Biological Foundations 112, Lecture 31

Gymnosperms I

Chapter 27, pages 560-563
Basic Botany-4   0:00-10:11
Basic Botany-4 19:18-23:48
Five Kingdoms-5 12:24-16:33

I.   Introduction to Gymnosperms

     A.   Meaning of gymnosperm

            1.   Naked seed

            2.   Ovules (megasporangia) are borne in an exposed position on the sporophylls (cone  

            3.   Angiosperm ovules (megasporangia) develop within a closed ovary

     B.   Leaf forms

            1.   Palm-like - cycads

            2.   Needle-like - pines and firs

            3.   Scale-like - cypress and cedars

            4.   Broadleaved - ginkgo

            5.   Deciduous - larch and ginkgo

            6.   Evergreen - pines and cedars

     C.   Plant form - trees and shrubs

     D.   Vascular tissue

            1.   Like angiosperms

            2.   No vessels except in a few species

            3.   Sieve cells (contain no companion cells) in the phloem instead of sieve tubes

     E.   Pith

           1.   Occurs in stems

           2.   Does not occur in roots

II.  Division Cycadophyta

      A.   Commonly known as cycads

      B.   Extinct and extant (living) forms

             1.   Extinct - buried in Mesozoic rocks

             2.   Extant

                   a.   9 genera

                   b.   100 species

                   c.   Generally native to the tropics

                   d.   Examples

                         (1)  Zamia - native of U.S. (southern Florida)

                         (2)  Cycas revoluta

                                (a)  Commonly called sago palm

                                (b)  Native of East Asia

                         (3)  Dioon spinulosum

                   e.   General characteristics

                         (1)  Palm-like in appearance

                         (2)  Trunk subterranean in Zamia

                         (3)  Straight above ground trunk in Cycas

                         (4)  Very slow growing - 6 foot specimen may be 1000 years old

      C.   What makes cycads gymnosperms?

             1.   They produce cones (strobili) with seed born on the cone scales

             2.   Pollen cones (microsporangiate strobili)

             3.   Seed cones (megasporangiate strobili)

III. Division Ginkgophyta

      A.   Commonly called the maiden-hair tree because its leaves are shaped like maiden-hair    
             fern leaves

      B.   Broadleaf deciduous tree

      C.   Only extant species is Ginkgo biloba

      D.   Geographic distribution

             1.   Wild in the forests of remote western China

             2.   Cultivated and grown around Chinese and Japanese temples

      E.    Fan-shaped leaves with two lobes that look like the leaves of maiden-hair fern

      F.    Trees dioecious

             1.   Male trees nice to have around.  They only produce pollen.

             2.   Female trees produce a fruit that, when ripe, smells like rancid butter or body odor

IV. Division Gnetophyta

      A.   Very diverse group of plants

      B.   Characteristics

             1.   Since this is such a diverse group, the characters given are for the genus Ephedra    
                   and not the Division Gnetophyta

             2.   Jointed stems

             3.   Leaves are small and scale-like in widely separated whorls

             4.   Photosynthesis occurs in the stems

             5.   Cones are small and with thin scales

      B.   Ephedra

             1.   Called Mormon tea in California because the Mormons used it to make tea when    
                   they came west

             2.   Desert -dwelling species

             3.   Looks like a dead shrub of straw-colored sticks when view from a distance

V.  Division Coniferophyta

      A.   Largest division of extant gymnosperms

      B.   Characteristics

             1.   Fruits are dry woody cones generally with several to many scales

             2.   Stems are not jointed as in Gnetophyta

             3.   Leaves are either needle-like or overlapping and scale-like

VI. Families of Coniferophyta

      A.   Family Pinaceae

             1.   Characteristics

                   a.   Leaves needle-like

                   b.   Cones with overlapping scales, each bearing 2 seeds

             2.   Genera

                   a.   Pinus - pines

                         (1)  Cones reflexed or pendulous

                         (2)  Leaves fascicled in bundles of 1-5 needles/bundle

                   b.   Abies - firs

                         (1)  Cones erect with cone scales falling separately at maturity

                         (2)  Needles not in bundles, rather they grow separately on the stem

                   c.   Pseudotsuga - douglas fir

                         (1)  Cones reflexed or pendulous

                         (2)  Needles separate and solitary

                         (3)  Very visible bracts occur between the cone scales that look like mouse tails

                         (4)  Branchlets smooth

                   d.   Tsuga - hemlocks

                         (1)  Cones reflexed or pendulous

                         (2)  Needles separate and solitary

                         (3)  Branchlets roughened by persistent leaf bases

                         (4)  Leaves with short petioles

                   e.   Picea - spruces

                         (1)  Cones reflexed or pendulous

                         (2)  Needles separate and solitary

                         (3)  Branchlets roughened by persistent leaf bases

                         (4)  Leaves sessile, without short petioles

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