- bundle sheath cells do not contain chloroplasts; - carbon fixation and Calvin Cycle reactions occur in mesophyll cells - (and in the presence of oxygen). - more adapted to environments with more carbon dioxide.
In C4 plants,
- the bundle sheath cells contain chloroplasts; - carbon is fixed in mesophyll cells too, then transported to bundle sheath cells where - Calvin Cycle reactions occur in the absence of oxygen. - more adapted to environments with more oxygen
In both, photosynthesized sugars then enter the plant's vascular system.
C4 have a concentric arrangement of the bundle sheath and mesophyll layer, the bundle sheath is also thicker.
Another difference is their intervenial distances, from one bundle sheath to another you have in C4 only around 4 mesophyll cells but on 3 they are separated by 12.
C3 Photosynthesis : C3 plants.
• Called C3 because the CO2 is first incorporated into a 3-carbon compound.
• Stomata are open during the day.
• RUBISCO, the enzyme involved in photosynthesis, is also the enzyme involved in the uptake of CO2.
• Photosynthesis takes place throughout the leaf.
• Adaptive Value: more efficient than C4 and CAM plants under cool and moist conditions and under normal light because requires less machinery (fewer enzymes and no specialized anatomy)..
• Most plants are C3.
C4 Photosynthesis : C4 plants.
• Called C4 because the CO2 is first incorporated into a 4-carbon compound.
• Stomata are open during the day.
• Uses PEP Carboxylase for the enzyme involved in the uptake of CO2. This enzyme allows CO2 to be taken into the plant very quickly, and then it "delivers" the CO2 directly to RUBISCO for photsynthesis.
• Photosynthesis takes place in inner cells (requires special anatomy called Kranz Anatomy)
• Adaptive Value: o Photosynthesizes faster than C3 plants under high light intensity and high temperatures because the CO2 is delivered directly to RUBISCO, not allowing it to grab oxygen and undergo photorespiration.
o Has better Water Use Efficiency because PEP Carboxylase brings in CO2 faster and so does not need to keep stomata open as much (less water lost by transpiration) for the same amount of CO2 gain for photosynthesis.
• C4 plants include several thousand species in at least 19 plant families. Example: fourwing saltbush, corn, and many of our summer annual plants.
Examples: C3----->wheat, barley, potatoes and sugar beet. (most of the plants are C3) C4----->fourwing saltbush, corn ,many of summer annual plants. CAM---> cactuses, aloe vera, some orchids and bromeliads (required less water)
The most significant difference between primary and accessory pigments is that they absorb and give off light at different wavelengths.
When photons of light hit a leaf, they have a specific wavelength. Chlorophyll has a specific wavelength that it can absorb and give off light as. If chlorophyll was the only pigment a plant had, it could only use light that was of this particular wavelength. However, the presence of accessory pigments allows the plant to use light of all wavelengths.
Primary and accessory pigments also vary in color. Chlorophyll is green, while others are different. Carotenoids can be red, yellow or orange. Photosynthetic aquatic organisms like cyanobacteria also have phycobilins.
1.Primary pigments:
primary pigmentsIn photosynthesis, pigments that emit electrons which directly drive the photosynthetic reactions.
In green plants there are two primary pigments,
both of which are forms of Chorophyll a: P680 and P700.
2.Accessory pigments:
a pigment in plants that can absorb light energy and pass the electrons along to the primary pigment which starts the process of photosynthesis.
In the flowering plants (angiosperms),
chlorophylls a and b provide the green color and absorb the light energy needed for photosynthesis.
However, other accessory pigments, such as yellow xanthophylls and orange carotenes are also present in the chloroplasts and collect additional light energy for photosynthesis.
All plants, algae, and cyanobacteria which photosynthesize contain chlorophyll "a".
A second kind of chlorophyll is chlorophyll "b", which occurs only in green algae and in the plant.
Carotenoids act as \"SHIELD PIGMENTS\" as they are located over the chlorophylls thus protecting them from photo-oxidation and photo-bleaching. (antioxidants)
Phycobilins are water-soluble pigments, and are therefore found in the cytoplasm, or in the stroma of the chloroplast. They occur only in Cyanobacteria and Rhodophyta.
Bonded to certain water-soluble proteins, ‘Phycobiliproteins’ then pass the light energy to chorophyll for photosynthesis.
The phycobilins are especially efficient at absorbing red, orange, yellow and green light, wavelengths which are not well absorbed by chlorophyll a. Organisms growing in shallow waters tend to contain phycobilins that can capture yellow/red light, while those at greater depth often contain more of the phycobilins that can capture green light, which is relatively more abundant there.
