11. Transport in plants Flashcards
what is a palisade cell
-specialised for absorbing light energy for photosynthesis
-large number of chloroplasts
-arranged near the top of leaf
what is a root hair cell
-a cell specialised for absorbing water and mineral ions
-it has a large SA:V for efficient diffusion
-it contains many protein pumps for taking up mineral ions
why would phosphate ions and nitrate ions be useful to the plant
makes up proteins, DNA and phospholipids
describe movement in xylem vessels
-transports water and mineral ions move in one direction-from roots to leaves
-the tissue is formed from elongated dead cells with no nucleus (to make space for more water) joined end to end
-cell wall strengthened with lignin that adheres to water
-xylem vessels have no sieve plates/ are continuous vessels
describe movement in phloem tissue
-movement of sucrose and other dissolved substances (hormones, amino acids) in both directions- translocation
-sieve tube cells are living cells with a cell wall but no nucleus
-cell wall of each sieve tube cell is perforated by a number of pores to form a sieve plate
what are stomata
holes in a leaf which allow carbon dioxide in & water, oxygen out
define transpiration
transpiration is the loss of water from the leaves of a plant through stomata due to evaporation
how are leaves adapted
-large sa:v ratio to capture light energy and generally thin so there is a short diffusion pathway
why do stomata close at night
Carbon dioxide is not required at night as there is no sunlight for photosynthesis to occur, so closing the stomata reduces water loss
how does transpiration help with water movement in plants
It creates a suction pressure which helps to draw water up the xylem from the roots
identify factors that affect transpiration
humidity, temperature, wind velocity
how does humidity affect transpiration
As humidity increases, transpiration decreases due to reduction in the water diffusion gradient
how does temperature affect transpiration
As temperature increases, transpiration increases due to the increased kinetic energy of the water molecules
how does wind velocity affect transpiration
As wind speed increases, transpiration increases due to maintenance of a steep water diffusion gradient
which cells are responsible for opening and closing stomata
guard cells
