igcse bio - topic 6 plant nutrition

photosynthesis

process by which plants synthesize carbohydrates from raw materials using energy from light

oxygen

by-product from photosynthesis when water is split

palisade mesophyll

long slender cells under upper epidermal cells where most of photosynthesis happens

limiting factor

something present in the environment in such short supply that it restricts life processes

elodea

water plant often used to determine the rate of photosynthesis by counting the oxygen bubbles under water over time

chlorophyll

green (mainly) pigment that is involved in photosynthesis; absorbs at blue and red wavelengths; reflects light at green wavelength

raw materials/reactants

the starting ingredients needed for a chemical reaction; in photosynthesis: CO₂ + H₂O

pigment

colored proteins such as chlorophyll which can absorb specific wavelengths of light energy

chloroplast

organelle mainly found in the palisade of plant cells where photosynthesis happens; chlorophyll is located here

control group

an experimental set-up, which is used to prove that nothing other than the independent variable is creating a change in results

glucose

the simple carbohydrate sugar produced from photosynthesis

waxy cuticle

waterproof layer on outside of leaves; protects leaf and reduces transpiration

stoma

a pore present mostly in lower epidermis of leaves where gases and water vapour can diffuse into and out of the leaf

iodine

indicator that tests positive for starch by turning dark blue/black

rate of photosynthesis

how fast photosynthesis is happening; determined either by reactants: CO₂ & H₂O being used or how fast glucose & O₂ are appearing

spongy mesophyll cells

irregularly shaped cells that create air spaces for gas exchange in leaves; some photosynthesis happens here

temperature effect on photosynthesis

reaction rate increases initially due to speeding up collisions of molecules, then it reaches a peak where the rate is happening as quickly as possible, then rate rapidly decreases due to the denaturation of enzymes

products

the outcome of a chemical reaction; in photosynthesis: glucose + oxygen

enzymes

proteins which increase the rate of reactions involved in photosynthesis

glass/plastic heat shield

something that is placed between the light and beaker with the elodea so that heat isn't a factor in the rate of photosynthesis, only the light waves

destarch technique

place plant in the dark for 24 hours so they can only respire, so convert all starch stores to glucose which is then used in respiration

carbon dioxide

reactant in photosynthesis; found in the air and enters the plant through the stomata of leaves

lower epidermis

bottom layer of cells in leaves which contain guard cells

air spaces

created by spongy cells’ irregular shape in the mesophyll of the leaf; allows a space for water vapor and gases to diffuse into and out of the leaves.

upper epidermis

top layer of cells in leaves that secrete the waxy cuticle and allow light through to palisade layer; protects leaves; don't contain chloroplasts

starch

large polysaccharide made of glucose; used for energy storage in plants

sodium hydrogen bicarbonate

when added to water, it dissociates into CO₂ and H₂O so that CO₂ isn't a limiting factor for photosynthesis

diffusion

how gases move into and out of stomata

veins/vascular bundles

bundles of xylem and phloem tubes

soda life/potassium hydroxide

chemicals that absorb CO₂; used to take the C0₂ out of an experimental group's air so that you can test if CO₂ is necessary for photosynthesis

light energy

absorbed by pigments and changed to chemical energy by photosynthesis

magnesium

mineral needed for production of chlorophyll

NPK fertilizer

used for providing essential ions to the soil; nitrogen, phosphorous and potassium

light intensity

a limiting factor of photosynthesis