6 - Plant Nutrition

Created by

Caitlyn Chia

Cards (20)

Photosynthesis
an endothermic reaction (meaning it takes in energy)
the process by which plants synthesise carbohydrates from raw materials using energy from light
carbon dioxide + water → glucose + oxygen
6CO₂ + 6H₂O → C6H₁₂O₆ + 6O₂
Process of photosynthesis -
Green plants take in carbon dioxide through their leaves (via diffusion)
Water is absorbed through the plants’ roots by osmosis and transported to the leaf through xylem vessels.
Chloroplasts, containing a green pigment called chlorophyll, are responsible for transferring light energy into chemical energy for the synthesis of carbohydrates.
This energy is used to break up water molecules and then to bond hydrogen and carbon dioxide to form glucose.
This is usually changed to sucrose for transport around the plant.
Use of carbohydrates by the plant -
starch = an energy store; starch is insoluble and causes no osmotic problems
sucrose = transport in the phloem
cellulose = build cell walls; all plant cells have cellulose cell walls
glucose = used in respiration to provide energy; this is needed for processes such as active uptake of mineral ions by the roots
nectar = in the flowers to attract insects for pollination
Chlorophyll -
some plants have variegated leaves (only some parts of each leaf constrain chlorophyll)
when tested for scratch, only the parts of the leaf will contain starch
Nitrate ion -
NO3- = nitrate ion
nitrate ions are necessary for the production of amino acids
glucose (from photosynthesis) + nitrate → amino acids
proteins are used to make cytoplasm and enzymes (without the amino acids, plant can’t make proteins)
Magnesium ion -
Mg2+ = magnesium ion
magnesium is necessary for the production of chlorophyll (each chlorophyll molecule contains one magnesium atom)
without the chlorophyll, the plant leaf can’t absorb sunlight for photosynthesis
Light intensity -
from point A to point B, there’s increase in the rate of photosynthesis
this is cause more light energy is benign gathered and utilised by chlorophyll
from point B to point C, rise in light intensity has no effect on the rate of photosynthesis as the other factors such as temperature and carbon dioxide become limiting
How to calculate light intensity
the distance(D) between the source of light and plant
light intensity = 1D2
rate of photosynthesis is directly proportional to light intensity
Carbon dioxide concentration -
from point A to point B, there’s increase in the rate of photosynthesis
this’s cause more carbon dioxide energy is taken into the leaves by diffusion
from point B to point C, rise in carbon dioxide concentration has no effect on the rate of photosynthesis as the other factors such as temperature and carbon dioxide become limiting
Temperature -
from point A to point B, there's increase in the rate of photosynthesis
rise of temperature increases the chemical reaction
from point B to point C, the rate of photosynthesis starts to go down
because the enzymes involved in the chemical reactions of photosynthesis are temperature sensitive and destroyed at higher temperatures (enzymes become denatured)
Adaptations of leaves for photosynthesis (Part 1):
Their broad, flat shape offers a large surface area for absorption of sunlight and carbon dioxide.
Most leaves are thin, so the carbon dioxide only has to diffuse across short distances to reach the inner cells.
The large spaces between cells inside the leaf provide an easy passage through which carbon dioxide can diffuse
Adaptations of leaves for photosynthesis (Part 2):
There are many stomata (pores) in the lower surface of the leaf. These allow the exchange of carbon dioxide and oxygen with the air outside.
There are more chloroplasts in the upper (palisade) cells than in the lower (spongy mesophyll) cells. The palisade cells, being on the upper surface, will receive most sunlight and this will reach the chloroplasts without being absorbed by too many cell walls.
The branching network of veins provides a good water supply to the photosynthesising cells
Waxy Cuticle
Made of wax, it waterproofs the leaf
It is secreted by cells of the upper epidermis
Upper Epidermis
Thin and transparent cells that allow light to pass through to the chloroplasts in the palisade cells
No chloroplasts are present (protects the leaf without inhibiting photosynthesis)
Acts as a barrier to disease organisms
Palisade Mesophyll Cells
Main region for photosynthesis
Contains lots of chloroplasts to absorb more light to provide energy for photosynthesis
Cells are columnar (quite long) and packed with chloroplasts to maximise light absorption
They receive carbon dioxide by diffusion from air spaces in the spongy mesophyll
Spongy Mesophyll Cells
Cells are more spherical and loosely packed
They contain chloroplasts, but not as many as in palisade cells
Air spaces between cells allow gaseous exchange – carbon dioxide to the cells, oxygen from the cells – during photosynthesis
Vascular bundle
A leaf vein made up of xylem and phloem
Xylem vessels bring water and mineral ions to the leaf
Phloem vessels transport sugars and amino acids away (translocation)
Lower epidermis
Acts as a protective layer
Stomata are present to regulate the loss of water vapour (transpiration)
Site of gaseous exchange into and out of the leaf
Stomata
Holes in the leaf to allow carbon dioxide to diffuse in and oxygen to diffuse out
Guard cells
open and close the stomata.
They can shrink to close the stomata to prevent water loss (when the guard cells lose water, they shrink and the stomata close and prevent further water loss in the form of water vapour from the stomata - when the guard cells absorb water into the vacuoles they expand and allow the stoma to open)
They can expand to open the stomata to allow gases to diffuse in and out
Leaf Structure
A) cuticle
B) upper epidermis
C) palisade mesophyll
D) spongy mesophyll
E) lower epidermis
F) guard cell
G) stoma
H) xylem
I) phloem
J) vascular bundle