Plant Osmoregulation - C6 Flashcards
What are the main plant organs?
Roots, shoots (stem, leaf, bud, flower, fruit)
What are the three kinds of non-replicating plant tissues?
Ground: support, storage & photosynthesis
Vascular: transport food & water
Dermal: protection – water loss
Define meristematic
It consists of undifferentiated cells capable of cell division
What are ground tissues responsible for?
In charge of support, storage and photosynthesis
What are ground tissues made of?
Palisade mesophyll:
Elongated cells below epidermis (Main site of photosynthesis)
Spongy mesophyll:
(Below palisade cells
Fewer chloroplasts
Gaps allow gas movement (water vapour too))
What are vascular bundles?
Transport food and water
Made of Xylem (water transport)
Phloem: sucrose (food) transport
Which way do nutrients travel in the Xylem?
Up (roots to leaves)
Is travel in the Xylem passive or active?
Passive, as the tissue is dead
What carbohydrate within the walls stops gas and water exchange?
Lignin (cells die, leaving an empty tube)
What does Phloem transport?
Sugar and mineral ions (Translocation)
Is Phloem transport active or passive?
Active, as it goes both up and down
What cells make up the Pholem tube?
Sieve cells, with sieve tubes at the ends, to allow sugar molecules movement (companion cells provide energy)
What is the role of Dermal tissues?
Protection, homeostasis and gas exchange
What are dermal tissues made of?
The Epidermis (preventing water loss)
Stomata (guard cells that exchange O2, Co2 and H2O)
Gas exchange means water loss as stomata are open - plants need to regulate this to avoid dehydration
What are Stomata?
Holes between guard cells that allow gas exchange and transpiration. When open, they take in water and swell (turgid)
Blue light activates proton pump that lets in K+ and water follows due to concentration gradient. When closed, they lose water and shrink (flaccid). A high Co2 concentration/Abscisic acid from wilting leaves = K+ moves out and water follows due to concentration gradient
What is transpiration?
Evaporation of water out of the spongy mesophyll through the stomata in leaves
Pulls water up the stem in the xylem
Works like a straw
What is water movement from the roots to the leaves due to?
Root pressure (water moves in via diffusion constantly and pushes itself up part of the way)
Transpiration (evaporation of water from stomata means room for more water to fill the space)
Adhesion (attraction of polar water molecules inside xylem to the walls)
Cohesion (attraction of the water molecules to each other).
As water leaves via the stomata, the column us pulled up and continues to transport substances.
What are the two ways for water to enter the roots?
Alloplastic (through the cell wall but not into cytoplasm)
Symplasmic (through cytoplasm)
How long do root hairs (extra structures to pick up water) live
Less than a day
What are the three factors effecting transpiration?
Humidity (low humidity increases the water potential gradient between the leaf and the air, increasing transpiration)
Light intensity (high light intensity makes stomata open to allow photosynthesis and allows more water to escape)
Wind (moves humid air away from leaf and increases transpiration - sweating)
Give an example of osmoregulation in plants
Low water levels
Guard cells lose water = flaccid = stomata close
Closed stomata = less water loss via evaporation, but also less photosynthesis
Plant water levels maintained (not dropping further) until more water is obtained
Then guard cells fill with water, open and transpiration starts again
