Lesson 2&3 Flashcards
Stems
Can be quite tall (sunflower) or compact and compressed (onion) where the stem may never get above the soil surface.
Distinguishing external feature of stems: repeated node - internode - node - internode construction
Shoot
made up of a central axis called the stem and components that grow from specific places on that stem
4 Components that Can Attach to the Stem
- Branches
- Leaves
- Inflorescences (reproductive structures made up of one or more flowers)
- Continuation of main stem
Node
- the place of origin on the stem for one or more of the components (branch, leaf, inflorescences, continuation of main stem)
- node can be swollen and obvious or not (depends on type of plant)
- At the nodes are buds (meristems) made up of cells that, given the correct biochemical signal, will rapidly divide and grow into branches, leaves, or inflorescences. More than one bud can grow from a node, so a node can support several structures
Internode
between the nodes. location of nodes determines whether the leaves are: alternate opposite whorled
Inflorescences
can be very simple (just one flower) or very complex with a central axis called a rachis and many branches off that rachis each terminating in a flower or floret
Apex
Tip of the stem.
The bud that is at the tip is called the apical bud or apical meristem.
Main function is to begin growth of new cells in young seedlings at the tips of roots and shoots (forming buds, among other things)
The crotch between the leaf petiole and the stem is called the leaf axil, and the buds in that crotch are called….
axillary buds or
axillary meristems.
Can develop into a stem or flower. If there is only one lead after an axillary bud, then the plant is considered single leafed.
Stolons
Specialized type of horizontal above-ground shoot. Produced from nodes on the stem that are very close to, or right at, the soil surface. These are MODIFIED, HORIZONTAL STEMS (shoot or stem tissue), NOT roots; although roots can form at their nodes.
Example: the “runners” on a strawberry plant are stolons.
One of the main purposes of a stolon is to propagate a plant. You can cut part of the stolon internode and transplant it elsewhere.
Stolons have the same node-internode structure of a stem, but unlike other branches of the plant, at the nodes of the stolon, adventitious roots can form.
Adventitious Roots
Roots that emerge from the stem rather than from roots.
Even though they emerge from the stem above ground, they act like roots.
They anchor the stolon to the ground and absorb water and nutrients for the plant’s use. Leaves and even branches can also form from the stolon nodes.
Rhizomes
Many plants that have above-ground stolons also form these horizontal, below-ground rhizomes. These are MODIFIED, HORIZONTAL STEMS (shoot or stem tissue), NOT roots; although roots can form at their nodes.
Rhizomes typically originate from a node that is just below the surface of the soil, therefore having nodes and internodes, proving that it cannot be a root.
Example: Ginger root is actually a rhizome, see the nodes and internodes.
Roots
Typically found in the soil rather than above ground. No nodes, no internodes, no leaves, no branching from regular spots.
Function/Purpose of Roots
Anchorage for plant and soil.
Support for upright growth.
Absorption of water and soluble nutrients.
Symbiotic interaction with other organisms (rhizobia bacteria for legumes and mycorrhizal fungi for roots of a vascular plant)
Nutrient/Food Storage
Plant’s roots originate from where?
In the embryo formed within the seed
Radicle
The section of the embryo that is root tissue
