Abstract
Majority legumes in the temperate and arctic zones have water-impermeable seeds (physical dormancy, PY). However, various authors have reported that seeds of some Caragana species are water-permeable and thus non-dormant. We (1) tested seeds of 15 species of Caragana matured in the same site in 2014, 2016 and/or 2017 for presence of PY, (2) determined if dry storage decreased or increased the percentage of seeds with PY and (3) located the site on the seed coat of 11 species where water enters the seed. Sixty-three percent and 45% of the seeds of C. roborovskyi had PY in 2016 and 2017, respectively, but only 0–14% of the seeds of the other 14 species had PY. The palisade layer in the seed coat of water impermeable seeds had no cracks in it, whereas cracks were present in the palisade layer of water-permeable seeds. Year of collection and dry storage had significant effects on imbibition of two species (C. acanthophylla and C. roborovskyi). In two (C. acanthophylla and C. roborovskyi) of the 11 species tested, the hilum was the site of water entry into seeds (control seeds, not any dormant broken treatments), but for the other nine species tested water entered through all parts of the seed coat.
Highlights
The about 100 species of Caragana are mainly distributed from the arid areas of northern China to the humid and forested areas of East Asia; approximately 70 species occur in China, and differentiated into different species depending on the habitats (Zhang, 2005; Guan & Ma, 2014; Fang et al, 2017)
Our aims were to (1) determine the percentage of impermeable fresh and dry-stored seeds of Caragana species collected in different years; (2) compare the structure of the seed coat of Caragana species with and without PY; and (3) identify the site(s) of water entry into the seeds
Mature seeds were collected from plants of 15 Caragana species growing in the Desert Botanical Garden in Minqin County (102◦59 E, 38◦34 N; 1,378 m a. s. l.), Gansu Province, China, in June and July in 2014, 2016 and 2017 (Table 1) (Seeds were used in our study were permited to collect by Changlong Li, who is the director of Minqin Deseart Botanical Garden)
Summary
The about 100 species of Caragana are mainly distributed from the arid areas of northern China to the humid and forested areas of East Asia; approximately 70 species occur in China, and differentiated into different species depending on the habitats (Zhang, 2005; Guan & Ma, 2014; Fang et al, 2017). Caragana species are a food resource for wild animals and are preferred for reforestation in regions where desertification and erosion are problems (Su et al, 2005; Fan, Freedman & Gao, 2007). Their flowers are a good source of honey, and their seeds are used as an herbal medicine in China (Zhao et al, 2005). Seeds of the majority of Fabaceae species (legumes) in the temperate and arctic zones are water-impermeable, i.e., physical dormancy (PY) Water permeability/impermeability in seeds of 15 species of Caragana (Fabaceae).
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