Na_2CO_3胁迫对青龙桑、蒙古桑叶片生理和叶片光系统Ⅱ活力的影响

Effects of Na_2CO_3 stress on physiological characteristics and photosystem Ⅱ activity in leaves of mulberry 'Qinglong' and mulberry 'Mongolia'

以青龙桑Moros alba‘Qinglong’和蒙古桑Moros alba‘Mongolia’为试验材料,研究了不同浓度Na2CO3对青龙桑和蒙古桑叶绿素含量、渗透调节能力、叶片PSⅡ活力的影响。结果表明:随着Na2CO3浓度的提高,青龙桑和蒙古桑的叶绿素含量均呈现下降趋势,在相同Na+浓度条件下,青龙桑降低的幅度明显低于蒙古桑;随着Na2CO3浓度的提高,青龙桑和蒙古桑的脯氨酸、可溶性糖、可溶性蛋白含量呈现增加趋势,当Na+浓度>80 mmol/L时,在相同Na+浓度条件下,青龙桑的各组分含量明显高于蒙古桑;当Na+浓度低于120 mmol/L时,各项叶绿素荧光指标变化均不明显;当Na+浓度超过120 mmol/L时,随着Na+浓度的增加,桑树叶片的Fv/Fm、Fv/Fo、Sm、φPo、φEo、TRo/RC和ETo/RC呈现降低的趋势,而VJ、Mo、φDo以及DIo/RC增加;在相同Na+浓度条件下,青龙桑的各项叶绿素荧光指标变化幅度明显低于蒙古桑,说明盐胁迫抑制了PSⅡ受体侧QA向QB的电子传递,使桑树叶片捕获的光能比例降低,而用于热耗散的比例增加,用于QA-以后的电子传递能量比例减少。以上结果表明青龙桑对Na2CO3胁迫的适应能力高于蒙古桑。

The effects of Na2CO3 stress treatments with different concentrations to Moros alba‘Qinglong’ and Moros alba‘Mongolia’ on osmotic adjustment ability, leaf chlorophyll content, PS II activity of the two mulberry trees were investigated. The results show that chlorophyll contents of mulberry ‘Qinglong’ and mulberry‘Mongolia’ presented a decreasing trend with increasing of Na2CO3 concentration, the reduction of ‘Qinglong’ was significantly lower than that of ‘Mongolia’ under the same Na＋ concentration; the contents of proline, soluble sugar and solbule protein of‘Qinglong’ and‘Mongolia’ presented a decreasing trend with increasing of Na2CO3 concentration, when the Na＋concentration was higher than 80 mmol/L, the contents of proline, soluble sugar and solbule protein of‘Qinglong’ were signiifcantly higher than that of mulberry‘Mongolia’;The fluorescence parameters had no difference under low concentration Na＋（〈120 mmol/L） treatment, but the fluorescence parameters of normalised total complementary area above the OJIP transie（Sm）, quantum yield for electron transport（φEo）, maximal trapped energy flux per reaction center（TRo/RC） and electron transport flux per reaction center（ETo/RC） decreased obviously when Na＋concentration was above 120 mmol/L, while the parameters of relative variable fluorescence intensity at the J-step（VJ）, the reduction of QA maximum rate（Mo）, quantum yield for dissipated energy（φDo） and dissipated energy flux per reaction center （DIo/RC） increased.The fluorescence parameters increase of‘Qinglong’ were signiifcantly lower than that of‘Mongolia’ under the same Na＋concentration, electron transports in the receptor side of PSⅡfrom QA to QB were impeded under salt stress, the main reason was that the locus of QB and capacity of PQ had been changed, the ratio of capture photons had been decreased, the ratio of heat energy had been increased,the electron had been reduced after QA. The above results show that the adaptive capacity of‘Qinglong’ to Na2CO3 stress was higher than that of‘Mongolia’.