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#gnetophytes

2 public questions tagged with this topic.

Plant Classification

Double fertilization in gnetophytes produces

Fertilization behavior in Gnetales demonstrates parallel to angiosperms: two non-flagellated sperm nuclei delivered via pollen tube, one syngamy with egg forming diploid zygote future embryo, second fuses typically with ventral canal nucleus creating additional diploid nucleus which aborts undergoing degeneration without forming persistent triploid nutritive tissue unlike angiosperms where triploid endosperm proliferates. Initial products therefore two diploid nuclei from double fertilization, contrasting triploid product in flowering plants. This homoplasious double fertilization illustrates

Ref: Campbell Biology, 12th ed., Chapter 30: Double fertilization Gnetophyte diploid products aborting endosperm

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Plant Classification

Gnetophytes are unique among gymnosperms because they possess

Gnetophytes comprising three disparate genera Gnetum tropical lianas, Ephedra desert shrubs, Welwitschia Namib Desert two-leaf plant exhibit several angiosperm-like features uncommon other gymnosperms: presence true xylem vessel elements with open perforation plates simple foraminate allowing efficient conduction, broad net-veined leaves in Gnetum resembling dicots, double fertilization event producing two diploid fertilizations but second product aborting without persistent triploid endosperm, and flower-like compound strobili with perianth-like bracts. Swimming sperm absent non-motile, seeds

Ref: Campbell Biology, 12th ed., Chapter 30: Gnetophytes vessel elements convergent with angiosperms

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