The relationship of host and endophyte during flowering, seed formation, and germination of Lolium perenne

Abstract

The development of a fungal endophyte in the tissue of Lolium perenne during flowering, seed set, and germination is described. The endophyte progresses intercellularly from the vegatative apex into the inflorescence primordium and floral apices, from where it penetrates the tissues of ovary and ovule. At megagametophyte maturity, hyphae are concentrated outside its wall adjacent to the large lateral antipodal cells and subsequently gain entry to the embryo sac, probably soon after fertilisation. During early embryogenesis, hyphae occur on the surface of the embryo, and penetrate it at the ‘notched’ stage. At seed maturity, hyphae are widespread within the embryo, including the plumule apex, as well as below the testa, between cells of the aleurone layer, and between scutellum and endosperm. At germination, hyphae outside the embryo appear to play no further part in invasion of the already infected embryo. The endophyte of Festuca arundinacea has a similar relationship with its host and appears to be ultrastructurally indistinguishable from that of Lolium perenne

Keywords:

• endophyte
• Lolium perenne
• ryegrass
• flowering
• megagametophyte
• embryo sac
• embryo
• infection
• primordium
• seed
• germination
• Festuca arundinacea