6: Plant nutrition Flashcards
Photosynthesis definition
- the process by which plants manufacture carbohydrates
- from raw materials
- using energy from light
Photosynthesis Word and symbol equation
carbon dioxide + water ➝ glucose + oxygen,
in the presence of light and chlorophyll
(light & chlorophyll)
6CO2 + 6H2O ➝C6H12O6 + 6O2
What is chlorophyll used for in photosynthesis? (2)
- transfers light energy into chemical energy (used to build complex organic molecules, like glucose)
- synthesis of carbohydrates
What are carbohydrates stored as? Their uses?
Stored as starch in granules (starch is insoluble)
Uses:
- respiration to produce produce energy structured components - cellulose for cell walls
- carbohydrates ➝ glucose ➝ sucrose for transport
Limiting factor definition
something present in the environment in such short supply that it restricts life processes
Limiting factors of photosynthesis (3)
↑ CO2 concentration = ↑ rate
↑ Light intensity = ↑ rate
can heat up the plant above the opt temperature, so temperature = limiting factor
↑ Temperature = ↑ rate enzyme activity (refer to topic 5)
How can greenhouses provide the opt conditions for photosynthesis
- Gas heaters provide a suitable temp and provide CO2 enrichment
- Optimum lightning conditions
Describe the pathway of carbon dioxide from atmosphere to chloroplasts
diffusion
atmosphere → air spaces around spongy mesophyll tissue → leaf mesophyll cells → chloroplast
Upper and Lower Epidermis adaptation
act as a protective barrier around the leaf to prevent pathogens entering
Upper e. - THIN and TRANSPARENT to allow more light to enter (palisade mesophyll layer underneath)
Lower e. - contains GUARD CELLS and STOMATA
Palisade and Spongy mesophyll tissues adaptation
Spongy mesophyll - lower layer
- cells are packed loosely + large SA = to allow gases to diffuse through the plant (CO2 in, O2 out)
Palisade mesophyll - near the top; adapted to absorb light
- long and thin, has gaps: for gas exchange, osmosis
- many chloroplasts: to carry out photosynthesis.
Guard cell function
what does it do when there isn’t enough water?
surrounds stomata; controls opening & closing of stomata to limit water loss
When not enough water:
guard cells close stomata = reduce diffusion of CO2 = causes CO2 to become the limiting factor = reduces the rate of photosynthesis.
Stomata function
gas exchange occurs
IN: CO2 by diffusion
OUT: water vapour by osmosis + O2 by diffusion
Cuticle
clear, waxy layer that surrounds the leaf
wax = provides waterproofing, reduces water loss without reducing light absorption
Vascular bundle
xylem + phloem
transport system - has thick cell walls to support the stem and leaf
XYLEM
transports WATER, MINERALS by TRANSPIRATION
ONE way direction of flow (roots ➝ leaves)
Adaptation: - hollow, dead cells (lose their organelle, cytoplasm) - join in continuous flow of water
- lignin strengthens
PHLOEM
transports SUCROSE (glucose + fructose), AMINO ACIDS by TRANSLOCATION
BOTH directions
no nucleus
Position of xylem and phloem in a leaf, stem, a root
Leaf: Xylem always on top of phloem
Stem: xylem inside of stem; phloem outside
Root: xylem in the middle in an X shape; phloem outside
