Biology 2500

1
Lecture 15

• Biology 2500
• Chapter 20 Gymnosperms

2
Learning Objectives

• Define
• Pollen grain
• Recall
• The scientific names of Coastal Redwood, General
  Sherman Tree
• Examples of families Pinaceae, Taxodiaceae
• Identify
• Tallest, largest, longest-lived trees!
• Contrast
• Pollenate vs. ovulate cones

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Early Announcement Next Exam

• See website

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Pollen Grain

• The gymnosperms real contribution to plant
  evolution
• A partly-developed male gametophyte
• Carried (by wind or pollinators) to female
  gametophyte (pollination)
• Pollen tube forms
• In most gymnosperms, this carries sperm to
  archegonium
• Gingko trees are more primitive (sperm still swim)

5
Ginkgo Pollination

• Pollination sperms intermediate between
  non-vascular plants typical gymnosperms
• Pollen grows pollen tube, but to absorb nutrients
• Male gametophyte develops
• Pollen grain bursts
• Sperm swim to eggs

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Phylum Coniferophyta

• THE most important of the gymnosperms
• Includes
• Pines (these are familiar to us)
• Less familiar, but also conifers
• Douglas Pines
• Firs
• Larches
• Spruces
• Hemlocks
• Yews (remember Pacific Yew?)
• Redwoods (Family Taxodiaceae)

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Pines

• Genus Pinus
• These are the family Pinaceae
• About 90 species worldwide
• In adult trees, needles occur in bundles called
  fascicles
• Developmentally speaking, just very short
  branches!
• Number varies per species from 1 to 8

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Pine Needles

• Well-suited for growth in drier conditions
• Remember non-vascular mosses need lots of water
• Thick waterproof cuticle holds moisture inside
• Stomata well protected
• Usually needles kept 2 to 4 years

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Bristlecone Pines

• Bristlecone pine keeps needles for up to 45
  years!
• Note its the longest-lived tree species
• One particular individual named Methuselah is
  4,700 years old!
• Ancient Bristlecone Pine website

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Pine Cones

• Two basic types, both can be on one tree
• Microsporangiate (ie male)
• Produce pollen (hence, pollenate cones)
• Usually on lower branches
• Small (1 to 2 cm)
• Megasporangiate (ie female)
• Contain archegonia (hence ovulate cones)
• Usually on upper branches

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7th Inning Stretch
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Interesting Members of Family Taxodiaceae

• These are non-pine conifers
• Tallest vascular plant
• Redwood (Sequioa semperviruens)
• Biggest plant by volume
• General Sherman tree, a giant redwood
  (Sequioadendron giganteum)
• Once thought extinct!
• Dawn Redwood Metasequoia

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Worlds Biggest Plant

• The General Sherman Tree
• Species is Sequoiadendron gigantea
• Central California
• 2500 years old!!!
• National Park Service site
• US Geological Survey site
• Note growth rate!!

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Metasequoia

• The Dawn Redwood
• Also member of Taxodiaceae
• First described in 1941 as a fossil by Japanese
  paleobotanist Shigeru Miki
• Looked like Sequoia, but different
• Discovered living in 1944 by Chinese forester
  Tsang Wang
• Found in a temple
• Many later found in a valley

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Metasequoia Controversy

• Most U.S. specimens may have come from just 1
  tree in the Chinese temple
• Some experts feel that inbreeding depression is
  occuring
• Michigan State website
• Dawes Arboretum website
• Captive breeding program started
• Note that many ancient trees in China have been
  cut (now stumps)
• Note 1993 connection to Calloway Gardens