Chapter 7: Nutrition in plants Flashcards
What is the word and symbol equation for photosynthesis?
Carbon dioxide + Water| light energy(arrow)chlorophyll Glucose + oxygen + water
6CO2 +12H2) (arrow) C6h1206 + 602
What is photosynthesis and briefly describe the 2 stages
Photosynthesis is the process where light energy is absorbed by chlorophyll and transformed into chemical energy for the formation of carbohydrates from water and carbon dioxide. Water and CO2 are raw materials for photosynthesis, and oxygen is released during this process
Light-dependant stage: Light energy is absorbed by the chlorophyll and then converted into chemical energy. Light energy is also used to split up water molecules into oxygen and hydrogen atoms via photolysis.
Light-independent stage: The hydrogen atoms produced in the light-dependent stage is used to reduce carbon dioxide into carbohydrates in the form of glucose. Chemical energy for this reduction comes from the light-dependent stage. Enzymes are used in both stages.
What is a limiting factor?
Limiting factors are factor that directly affect a process when its quantity is changed.
How does light intensity affect the rate of photosynthesis?
The closer the light source is to the plant, the higher/greater the light intensity. When light intensity increases, the rate of photolysis increases so the rate of reduction of carbon dioxide into carbohydrates in the light independent stage also increases. This causes the rate of photosynthesis to increase. When light increases further after the point when light intensity is no longer a limiting factor, the rate of photosynthesis becomes constant.
How does carbon dioxide concentration affect the rate of photosynthesis?
When carbon dioxide concentration increases, there is more CO2 for reduction to make more carbohydrates in the form of glucose in the light-independent stage. thus the rate of photosynthesis increases as the concentration of CO2 increases. When Co2 continues till it no longer becomes a limiting factor, the rate of photosynthesis remains a constant.
How does temperature affect the rate of photosynthesis?
As temperature increases, the rate of photosynthesis increases as the enzyme and substrate molecules gain kinetic energy. This increases the chance of collision between enzyme and substrate molecules, increasing the rate of enzyme-substrate complexes formed, leading to an increased rate of photosynthesis.
When the enzymes are denatured due to the temperature being past the optimum temperature, the rate of enzyme-substrate complexes formed decreases as the enzyme loses the specific 3-dimensional conformation of the active site, thus the substrate is unable to fit into the enzyme’s active site.
Describe the petiole and its function
The petiole holds the lamina away from the stem, to allow the lamina to obtain sufficient sunlight and air
Describe the Lamina and explain its function
The lamina has a large flat surface compared to its volume to enable maximum sunlight to be absorbed for photosynthesis. The Lamina is also broad and thin to allow for CO2 to reach the inner cells quickly via diffusion
Describe the network of veins and its functions
The network of veins transport sucrose and amino acids from these cells to other parts of the plant, at the same time carries water and mineral salts to the cells in the lamina.
Explain how the leaf arrangement allows a leaf to obtain maximum sunlight
Leaves that grow in pairs/singly in an alternate arrangement ensure that leaves are not blocking each other so that each leaf is able to obtain maximum sunlight for photosynthesis.
Describe the structures of the upper epidermis
The lamina has an upper epidermis made up of single-layered cells that are closely packed, and its outside is covered by a waxy and transparent cuticle to prevent excessive water loss and to allow light to pass through to increase the rate of photosynthesis.
Describe the structure of the Palisade mesophyll
The palisade mesophyll consists of one or two closely packed, long and cylindrical cells that contain numerous chloroplasts, to allow for maximum rate of photosynthesis.
Describe the structure of the spongy mesophyll
The spongy mesophyll consists of irregularly shaped, loosely hanged cells that contain numerous large intercellular air spaces to allow for gaseous exchange between leaf and the surrounding. The cells also have a thin film of moisture to allow gases to diffuse in for a faster rate of diffusion into the cell. Lastly, the palisade mesophyll contains transport tissues, xylem and phloem. The xylem helps to transport water and mineral salts to the mesophyll cells, while the phloem transports sucrose and amino acids away from the leaf to other parts of the plant.
Describe the lower epidermis and its functions
The Lower epidermis consists of a single layer of closely packed cells with a waxy and transparent cuticle on the outside to reduce excess water loss through epidermal cells.
How do guard cells control the size of the stomata during the day?
Guard cells photosynthesise, converting light energy to chemical energy (light-dependent stage). The chemical energy is used to pump potassium ions into the guard cells from neighbouring epidermal cells. This causes the water potential of guard cells to lower. This increases the turgidity of the guard cells and causes them to become swollen. Thus causes the swollen guard cells to become more curved and pull the stomata open.
