title: Novel seed adaptations of a monocotyledon seagrass in the wavy sea.
abstract: Returning to the sea, just like invasion of land, has occurred in many groups of animals and plants. For flowering plants, traits adapted to the terrestrial environments have to change or adopt a new function to allow the plants to survive and prosper in the sea where water motion tends to rotate and move seeds. In this investigation, how seeds of the seagrass Thalassia hemprichii (Hydrocharitaceae), a common monocotyledon in the Indo-Pacific, adapt to the wavy environment was studied. Mature seeds were collected from Dongsha Atoll in South China Sea. The effects of light qualities on seed germination, the seed morphology, the unipolar distribution of starch granules in the endosperms and growth of root hair-like filamentous cells from basal surface of the seeds were all found to differ from those of terrestrial monocotyledons. Physiologically, germination of the seeds was stimulated by blue light rather than red light. Morphologically, the bell-shaped seeds coupled with the unipolar distribution of starch granules in the enlarged bases helped maintain their upright posture on the tidal seafloor. Growth of root hair-like filamentous cells from the basal surface of the seeds prior to primary root growth served to attach onto sediments, providing leverage and attachment required by the primary roots to insert into sediments. These filamentous cells grasped coral sand but not silicate sand, demonstrating a habitat preference of this species.
authors.affiliation: Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung, Taiwan ; Asia-Pacific Ocean Research Center, National Sun Yat-sen University, Kaohsiung, Taiwan.
authors.forename: Keryea
authors.initials: K
authors.lastname: Soong
authors.forename: Shau-Ting
authors.initials: ST
authors.lastname: Chiu
authors.forename: Ching-Nen Nathan
authors.initials: CN
authors.lastname: Chen
mesh_terms: D000222:Adaptation, Physiological; D005638:Fruit; D018525:Germination / Q000528:radiation effects; D031321:Hydrocharitaceae / Q000502:physiology* / Q000528:radiation effects; D008027:Light; D010641:Phenotype; D012623:Seawater; D036226:Seedlings / Q000528:radiation effects; D012639:Seeds / Q000502:physiology* / Q000528:radiation effects; D014872:Water Movements
references.citation: Proc Natl Acad Sci U S A. 2009 Jul 28;106(30):12377-81
references.pmid: 19587236
references.citation: Photochem Photobiol. 2011 May-Jun;87(3):491-510
references.pmid: 21352235
references.citation: J Exp Bot. 2011 Mar;62(5):1669-75
references.pmid: 21109580
references.citation: Am J Bot. 2013 Jan;100(1):91-100
references.pmid: 23115136
references.citation: J Exp Bot. 2010;61(1):11-24
references.pmid: 19815685
references.citation: J Biosci. 2013 Mar;38(1):157-66
references.pmid: 23385823
references.citation: BMC Evol Biol. 2011 Jan 12;11:8
references.pmid: 21226908
references.citation: PLoS One. 2012;7(1):e29987
references.pmid: 22253849