Complexities in identifying seed storage behavior of hard seed-coated species: a special focus on Lauraceae

ABSTRACT

Seeds are broadly grouped into orthodox (desiccation-tolerant), intermediate and recalcitrant (desiccation-sensitive) based on their ability to withstand drying. Whilst the protocols developed to classify seeds into one of the three groups have aided ex-situ storage of germplasm, the classification of many species with seeds having a hard coat appears to be perplexing. Using Lauraceae as a model family, we address the possible reasons for this confusion. We collected data available in the literature on Lauraceae and found 30 species studied that were respectively assigned to orthodox (3 species), intermediate (4 species) or recalcitrant (23 species) groups. In addition, another 16 species (2 orthodox and 14 recalcitrant) were doubtfully classified and 6 species were labeled as uncertain. We speculate a hard seed coat found in many of Lauraceae species present substantial challenge in seed desiccation studies and identified five key problems including (1) inferring storage behavior without conducting desiccation-sensitivity assessment to evaluate the germination ability of seeds by drying to low moisture contents; (2) seed storage behavior was determined by germinating the seeds after partial drying and storing at various temperatures, e.g. 0 or −18°C; (3) seeds that failed to germinate at narrow range of temperatures and light conditions were concluded as dead, without considering the possibility that they might be dormant; (4) culminating germination studies quickly, sometimes within few days; and (5) not testing the drying ability of seeds without seed coat. We highlight that addressing these issues would lead to accurate categorization of seed storage behavior that can ensure better seed storage practices.

KEYWORDS:

• Desiccation
• dormancy
• hard seed coat
• oil content
• recalcitrant seeds

Author contribution

GKJ – conceived, written the ms; LJ – prepared figures; YY and YH – helped in revision; BL – provided supervisory support, consumables and discussion. All authors read and accepted the final version of the ms.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Financial support by National Science Foundation China (NSFC) (grant number 31750110474) for ongoing studies of dormancy and germination in hard coated species is gratefully acknowledged

Notes on contributors

Ganesh K. Jaganathan

Dr. Ganesh K. Jaganathan has recently completed his post-doctoral position and he is interested in the evolution and adaptation of maturation drying and dormancy in seeds. His work also focuses on optimizing seed storage practices and freezing patterns in seeds.

Jiajin Li

Ms. Jiajin Li is a master student working on cryopreservation of seeds with hard seed coats. Her work focuses on Lauraceae and Meliaceae in particular.

Yashu Yang

Ms. Yashu Yang is a master student working on cryopreservation problems associated with seed coats. She is interested in species with an impermeable seed coat and her work focuses mainly on Fabaceae. She is currently studying the relationship between moisture content and storage of physical dormant species.

Yingying Han

Dr. Yingying Han is an associate professor and teaches two courses. She is interested in molecular techniques including PCR, gene expression studies and sequencing of plants. In particular, she has keen interest in seed storage and genes that guide maturation drying in seeds.

Baolin Liu

Prof. Baolin Liu holds the position as dean and he currently teaches two courses. His research interests include cell cryopreservation and food storage. He is also interested in heat and mass transfer.