Principles of Agricultural Science – Plant 1
Jan 13, 2016
Principles of Agricultural Science – Plant
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Stem Facts
Unit 4 – Anatomy and PhysiologyLesson 4.3 Stems, Stalks, and Trunks
Principles of Agricultural Science – Plant
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Function of Stems
• Provide physical support
• Aid in translocation of nutrients
• Store food reserves
• Site of photosynthesis
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External Parts
• Buds
• Nodes
• Internodes
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External Parts
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Strength of Stems
Rigid stems, such as woody plants and trees derive their strength from extra thick cell walls. Herbaceous stems rely on water pressure, known as turgor.
The specific material, which comprises the rigid cell walls, is called hemicellulose and lignin.
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Internal Parts
• Annual rings (woody plants)
• Phloem (cambium – woody plants)
• Pith or Secondary Xylem (woody plants)
• Xylem
Phloem and xylem comprise the vascular system
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Function of Xylem and Phloem
Xylem• Uptake of water and dissolved nutrients are
translocated from the roots throughout the plant via the xylem.
Phloem• Synthesized food (sugars) from leaves and other
photosynthetic regions are carried throughout the plant growing regions via the phloem.
A rule to help you remember the difference: Xylem → Up Phloem → Down
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Internal Parts Labeled
Annual Ring
Bark
Pith
Phloem/Cambium
Xylem
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Internal Parts Labeled
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Monocotyledon versus Dicotyledon
The arrangement of the vascular system provides evidence to distinguish between monocotyledon and dicotyledon plants
Parker, 2004
Monocotyledon Dicotyledon
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Types of Stems
• Herbaceous
• Modified
• Woody
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Herbaceous Stems
• Physical support is a result of turgor or internal water pressure.
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Modified Stems
Types of modified stems:
• Bulbs
• Corms
• Rhizomes
• Runners
• Tubers
Tuber
Runner
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Woody Stems
• Physical support is a result of rigid cell walls.
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References
Parker, R. (2004). Introduction to plant science (Rev. ed.). Clifton Park, NY: Delmar.
Parker, R. (2010). Plant and soil science: Fundamentals and applications. Clifton Park, NY: Delmar.
Schooley, J. (1997). Introduction to botany. Albany, NY: Delmar Publishers.