Endosperm tissue that nourishes the embryo during seed development, upon maturity, nourishes the global population with special reference to cereal crops like maize, wheat and rice. In about 70% of the angiosperms, endosperm genome content is ‘3n’ with 2:1 (maternal:paternal) contribution, as a result of the second fertilization event. However, angiosperms evolution also documents diversity in endosperm genome content from ‘2n’ to ‘15n’, in scale with the corresponding maternal genome dosage variability (‘1n’ to ‘14n’), whereas paternal contribution is invariable. In apomicts, due to lack of fertilization, or pseudogamy (fertilization of the central cell for endosperm formation), endosperm genome dosage (m:p) has been reported to range between 1:1 and 8:3. Exceptionally, the central cell with one unreduced nucleus and fused with a reduced sperm cell, with 2:1 normal genome dosage, has been reported inPanicum. Altered genome dosage levels are reportedly correlative with eccentricities among maternal and paternal contribution to seed resource allocation. Besides endosperm ploidy variability between species of angiosperms, the present review gives an overview of the ploidy variability in endosperm cells within a seed, up to ‘690n’. In addition to genome-scale variability in the endosperm, some taxa of angiosperms exhibit chlorophyllous endosperms and some chlorophyllous embryos. Also, endosperm cell number during seed development is reported to have a strong association with grain weight at maturity. Genes underlying these traits of variability are unknown, and the present review underscores the variability and highlights the potential of the single-cell sequencing techniques towards understanding the genetic mechanisms associated with these variable traits.

中文翻译：

---

胚乳变异性：从种子内的核内复制到跨物种的更高倍性及其能力

胚乳组织在种子发育过程中滋养胚胎，成熟后滋养全球人口，特别是玉米、小麦和水稻等谷类作物。在大约 70% 的被子植物中，由于第二次受精事件，胚乳基因组含量为“3n”，比例为 2:1（母本：父本）。然而，被子植物进化还记录了从“2n”到“15n”的胚乳基因组含量的多样性，与相应的母体基因组剂量变异性（“1n”到“14n”）成比例，而父本的贡献是不变的。在无融合生殖动物中，由于缺乏受精或假配（中央细胞受精以形成胚乳），据报道胚乳基因组剂量（m:p）在 1:1 和 8:3 之间。特别是，苦参. 据报道，改变的基因组剂量水平与母系和父系对种子资源分配的贡献之间的偏心相关。除了被子植物物种之间的胚乳倍性变异性外，本综述还概述了种子内胚乳细胞的倍性变异性，最高可达“690n”。除了胚乳的基因组规模变异外，一些被子植物分类群还表现出叶绿素胚乳和一些叶绿素胚。此外，据报道，种子发育过程中的胚乳细胞数量与成熟时的粒重密切相关。这些变异性状背后的基因是未知的，