Plant Nutrition Flashcards
what are heterotrophs
organisms unable to make their own food and obtain food by feeding on others
what is the energy conversion in photosynthesis
chlorophyll traps light energy and converts it into chemical energy
what is the chemical equation for photosynthesis
6CO₂ + 12H₂O —(light energy/chlorophyll)—> C₆H₁₂O₆ + 6O₂ + 6H₂O
what is the word equation for photosynthesis
carbon dioxide + water —(light energy/chlorophyll)—> glucose + oxygen + water
2 points
how do chlorophylls give the green colour in plants
chlorophylls are the main photosynthetic pigment in plants
they absorb red and blue-violet light, reflect green light
(refer to band of visible light segment of electromagnetic spectrum)
2 points
what are the external structures of a leaf
lamina (leaf blade)
leaf stalk (petiole)
2 points
what are the functions of the lamina
large surface area to maximise absorption of sunlight
thin lamina reduces distance and allows rapid diffusion of carbon dioxide to reach inner cells of the leaf
1 point
what is the function of the leaf stalk
positions the lamina for maximum absorption of sunlight and gaseous exchange
2 points
what are the functions of the network of veins in leaves
veins allow transport of water and mineral salts to cells of the lamina
transport manufactured food from leaves to other parts of the plant
6 points
what are the internal structures of a leaf
cuticle
upper epidermis
palisade mesophyll
vascular bundle
spongy mesophyll
lower epidermis
2 points
what is the cuticle and its function
waxy layer above epidermis which reduces excessive water loss
transparent to allow sunlight to penetrate to the mesophyll
what is the upper epidermis
single layer of closely packed cells (no chloroplast)
what is the palisade mesophyll and its function
a few layers of closely packed cells which are long, cylindrical
contain numerous chloroplasts for maximum absorption of light (where photosynthesis occurs)
what is the vascular bundle and its function
contains xylem and phloem
allows for transport of water and food within the plant
2 points
what is the spongy mesophyll and its function
irregularly shaped cells with numerous large intercellular air spaces (contains fewer chloroplasts than palisade mesophyll cells)
air spaces to allow for rapid diffusion of gases inside the leaf
what is the lower epidermis
single layer of closely packed cells where many minute openings called stomata are found
2 points
what are the characteristics of stomata
each stoma is surrounded by guard cells which control the size of stomata
stomata generally open in the light and close in the dark
*guard cells contain chloroplasts
4 points
what happens to guard cells in presence of light
guard cells manufacture glucose by photosynthesis
water potential of guard cells decrease
water from adjacent epidermis cells (higher w.p.) enters guard cells (lower w.p.) by osmosis
guard cells swell and become turgid, causing them to become curved and pull the stoma open
4 points
what happens to guard cells in absence of light
glucose is used up or converted to starch
water potential of guard cells increase
water exits to the adjacent epidermis cells by osmosis
guard cells become flaccid and stoma closes
4 points
how does carbon dioxide enter the leaf
carbon dioxide is rapidly used up in the cell during photosynthesis
carbon dioxide concentration is lower than atmospheric air
carbon dioxide diffuses into leaf through stomata down a diffusion gradient
carbon dioxide dissolves into the film of water surrounding the mesophyll cells and diffuses into the cells
2 points
how does water enter the leaf
water is brought to the leaves via the xylem vessels in the veins
water leaves the xylem and moves from mesophyll cell to mesophyll cell by osmosis
5 points
what happens to glucose in plants
broken down by plant cells during cellular respiration to release energy
used to form cellulose cell wall
excess glucose temporarily stored as starch
can be used to form amino acids and fats
converted to sucrose which is transported to storage organs
