Abstract
The freezing behavior of xylem ray parenchyma cells in several boreal hardwood species, namely,Betula platyphylla, Populus canadensis, P. sieboldii,andSalix sachalinensis,was examined by differential thermal analysis (DTA), cryo-scanning electron microscopy (Cryo-SEM), and freeze-fracture replica electron microscopy. Although DTA profiles of samples harvested in summer and in winter suggested that the xylem ray parenchyma cells in all four species responded to freezing stress by extracellular freezing, Cryo-SEM showed clearly that the xylem ray parenchyma cells in all these species responded to freezing stress by shallow supercooling in summer and by extracellular freezing in winter. It is suggested that DTA failed to reveal the true freezing behavior of xylem ray parenchyma cells because of an overlap of temperature ranges between the high-temperature exotherm and the low-temperature exotherm and/or because of the limited extent of the LTE. The seasonal changes in freezing behavior of xylem ray parenchyma cells in all these boreal species, which are results of seasonal cold acclimation, support the hypothesis that a gradual shift of freezing behavior in xylem ray parenchyma cells from shallow supercooling in hardwood species that grow in tropical zones to extracellular freezing in hardwood species that grow in cold areas might be a result of the evolutionary adaptation of hardwood species to cold climates.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.