Differential development of plastids during microspore embryogenesis in barley

In order to understand and limit albino plantlet formation during pollen em bryogenesis in barley (Hordeum vulgare L, cv. Igri), plastid feature was fo llowed during pollen embryogenesis under two anther culture conditions and compared to plastid development in the zygotic embryo. The first condition was characterized by cold pretreatment and maltose in the induction medium. Both embryos and calli were then obtained. During pollen embryo developmen t, up to 30% of plastids had abnormal features. Disruptions mainly affected the plastid size, the feature of plastid envelopes, thylakoid and granum o rganization, as well as starch accumulation. In pollen calli, superficial c ells had meristematic features. Up to 50% of plastids exhibited the above m entioned abnormalities. Internal cells were highly vacuolated with amylopla st-like plastids; envelopes had normal features but no internal membrane wa s detected. Pollen embryo-derived plantlets had a green-to-albino ratio (G/ A) bring equal to 1.0, whereas calli-derived embryos only formed albino pla ntlets. The second condition was characterized by mannitol pretreatment and the presence of both maltose and mannitol in the induction medium. No call us was formed but most of microspore-derived structures developed haploid e mbryos and then the green plantlets (200 plantlets per 100 responding anthe rs, G/A = 9.4). In this case, plastid development in zygotic and pollen emb ryos were similar and almost no albino plantlets were formed.