木薯种子休眠特性及破除方法研究

Seed Dormancy Characteristics and Breaking Technique of Manihot esculenta

木薯(Manihot esculenta Crantz)作为全球重要的粮食作物和生物能源作物,杂交育种是木薯种质改良和品种选育的重要手段之一。然而,由于木薯存在种子萌发困难等一系列问题,极大限制了新品种的选育。本研究以新收获的华南124号母本自然结实种子为材料,通过一系列室内试验,对木薯种子休眠特性及休眠破除方法进行研究,结果表明:(1)解剖学和扫描电镜发现,木薯种子呈卵圆形,由种皮、胚乳和胚组成;其中,种子外表皮整体光滑,由外至内依次为表皮层、海绵组织层和栅栏组织,且栅栏层细胞排列较为致密。(2)种阜和种皮虽减缓木薯种子本身吸水速率,但种阜不是诱导其休眠的原因,而种皮的机械阻碍作用或抑制物的存在是诱导种子休眠的主要原因,从而判断木薯种子休眠类型为生理休眠。(3)采用砂纸打磨发芽口、去种皮和砂纸打磨发芽口+冷热循环2次处理均可有效破除种子休眠,显著提高种子萌发率;其中,砂纸打磨发芽口效果最佳,可使萌发率由2%提高至88%,处理后萌发速率最快。(4)35℃是木薯种子萌发的最佳温度,其萌发率和萌发指数分别达88%和36.6。本研究从木薯种子结构、种子休眠特性及其有效破除方法等方面为生产实践提供科学依据,也为木薯杂交后代优良性状得以表达提供理论参考。

Cassava(Manihot esculenta Crantz)is an important food and bioenergy crop globally.One of the most sig-nificant methods for germplasm development and variety selection is hybridization.However,a series of problems in-cluding difficulty in seed germination hinder severely the development of new cultivars.Thus,in present study,seed dormancy characteristics as well as dormancy breaking methods were investigated with freshly harvested natural hybrid seeds of SC124.The cassava seeds are oval and contain a seed coat,endosperm and embryo according to the observation of anatomy and scanning electron microscopy.The outer epidermis is smooth and contains epidermal layer,spongy parenchma and densely arranged palisade parenchma from outside to the inside.The seed coat and seed caruncle slow down the water absorption of cassava seeds,while the primary reason for inducing seed dormancy is the mechanical hindrance of seed coat and the existence of the inhibitor,which could be classified as physiological dor-mancy.Treatments by scarified seed micropyle,removing seed coat and scarified seed micropyle+two alternating cy-cles of moist cold temperature(0℃)for 2 h followed by moist warm temperature(30℃)for 2 h could effectively break seed dormancy and improve seed germination percentage.Treatment by scarified seed micropyle was the most effective methods,which promoted seed germination from 2%to 88%and germination rate was also the fastest.The optimum temperature for germination of cassava seeds was 35℃,and the germination percentage and germination index was 88%and 36.6,respectively.The research could provide scientific basis for understanding seed structure,seed dormancy characteristics and the best broken method for cassava seeds in production practice,and also provide a theoretical ref-erence for the expression of excellent traits of cassava hybrid offspring.