摘要 : The dispersal unit of C. mopane consists of a seed borne within an indehiscent fruit. Both the seed and fruit are short-lived. Under natural environmental conditions the seeds seldom remain viable for more than a year and pericarp... 展开 The dispersal unit of C. mopane consists of a seed borne within an indehiscent fruit. Both the seed and fruit are short-lived. Under natural environmental conditions the seeds seldom remain viable for more than a year and pericarps of fruits are usually completely degraded after one year. The transitory nature of the testa is reflected in its anatomical structure as it is thin-walled and unlignified at maturity. Seed structure does not conform to that of the typical legume. The thin testa is highlypermeable to water and lacks the characteristic malpighian cells and other sclerenchymatous elements. Although water does not penetrate the pericarp of newly-matured fruits, the pericarp soon becomes permeable under natural environmental conditions. Dyeexperiments using the apoplastic tracer acid fuchsin, revealed that once the fruit becomes permeable, it initially allows water to enter mostly through the ventral and dorsal sutures. With increased scarification of the pericarp, water is able to penetrate over its entire surface. An aril that originates partly from the funicle and partly from the outer integument circumvents the seed. The cells of the aril contain gum-like or mucilaginous substances that swell considerably when they are in contact with water. The aril is situated along the circumference of the seed, in close proximity to the carpel sutures and may aid fruit opening by increasing tension on the fruit valves. The aril is abundantly supplied with vascular bundles as well as with an aircanal that forms a highly efficient water transporting system during imbibition. If seeds are removed from fruits prior to imbibition, the aril swells to such an extent that its cells, including the vascular tissue, become disrupted. Imbibitional damagewas constantly observed in seedlings that originated from seeds that were removed from fruits prior to imbibition. Seedlings originating from seeds left enclosed in fruits did not show similar damage. In enclosed seeds the aril cells and vascular connections remained intact during imbibition. As the seeds of C. mopane are highly water permeable and lack a functional lens to control the rate of water entry, it is proposed that the pericarp governs the passage of water to the seed. 收起