LECTURE OBJECTIVES
• What’s photosynthesis
• Reasons for studying photosynthesis.
• Location(structure) of photosynthesis in plants
• Processes of Hill reactions or photolysis.
• Light and Dark reaction (Calvin cycle)
• Stabilization and storage of chemical potentials of photosynthesis.
• Link between photosynthesis and other metabolic processes in
plants.
CONTENT
CONCEPT OF PHOTOSYNTHESIS
Studying photosynthesis is crucial in crop science because it directly impacts
crop yield and overall food production. Understanding how plants convert light
energy into chemical energy (photosynthesis) is essential for developing
strategies to enhance crop productivity, improve resource use efficiency, and
ensure food
security.
Here's why it's important:
Crop Yield:
, •
• Photosynthesis is the primary driver of biomass production in crops. The
efficiency of this process directly influences how much grain, fruit, or other
harvestable product a plant produces.
For example, growing plants in an environment with elevated carbon dioxide
levels can stimulate photosynthesis.
• One approach to improve crop yield is to enhance Rubisco's efficiency by
increasing its ability to bind carbon dioxide and decreasing its binding to oxygen.
This can be achieved through genetic modifications or by introducing enzymes
that can help recycle carbon from photorespiration more efficiently.
• A recent study showed that overexpressing Rubisco in paddy rice led to a 17-
28% increase in yield when nitrogen was available.
Food Security:
• With a growing global population, increasing crop yields is vital to meet the
demand for food. Improving photosynthetic efficiency offers a path to enhance
food production sustainably.
• One example of how photosynthesis research is impacting food security in crop
science is the work on manipulating the photo respiratory pathway in crops like
rice and tobacco.
• By engineering plants to bypass certain steps in photorespiration, scientists have
observed increased biomass and grain yield in these crops. This approach,
, •
among others, offers promising avenues for boosting food production and
ensuring food security in the future.
Improving the efficiency of the Calvin cycle, where carbon dioxide is fixed into
sugars, and manipulating the activity of Rubisco, a key enzyme in the cycle, is
crucial in maintaining food security as well.
Resource Use Efficiency:
• Photosynthesis is linked to how efficiently plants use resources like water
and nutrients. By optimizing photosynthesis, it may be possible to develop
crops that are more drought-tolerant or require less fertilizer, reducing
environmental impact.
• For example, changes in leaf thickness and angle can influence light capture and
distribution within the canopy, impacting overall photosynthetic efficiency. Thicker
leaves can have more photosynthetic biomass per unit area.
• Rubisco (Ribulose 1,5-bisphosphate carboxylase-oxygenase), the enzyme
that fixes carbon dioxide, can be modified to improve its catalytic rate or reduce
its oxygenase activity (photorespiration), which reduces photosynthetic efficiency.
• Researchers use biotechnology tools and genetic engineering to improve
photosynthesis by changing the structure or function of Rubisco.
• One method is called chloroplast transformation and involves modifying the
chloroplast genome by inserting foreign genes.
, •
• Using these methods, researchers have produced new varieties of tobacco with
modified Rubisco and observed how these changes impact the plant's growth
and development.
Current research involves manipulating the genes that encode for Rubisco
to allow researchers to test theories about photosynthesis and develop
plant mutants that have more efficient photosynthesis.
• Selecting or genetically modifying plants to be more drought-tolerant can help
them maintain photosynthetic activity under water-limited conditions. This can
involve traits like deeper root systems, reduced transpiration rates, or more
efficient stomatal control.
Climate Change Mitigation:
• Photosynthesis also plays a role in regulating the Earth's climate by absorbing
carbon dioxide from the atmosphere. Understanding how to enhance this process
in crops could contribute to carbon sequestration efforts.
• For example, in carbon sequestration, plants absorb atmospheric CO2 during
photosynthesis and store it as biomass (e.g., leaves, stems, roots).
• This process effectively removes CO2 from the atmosphere, reducing its
concentration and the associated greenhouse effect.
