榨菜(Brassica juncea)和紫甘蓝(Brassica oleracea)种间周缘嵌合体光合特性研究

PHOTOSYNTHESIS CHARACTERISTICS OF PERICLINAL CHIMERAS GRAFTED FROM Brassica juncea AND Brassica oleracea

对榨菜和紫甘蓝种间嫁接嵌合体的光合作用、叶绿素荧光、叶绿素含量、Rubisco的活性以及Rubisco酶大亚基和小亚基基因的转录水平等进行了测定分析。研究发现,种间周缘嵌合体TCC(茎尖分生组织细胞层LI-LII-LIII=TCC,T代表榨菜,C代表紫甘蓝;)的净光合速率为18.09μmol CO2·m-2·s-1,与亲本榨菜相当,但比亲本紫甘蓝高出24.8%。嵌合体的气孔导度和胞间CO2浓度显著高于2个亲本。叶绿素荧光参数中光系统II的实际电子传递量子效率(ФPSⅡ)和光化学猝灭系数(qP)在榨菜中最高,而嵌合体和紫甘蓝的这2个参数基本一致。对叶绿素含量测定后发现,嵌合体的叶绿素a、b及总含量与榨菜比较接近,比紫甘蓝高97%。TCC嵌合体Rubisco酶的初始活性和总活性处于榨菜(最高)和紫甘蓝(最低)之间,为1.76和3.75μmol CO2·g-1·min-1。而TCC嵌合体的Rubisco酶大亚基和小亚基基因的mRNA转录丰度与榨菜和紫甘蓝相比明显增高。以上结果说明,与TCC嵌合体光合机构的层源亲本——紫甘蓝相比,其叶绿素含量升高、Rubisco酶的活性以及其大小亚基基因的转录水平的增强可能是导致其净光合速率提高的原因。可见,TCC嵌合体的异源表皮(来自榨菜)对改善其内部光合组织(来自紫甘蓝)的光合能力有很大的促进作用。

In this study,the photosynthesis,fluorescence and content of chlorophyll,Rubisco activities and the large and small subunits of Rubisco were analyzed in the periclinal chimera TCC（LI-LII-LⅢ：TCC;LI：the outmost layer of shoot apical meristem;LII：the middle layer;LⅢ：the innermost layer.T：tuber mustard;C：red cabbage） synthesized by grafting in vitro between tuber mustard（Brasscia juncea） and red cabbage（B.oleracea）.The net photosynthesis rate of TCC chimera was 18.09μmol CO2·m-2·s-1 higher by 24.8% than that of its donor plant red cabbage,and the stomatal conductance and intercellular CO2 concentration of TCC chimera was significantly higher than that of both donor plants.The quantum efficiency of photosystem II（ФPS Ⅱ ） and photochemical quenching coefficient（qP） were almost consistent in TCC and red cabbage,but distinctly lower than that of tuber mustard.The total content of chlorophyll a and chlorophyll b in TCC chimera were close with that of tuber mustard,but remarkably higher by 97% than that of red cabbage.The initial and total activities of Rubisco of TCC chimera were 1.76 and 3.75μmol CO2·g-1·min-1,respectively,in between tuber mustard and red cabbage,while the expression of rbcL（the large subunit of the ribulose-bisphosphate carboxylase gene） and rbcS（the small subunit of the ribulose-bisphosphate carboxylase gene） in TCC chimera exceeded both donor plants.The results suggested that the enhancement of stomatal conductance,chlorophyll content,Rubisco activities and transcription of rbcL and rbcS genes may contribute to higher Pn of TCC chimera than the donor red cabbage,and heterogenous epidermis（LI） in TCC chimera exerted large effects on these physiological characteristics determined by inner tissues（LII and LⅢ）.