| Raspberry is a perennial semi-bush small berry fruit tree.Its fruit has high edible and medicinal value with strong consumer demand and broad market prospects.Cross breeding is the main technical raspberry breeding means,but the germination rate of raspberry seeds is low as well as a long germination time,affected the acquisition of hybrid seedlings.Therefore,the summer fruit type raspberry variety "DNS-1" was used as material in this study to find the reason why the seed dormancy according to the anatomic structure of the seed,the inhibition of the seed coat,the contents of inhibitors and endogenous hormones in different parts of the seed(endocarp,seed coat,embryo and endosperm).Moreover,a variety of treatment methods were used to find the best way to relieve seed dormancy,such as treatment with different concentrations of sulfuric acid,skin breaking,exogenous hormones,sandpaper grinding,heat shock,drying for different durations and the stratification time.The main results are as follows:(1)It was showed by observing the anatomical structure of the seed that the inner skin of the seeds collected during the fruit ripening period was thicker,with a thickness of 133.40 μm,about 5 times of the seed coat thickness,and the structure was dense.When the seed coat was broken,the air and water permeability were increased.The endosperm layer was tightly wrapped around the embryo and was not completely absorbed by the embryo during the fruit ripening period,which might affect the seed germination.These showed that the thick and dense endocarp and endosperm layer were the primary factors affected on the seed germination.(2)The methanol extracts of three parts(endocarp,seed coat,embryo and endosperm)in unrefrigerated and refrigerated for 180 d raspberry seeds which collected during fruit ripening period significantly inhibited the germination rate and radicle growth of cabbage seeds.Among the three parts,the inhibitory effection of the embryo and endosperm was the strongest,with the germination rate of 12.23% and 0%.Among the seven separated phases obtained,the main inhibition of endocarp in unrefrigerated seeds were B and D phases,the main inhibition of seed coats were A,B and F phases,and the main inhibition of embryo and endosperm were G and B phase.Moreover,phase A,B and F were the strongest inhibitors of each part after refrigerated for 180 days.(3)The changes of the content of different endogenous hormones in different cold storage periods were as following: The content of IAA gradually increased with the fruit ripening and the refrigeration longer,then decreased after refrigeration for 90 days;The content of ABA decreased to the minimum value during the white fruit period,and increased to the maximum value during the fruit ripening period then decreased again;The content of 6-BA increased significantly during the whole period;The GA3 content decreased to the minimum in the ginkgo period,then increased significantly.In the fruit ripening stage,the highest content of endogenous hormone in endocarp,seed coat,embryo and endosperm was ABA,and IAA was the most after refrigeration for 90 days.(4)So far,sulfuric acid treatment was the most effective way to relieve dormancy of raspberry seeds.In the sulfuric acid treatment experiment,the highest germination rate of seed was treated with 95% sulfuric acid for 10 minutes and stratified for 30 days,and the emergence rate reached 18.00%,followed by 75% sulfuric acid treatment for 30 minutes and stratified for 90 days,and the highest emergence rate was 14.67%.(5)In the experiment of peeling treatment,the seeds of fruit in mature stage were cutted at the endosperm end,the radicle end and the back of the seed for transverse incision.The emergence rate was 13.04%,0.10%,0% after two weeks respectively.Other treatment methods including exogenous hormone,sandpaper grinding,heat shock and drying for different durations didn’t work. |
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