stem functions and its modifications
TRANSCRIPT
STEM FUNCTIONS AND MODIFICATIONS
Made By:Pranav Ahlawat
What Exactly is a Stem? Before we go any further in this
presentation, let’s define a stem. A stem:
is generally considered to be the central axis of the plant.
supports the leaves and flowers of a plant. has nodes from which new shoots and
sometimes new roots can arise. is usually found above-ground, but can be
modified and found below-ground as well.
The Plant Body: StemsFUNCTION OF STEMS Stems support leaves and
branches. Stems transport water and
solutes between roots and leaves.
Stems in some plants are photosynthetic.
Stems may store materials necessary for life (e.g., water, starch, sugar).
In some plants, stems have become adapted for specialized functions.
Stems support a display of leaves.
Stems orient the leaves toward the light with minimal overlap among the leaves.
Asclepias - milkweed
Modified & Specialized Stems
Food Storage Stems - Asparagus
Cacti - stout fleshy stems that are modified for food and water storage and photosynthesis.
Photosynthetic Stems
Tuber
Tubers - accumulation of food at the tips of underground stolons
The "eyes" of a potato are the nodes of a starch-ladened stem
Corms
A corm is a swollen, vertical stem with a papery covering.
Gladiolus and Crocus are examples of plants that form corms.
Crocus corms
Bulb
Bulbs - large buds with a small stem at the lower end surrounded by numerous fleshy leaves, adventitious roots at base
Examples include onion, tulip, and lily
Rhizomes
Rhizomes - horizontal stems that grow below the ground with adventitious roots
Examples of plants that can produce rhizomes are irises, ferns, and grasses.
Rhizomes
Other plants, like ginger, produce large, thick rhizomes called pachymorphs.
The pachymorph rhizome of Ginger
Thorns
Honey locust (modified stem)
Black Locust (modified leaf stipules)
Tendrils
Grape Tendrils
Stolons
Stolons or runners - horizontal stem that grows above the ground with long internodes
Examples of plants that can produce stolons are strawberry and airplane plants
Conclusion
A stem : supports leaves and branches. transports water and stores food. performs photosynthesis. performs specialized functions in different
conditions.
Stem Modifications:
• Tuber• Stolon• Corm• Tendril• Bulb• Rhizome
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