nutrition in plants Flashcards
what do leaves do?
leaves are the primary photosynthetic organs for most plants and are highly adapted to maximise light capture and co2 absorption, all while minimising water loss.
what is the function of the upper and lower epidermis?
-single layer of cells that do not contain chloroplasts
-protects cells inside the leaf from physical damage
-upper epidermis is translucent to allow as much light to pass through as possible
what is the function of the waxy cuticle?
-waterproof layer to reduce the rate of water loss via evaporation
-transparent to allow as much to pass through as possible
what is the function of the palisade mesophyll?
-elongated, cylindrical cells with the most chloroplast in the leaf to trap the most light
-tightly packed and perpendicular to upper epidermis to increase surface area available to trap light
what is the function of the spongy mesophyll?
-irregularly shaped cells with some chloroplast to trap light
-spaced out randomly in the leaf, forming intercellular air spaces
-vascular bundles found here
what is the function of the intercellular air spaces?
-mesophyll cells exchange oxygen and co2 with the air in the intercellular air spaces
what is the function of the thin film of moisture?
-allows atmospheric gases to dissolve into their aqueous states for more efficient movement across membranes
-water is also lost from the film via evaporation
what is the function of the vascular bundle?
-xylem transports water from the roots to the leaves
-phloem transports sucrose from the leaves to all parts of the plant
what is the function of the guard cells?
-swell and shrink to open and close the stoma respectively , based on water availability
-contains the least chloroplast
what is the function of stoma?
-allows the leaf to undergo gaseous exchange with the surrounding air
what is the equation for photosynthesis?
co2+water->glucose + oxygen
in the presence of light energy and chlorophyll
explain chlorophyll and glucose
photosynthesis occurs in the chloroplasts of cells because of its green pigment, chlorophyll. it traps light energy and converts in into chemical energy for the formation of glucose. chlorophyll is the only pigment that can transfer that energy into the photosynthetic process.
the mesophyll cells first use whatever glucose they require for respiration to meet their energy needs, then convert the excess glucose produced into sucrose for transport out of the cell and through the phloem to all parts of the plant. any further excess sucrose will then be transported to specialised storage organs like the roots, stems, and fruits to be converted into starch for long-term storage.
explain intake of co2
with plants photosynthesising for most of the day, the concentration of co2 in the mesophyll cells and therefore, the intercellular air spaces, is much lower than the surrounding air. this creates a concentration gradient for atmospheric co2 to diffuse through the stomata into the intercellular air spaces where they dissolve into the thin film of moisture before diffusing into the mesophyll cells.
explain the intake of water
most land plants grow in soil with ample water and can easily absorb water from the soil via osmosis. from there, water moves from cell to cell via osmosis until it enters the xylem which transports water to all parts of the plant, leaves included, via transpiration pull.
with the constant use of water for many of the life processes in the leaf cells, including photosynthesis, the water potential in the mesophyll cells is much lower than that in the xylem. this creates a water potential gradient for water molecules to exit the xylem and enter the mesophyll cells via osmosis.
