灭系数(Photochemical quenching coefficient, qP)和非 光化学猝灭系 数(Non-photochemical quenching coefficient, NPQ)没有显著影响,随着浓度的增加,各项生理指标与对照相比除了NPQ显著 增加,其余均显著降低;2)在Na₂CO₃胁迫处理下,随着Na₂CO₃浓度的增加,与对照相比菊芋幼苗叶绿素含量、P_n、G_s以及叶绿素a荧光诱导动力 学参数F_m/F_o、F_v/F_m、φPSⅡ和qP均显著降低,NPQ显著增加;3)就NaCl和Na₂CO₃相比而言,在相同Na⁺浓度情况下,处于Na₂CO₃胁迫下的菊芋 幼苗的叶绿素含量、P_n、G_s以及叶绿素a荧光诱导动力学参数F_m/F_o、F_v/F_m、φPSⅡ和qP下降幅度和NPQ的增加幅度均显著大于NaCl,这说明 NaCl和Na₂CO₃胁迫均对菊芋幼苗造成不同程度的伤害,但在相同Na⁺浓度情况下,Na₂CO₃的伤害程度大于NaCl。由此说明菊芋对盐的忍耐程度高 于碱。

EFFECTS OF NaCl AND Na2CO3 STRESSES ON PHOTOSYNTHESIS AND PARAMETERS OF CHLOROPHYLL FLUORESCENCE IN HELIANTHUS TUBEROSUS SEEDLINGS

Aims Our objective was to explore the effects of saline-alkali stress on photosynthetic apparatus of Helianthus tuberosus seedlings.  Methods H. tuberosus seedlings were treated with NaCl (50, 100, 150 , 200, 250 mmol&;#8226;L^－1) and Na₂CO₃ (25, 50, 75, 100, 125 mmol&;#8226;L^－1) in plastic pots with sand. Others were cultured in modulated half-strength Hoagland solution as a control. We studied the effects of NaCl and Na₂CO₃ on net photosynthetic rate (P_n) and parameters of chlorophyll fluorescence by measuring chlorophyll content,P_n, stomatal conductivity (G_s) and fluorescence parameters after 7 days. Important findings Significant increases of chlorophyll content, Pn and Gs compared with the control were observed under the 150 mmol&;#8226;L^－1 NaCl treatment, whereas there were no effects on fluorescence parameters, F_v/F_m (maximal photochemical efficiency of photosystem Ⅱ (PSⅡ) while all PSⅡ reaction centers are open), F_m/F_o(another expression for the maximal photochemical efficiency of PSⅡ), φPSⅡ(actual quantum yield of PSⅡ under actinic irradiation), qP (photochemical quenching coefficient), and NPQ (non-photochemical quenching coefficient). But with greater NaCl concentration, the chlorophyll content, P_n, G_s and fluorescence parameters significantly decreased except for an increase of NPQ compared with the control. When H. tuberosus seedlings were treated with Na₂CO₃, chlorophyll content, P_n, G_s, F_v/F_m, F_m/F_o, φPSⅡ and qP significantly decreased and NPQ increased compared with the control. At the same concentration of Na⁺, the decrease of chlorophyll content, P_n, G_s, F_v/F_m, F_m/F_o, φPSⅡ,qP and the increase of NPQ were higher in Na₂CO₃ stress than in NaCl stress. All results suggested that the tolerance of H. tuberosus seedlings to saline stress was higher than to alkaline stress.