Plants + Osmosis

Osmosis definition

The diffusion of water from a dilute solution to a more concentrated solution through a partially permeable membrane

Dilute solution...

High conc. water
low conc. solutes
hypotonic

concentrated solution ...

low conc. water
high conc. solutes
hypertonic

red onion + distilled water

hypotonic solution
water INTO cells via OSMOSIS
cells became TURGID
didn't burst due to CELL WALL

red onion + salt solution

hypertonic solution
water OUT OF cells via OSMOSIS
cells became PLASMOLYSED
cell membrane ripped away from cell wall

hypotonic

HYPO = LOW conc
High conc. water
water moves INTO cell
from higher conc. h2o outside to lower conc. inside
animal cell = BURST
Plant cell = TURGID

hypertonic

HYPER - HIGH conc. solution
low conc. of water
water moves OUT OF cell
from higher conc h2o inside to lower outside
ANIMAL = shriveled
plant = PLASMOLYSED

Isotonic

ISO = same
NO net osmosis
ANIMAL = normal
PLANT = flaccid

Roots function

absorb water/mineral ions soil
anchor plant
transport water/sugars too/from soil

Stem function

transport of water/minerals from roots to leaves by xylem
sugars leaves ---> roots, seeds, flowers, fruits, tubers

leaves function

photosynthesis

Sugars used for

respiration
starch (storage)
cellulose
amino acids
fatty acids + lipids

waxy cuticle

prevents water loss

upper epidermis

Transparent so light can pass through it to reach the palisade layer

pallisade mesophyll

most photosynthesis - lots of chloroplasts

spongy mesophyll

air spaces - increase SA for gas exchange

Lower epidermis

contains guard cells and stomata

stoma

pores through which exchange occurs

guard cell

Pairs of cells that surround stomata and control their opening and closing.

root hair cell function

take up water via osmosis
take up mineral ions via active transport

root hair cell adaptations

thin cell wall = short diffusion distance
large SA - water can move into cell
lots of mitochondria- transfer energy needed for active transport
large permanent vacuole- speeds up movement of water by osmosis from soil

Xylem function

carries water + mineral ions from roots to leaves + shoots - supports plants

xylem adaptations

cells die - become lignified
form long hollow tubes
strong to withstand water pressure
unidirectional - transpiration stream

phloem function

carries sugars from photosynthesis around plant

phloem adaptations

form long tubes - not lignified
sieve plates - water carrying sugars can move freely
has cytoplasm
bi directional movement
mitochondria from companion cells transfer energy needed to move dissolved food

guard cell function

allow water vapor + O2 out and CO2 into leaf

guard cell adaptations

Close the stomata during the night to reduce water loss (flaccid)
plants in dry conditions have less

Transpiration definition

Loss of water vapour from the stomata of leaves due to vaporation

factors effecting transpiration rates

-temperature (molecules have more kinetic energy)
- humidity (high humidity, less transpiration - shallow diffusion gradient)
-wind
-light (more photosynthesis happens, more co2 needed)
stomata open

plant disease symptoms

-stunted growth
- spots on leaves
- areas of decay
-growths
- malformed stems/leaves

How to tell if a plant has a disease

- gardening manual
- testing kit with monoclonal antibodies
-identifying pathogens in a lab

Plant disease eg.

tobacco mosaic virus
rose black spot
aphids

nitrate ions used for ....

combining with glucose to form amino acids ---->proteins for growth

nitrate ion deficiency

stunted growth

magnesium ions needed for ....

making chlorophyll (photosynthesis)

magnesium ion deficiency

chlorosis

Physical defences of plants

cell walls made of cellulose
tough waxy cuticle
dead cells (e.g bark) which fall off)

Chemical plant defences

Antibacterial chemicals
poisons to deter herbivores

mechanical defences

thorns and hairs deter animals
leaves which droop/curl when touched
mimicry to trick animals