Physiological epicotyl dormancy and its alleviation in seeds of Yunnanopilia longistaminea: the first report of physiological epicotyl dormancy in China.

Guan-Song Yang,Shi-Kang Shen,Liu Yang,Yue-Hua Wang

doi:10.7717/peerj.3435

Abstract

Yunnanopilia longistaminea is an endangered monotypic species belonging to Opiliaceae. This edible plant is an important germplasm source with a high economic value in China if propagation were less difficult. Seed dormancy and germination of this species were investigated to improve propagation. Considering seeds have a fully developed embryo and mature and are dispersed in summer, and radicles and epicotyls emerge the following autumn and next spring, respectively, we hypothesized that Y. longistaminea seeds may undergo physiological epicotyl dormancy. Seed moisture content and viability decreased as dehydration occurred. Thus, the seeds may be recalcitrant. The seed germination of this species involves two stages: radicle emergence and epicotyl (shoot) emergence. The optimum temperature was 28 °C and 28 °C/20 °C to radicle emergence. The optimum GA3 solution for the seeds undergoing shoot emergence was 100 mg L−1. The percentages of shoot emergence in seven and 14 days stratification at 5 °C were slightly higher than those in other groups. This study is the first to describe physiological epicotyl dormancy in Y. longistaminea seeds. Under natural conditions, seeds are subjected to Y. longistaminea a autumn → winter → spring temperature. Warm moist conditions and cold stratification can improve radicle emergence and alleviate epicotyl dormancy, respectively. The duration of cold stratification also significantly affects the epicotyl dormancy release of Y. longistaminea. Optimal dormancy breakage methods are warm (28 °C/20 °C) → cold (5 °C) → GA3(100 mg L−1) → warm (28 °C/20 °C).

Highlights

Seed dormancy is a survival mechanism through which the timing of germination and distribution area are adjusted on the basis of different environmental conditions (Copete et al, 2011)
This delay in shoot emergence, could be considered as a type of epicotyl dormancy according to the epicotyl dormancy definitions
This phenomenon is consistent with that of Jayasuriya et al (2010), who reported that seeds of Humboldtia laurifolia have physiological epicotyl dormancy, a subclass of physiological dormancy (Jayasuriya et al, 2012)

Summary

Introduction

Seed dormancy is a survival mechanism through which the timing of germination and distribution area are adjusted on the basis of different environmental conditions (Copete et al, 2011). Yunnanopilia longistaminea (WZ Li) CY Wu et DZ Li, a monotypic species belonging to Opiliaceae, is a vulnerable plant endemic to Red River Valley, Yunnan Province, Southwest China. Y. longistaminea is an important resource plant consumed as a delicious wild woody vegetable. This species is threatened because of excess utilization and habitat destruction. As a key component of germplasm conservation and access to wild plant resource, artificial propagation, including seed germination and seedling establishment, is an essential step in conservation procedure plans (Shen et al, 2015; Khanna et al, 2013). No study has been conducted on the germination characteristics of Y. longistaminea seed

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