大花四照花种子休眠解除过程中种皮和胚乳结构变化1）

摘要

In order to investigate the effect of seed coat and endosperm on the germination of Cornus florida seeds, the ultrastruc-ture of seed coat and endosperm ingredients of C.florida seed with different treatments was systematically investigated by u-sing scanning electron microscope( SEM) and transmission electron microscope( TEM) , combining with the study of wa-ter permeability .Results of water uptake revealed the seed coat of C.fol rid could retard water uptake .By SEM images , from the exterior to the interior , the seed coat of C.florid consisted of four layers:the epidermal layer , the palisade layer , the parenchymatous layer and the fibrocyte layer .The epidermal layer consisted of multilayer sclerenchymatous cell .The palisade layer consisted of a monolayer macrosclereids with thick walls elongated longitudinally , and it may be the main barrier controlling the entrance of water through seed coat .Both of cold stratification and acid etching could change the seed coat structure of C.florid.The epidermal layer and the palisade layer of C.florid seed coat were damaged after treated by concentrated sulphuric acid .Cold stratification could destroy the out layer of C.florid seed coat and change the structure of palisade layer to some extent .When seeds were cold stratified at 5℃for 90 d, the cracks were appearing through the epi-dermal layer and the palisade layer .By TEM, with the C.florid seed dormancy released , macromolecule nutrients in the endosperm gradually decomposed and metabolism boosted .When seeds were cold stratified for 90 d, nutrients in the endo-sperm gradually decomposed , mitochondria , endoplasmic reticulum , golgi apparatus appeared , and its dormancy was bro-ken.In addition, proper sulfuric acid treating could accelerate the break of C.florid seed dormancy by expediting the change of seed coat structure and the metabolism of endosperm cell .%为探讨种皮、胚乳对大花四照花种子萌发的影响，以不同解除休眠处理后大花四照花种子为材料，开展了种皮透水性试验，并分别对其种皮和胚乳进行了扫描电镜（SEM）和透射电镜（TEM）观察。结果表明：大花四照花种皮存在透水性障碍。扫描电镜观察发现，其种皮由外到内依次为表皮层、栅栏层、薄壁细胞层以及纤维细胞层。表皮层由多层排列紧密的厚壁细胞组成。栅栏层则由单层紧密排列的长柱状大石细胞构成，栅栏层可能是阻碍种子吸水的主要原因。酸蚀和低温层积对种皮结构都会产生一定影响。低温层积处理能破坏种皮表层结构，同时还能改变内部栅栏层细胞结构，种子低温层积90 d后，种皮出现裂缝直达内部薄壁细胞层。透射电镜观察发现，低温层积过程中，胚乳细胞内大分子营养物质不断降解，细胞内物质代谢速度逐渐加快，低温层积90 d，营养物质基本降解，线粒体、内质网、高尔基体等细胞器相继出现，种子休眠解除。浓硫酸酸蚀能加快大花四照花种皮结构的改变和胚乳细胞内物质代谢，促进该种子休眠的解除。