2种培养方式的桑种子萌发状态及萌发过程中内源激素含量与SOD活性变化

Germination and Variations of Endogenous Phytohormone Content and SOD Activity of Mulberry Seeds Under Two Cultural Conditions

植物内源激素和生理活性物质对种子的萌发及幼苗的生长具有调节作用。为了高效获取桑种子萌发的子叶和胚轴作为桑树组织培养的外植体,以"桂优62号"杂交桑种子为材料,观察与检测静置培养和振荡培养2种培养方式的桑种子萌发状态及萌发过程中内源激素含量和超氧化物歧化酶(SOD)活性的变化。观察2种培养方式的桑种子发芽态势可见,振荡培养的桑种子萌发快而整齐,其发芽率高达99%,发芽势为81%,分别比静置培养高9个百分点和7个百分点。测定桑种子萌发过程中的SOD活性为静置培养组高于振荡培养组。用高效液相色谱(HPLC)法测定2种培养方式的桑种子萌发过程中吲哚乙酸(IAA)的含量,均随培养时间的延长而减少,至发芽高峰时都检测不到IAA;虽然2种培养方式的桑种子萌发分先后,但2组桑种子萌发第1天的赤霉素(GA)含量均较高;在整个萌发期,抑制型内源激素脱落酸(ABA)含量表现为静置培养组高于振荡培养组,但2组桑种子在萌发过程中的ABA含量始终低于GA的含量。试验结果提示:采用振荡培养方式能加快桑种子的萌发和提高发芽率,获得桑组织培养所需的外植体;IAA和GA均参与了桑种子的萌发过程,且相对较低浓度的IAA和较高浓度的GA能促进桑种子的萌发;当GA含量远高于ABA含量时,能大大促进桑种子的萌发与幼苗的生长。

Endogenous phytohormones and physiological active substances play important regulatory roles in seed germination and seedling growth.In order to obtain large number of cotyledons and hypocotyls from germinated mulberry seeds as explants for mulberry tissue culture,we took ＂Guiyou 62＂ hybrid mulberry seeds as experimental material for observing seed germination and measuring variations of endogenous phytohormone content and SOD （superoxide dismutase） activity during germination of the seeds under static and shaking cultural conditions.The results showed that the seeds germinated quickly and uniformly under shaking condition.The seed germination rate was as high as 99% and the germination vigor was 81%,being 9 and 7 percentage points higher over the static condition respectively.SOD activity of mulberry seeds during germination was higher under static condition than that under shaking condition.High performance liquid chromatography （HPLC） revealed that indoleacetic acid （IAA） contents under both cultural conditions decreased with culture time and no IAA was detected while seed germination culminated.Although germination of mulberry seeds under the two cultural conditions started at different time,gibberellin （GA） contents in mulberry seeds under both conditions were relatively higher on the first day of seed germination.In the whole germination period,the content of inhibitory endogenous hormone abscisic acid （ABA） was higher under static condition than that under shaking condition.However,ABA contents were always lower than GA contents under both conditions in the whole germination period.The above results suggest that shaking condition could speed up mulberry seed germination and improve germination rate,thus providing necessary explants for mulberry tissue culture.Both IAA and GA participate in the germination of mulberry seeds,and relatively low concentration of IAA and high concentration of GA are favorable for seed germination.When the content of GA is far beyond that of ABA,seed germination and seedling growth could be greatly promoted.