抗褐变剂对阿月浑子外植体褐变以及几种酶活性的影响

为了探明阿月浑子组织培养过程中的褐变机制,以阿月浑子组培丛生芽为外植体,在其继代培养基(1/2DKW)中分别添加抗褐变剂PVP和Cys,分析组培苗叶片、茎段和愈伤组织的总酚含量以及PPO、POD、PAL、C4H酶活性的变化,研究其与褐变的关系。结果表明,在一个继代培养周期内,愈伤组织中PPO活性呈增加趋势,而叶片和茎中PPO活性呈"V"字形变化。POD活性随继代时间增长而逐渐升高,继代28 d后开始下降,愈伤组织中POD活性变化范围较叶片和茎段中要高一个数量级。PAL活性总体呈下降趋势,而C4H酶活性在继代前期上升,继代14 d或21 d后下降。结合相关性分析可知,阿月浑子各组织的总酚含量与褐变率呈显著正相关,并且POD酶在促褐变反应中发挥主要作用。在实验中发现,PVP与Cys虽然对POD、PPO、CH4酶活性也有一定影响,但其主要是通过抑制PAL的酶活性,显著减少了组培苗和愈伤组织的酚类物质含量,从而降低褐变率。

Effect of browning inhibitors on browning rate,activities of PPO,POD,PAL and C4H in explants of Pstacia vera

To find out the browning mechanism during tissue culture of Pistacia vera L.,the in vitro shoot were used as explants,and browning inhibitor,polyvinylpyrrolidone(PVP) and cysteine(Cys) were added to the subculture medium(1/2DKW) respectively.Then the browning ratio,total phenol content,and activities of polyphenol oxidase(PPO),peroxide(POD),phenylalnine ammonialyase(PAL),and cinnamate 4-hydroxylase(C4H) in leaves,stems and calli of cultured shoots were investigated.The results showed that during the subculture cycle,the four enzymes exhibited different change patterns: in the calli,PPO activity increased gradually,while in leaves and stems it showed "V" type patterns;POD activity reached gradually to the peak value on the 28th day after subculture,then decreased,and POD activity were 10 times higher in calli than in leaves and stems;PAL activity showed a decreased pattern in all examined tissues;C4H activity rose gradually at early stage,then decreased on 14 d or 21 d after subculture.It was found that PVP and Cys significantly decreased the total phenol content,browning ratio and PAL activity in shoot and calli of P.vera L.Moreover,the correlation analysis indicated that there existed significant positive correlation between browning ratio and total phenol content during culture,and POD played a key role in this enzyme-browning reaction.PVP and Cys could decrease browning ratio mainly by inhibiting PAL activity,though the activities of PPO,POD and C4H were also influenced at different degrees.