bio plant nutrition

Why are plants important

1. Primary food source

2. Prevents soil erosion

3. Main oxygen producer

Autotrophs

Organisms that can make their own food using simple sources like carbon dioxide and water

Photo-autotrophs

Green plants use the energy of sunlight to make organic molecules (eg,glucose) from carbon and water

Heterotroph

Organisms that requires complex organic molecules that have been preprocessed by other life forms. Eg .animals

Only energy source for Photosynthesis

Light energy

Photosynthesis definition

Light energy from the sun is absorbed by chlorophyll in the leaf , together with carbon dioxide and water ,glucose and oxygen is produced

Benefit of photosynthesis on humans

Provide oxygen, food + fuel energy

How does photosynthesis benefit plants

Enables plants to produce molecules, which are storehouses for energy

to show starch is produced during photosynthesis ( starch test)

1. Remove a leaf from a plant that has been placed in bright light

2. Place the leaf in boiling water ( kill the leaf /weaken cell structure)

3. Place the lead in boiling ethanol (this will remove the chlorophyll )

4. Dip the leaf in boiling water (make it soft)

5. Spread the leaf on a tile and add iodine to the leaf

6. Have starch = iodine will turn Blue black / no starch iodine turns yellowish brown

To test for importance of chlorophyll

Use variegated ( part of the leaf have chlorophyll, other part does not) leaf, remove the starch, put it in sunlight , test for iodine

Methods to de- starch leaf

1. Place in darkness for 2 days

2. Boil in ethanol (removes chlorophyll)

Importance of carbon dioxide procedure

2 pots of de starched plants are enclosed in plastic bags , then placed in sunlight. soda lime / sodium hydroxide is added inside to one of the pots to absorb carbon dioxide ( acidic gas). After 3 hours, iodine test .

To investigate whether light is required for photosynthesis

1. A lot of plant is destarched (place in darkness for 2 days)

2. One of the leaves is masked by an aluminium foil partially

3. Then the plant is exposes to light

4. After 3 hours, iodine test

effects of light intensity on rate of photosynthesis

Plant in the dark = indicator turns yellow (more co2 as only respiration occurs)

Plant in light = indicator turns purple (less co2 as photosynthesis [co2–>o2]and respiration [o2–>co2]occurs

OG indicator colour —> pink/red

Chemical equation for photosynthesis

6CO2 + 6H2O = C6H12O6 (glucose) + 6O2

In the chloroplast, water and carbon dioxide combine to form glucose

Conditions for photosynthesis

1. Chlorophyll

2. Carbon dioxide

3. Water

4. Sunlight energy (any light but green light)

5. Suitable soil and air temperature

Limiting factor def

• Any factor that affects a process if its quantity is altered ( anything that restricts rate of reaction)

Limiting factors of photosynthesis

1. Light intensity

2. Temperature

3. Carbon dioxide

Light intensity

Greater the light intensity =the plant can photosynthesise faster

• when the line is straight = max rate of photosynthesis , light intensity is not the limiting factor

• Put the light nearer to the experiment or increase the amount of light intensity

Temperature

Temp increase = rate of photosynthesis increase

• because the particles in the reaction move quicker and collide more

• Beyond optimum temp , enzymes controlling the reaction will become denatured and the reaction will stop

Carbon dioxide

Concentration of carbon dioxide low = low rate of photosynthesis ( plant spends a certain amount of time doing nothing, waiting for more co2 to arrive )

• when line is straight = the enzymes controlling the reaction are already maximise, additional amount of carbon dioxide will not increase rate of photosynthesis , co2 not limiting factor

Greenhouse

Can artificially increase carbon dioxide to increase crop yield , help to prevent crop damage due to pests and diseases

Structure of leaf

Leaf stalk = petiole

Leaf blade = lamina

Veins = support blade ( contains vascular bundles to transport water , minerals and glucose )

• vascular bundles =xylem + phloem

Leaf structure

top to bottom

1. Cuticle

2. Upper epidermis

3. Mesophyll cells

• palisade mesophyll

• Spongy mesophyll

• Bundle sheath (outer), vascular bundle ( inner)

4. Lower epidermis

• stoma

• Guard cell

• Cuticle

Advantages of thin and large surface area to volume ratio leaves

1. Large surface area = ideal for diffusion and absorption , allow more sunlight to be absorbed

2. Thin = so that mesophyll cells are close to the surface, reducing the diffusion distance of carbine dioxide from the surrounding to the mesophyll cell

Cuticle

Made of wax, waterproof , secreted by cells of upper epidermis, reduce rate of evaporation

Upper epidermis

Cells are thin and transport to allow light to pass through (no chloroplast) , act as a barrier to disease organisms

Palisade mesophyll

Contains numerous chloroplasts, main region for photosynthesis

Spongy mesophyll

• has air spaces = allows rapid diffusion of carbon dioxide and oxygen in and out of the mesophyll cell

• Has chloroplasts

• Contains vascular bundle

Lower epidermis

• guard cells that surround the stomata = regulate the opening and closing of stomata for diffusion of carbon dioxide and oxygen in and out of the leaf

• Has cuticle

• Protective layer

• Gas exchange into and out of the leaf

Stomata

Regulates the loss of water vapour (transpiration) x

Use of glucose produced from photosynthesis

1. Glucose is converted to protein , proteins are components of cytoplasm

2. Glucose is converted into other sugars which can be found in fruit

3. Glucose is broken down during respiration to release energy which can be used by living things to carry out daily activities

4. Glucose can be converted into starch used for storage in plants

Stomata

Opens in the day (sunlight) closes at night (no carbon dioxide intake is needed , plant is short of water causing guard cells to become flaccid )

Guard cells

• cells that occur in pairs and control the size of stomata to regulate the exchange of gases

• When turgid (filled with water) = one side of the guard cell is thicker than the other and does not stretch . Guard cells buckle and stomata opens (day)

• When flaccid = guard cells sag and stomatal opening close ( water exits) (night)

How does water deficiency affect the guard cells

Become flaccid and stomata closes , stimulated by the presence of abscisic acid

Plants without nitrate ions

Stunted growth , fewer smaller leaves

Nitrate deficiency

Plants without magnesium

Small plants , yellowish eaves (chlorosis)

Magnesium deficiency