Seed Coat Anatomy of Cercis chinensis and its Relationship to Water Uptake

The hard seed coat of Cercis chinensis Bunge is an important cause of its dormancy. A study of the characteristics of water absorption is vital for understanding seed dormancy and germination. This investigation found that soaking in water at an initial temperature of 80 C for 5 min was optimum in breaking the hardness of C. chinensis seeds. Scanning electron microscopy (SEM), dye-tracking and blocking experiments were used to examine the major water entry sites and the relationship between water uptake and seed coat structure during C. chinensis seed imbibition. The SEM images showed that the seed coat consisted of three layers: epidermis, palisade and sclereid. Special light line, vascular bundle and counter-palisade layer structures were found in the side of the hilum. The blocking experiments showed that the hilar region was the important water absorption site because, if the region was not blocked, it showed the highest water absorption when imbibed for 3–12 h. However, all parts of the seed coat can absorb water if enough time is allowed after the seed coat hardness has been broken. The dye-tracking test showed that, after 3 h, water entered the seed only via the hilum fissure. Therefore, the hilum fissure acts as the initial site of water absorption. When more time was allowed, water moved more rapidly on the side having vascular bundles than on the opposite side.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author