Breeding for Improved Traits:
• What’s photosynthesis
• Reasons for studying photosynthesis.
• Location(structure) of photosynthesis in plants
• Processes of Hill reactions or photolysis.
• Light and Dark reaction (Calvin cycle)
• Stabilization and storage of chemical potentials of photosynthesis.
• Link between photosynthesis and other metabolic processes in
plants.
CONTENT
CONCEPT OF PHOTOSYNTHESIS
Studying photosynthesis is crucial in crop science because it directly impacts
crop yield and overall food production. Understanding how plants convert light
energy into chemical energy (photosynthesis) is essential for developing
strategies to enhance crop productivity, improve resource use efficiency, and
ensure food
security.
Here's why it's important:
Crop Yield:
, •
• Photosynthesis is the primary driver of biomass production in crops. The
efficiency of this process directly influences how much grain, fruit, or other
harvestable product a plant produces.
For example, growing plants in an environment with elevated carbon dioxide
levels can stimulate photosynthesis.
• One approach to improve crop yield is to enhance Rubisco's efficiency by
increasing its ability to bind carbon dioxide and decreasing its binding to oxygen.
This can be achieved through genetic modifications or by introducing enzymes
that can help recycle carbon from photorespiration more efficiently.
• A recent study showed that overexpressing Rubisco in paddy rice led to a 17-
28% increase in yield when nitrogen was available.
Food Security:
• With a growing global population, increasing crop yields is vital to meet the
demand for food. Improving photosynthetic efficiency offers a path to enhance
food production sustainably.
• One example of how photosynthesis research is impacting food security in crop
science is the work on manipulating the photo respiratory pathway in crops like
rice and tobacco.
• By engineering plants to bypass certain steps in photorespiration, scientists have
observed increased biomass and grain yield in these crops. This approach,
, •
among others, offers promising avenues for boosting food production and
ensuring food security in the future.
Improving the efficiency of the Calvin cycle, where carbon dioxide is fixed into
sugars, and manipulating the activity of Rubisco, a key enzyme in the cycle, is
crucial in maintaining food security as well.
Resource Use Efficiency:
• Photosynthesis is linked to how efficiently plants use resources like water
and nutrients. By optimizing photosynthesis, it may be possible to develop
crops that are more drought-tolerant or require less fertilizer, reducing
environmental impact.
• For example, changes in leaf thickness and angle can influence light capture and
distribution within the canopy, impacting overall photosynthetic efficiency. Thicker
leaves can have more photosynthetic biomass per unit area.
• Rubisco (Ribulose 1,5-bisphosphate carboxylase-oxygenase), the enzyme
that fixes carbon dioxide, can be modified to improve its catalytic rate or reduce
its oxygenase activity (photorespiration), which reduces photosynthetic efficiency.
• Researchers use biotechnology tools and genetic engineering to improve
photosynthesis by changing the structure or function of Rubisco.
• One method is called chloroplast transformation and involves modifying the
chloroplast genome by inserting foreign genes.
, •
• Using these methods, researchers have produced new varieties of tobacco with
modified Rubisco and observed how these changes impact the plant's growth
and development.
Current research involves manipulating the genes that encode for Rubisco
to allow researchers to test theories about photosynthesis and develop
plant mutants that have more efficient photosynthesis.
• Selecting or genetically modifying plants to be more drought-tolerant can help
them maintain photosynthetic activity under water-limited conditions. This can
involve traits like deeper root systems, reduced transpiration rates, or more
efficient stomatal control.
Climate Change Mitigation:
• Photosynthesis also plays a role in regulating the Earth's climate by absorbing
carbon dioxide from the atmosphere. Understanding how to enhance this process
in crops could contribute to carbon sequestration efforts.
• For example, in carbon sequestration, plants absorb atmospheric CO2 during
photosynthesis and store it as biomass (e.g., leaves, stems, roots).
• This process effectively removes CO2 from the atmosphere, reducing its
concentration and the associated greenhouse effect.
Breeding for Improved Traits:
