关键词: 多叶苜蓿, 顶端分生组织, 叶原基, 复叶

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