Order ISOETALES - the Quillworts

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Order ISOETALES - the Quillworts
Called Quillworts because of narrow, quill-like
leaves Exclusively aquatic (fresh water,
world-wide) Most of the leaves are potentially
sporophylls, which are not aggregated into a
strobilus The stem is a short, vertical corm
The corms displays a peculiar form of secondary
thickening, in which the cambium produces a
mixture of xylem and phloem (the prismatic
layer) to its interior Quillworts display CAM
(Crassulacean Acid Metabolism) photosynthesis,
normally a characteristic of xerophytes
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Isoëtes looks nothing like Selaginella or
Lycopodium, so why it it placed in the same
Division?
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Similarities between Isoëtes and Selaginella
-Microsporophyll
Megaspore
They both possess ligules They are both
heterosporous
Selaginella, l.s. strobilus
-Megasporopyll
Ligule
Megasporophyll
Microsporophyll
Ligule
Isoëtes sporophylls, adaxial view
Selaginella sporophylls, adaxial view
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Some External Features of Isoëtes
Air chambers---
--Expanded bases of sporophylls
--Roots
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Various Sections of Isoëtes Corm
Basal meristem
Secondary cortex
Root trace
Root primordium
Cambium
Cross section of upper corm
Cross section of lower corm
Prismatic layer
Leaf trace
Cambium
2ary cortex
Longitudinal section through lobes
Leaf bases
Shoot apex
Leaf traces
Cambium
Upper c
Xylem core
Prismatic layer
Longitudinal section through grooves
Lower c
--Root
Xylem core
Basal meristem
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Isoëtes - Sporophyll Sporangium Structure
Air chamber
Ligule
Vascular b
Megaspore
Velum
Spum wall
Trabecula
l.s. of corm sporophylls
l.s. of megasporophyll
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Isoëtes - Cross Section of Microsprangium
M
(VEIN or VASCULAR BUNDLE)
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Isoëtes - Male Gametophyte (Germinated
Microspore)
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Isoëtes - Longitudinal Section of Female
Gametophyte and Embryo
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Root Structure of Isoëtes - a Link with the Tree
Lycopods of the Carboniferous Coal Swamps??
Cross-section of Isoëtes root
Cross-section of stigmarian appendage of
form-genus Stigmaria
Lepidodendron reconstruction, showing stigmarian
rootlets
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Division EQUISETOPHYTA - the Horsetails
Have true leaves, but these are reduced tom
scale, the stem being the main photosynthetic
organ Stems break easily at the nodes, where
structure of stem and stele are different from
that of internodes (eustele become
siphonostele) Lateral branches, when present,
sprout from BETWEEN the leaves, not from their
axils The epidermis has siliceous nodules in
some species, giving rise to the name scouring
rush Plants are homosporous, the sporangia
occurring in terminal strobili on umbrella-like
sporangiophores
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Some Unbranched Horsetails Found in Northern
Ontario
Equisetum variegatum - Variegated Scouring Rush
Equisetum hyemale - Scouring Rush
E. scirpoidea - Dwarf Scouring Rush
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Distinct Fertile Sterile Stems - Equisetum
arvense - the Field Horsetail
--Fertile stem
--Young sterile stems
Branching sterile stem------------
Fertile stems with senescent strobili, sterile
stems in background
Non-green fertile stems in early spring
Spring
Summer
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Equisetum Species in Which Fertile Stems Later
Produce Green Branches
n.b Wagon Wheels (short first internode)
n.b. curved young branches
Branched branches
Fused scales
E. pratense - Meadow Horsetail
Equisetum sylvaticum - Wood Horsetail
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Equisetum - Variation in Canal Size
Distribution in Stems
Small central canal, large vallecular canals in
E. fluviatile (River Horsetail)
Large central canal, small vallecular canals in
E. palustre (Marsh Horesetail)
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Equisetum Stem - Canals Vascular Bundles
--Vallecular canal
-Central canal-
Carinal canal--
Stem in cross-section
Single vascular bundle in c.s.
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Cross Section of a Typical Equisetum Vascular
Bundle
Note the following unique features Metaxylem
is sparse Protoxylem is adjacent to the carinal
canal
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Equisetum - Variations in Endodermis
Configuration Position
Rhizome of E. sylvaticum
Aerial stem of E. sylvaticum
Rhizome of E. hyemale
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Equisetum - Venation at the Node
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Equisetum - Structure of Strobilus
Sporangiphores
Sporangiophore sporangia
Cross section
Longitudinal section
Strobilus
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Spores of Equisetum Hygroscopic Movement of
Elaters
Moist
Dry
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The Gametophyte of Equisetum
Note the presence of vertical photosynthetic
lobes
Whole mount of gametophyte
Gametophyte with young sporophytes
Cross section of gametophyte