Journal of the Japanese Society of Snow and Ice

Show abstractHide abstract

In order to clarify the physical mechanism of ice segregation phenomenon by Keisukea japonica Miq., Lamiaceae, field observations and laboratory experiments were conducted. While the plant segregates many thin ice sheets radially from the xylem surface sucking soil water through alive roots and stem in the field, it makes the same things sucking water through the only alive or dead stems without roots in the laboratory. As a result, it was verified that the stem structure makes the phenomenon, regardless of the existence of roots and the alive or dead stems. According to the electron microscopic analysis, xylem consists of various porous structures; pits having about 1μm in size distribute on the xylem surface, xylem ray parenchyma and vessel. Calculating the degree of super cooling, it can be explained that small pits play a role as a barrier to interrupt the ice intrusion into the xylem, so that the temperature of water layer facing to growing ice decreases due to super cooling which causes to decrease the pore water pressure −1.4×10⁵Pa as a driving force to move water continuously from the inside of xylem to the surface. Moreover, it seems that the phenomenon occurs in the region less than the linear relationship between cooling degree (the difference between 0℃ and the air temperature surrounding stems) and the growth rate of ice, which depends upon the hydraulic conductivity of xylem, the thermal conductivity of ice, active temperature for nucleation and so on.

View full abstract

Download PDF (5857K)

Register with J-STAGE for free!