Poster: Seed biology
Abs #
711: Testa and endosperm rupture in germinating Arabidopsis seeds
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Presenter: |
Hewitt, Jessica R, hewittje@onid.orst.edu |
Authors | Hewitt, Jessica R (A) Liu, Po-Pu (B) Nonogaki, Hiroyuki (B) | | Affiliations: |
(A): Department of Biochemistry/ Biophysics, Oregon State University
(B): Department of Horticulture, Oregon State University
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| Web Site: | http://www.science.oregonstate.edu/isb/ | |
Seed germination is completed by radicle protrusion which is determined by two conflicting forces, the growth potential of the embryo and the mechanical resistance of the surrounding tissues such as testa and the endosperm. It is essential for the balance of these two forces to be altered for the radicle to penetrate the covering tissues. It is known that enzymatic degradation of the endosperm is necessary for radicle protrusion to occur in tomato seed. In Arabidopsis seed, the property of testa is known to affect germination performance, yet, it is unclear whether the endosperm plays a similar role to that observed in tomato seed. Morphological changes in testa, the endosperm and the embryo of imbibed Arabidopsis seeds were characterized using a dissection and a scanning electron microscope. The embryo and the endosperm tissues are white and hardly distinguishable from each other under a dissection microscope. By aid of a scanning electron microscope, the endosperm and the embryo were distinguished because the two tissues have distinct surface cell structure. The first visible evidence of germination in Arabidopsis seed was testa rupture (termed as “cracking”) which exposed the surface of the endosperm outside. While cracking occurred above the embryonic axis as early as 18 h after incubation at 22οC, radicle emergence did not immediately follow: there was a 12 h delay in initiating radicle protrusion through the endosperm, during which slight elongation of the endosperm tissue out of cracked testa was observed. The lag phase between testa and endosperm rupture possibly reflects the restriction of embryo growth by the endosperm layer and suggests that the endosperm potentially needs to be weakened before radicle emergence.
