Double Fertilization in Gnetales: Implications for Understanding Reproductive Diversification among Seed Plants

  title={Double Fertilization in Gnetales: Implications for Understanding Reproductive Diversification among Seed Plants},
  author={William E. Friedman and Jeffrey S. Carmichael},
  journal={International Journal of Plant Sciences},
  pages={S77 - S94}
The coupled processes of double fertilization and postfertilization endosperm formation have long been viewed as important and synapomorphic features of flowering plants. Recent developmental studies of fertilization in the nonflowering seed plants Ephedra and Gnetum clearly document a regular process of double fertilization. The condition for Welwitschia remains unknown. Unlike angiosperms, the product of the second fertilization event in Ephedra and Gnetum is diploid and expresses the… 

The evolution of double fertilization and endosperm: an ”historical” perspective

Developmental analyses of Ephedra and Gnetum indicate that these nonflowering seed plants undergo a regular process of double fertilization that yields two diploid zygotes, demonstrating congruence with the hypothesis thatdouble fertilization processes in Gnetales and angiosperms were inherited from a common ancestor of the two lineages.

Double Fertilization in Flowering Plants: Origin, Mechanisms and New Information from in vitro Fertilization

The interest in fertilization, the central step of sexual reproduction, has therefore been renewed over the last ten years and the underlying mechanisms are not well known.


A complex array of heterochronic and nonheterochronic developmental innovations have played critical roles in the ontogenetic evolution of the highly apomorphic female gametophyte of Gnetum.

Development and evolution of the female gametophyte and fertilization process in Welwitschia mirabilis (Welwitschiaceae).

An analysis of character evolution indicates that the female gametophyte of Welwitschia is highly apomorphic both among seed plants, and specifically within Gnetales, but also shares several key synapomorphies with its sister taxon Gnetum.


It is demonstrated how the new phylogenetic hypotheses for seed plants and angiosperms can significantly alter previous interpretations of evolutionary homology and firmly entrenched assumptions about what is synapomorphic of flowering plants.

Endosperm of Angiosperms and Genomic Imprinting

A brief overview of a wide diversity of embryo sacs and endosperm types and ploidy levels, as well as their distribution in the angiosperm families, positioned according to the Angiosperm Phylogeny Group IV (APG IV) phylogenetic classification is provided.

Gnetum and Nymphaeaceans as Models for a Scenario of the Origin of Morphotype of Flowering Plants

A morphological analysis of the available data shows that the true angiosperm ancestor must have differed from Gnetum in some important respects, e.g., it must have had a more primitive xylem and bisexual fructifications.

Plant sexual reproduction: aspects of interaction, history and regulation

Sexual reproduction in angiosperms is an interactive process involving the sporophyte, gametophytes, embryo and endosperm as well as the environment, aimed at achieving pollination, fertilization and

Polyspermy barriers in plants: from preventing to promoting fertilization

Evidence is presented suggesting that a polyspermy block on the egg may be part of the mechanism that promotes faithful double fertilization in plants.

Epigenetic regulation of repetitive DNA through mitotic asynchrony following double fertilization in angiosperms

It is conceivable that double fertilization can drive angiosperm evolution by facilitating crosses between genetically diverse parents and challenges previous notions that the primary purpose of endosperm is for improved seed reserve storage and utilization.



Organismal duplication, inclusive fitness theory, and altruism: understanding the evolution of endosperm and the angiosperm reproductive syndrome.

  • W. Friedman
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1995
Endosperm is shown to be derived from one of two embryos formed during a rudimentary process of "double fertilization" that evolved in the ancestors of angiosperms, and inclusive fitness analysis demonstrates that the embryo-nourishing properties of endosperm initially evolved in a diploid condition.

Double Fertilization in Gnetum gnemon: The Relationship between the Cell Cycle and Sexual Reproduction.

The results show definitively a pattern of G2 karyogamy in G. gnemon, a nonflowering seed plant and member of the Gnetales that expresses a rudimentary pattern of double fertilization that results in the formation of two zygotes per pollen tube.

Double Fertilization in Ephedra, a Nonflowering Seed Plant: Its Bearing on the Origin of Angiosperms

Double fertilization and the associated formation of endosperm have long been considered unique and defining characters of the angiosperms and may represent an evolutionary homology.

Parent-Specific Gene Expression and the Triploid Endosperm

The polyploid-vigor explanation does not explain why genome doubling should occur in the female gametophyte before fertilization, particularly given that endosperm cells often increase their ploidy by other means after fertilization.


A new interpretation of the significance of some major features of vascular plant reproductive biology is put forward, which is that the integuments and endosperm allow the mother to retain control of how her investment is allocated, while deferring the investment until offspring with genotypes different from her own have been created.

Genetic analysis of conflicts arising during development of seeds in the Angiospermophyta

  • R. LawC. Cannings
  • Biology
    Proceedings of the Royal Society of London. Series B. Biological Sciences
  • 1984
A population-genetic model is developed to give first, second and third order conditions for initial increase of a mutant that affects interactions among relatives in a diploid, diallelic, random-mating population, and an attempt is made to interpret some features of the genetic system of endosperm.

Seed Plant Phylogeny and the Relationships of Gnetales

  • J. Doyle
  • Biology
    International Journal of Plant Sciences
  • 1996
Results imply that glossophytes originally had glossopterid-like leaves and bract-sporophyll complexes, which were transformed into carpels with bitegmic ovules in angiosperms, but reduced to single, terminal Ovules in Gnetales; flowers arose independently in the two lines.

Origin of the Angiosperm Flower

No topic in plant evolution has been more controversial or generated a larger literature than the origin of the angiosperm flower and its components, and the leading contender at the present time would be the Magnolialean hypothesis.