Arnold Arboretum of Harvard University, 1300 Centre Street, Boston, MA 02131, USA.
Am J Bot. 2013 May;100(5):906-15. doi: 10.3732/ajb.1200632. Epub 2013 Apr 25.
Seeds of most families in the ancient angiosperm lineage Austrobaileyales produce a full-fledged genetically biparental embryo-nourishing endosperm. However, seeds of fossil and extant Trimeniaceae have been described as having a perisperm, a maternal nutrient-storing and embryo-nourishing tissue derived from the nucellus of the ovule. Because perisperm is also found in Nymphaeales, another ancient angiosperm clade, the presence of a perisperm in Trimeniaceae, if confirmed, would be congruent with the hypothesis that the first angiosperms used a perisperm in addition to a minute (nutrient-transferring) endosperm. •
Seed development was studied from fertilization through maturity/dormancy in Trimenia moorei and in maturing fruits of T. neocaledonica. •
A persistent layer of nucellar tissue surrounds the endosperm but does not contain stored nutrients and does not function as a perisperm. The nutrient-storing and embryo-nourishing tissue in Trimenia seeds is an endosperm, as is the case in all other members of the Austrobaileyales studied to date. •
The absence of a perisperm and the presence of a typical nutrient-storing and embryo-nourishing endosperm in Trimeniaceae may represent the ancestral condition for angiosperms. However, the combination of a copious nutrient-storing and embryo-nourishing perisperm with a minute endosperm, as in Nymphaeales, remains a plausible plesiomorphic condition for angiosperms as a whole. In either case, the developmental and functional biology of the diploid endosperm of Trimenia (and other Austrobaileyales) differs markedly from the diploid endosperm of Nymphaeales, and is fundamentally similar to the triploid endosperms of most other angiosperms.
大多数 Austrobaileyales 谱系中的远古被子植物的种子会产生完全成熟的、具有双亲遗传特性的胚胎营养(endosperm)。然而，化石和现存的 Trimeniaceae 种子被描述为具有胚乳(perisperm)，胚乳是一种来源于胚珠珠心的母体营养储存和胚胎营养组织。由于胚乳也存在于另一个古老的被子植物分支 Nymphaeales 中，如果 Trimeniaceae 中存在胚乳，那么这与第一个被子植物除了具有微小的（营养传递）胚乳外还使用胚乳的假说相一致。
通过受精、成熟/休眠对 Trimenia moorei 和 T. neocaledonica 的成熟果实中的种子进行发育研究。
一层持久的珠心组织围绕着胚乳，但不含有储存的营养物质，也不作为胚乳发挥作用。Trimenia 种子中的营养储存和胚胎营养组织是胚乳，这与迄今为止研究过的 Austrobaileyales 中的所有其他成员的情况一样。
Trimeniaceae 中没有胚乳，而存在典型的营养储存和胚胎营养胚乳，这可能代表了被子植物的祖先状态。然而，在整个被子植物中，胚乳与大量的营养储存和胚胎营养胚乳相结合，而胚乳较小，如在 Nymphaeales 中，仍然是一个合理的原始状态。在任何一种情况下，Trimenia（和其他 Austrobaileyales）的二倍体胚乳的发育和功能生物学都与 Nymphaeales 的二倍体胚乳明显不同，与大多数其他被子植物的三倍体胚乳在根本上相似。
