Journal
AMERICAN JOURNAL OF BOTANY
Volume 90, Issue 7, Pages 965-972Publisher
BOTANICAL SOC AMER INC
DOI: 10.3732/ajb.90.7.965
Keywords
fiber development; gelatinous fiber; Gnetales; Gnetum gnemon; reaction fiber; stem anatomy
Categories
Ask authors/readers for more resources
In extraxylary tissues of the stem Gnetum gnemon produces gelatinous fibers that can also function as reaction or tension fibers. These gelatinous fibers occur in all axes in the outer cortex and in displaced axes progressively in the middle and inner cortex and finally in the secondary phloem. Early cell differentiation in the cortex produces initials of laticifers that are unique in gymnosperms. Subsequently narrow fibers differentiate from cells that undergo both extensive passive elongation, as a result of internodal elongation, together with their active apical intrusive growth. Outer fibers always complete secondary wall development and become an important mechanical component of stems. Differentiation of fiber initials continues in the middle and inner cortex, but secondary wall formation can only be determined by a gravimorphic stimulus that produces eccentric development of fibers. Further eccentric development of fibers then continues in the outer secondary phloem from dedifferentiated phloem parenchyma cells that initially undergo extensive intrusive growth. All such cells have characteristic features of tension fibers of angiosperms. They exhibit a pronounced purely cellulosic innermost layer of the secondary wall (Sg layer). In addition, fiber initials are coenocytic, including up to eight nuclei that become distributed uniformly throughout the length of the cell. Mature macerated fibers are markedly brittle, making accurate length measurements difficult. Although cytologically uniform, these fibers thus originate from two kinds of initial (primary and secondary). They also differ in their response to a gravimorphic stimulus determined by their times of inception and their eccentric location. These cells show a suite of positional and gravimorphic responses that illustrate the complexity of plant cell differentiation.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available