Morphophysiology and Cryopreservation of Seeds of Dendrobium Nobile Lindl. (Orchidaceae) at Different Stages of Development

We studied the seed maturation of Dendrobium nobile Lindl to establish the optimal stage for green pod culture and long-term storage in liquid nitrogen. It was found that the immature seeds can germinate in vitro starting from 3 months after pollination (MAP) but only develop up to the stage of embryo swelling or protocorm without rhizoids. The maximum staining of embryos with vital dyes FDA and TTC occurs at 4 and 5 MAP that corresponds to the release of suspensor beyond the embryo sac. Embryo staining does not correlate with germination capacity and seed viability in cryogenic storage. The immature seeds acquire resistance to freezing and drying in airflow at the age of 6 MAP. The time of technical maturity for green pod culture and cryopreservation may be reduced from 12 MAP to 6–7 MAP.

Seed and Embryo Growth in Pod Cultures of Phaseolus vulgaris and P. vulgaris × P. acutifolius

Interspecific hybrid embryos resulting from crosses between Phaseolus species generally fail to reach maturity, and embryo rescue techniques are required to recover plants. To determine if ovary (pod) culture could permit interspecific hybrid embryo development, pods of P. vulgaris L. × P. acutifolius A. Gray and P. vulgaris L. (control) were cultured upright, supported by glasswool, in modified Murashige-Skoog liquid medium. The weight of seeds and length of embryos in P. vulgaris pods increased significantly during culture. However, usually only one or occasionally two seeds located at the middle positions of the pods developed to maturity. The same pod culture procedure promoted precocious germination of early cotyledonary-stage P. vulgaris × P. acutifolius embryos without further maturation of the embryos. These findings confirm that developmental arrest of the interspecific hybrid embryos in vivo is due to intrinsic deficiencies.