Biological Foundations 112, Lecture 29


Chapter 27, pages 558
Five Kingdoms-5 3:53-7:51

I.   Characteristics

     A.   True roots

     B.   True stems

     C.   Microphylls in whorls at nodes

     D.   Stems ribbed and furrowed

     E.   Sporangia borne in strobili

II   Equisetum

     A.   One genus and about 25 genera in this Division

     B.   Habitat

            1.   Mostly cool and moist places

            2.   Equisetum arvense - only species of arid habitats

     C.   Distribution

            1.   All over the world

            2.   Not in Australia or New Zealand

     D.   Sporophyte structure

            1.   Herbaceous to shrubby

            2.   Rhizome

                  a.   Grows horizontal just under the soil surface

                  b.   Branched

                  c.   Perennial

            3.   Roots - adventitious at stem and rhizome nodes

            4.   Stems

                  a.   Up to five feet tall (one vine-like species that grows 36 feet long)

                  b.   No secondary growth

                  c.   Stems are annual and die down each year in the fall

                  d.   Nodes and internodes present

                  e.   Stems ribbed and furrowed with the ribbing and furrowing alternating at the  

                  f.    Two stem forms:

                        (1)   Sterile stems

                                (a)  Contain chlorophyll and therefore are green

                                (b)  Do not produce any spores

                                (c)  Come up from the rhizomes after the fertile stems come up in the  

                                (d)  Branching only occurs on sterile stems

                                       i)   Branching only occurs at the nodes

                                       ii)  Branching occurs below the microphylls

                        (2)   Fertile Stems

                                (a)  Contain no chlorophyll and therefore are light tan in color

                                (b)  Usually the first stems to come up in the spring

                                (c)  The strobilus is at the tip of the stem

                  g.   Meristem at the nodes

                        (1)  Causes the stem to grow in the length

                        (2)  Causes the stem to be structurally weak at the nodes (called joint grass)

                  h.   Cross section of stem

                        (1)  Epidermis

                               (a)  Has silica embedded in the epidermis

                               (b)  Called scouring rushes

                                      i)   Named scouring rushes by the pioneers as they came west

                                      ii)  The "rush" name came because the stems were round

                                      iii)  The "scouring" name came because they used them to scour their    
                                            dirty dishes

                                      iv)  The silica in the epidermis made them abrasive for scouring

                        (2)  Cortex

                               (a)  Parenchyma tissue

                               (b)  Ring of vallecular canals are embedded in the cortex opposite each    

                        (3)  Vascular bundles

                               (a)  A ring of vascular bundles are embedded in the cortex opposite the ribs

                               (b)  Each vascular bundle contains a carinal canal

                               (c)  Endodermis is associated with each bundle

                  i.    Reproductive structures

                        (1)  Sporangiophores

                               (a)  A special kind of sporophyll

                               (b)  Best described as an "umbrella" with sporangia attached at the ends of  
                                      the umbrella ribs

                               (c)  The spores are produced inside the sporangia

                        (2)  Strobili - group of sproangiophores at right angles to main vertical axis

                        (3)  Spores

                               (a)  Four spores form from each spore mother cell

                               (b)  The spores are homosporous

                               (c)  The spores contain a thick double wall

                               (d)  Elaters

                                      i)   Elaters are in the form of hydroscopic ribbons

                                      ii)  These hydroscopic ribbons circle the spore

                                      iii)  They aid in spore dispersal

                               (e)  The spores are fragile and are viable for only a few days

                  j.    Gametophyte

                        (1)  Germinates from the spores

                        (2)  About the size of a pin head

                        (3)  Many erect delicate lobes one cell layer thick

                        (4)  Produces antheridia and archegonia

                        (5)  Sperm are multiciliated and spiral in shape

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