Effects of H2SO4, GA3, and cold stratification on the water content, coat composition, and dormancy release of Tilia miqueliana seeds

Yu Wu; Wen Hui Huang; Chen Yin Peng; Yong Bao Shen; Anne M Visscher; Hugh W Pritchard; Qiu Gao; Xiao Rui Sun; Ming Zhu Wang; Zhiyun Deng

doi:10.3389/fpls.2023.1240028

Effects of H₂SO₄, GA₃, and cold stratification on the water content, coat composition, and dormancy release of Tilia miqueliana seeds

Front Plant Sci. 2023 Nov 9:14:1240028. doi: 10.3389/fpls.2023.1240028. eCollection 2023.

Authors

Yu Wu^{1

2}, Wen Hui Huang^{1

2}, Chen Yin Peng^{1

2}, Yong Bao Shen^{1

2}, Anne M Visscher³, Hugh W Pritchard^{3

4}, Qiu Gao⁵, Xiao Rui Sun¹, Ming Zhu Wang¹, Zhiyun Deng^{1

2}

Affiliations

¹ College of Forestry, Nanjing Forestry University, Nanjing, Jiangsu, China.
² Co-innovation Center for Sustainable Forestry in Southern China, Southern Tree Inspection Center National Forestry Administration, Nanjing, Jiangsu, China.
³ Trait Diversity and Function Department, Royal Botanic Gardens, Kew, Wakehurst, Ardingly, West Sussex, United Kingdom.
⁴ Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China.
⁵ Ministry of Agriculture and Rural Affairs of the People's Republic of China, National Animal Husbandry Service, Beijing, China.

Abstract

Introduction: Tilia miqueliana is an endemic species whose population is declining. The permeability barrier and mechanical constraint of the pericarp (seed coat) are important causes of its seed dormancy. Although there has been considerable research on this subject, questions remain regarding how the permeability barrier and mechanical constraint of the seed coat are eliminated during dormancy release and how water enters the seed. Therefore, protecting the species by improving its germination/dormancy breaking in the laboratory is urgent.

Methods: In this study, the changes in the cellular structure, mechanical properties, and components of the Tilia miqueliana seed coat after an H₂SO₄-gibberellic acid (GA₃) treatment were analyzed during dormancy release. Various analyses (e.g., magnetic resonance imaging, scanning electron microscopy, and paraffin section detection) revealed the water gap and water channel.

Results: The H₂SO₄ treatment eliminated the blockage at the micropyle and hilum of the seeds. Water entered the seeds through the water gap (micropyle) rather than through the hilum or seed coat, after which it dispersed along the radicle, hypocotyl, and cotyledon to the endosperm. During the cold stratification period, the cellular structure was damaged and an increasing number of holes appeared on the inner and outer surfaces of the seed coat. Vickers hardness tests showed that GA₃ decreased the seed coat hardness. Additionally, the seed coat lignin and total phenol contents continuously decreased during the cold stratification period. Notably, the Liquid chromatography-mass spectrometry (LC-MS) analysis of the seed coat detected polyethylene glycol (osmoregulator), which may have destabilized the water potential balance inside and outside the seed and increased the water content to levels required for germination, ultimately accelerating seed dormancy release.

Discussion: This sophisticated and multi-level study reveals how H₂SO₄ and GA₃ eliminate the permeability barrier and mechanical constraints of the seed coat during dormancy release of Tilia miqueliana seeds. This will be beneficial to artificially assist the natural regeneration and population expansion of Tilia miqueliana.

Keywords: H2SO4-GA3 treatment; dormancy release; mechanical properties; seed coat components; water gap and channels.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by two projects. Project “Innovation and popularization of forest technology in Jiangsu Province, Long-term scientific research base for the in vitro conservation of ray native tree germplasm resources in Jiangsu Province: LYKJ [2001] 03” provides most of the experiment costs. Project “Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)” and “Jiangsu Provincial Education Department, Jiangsu Postgraduate Training Innovation Project, KYCX20_0873” provide the rest of the experiment costs.