Embryo development in association with asymbiotic seed germination in vitro of Paphiopedilum armeniacum S. C. Chen et F. Y. Liu.

Yan-Yan Zhang,Wei-Chang Huang,Jun Duan,Ru-Fang Deng,Song-Jun Zeng,Kun-Lin Wu,Jaime A Teixeira Da Silva,Jian-Xia Zhang

doi:10.1038/srep16356

Abstract

This paper documents the key anatomical features during the development of P. armeniacum zygotic embryos and their ability to germinate asymbiotically in vitro. This study also examines the effect of media and seed pretreatments on seed germination and subsequent seedling growth. Seeds collected from pods 45 days after pollination (DAP) did not germinate while 95 DAP seeds displayed the highest seed germination percentage (96.2%). Most seedlings (50%) developed to stage 5 from 110 DAP seeds whose compact testa had not yet fully formed. Suspensor cells were vacuolated, which enabled the functional uptake of nutrients. The optimum basal medium for seed germination and subsequent protocorm development was eighth-strength Murashige and Skoog (1/8MS) for 95 DAP seeds and ¼MS for 110 DAP seeds. Poor germination was displayed by 140 DAP seeds with a compact testa. Pretreatment of dry mature seeds (180 DAP) with 1.0% sodium hypochlorite solution for 90 min or 40 kHz of ultrasound for 8 min improved germination percentage from 0 to 29.2% or to 19.7%, respectively. Plantlets that were at least 5 cm in height were transplanted to a Zhijing stone substrate for orchids, and 85.3% of plantlets survived 180 days after transplanting.

Highlights

The success of tissue culture protocols based on ex vitro-derived Paphiopedilum explants is limited due to the rarity of materials, difficulties caused by bacterial and fungal decontamination and the poor development of explants that survive under in vitro conditions[6,9,10]
At 52 days after pollination (DAP) the zygote divided into two cells (Fig. 2b) and derivatives of the basal cell gave rise to the suspensor, which only consisted of a single cell that was highly vacuolated
Asymbiotic seed germination of fully mature Paphiopedilum orchid seeds is often difficult and immature seeds need to be germinated more readily; even though mature seeds are suitable for storage, seed germination of mature dry seeds following storage has not yet been reported[5,6,12,13,14,19,21]

Summary

Introduction

The success of tissue culture protocols based on ex vitro-derived Paphiopedilum explants is limited due to the rarity of materials, difficulties caused by bacterial and fungal decontamination and the poor development of explants that survive under in vitro conditions[6,9,10]. The highest seed germination percentage was 75.0% in 110 DAP seeds, a value that was significantly higher than all other collection periods, 50% of the protocorms developed to stage 5.

Results

Conclusion