Sunflower Stem Under the Microscope
Sunflower Stem (Longitudinal Section), Helianthus annuus
This is a lengthwise section of a sunflower stem stained with safranin and fast green. Cutting along the stem shows xylem vessels as long tubes with spiral and ring patterns in their walls.
This is a longitudinal section of a sunflower stem (Helianthus annuus), cut along its length and stained with safranin and fast green. The wide middle is the pith, made of large, thin-walled cells that store food and water. Along each side, bands of long, narrow cells run the length of the stem. These are the epidermis, cortex, and vascular bundles, where thin red-stained strands of xylem carry water up from the roots. Compare the round pith cells with the long side cells to see how shape fits the job of each tissue.
What to look for
- Epidermis and cortex: Outer layers of long cells running along the edges of the section.
- Xylem vessels: Long tubes stained red, with spiral, ring, or net-like thickenings in their walls.
- Phloem: Narrow, green-stained cells running beside the xylem.
- Pith: Large, thin-walled cells in the center of the stem.
Questions and answers
What do xylem vessels look like in a longitudinal section?
In a longitudinal section, xylem vessels look like long tubes. Their walls have red-stained thickenings in patterns such as spirals, rings, or nets, which help keep the tubes from collapsing.
Why do xylem vessels have spiral walls?
Spiral and ring thickenings strengthen the vessel walls while still letting young stems keep growing longer. Later-forming vessels often have more solid walls with pits.
- Category
- Botany & Plants
- Scan magnification
- 20x
- Stain
- Safranin / Fast Green
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