Plant Transport (Final)

Question 1

STATE HOW mineral ions and water are taken up by the roots of plants.

Answer 1

Mineral ions are dissolved in water and move passively into the roots with water (mass flow).

Question 2

What is the definition of transpiration?

Answer 2

Transpiration is the loss of water (as vapor-through evaporation) of leaves and stems of plants through pores (openings) called stomata.

Question 3

List and describe the factors that affect the rates of transpiration

Answer 3

Light
More light = more transpiration (causes stomata to open → more photosynthesis/more heat so more transpiration for more CO2/gas exchange and cooling of the leaves).
Temperature
Higher temperature = more transpiration (more evaporative cooling necessary).
Wind
More wind = more transpiration (evaporating water is removed faster, so more water diffuses out of the leaf)
Soil Water
LESS soil water (can’t keep up with transpiration) = less transpiration (loss of turgor and stomata close).
Carbon dioxide
High CO2 levels (in the air around the plant) = less transpiration (guard cells lose their turgor and stomata mostly close - to conserve water, as they do not need to be open AS MUCH to get the same amount of CO2 into the leaves of the plant, as there is more in the air).

Question 4

Outline how sucrose is transported in the phloem in this process.

Answer 4

Sucrose is produced at “sources” within the plant, like leaves and storage organs, and travels to “sinks” like roots and seeds

The sucrose is actively transported (from the “sources”) into the phloem by companion cells

Lots of sugars at the “source” side of the phloem cause water to osmose into the phloem from the xylem

This increases hydrostatic pressure, moving phloem sap downwards towards “sinks.”

At the “sinks” sugars are actively transported from the phloem to the “sink” by companion cells

At the “sink,” sucrose is converted to insoluble starch. This decreases osmotic pressure, so the water osmosis out of the phloem and into the xylem