ASGSB 1999 Annual Meeting Abstracts

HYPERGRAVITY AND CLINOROTATION EFFECTS ON SOMATIC EMBRYOGENESIS IN ORCHARDGRASS. J.K. McDaniel, Z. Tomaszewski, and B.V. Conger. Dept of Plant & Soil Sciences. Univ of Tennessee.

A system in which embryos initiate and develop directly from single mesophyll cells in in vitro cultured leaf segments of orchardgrass (Dactylis glomerata L.) was used to study the effects of hypergravity and clinorotation on somatic embryogenesis. Whole tillers were excised from greenhouse grown plants and the leaves were separated. The basal 3 cm portion of the innermost two were split along the midvein and cut transversely into 3 mm x 3 mm segments. Segments from one leaf half were used for the treatment (hypergravity or clinorotation) and the corresponding "sister" segments from the other half served as a control. The segments were plated onto solid Schenk and Hildebrandt (SH) medium amended with dicamba. Embryogenesis was estimated by counting seedlings and the number of seedlings from treatment leaves was compared to that of its corresponding control. The hypergravity experiments showed no significant differences in embryogenic response between treated (50 g for either 1 d or 3 d) and control leaf segments. Centrifugation for 5 d at 5 g produced significant differences. The 1 d and 3 d treatments, even though the g force was higher, did not produce an effect probably because the cells were not yet initiating division. The orientation of the leaf segments during centrifugation for 5 d at 5 g (horizontal versus vertical) did not have an apparent effect. Fast clinorotation (50 rpm) of vertical oriented leaf segments reduced embryogenesis (number of plantlets) to about 50% of control. Slow clinorotation (1 rpm) had no effect.

(Supported by NASA: NAG10-0221.)

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