Nutrients in plants

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Leaf structure (internal)

Upper epidermis

no chloroplast

mesophyll

palisade

spongey

has 1 or 2 layers of closely packed cylindrical cells

contain numerous chloroplasts

irregular in shapes

numerous large intercellular air spaces between them

lesser chloroplasts than palisade

thin film of moisture

vascular bundle made up of the xylem and the phloem

lower epidermis

many openings called stomata

no chloroplasts

waxy and transparent cuticles

reduce water loss through evaporation and allows sunlight to enter

external leaf structure

lamina

how carbon dioxide enter the leaf through stomata

large flat surface

leaf arrangement

maximize sunlight for maximum rate of photosynthesis

thin layer

carbon dioxide can rapidly reach the inner cells of the leaf

network of veins

petiole

leaves always grow opposite each other to prevent blocking each other from sunlight

carry water and minerals to the cells in the lamina

hold the lamina away from each other to prevent the leaves from blocking each other from sunlight

carry manufactured food such as glucose from these cells to other parts of the plant

functions of stomata

during the day

during the night

  1. the guard cells photosynthesize, converting light energy into chemical energy
  1. chemical energy is then used to pump potassium ions into the guard cells from neighboring epidermal cells
  1. water potential of the guard cells is lowered, the water from neighboring epidermal cells enters the guard cells through osmosis
  1. increasing the turgidity of the guard cells causing them to be swollen
  1. the guard cell's cell wall is thicker on one side therefore 1 side of the stomata becomes more swollen and curved, pulling the stoma open
  1. the accumulated potassium ions will be diffused out, increasing the water potential
  1. water leaves the cell via osmosis, causing the guard cell to be flaccid, leading to the stomata closing

when photosynthesis occurs, carbon dioxide is used up rapidly. this causes the leaf to have a lower concentration of carbon dioxide compared to the concentration of carbon dioxide in the atmosphere, creating a concentration gradient. Therefore, carbon dioxide diffuses from the surrounding air through the stomata into the air spaces in the leaf

surface of mesophyll cells are covered with a thin film of moisture so that carbon dioxide can dissolve in it

dissolved carbon dioxide can then enter the cell

how water and mineral salts enters the leaf

xylem transports water and mineral salts from the roots to the leaf

once out of the veins, the water and mineral salts move from cell to cell right through the mesophyll of the leaf

photosynthesis has 2 stages

light dependent stage

light independent stage

  1. light energy is absorbed by chlorophyll and then converted into chemical energy
  1. light energy is also used to split water molecules into oxygen and hydrogen atoms. this is called photolysis
  1. hydrogen produced in photolysis is used to reduce carbon dioxide to carbohydrates such as glucose
  1. the formation of glucose from carbon dioxide does not require light.

both stages needs enzymes

12H2O goes through photolysis to give you 6O2 and 24H

6CO2 + 24H = C6H12O6 + 6H2O

6CO2 + 6H2O = C6H12O6 + 6O2

what happens to glucose

  1. used immediately for cellular respiration and create cellulose cell walls
  1. during day time, rate of photosynthesis is so great that the glucose produced cannot be used up fast enough and is stored in the form of starch
  1. in darkness, photosynthesis stops and and starch is converted back into glucose
  1. glucose converted to sucrose

transported to other parts of plant or storage organs, like seeds, stem tubers or root tubers via the phloem

  1. reacts with nitrates and other mineral salts to form amino acids in leaves. amino acids in the leaves will form protein which is used for synthesis of new protoplasm
  1. glucose gets converted into which are then used for storage, cellular respiration, and synthesis of new protoplasm