plant cells

what are the main three organs

roots, leaves and stems

what is the stomata and where is it found

they are found in the lower epidermis

they are small gaps that make it easier for gas to diffuse in and out the cell

guard cells are capable of closing these gaps

what is the palisade mesophyll

the palisade mesophyll is a layer of tightly packed cells below the upper epidermis. the cells are exposed to lots of sunlight and therefore have lots of chloroplasts

what are chloroplats

where photosynthesis takes place

what is spongy mesophyll

spongy mesophyll contain many airpsaces which help with gas exchange throughout the leaf

what is the epidermal tissue

tissue that covers the outer surface of leaves

name three physical plant defences

bark - dead cells that act as a barrier against pathogens and pests

waxy cuticle - barrier on the surface of leaves and stems to stop pathogens invading leaf tissue

cell walls - made of cellulose

name three mechanical plant defences

thorns or hairs - stop animals eating the plant

leaves that close up rapidly when touched - decrease the surface area available to herbivores

some plants use mimicry to trick animals

name two chemical plant defences

antibacterial chemicals - such as mint, garlic and witch hazel that stop bacteria growing

poisons - such as foxglove and nightshade to put off herbivores

how does the phloem transport nutrients and sugars

sugars are loaded into the phloem sieve tubes and this causes water to enter by osmosis from the xylem increasing pressure. the pressure pushes the sugar through the tube to sinks (areas that need sugar). at the sink sugars are removed, used or stored. water then leaves the phloem.

or in other words by TRANSLOCATION

how can smaller leaves benefit plants living in dry conditions

reduces water loss

helps maintain turgor pressure

if a cell is placed in a hypertonic solution where will water move

out of the cell

if a cell is placed in a hypotonic solution where will water move

into the cell

if a cell is placed in a isotonic solution where will water move

it won’t