DIVERSITY OF LIFE |
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DESCRIPTION OF THE KINGDOM VIRIDIPLANTAE (CAVALIER-SMITH 1981) |
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EUKARYA>ARCHAEPLASTIDA>VIRIDIPLANTAE |
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Viridiplantae (ve-re-de-PLAN-te) is derived from two Latin roots that mean "green" (virida) and "shoot" (planta). The reference is to these as the green plants. |
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INTRODUCTION TO THE KINGDOM VIRIDIPLANTAE In recent years the kingdom has been called Viridiplantae (Green Plants) perhaps as a means to distance itself from the old concept of plant (a multicellular photosynthetic organism). In this sense, the term "plant" is an ecological term like "alga". Thus, the change to Viridiplantae serves to alleviate the confusion. Also, organisms in this group are generally accepted as being monophyletic and not related to other plant-like multicellular organisms such as the kelps. As with the other taxa of life, the past 25 years has seen quite an upheaval in our systematic understanding of these groups. Prior to Copeland (1956), Whittaker (1957, 1959, 1969, 1977), and Whittaker and Margulis (1978), life was divided into animals and plants. Since we had a pretty good idea of what animals were, the plant kingdom was defined by exclusion. That is, plants were those organisms that were not animals. With the advent of the five kingdom system, plants were defined in essentialist terms (see Margulis and Schwartz 1982, 1988, 1998). That is, plants were those organisms that fit the following description: photosynthetic multicellular organisms that developed from an embryo, a definition that excluded the groups of green algae from the plant kingdom.
A body of evidence from ultrastructural work (summarized by Pickett-Heaps 1975; Mishler and Churchill 1985; Mattox and Stewart 1984; and Graham et al. 1991) showed that the Viridiplantae is divided unequally between the chlorobionts and streptobionts (see Figure 1). We consider these groups, formalized to Chlorobionta and Streptobionta, to be subkingdoms. They differ in fundamental ways which are summarized in Table 1. |
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THE BASAL STREPTOBIONTS (CLADE ST)
THE EMBRYOPHYTES (CLADE EM)
THE VASCULAR PLANTS (CLADE VP)
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SYSTEMATICS OF THE VIRIDIPLANTAE
Molecular phylogeny (e.g. Soltis et al. 1999; and Duff and Nicrent 1999) also confirmed most of the long-standing relationships between the higher taxa of embryophytes (e.g. the systems of Bold et al. 1987 and Margulis and Schwartz 1982, 1988, 1998). Some surprises in the recent molecular phylogenetic work (summarized by Palmer et al. 2004) on the embryophytes included:
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PHYLA OF THE VIRIDIPLANTAE |
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FURTHER READING: | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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By Jack R. Holt. Last revised: 03/26/2013 |