Abstract: Five multifoliate alfalfa varieties imported from abroad were described. Different leaf developments of a single plant selected from accession WL323ML with trifoliate and quinquefoliolate compound leaves were compared using scanning electron microscopy. Results showed additional compound leaf types from the main stem of mutilfoliolate alfalfa having varied leaflet numbers. Leaf primordium developments of both trifoliate alfalfa and quinquefoliolate alfalfa compound leaves were divided into seven stages as observed by scanning electron microscopy. At S0 stage, an incipient leaf primordium emerged on the periphery of SAM. At S1, a common leaf primordium formed a strip of cells. At the subsequent S2, a pair of stipule primordium emerged as 3 protuberances on the proximal end of common leaf primordium in trifoliate alfalfa. Seven protuberances were formed in quinquefoliolate alfalfa. At S3, two- and four-lateral leaflet primordia formed between the stipule primordium and common leaf primordium of trifoliate alfalfa and quinquefoliolate alfalfa, respectively. At S4, Primordia of lateral and terminal leaflets were isolated with distinct boundaries. Meanwhile, spherical trichomes initiated on the abaxial surface of terminal leaf primordium. Then S5, tubular trichomes developed from the stipule primordial and lateral leaf primordial. Primordium of stipule, lateral leaf and terminal leaf were differentiated, and then formed original leaf structure. At the last stage (S6), the petiole was shaped between stipule primordium and lateral lobe primordium by cell division and expansion. Petiole (Pet) and trichomes were obviously differentiated. The research defined the development process of alfalfa leaf primordium and provided a basis for research on compound leaf developmental characteristics of leguminous plants.

Key words: Multifoliate alfalfa, Shoot apical meristem, Leaf primordium, Compound leaf

摘要： 通过对5个多叶苜蓿(Medicago sativa)品种叶片类型的形态研究,从品种WL323ML中筛选三叶型和五叶型复叶类型的单株为研究材料,利用扫描电镜对三叶型和五叶型苜蓿复叶发育进行对比分析。结果发现:多叶苜蓿主茎上表现有4,5,6,7,8和9叶等多种复叶类型,小叶的着生方式也表现为多种多样。扫描电镜下三叶型苜蓿和五叶型复叶叶原基的形态发育过程可划分为7个阶段。S0阶段,SAM外围形成早期的叶原基;S1阶段,出现条状共同叶原基;S2阶段,三叶型共同叶原基近端两侧产生一对托叶原基(ST),形成3个隆起的组织,而五叶型的则出现7个隆起的组织;S3阶段,三叶型苜蓿托叶原基和共同叶原基中间出现2个侧叶原基,而五叶型出现4个侧叶原基;S4阶段,侧生小叶和顶生小叶原基继续分离,出现明显的分界线,远端小叶的背面出现球状毛状体;S5阶段,侧叶和托叶原基发育出管状毛状体,侧叶、顶生小叶及托叶原基进一步伸长分化,相互之间部分重叠,表现为最初的叶结构;S6阶段,由于细胞的分裂和生长,托叶原基和侧叶原基之间出现叶柄;叶柄及叶柄表面毛状体分化明显。本研究明确了苜蓿叶原基的发育过程,对苜蓿乃至豆科复叶发育特征的研究提供依据,同时为苜蓿分子生物学和发育遗传学的研究奠定基础。

关键词: 多叶苜蓿, 顶端分生组织, 叶原基, 复叶