transpiration, potometer and xerophytes/ hydrophytes Flashcards
draw and annotate the structure of a leaf
what and how do environmental factors affected the rate of transpiration
-Humidity: reduced water vapour potential gradient between air spaces and atmosphere will reduce transpiration
-Wind speed: disperse water vapour diffusing out of the leaf increasing WV potential gradient = increase transpiration
-Temperature- increases kinetic energy of water molecules so the rate diffusion through stomata increases
draw the graphs for wind speed, humidity, temp / rate of transpiration
what are the other factors that can affect the rate of transpiration
-number of leaves
-number size and position of stomata
-cuticle
-light = more photosynthesis =stomata open = gas exchange
-water availability
explain how to set up a potometer
-airtight, can use vasaline to ensure this
-apparatus flooded with water
-leaf shoot cut underwater
-cut shoot attached through rubber tubing underwater
-air bubble introduced at end to scale area
-distance moved by air bubble measured per unit time
what is a hydrophyte?
What is a xerophyte
-aquatic plants adapted to live in the water
-Plants adapted to reduce water loss
how are cacti adapted?
Succulents so store water in there stems which can expand when water is available
Leaves reduced to spines = lower surface area so less transpiration
Roots are widespread
how is Maram grass adapted?
-Rolled up leaves= trap air inside that’s moist so less transpiration due to lower water vapour concentration gradient
-thick, waxy cuticle reduces evaporation
-Trapped air in centre. = high vapour potential
-Hairs on lower surface traps, moist
-Dense spongy mesophyll = less air spaces in leaf so less surface area for evaporation
how is a water lily adapted?
Money spaces in leaf keep it afloat so they are in the air and can absorb sunlight
Stomata on upper epidermis, so they are exposed to air to allow gas exchange
Leaf stem has many air spaces. Helps with buoyancy and quick diffusion of oxygen to roots for aerobic.
why must the leaf shoot be cut underwater
and slanted
-to prevent air bubbles form forming in the vascular tissue
-to increase surface availability for water uptake
what are some limitations of using the potometer method
Not all of the water taken up is transpired. some is used to maintain turgidity and photosynthesis.
The plant is dying when the stem is cut so rate of water uptake is lower than normal
