Photo credit: AllPosters
Ridged Stem of Horsetail or Scouring Rush (Equisetum Palustre) Showing Numerous Stomata – by Stanley Flegler
Characteristics unique to Equisetum species among living vascular plants
Read more: 2.fiu.edu
EXCERPT
2. Stomatal structure:
Dayanandan (1977) observed that Equisetum species “possess perhaps the most structurally complex stomata in the entire plant kingdom” (p. 175). The stomata of Equisetum are so unique that “a single well-preserved stomatal apparatus is all that is needed to identify the genus Equisetum (even the two subgenera) from among all other living plants” (Dayanandan, 1977). The uniqueness of Equisetum stomata is the result of two characteristics (Dayanandan, 1977):
1.) The two subsidiary cells overlie the guard cells completely, whereas in other plants the guard cells are the superficial cells.
2.) “The inner tangential wall of each subsidiary cell develops 7 to 24 ridge-like thickenings, a feature not found in any other genus.” (Dayanandan, 1977)
These unique features are nicely shown in illustrations from the plates accompanying Milde (1867) of:
1. a stoma of E. giganteum (subgenus Hippochaete)
2. a stoma of E. bogotense (subgenus Equisetum)
note: The subsidiary cells are illustrated transparently so that the kidney shaped guard cells can be seen beneath.
See also:
• Dayanandan P. and Kaufman P. B. 1973. Stomata in Equisetum. Canadian Journal of Botany 51:1555-1564.
• Dayanandan P. 1977. Stomata in Equisetum: A structural and functional study. Doctoral Dissertation (Botany). University of Michigan.
• Hauke R. L. 1957. The stomatal apparatus of Equisetum . Bulletin of the Torrey Botanical Club 84:178-181.
• Mehra P.N., and Soni S.L. 1983. Stomatal patterns in pteridophytes – an evolutionary approach. Proceedings of the Indian National Science Academy, Part B, Biological Sciences 49(2):155-203,
PLANT STOMATA ENCYCLOPEDIA 