Stems, Structure & Function Flashcards
What is a stem’s primary functions?
- Holding leaves in best position for photosynthesis.
- Holding flowers in the best position for pollination.
- Transport of water, nutrients and sugars.
- Holding fruits in the best position for seed dispersal.
What is the function of the epidermis?
Protects against funghi and bacteria. Cuticle conserves water. Keeps tissues air tight and reduces water loss.
Give an example of a specialised epidermis cell?
Trichomes - hairs.
What is the function of the cortex?
The cortex can contain chloroplasts.
Made of parenchyma tissue.
May contain stored carbohydrates.
May carry out photosynthesis if cells contain chloroplasts.
What is the Cambium and what is the function?
The Cambium (or vascular cambium) is the meristematic tissue between the phloem and the xylem. Part of the Vascular bundle.
Function is to make xylem, phloem and additional cambium cells.
Produces secondary thickening.
Secondary growth produces wood.
Where is Phloem located in the stem and what is it’s purpose?
Phloem is found in the vascular bundles. Sieve tubes and companion cells. Elongated and open ended. Function is for the movement of water, sugar, hormones around the plant. Up and down.
Where is the xylem located in the stem and what is it’s function?
In the vascular bundles with the Phloem and cambium. Xylem vessels are tube like wider than Tracheids.
Movement of water and mineral nutrients from root to aerial part of plant. May give structural support.
Where is the pith located in the stem, and what is it’s function?
Centre of the stem. Central core made up of Parenchyma tissue. Used to store food as starches. May store water as in cacti. Far inside so no chloroplasts. no photosynthesis.
Where is the Vascular Bundle located and what is it’s function?
Several bundles arranged in a ring between the cortex and the pith. Xylem, phloem and cambium encased in a bundle sheath. These are transport and meristematic tissue.
What are the differences between Monocotyledon and Dicotyledon stems?
Dicot Vascular cambium positioned between xylem & phloem. Vascular bundles arranged in a ring. Yes Secondary growth. Monocot No vascular cambium Vascular bundles scattered throughout the stem. No secondary growth.
What 6 things can you label on a stem?
Apical bud Axillary or lateral bud Node Bud scale scar Lenticel (breathing pore) Leaf scar
What is a lenticel on a stem?
It’s a breathing pore where gas and water exchange in the stem surface. Carbon dioxide can exit & oxygen can enter. Water can exit.
What is a node on the stem?
Growing points where leaves, buds, branches can arise. As stem grows the internodes elongate so branches and leaves are well spaced.
What are the axillary buds on a stem?
Axillary buds are lateral buds which sit on the side of the stem at a node, and may develop into a side shoot or flower. (not the tip)
What is the apical bud on a stem?
The bud situated at the tip of the stem. The terminal bud. This is the leader or lead shoot. If this is removed, the previous axillary bud further down the stem will gain dominance and resume growth resulting in a bushier plant.
