大麥花藥培養時小孢子發育途徑的組織學研究

Abstract

將含中期單細胞小孢子之大麥(Hordeum vulgare variety Dissa)花藥，培養在N6培養基上，於第一次小孢子細胞分裂，可產生兩個未分化的核，或形成形態上分化成生殖細胞核與營養細胞核之二核，此二核間無細胞壁，或有不完全或完全的壁形成。在繼續的培養過程中，這類小孢子皆有核融合現象發生。而經核融合來之小孢子往往能夠繼續分裂，並形成多細胞體，此外還有由營養細胞單獨分裂，或由生殖細胞與營養細胞各自分裂再共同組成的多細胞體存在。至於花藥培養之小孢子早期發育過程中所發生的普遍融合現象，我們認?是因生殖核在配子體時期的基因表現，也能於培養環境下持續表現，故生殖核具有傾向於與另一核融合的能力；此外在培養過程中生殖細胞細胞壁的形成與再消失，亦可能是生殖核基因持續表現的結果。本實驗共得到288棵花藥植株，其中28棵?綠苗，260棵?白苗。在根尖染色體檢查的部分，所檢查的78棵植株中二倍體有60棵，佔最優勢，此結果可能肇因於花藥培養早期小孢子發育過程中之普遍核融合現象。

The pathways to androgenesis in barley (Hordeum vulgare variety Dissa) were studied. When anthers of barley containing microspores at the mid-unicellular stage were cultured on a modified N6 medium, the first division of the nucleus gave rise to two similar nuclei or a large vegetative and a small generative nucleus. Division of the nucleus was accompanied or unaccompanied by wall formation. Nuclear fusion was observed in all types of microspores during subsequent development. It was hypothesized that the reprogramming of gene expression from gametophytic to sporophytic development during the first few days in culture is responsible for the fusion event. Microspores containing a fusion nucleus could usually divide and give rise to multicellular structures. Independent division of the vegetative and generative cell, and division of the vegetative cell alone resulted in two other pathways to multicellular structure formation. Among 78 plants regenerated from the microspores, 10 were found to be haploid, 60 diploid, 1 triploid, and 7 tetraploid. Most of these plants were albino.