plant nutrition Flashcards
Structure of chloroplast
- A typical mesophyll cell has about 30 to 40 chloroplasts. An envelope of two membranes encloses the stroma, the dense fluid within the chloroplast
- a system of interconnected membranous sacs known as thylakoids separates the stroma from the interior of the thylakoids. Chlorophyll is found in the membrane of the thylakoids
Chlorophyll
- The green pigment chlorophyll is the principal pigment involved in photosynthesis.
- chlorophyll absorbs light in the violet blue and red region of the visible light spectrum and reflects green light, thus giving leaves their green appearance
- chlorophyll traps light energy and convert it into chemical energy for the formation of glucose
Photosynthesis
Definition: photosynthesis is the process in which light energy absorbed by chlorophyll and is used to synthesize glucose from water and carbon dioxide. Oxygen is released during the process. Photosynthesis depends on enzymatic reactions in the chloroplasts
Chemical equation: 6C02 + 6H20 → C6HO6 + 602
What happens to glucose that is formed during photosynthesis?
- glucose is used during respiration to produce ATP for cellular activities
- glucose is used to form cellulose cell walls
- when rate of photosynthesis as higher than the rate of respiration, excess glucose is converted into starch for storage. When photosynthesis stops, starch is converted back to glucose for usage
-Glucose is converted into lipids for storage and the synthesis of cell membranes - glucose is converted to surge for transport to other parts of the plant via the phloem
- glucose reacts with nitrates and other mineral salts from the soil to form amino acids in leaves. Amino acids form proteins for new cellular materials
Photosynthesis makes chemical energy available to animals and other organisms. Explain.
Sunlight is the ultimate source of energy for living organisms. Photosynthesis enables the light energy to be converted into chemical energy which is then stored within the carbohydrate molecules. Fats, proteins and other organic compounds can be formed from carbohydrates. All these substances eventually become the food of other organisms. All living things thus obtain chemical energy directly or indirectly from plants.
Photosynthesis removes carbon dioxide and provides energy. Explain.
Photosynthesis removes carbon dioxide from the air and at the same time, produces oxygen. The oxygen released is used by living organisms in aerobic respiration to release energy for cell activities. This also maintains a constant level of oxygen and carbon dioxide in the atmosphere, to maintain a balanced ecosystem and prevent global warming, which is caused by disruptions to the carbon cycle.
Energy is stored in fossil fuels through photosynthesis. Explain.
All the energy in fossil fuels like coal, oil and gas, came from the sun, captured through photosynthesis. Burning of fossil fuel releases energy for human activities.
Effects of temperature on rate of photosynthesis
- photosynthesis is dependent on temperature as it is catalysed by enzymes
- when temperature increases, kinetic energy increases which increases the frequency of effective collisions between photosynthetic enzymes and substrates, thus increasing the rate of photosynthesis
-As the enzymes approach their optimum temperature, the overall rate of photosynthesis reaches a maximum - when the temperature increases beyond the enzymes’ optimum temperature, the rate of photosynthesis decreases until it stops. Enzymes are denatured
Effect of carbon dioxide concentration on rate of photosynthesis
- An increase in the carbon dioxide concentration increases the rate of photosynthesis up to a certain point
- beyond this point, when the concentration of carbon dioxide increases, the rate of photosynthesis remains constant
- this is because the rate of photosynthesis is limited by another factor such as light intensity or temperature. Carbon dioxide Is no longer the limiting factor
Effects of light intensity on rate of photosynthesis
- As light intensity increases, the rate of photosynthesis increases proportionately. During this period, light intensity is the limiting factor
-As light intensity increases beyond a certain point, the rate of photosynthesis remains constant. The rate of photosynthesis is limited by some other factor such as temperature and carbon dioxide concentration. - compensation point: the point where rate of photosynthesis equals the rate of respiration
- as the light intensity increases during the morning and fades during the evening, there will be a time when the rate of photosynthesis exactly equals the rate of respiration
- at this point, there will be no net intake or output of carbon dioxide or oxygen, this is known as the compensation point
- the glucose produced by photosynthesis exactly compensates for the glucose broken down by respiration
why is water not the limiting factor?
water is not a limiting factor because less than 1% of the water taken up is used for photosynthesis. However, it can affect the rate of photosynthesis indirectly by closing the stomata, which limits the intake of carbon dioxide.
