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SYNOPTIC DESCRIPTION OF THE PHYLUM GINKGOOPHYTA

SYNOPTIC DESCRIPTION OF THE PHYLUM GINKGOOPHYTA (BOLD 1956)

EUKARYA> ARCHAEPLASTIDA> VIRIDIPLANTAE> STREPTOBIONTA> EMBRYOPHYTA> TRACHEOPHYTA> SPERMOPHYTA> GINKGOOPHYTA
GINKGOOPHYTA LINKS

Introduction

Hierarchical Classification

The following description of the phylum comes from Bold et al. (1987) and Bierhorst (1971).

I. SYNONYMS: ginkgophytes.

II. NUMBER: 1 extant species.

III. PHYLUM CHARACTERISTICS

  • A. Structure
    • Habit: The ginkgos are conifer-like seed plants with fan-shaped leaves. The single extant species is dioecious (text with tooltip) Dioecious organisms have separate male and female individuals. .
    • Pollen: Pollen walls with 1 suture (text with tooltip) A pollen grain with one groove or furrow. and no saccus (text with tooltip) In the form of a sac. . The microgametophyte has 2 prothallial (text with tooltip) Prothallial cells are remnants of the vegetative microgametophyte in pollen grains. cells, a stalk cell (text with tooltip) One of the products of division of the initial cells in the pollen of some gymnosperms, said to be the homologue of the antheridial stalk. , 2 multiflagellate sperm and a tube cell (text with tooltip) A tube cell develops as part of the microgametophyte within the pollen grain. The tube cell directs the growth and development of the pollen tube, which carries the sperm to the egg in an ovule. .
    • Microstrobilus: Simple strobilus, open and pendant (text with tooltip) Hanging down. on spur shoots (text with tooltip) A slow growing, highly reduced shoot. .
    • Seeds: Ovules with 3 integument (text with tooltip) The outer covering of an ovule, which becomes the testa of the seed. tissue layers around a massive nucellus (text with tooltip) Central part of a plant ovule; contains the embryo sac. . Archaegonia (each with 2 neck canal cells (text with tooltip) The central row of cells in the neck of an archegonium; the ventral canal cell is the most proximal, i.e adjacent to the ovum. These cells dissolve allowing sperm to reach the ovum. ) develop at the micropylar (text with tooltip) An opening in the integuments of an ovule that exposes part of the megasporangial wall (a chamber called a pollen chamber in gymnosperms). Thus, in gymnosperms, pollen enters the micropyle and germinates in the pollen chamber. However, because the micropyle is not exposed in flowering plants, their pollen germinates on the stigma. The pollen tube grows through the style, and enters the ovule through the micropyle. end of the megagametophyte. The embryo is dicotyledonous (text with tooltip) Having two cotyledons in the same seed. .
    • Megastrobilus: Simple, with 2 ovules (text with tooltip) An ovule is a structure that contains the megagametophyte in seed plants. The megagametophyte remains within the megasporangium (the nucellus), which is surrounded by layers of integuments. After fertilization, the ovule develops into a seed. on a long peduncle. This can be interpreted as an open compound strobilus if the whole spur shoot is viewed as a megastrobilus.
    • Stems: Monopodial (text with tooltip) Monopodial growth is characterized by extreme overtopping which produces a large central stem with smaller lateral branches. growth with extensive wood. Leafy shoots of 2 types: long shoots and spur shoots. Reproductive structures occur only on the spur shoots. Stems with many mucilage canals (text with tooltip) Ducts or channels in the axes of cycads and ginkgophytes that contain mucilage, a water-soluble substance which solidifies upon exposure to the air and likely serves to protect against invasion of the tissue by fungi and bacteria. .
    • Leaves: Fan-like with dichotomous branching of the veins. Leaves on the long shoots are notched while those on the spur shoots are not notched.
    • Roots: Like many of the conifers.
    • Life History of:
  • B. Ecology: The extant species occurs naturally in China but is widely planted throughout the temperate regions. These plants have a fossil history which dates from the late Paleozoic to the present. They were very abundant during the Mesozoic.
LITERATURE CITED

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Bierhorst, D. W. 1971. Morphology of Vascular Plants. In: N. H. Giles and J. G. Torrey. The MacMillan Biology Series. The MacMillan Co. New York.

Bold, H. C., C. J. Alexopoulos, and T. Delevoryas. 1987. Morphology of Plants and Fungi. 5th Edition. HarperCollins Publishers, Inc. New York.

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Zhu, W.-Q. and P. Kenrick. 1999. A Zosterophyllum-like plant from the lower Devonian of Yunnan Province, China. Review of Palaeobotany and Palynology. 105: 111-118.
By Jack R. Holt. Last revised: 03/27/2013
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