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Lateral meristems do what?
add girth to woody plants through secondary growth
What is the vascular cambium?
a type of cell found in lateral (not apical) meristems and is involved in secondary (not primary) growth
Which structure determines the direction of root growth by sensing gravity
Root cap
What does plant growth involve?
both the production of new cells by mitosis and the expansion of cell volume
The vascular cambium is a layer of what type of cells?
undifferentiated cells that develops into secondary xylem and phloem
Why do plants need secondary growth?
To provide structural support for the plant
Which part of a plant remains on the plant even after several years of growth?
Primary xylem
Where is the primary xylem located at?
Close to the pith of the plant and remains a part of the plant even after several years of growth
What does primary growth result in?
increased length and occurs only at the apical meristems at the tips of the roots and stems in a plant
Where does secondary growth never happen?
In leaves
Where is wood (secondary xylem) formed in a stem?
Toward the stem's center
Where is the secondary phloem formed in a stem?
Towards the stem's surface
Vascular cambium forms
Wood
What is the function of cork?
It insulated and waterproofs roots and stems
How is the supply of vascular cambium maintained?
by the division of its cells
What happens when vascular cambium cell divides?
One cell differentiates and the other cell remains meristematic
Cell division in the vascular cambium adds to the girth of a tree by adding new _____ to the layer's interior and _____ to the layer's exterior
Xylem....phloem
In the vascular cambium whats in the interior and exterior
xylem at its interior and phloem at its exterior
As the epidermis is pushed outward and sloughed off, it is replaced by tissues produced by the _____
Cork cambium
What does the cork cambium produce?
It produces the phelloderm, phellogen, and cork cells, These cells move outward to replace epidermal cells
Cellular differentiation is responsible for _____
one daughter cell becoming a sieve tube whereas the other becomes a companion cell
How does cell differentiation occur?
As different genes are switched on and off
At which level in the hierarchy of plant structure is the polarity of a plant determined?
Cells
What does the first division of one-celled zygote establish?
It establishes the polarity of the future plant
Cellular differentiation and morphogenesis in plants depends primarily on _____
Regulation of gene expression
What part of the plant is the apical meristem?
The top tip of the plant
What are secondary compounds in vascular plants?
a diversity of chemicals with many functions related to living on land, including protection from UV radiation, signaling with symbiotic bacteria, etc
what does transpiration drive?
the transport of water and minerals from roots to shoots via the xylem
Plants can move what from their roots to shoots
Large volume of water
The movement of water is what?
Passive and dependent on combined water potential of soil & the cells in the plant and air
What is transpiration driven by
The evaporation from the leaves
How does water enter the root?
By root hairs
What regulated transpiration?
Stomata
Stomata is usually open when? close?
open in the day closed at night to minimize water loss
What triggers stomatal opening at dawn?
light , co2 depletion, and an internal "clock" in guard cells
What can stress signals cause?
For the stomata to close in the day
The transpiration-cohesion tension mechanism maintains what?
The movement of xylem sap against gravity
The lowering of water potential in leaves generates what?
Negative pressure(tension) that pulls water up through the xylem
What is the energy cost for the bulk flow of xylem sap?
None
What is regulated through the stomata?
Movement
How do carbohydrates move through the plant?
Sugars move from source to sink
What are the sources in a plant?
Photosynthetic site or storage site
What are the sinks in a plant
growing sites or actively storing sites
Phloem loading require what?
Active transport
What enables cells to accumulate sucrose?
Proton pumping of cotransport of sucrose and H+
What happens at the sink?
Sugar molecules diffuse from the phlowem to sink tissues and are followed by water
The abilitiy perform certain actions depends on an animal's what?
shape, size, and environment
Plants must always compromise between _____ and _____.
maximizing photosynthesis ... minimizing water loss
Mycorrhizae are _____.
mutualistic associations between plant roots and fungi
What does mycorrizae improve?
absorption of minerals and water from soil
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