Element 3: external parts of the plant Flashcards
Root functions
- Anchoring the plant
- Taking up water from the soil
- Taking up nutrients from the soil
- Spreading by modification (root suckers)
- Surviving winter by modification (tubers)
What is a tap root
One main root that develops from the root radicle.
It has smaller secondary roots branching from it - lateral or side roots
Benifits of a tap root
They can grow very deeply into the ground, so are able to draw up water from grater depths
What are fibrous roots
Roots that start at the base of the stem and are multi-branched. They occupy a large area in the upper topsoil
What are the benifits of fibrous roots
they help prevent soil erosion
What are the disadvantages of fibrous roots
as they rely on surface water, they are suseptible to drought
What is the root cap
A layer of cells protecting the root tip as it develops through the soil
the cells are constantly replaces, a the old ones decaying they help lubricate theh roots passage through the soil
What is the root tip
or meristem
where cell division takes place
What are root hairs
elongated epidermal cells occuring in the zonejust behind the growing tip
what is the function of root hairs
they greatly increase the roots surface area, bringing them into contact with more water and nutrients
What are the functions of a stem
- Supporting the plant
- spacing out the leaves for air movement, and to sunlight to maximise photosynthisis
- holding flowers above the ground to improve pollination
- green stems can photosynthisise
- link the roots to the leaves, transport water, nutrients, and food
what are nodes
the area where leaves and buds are produces
what are internodes
the spaces between nodes
what is a shoot
the collective name for a stem and its attachments
What is a bud
a compact undeveloped shoot, consisting of
* crowded, overlapping, immature leaves
* minute bud-precursors
what are the 2 types of bud
positionally
apical (terminal) and axillary (lateral)
Where is an apical bud positioned
terminal
the tip of a shoot
where is an axillary bud positioned
lateral
on the side of the stem
what are growth rings on the surface of a stem
also called girdle scars
they show where one years growth has ended and the following began, ie. the possition of the last terminal bud before it expanded
What does a leaf scar show
where a leaf or fruit has been attached
what is the functon of lenticels
is a pathway for gaseous exchange
What do conifer leaves look like
Either needle-like, or flat and overlapping as scale leaves
eg. Pinus and Thuja
What do monocot leaves look like
generally
narrow or strap-like; parrallel veination; never have leaf stalks, the leaves wrap around the stem
what is the lamina
the leaf blade, generally broad and flat to collect sunlight
