title: A proposed mechanism for physical dormancy break in seeds of Ipomoea lacunosa (Convolvulaceae).
abstract: OBJECTIVE
  The water-impermeable seeds of Ipomoea lacunosa undergo sensitivity cycling to dormancy breaking treatment, and slits are formed around bulges adjacent to the micropyle during dormancy break, i.e. the water gap opens. The primary aim of this research was to identify the mechanism of slit formation in seeds of this species.
  
  
  METHODS
  Sensitive seeds were incubated at various combinations of relative humidity (RH) and temperature after blocking the hilar area in different places. Increase in seed mass was measured before and after incubation. Scanning electron microscopy (SEM) and staining of insensitive and sensitive seeds were carried out to characterize these states morphologically and anatomically. Water absorption was monitored at 35 and 25 degrees C at 100 % RH.
  
  
  RESULTS
  There was a significant relationship between incubation temperature and RH with percentage seed dormancy break. Sensitive seeds absorbed water vapour, but insensitive seeds did not. Different amounts of water were absorbed by seeds with different blocking treatments. There was a significant relationship between dormancy break and the amount of water absorbed during incubation.
  
  
  CONCLUSIONS
  Water vapour seals openings that allow it to escape from seeds and causes pressure to develop below the bulge, thereby causing slits to form. A model for the mechanism of formation of slits (physical dormancy break) is proposed.
authors.affiliation: Department of Biology, University of Kentucky, Lexington, KY 40546, USA.
authors.forename: K M G Gehan
authors.initials: KM
authors.lastname: Jayasuriya
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Baskin
authors.forename: Robert L
authors.initials: RL
authors.lastname: Geneve
authors.forename: Carol C
authors.initials: CC
authors.lastname: Baskin
mesh_terms: D000042:Absorption; D001692:Biological Transport; D018533:Biomass; D004396:Coloring Agents / Q000378:metabolism; D018525:Germination / Q000502:physiology; D006813:Humidity; D027741:Ipomoea / Q000502:physiology*; D016015:Logistic Models; D008954:Models, Biological; D009995:Osmosis; D012639:Seeds / Q000166:cytology / Q000502:physiology*; D013227:Steam; D013696:Temperature
chemical_list: D004396:Coloring Agents; D013227:Steam