The Morphological Characteristics and Livability Measurement of Wild Cymbidium tortisepalum Seeds

Purpose To study the seed morphology and viability measurement of the national grade I protected plant Cymbidium tortisepalum, provide reference for the classification and conservation biology research of C. tortisepalum, and select the suitable method for the determination of seed viability.

Method The seed morphology was observed by optical microscopy and scanning electron microscopy using 170 d capsules of a naturally distributed C. tortisepalum. The seed pretreatment and staining were observed by NaClO and TTC solution.

Result C. tortisepalum capsules were ovoid. The length and width were 5.5-7.0 cm and 1.5-2.0 cm. The crust was yellowish green with 3 longitudinal edges. The seeds were small, abundant, milky white which shape were long and narrow spindle-shaped. The length and width was (1.245±0.180) mm, (0.139±0.039) mm. The volume was (0.007±0.003) mm³ and a thousand seed weight was 0.4 mg. The coat thickness of seed was (0.011±0.003) mm, and the surface was reticulated. The embryos were microscopically embryonic with a germ handle and yellow green. The length and width were (0.168±0.030) mm, (0.090±0.025) mm. The volume was 0.001 mm³, accounting for 14.29% of the seed volume. The seed chamber volume was 85.71%. The sequence of influencing factors for the determination of viability from large to small was NaClO mass fraction, TTC mass fraction and processing time. Treated with 2.5% NaClO solution for 20 min and stained with 1% TTC solution, the seed viability was highest, up to 100%.

Conclusion The cavity volume of C. tortisepalum seed is 85.71%, which is suitable for long-distance transmission. The seeds were treated with NaClO and TTC solution staining, which can effectively measure the viability of the seeds.