Study On Characteristics Of Seed Absorbing Systemic Compounds And Fluorescent Trace

Seed treatment can improve seed vigour and sowing quality.Systemic compounds are often used in seed treatments,however,little information has known the pathway that systemic compounds diffuse into the seed and seedling.The objective of this study is to simulate and clarify the pathway of systemic compounds transferring in different seeds and seedlings using fluorescent tracers with similar physical and chemical traits to systemic compounds,and investigate the effects of fluorescent tracers on germination and seedling establishment during seed treatment.Understanding uptake of systemic compounds will provide a basis for method improvement in seed treatments.Main results were as follows.Five fluorescent tracers,Fluorescein,Rhodamine B,Rhodamine 6G,3,6-Diamincacridine, fluorescein sodium,were used during seed soaking of rape(Brassica napus L.) in the fluorescent solution(0.5mg/ml) for 24h,then the seeds were observed under the blue light (495nm) and green light(546nm).The results showed that Rhodamine B excited with green light exhibited a yellow-orange fluorescence,and there were no negative effects to the seedling growth.Rape(dicotyledon,epigeal germination),pea(dicotyledon,hypogeal germination),onion (monotyledon,hypogeal germination) and maize(monotyledon,epigeal germination) seeds were used for soaking treatment in Rhodamine B(0.5mg/ml) by 8,12,16,20,24h, respectively.Then,the movement of Rhodamine B in the seed was observed.The results showed that the pathway of Rhodamine B into seed were various by the type of seeds.It entered the rape seed primarily through the micropyle,then diffused to the cotyledon,while it diffused into seed through seed coat for pea and maize.Rhodamine B was very difficult to enter the onion seed because of its hard seed coat.After seed priming with Rhodamine B solution for rape(0.5mg/ml,24h),pea(0.5mg/ml, 48h),onion(0.1mg/ml,24h) and maize(0.5mg/ml,24h),the root existed fluorescence phenomenon in four kinds of seeds compared to the treatment of priming with water.For the rape and onion,there was existed fluorescence at the base of stem,while no fluorescence was found in pea and maize.There was no fluorescence in the young leaf for all seedlings except rape.Priming with Rhodamine B solution significantly increased the germination index,and reduced the mean germination time for all four crop seeds.It significantly reduced the root length of the rape and onion and has no significant effects on pea and maize root length. Besides,priming with Rhodamine B solution had no significant effects on shoot height,dry weight,chlorophyll concentration and activities of superoxide dismutase(SOD),peroxidase (POD),catalase(CAT),malondialdehyde(MDA).After seed film coating with Rhodamine B(0.5mg/ml) for rape,pea,onion,maize seeds, the results showed that fluorescence existed in root and the base of stem of rape and pea,for pea and maize,only the root existed fluorescence phenomenon.After seed film coating with Rhodamine B,there were no significant effects on germination percentage,germination index and mean germination time.It has no significant effects on shoot height,seedling dry weight,chlorophyll concentration and activities of enzyme(SOD,POD,CAT,APX,MDA), however,it reduced the root length of four crop seeds.