Question

Comparing the physiological differences between C4, CAM and C3 plants, explain the reasons that C4 and CAM plants tend to be found more at low latitudes than at higher latitudes.

Answer 1

The physiological differences between the C3, C4 and CAM plants are as follows:

C3 Plants	C4 Plants	CAM Plants
When the photosynthetic plants produce 3-phosphoglyceric acid (PGA) or 3- carbon acid as the first product during CO2 fixation is called C3 pathway.	When the photosynthetic plant, prior going to the C3 pathway, produces oxaloacetic acid (OAA) or 4 -carbon compound as their first stable product is called as C4 or Hatch and Slack pathway.	When the plants absorb the energy of the sunlight at the day time and use this energy for the assimilation or fixing the carbon dioxide at night time is called as crassulacean acid metabolism or CAM.
Photorespiration is present in the higher rate	Photorespiration is not easily found	Photorespiration is detectable during the day
Optimum temperature required for photosynthesis is 15-25 °C	Optimum temperature required for photosynthesis is 30-40 °C	Optimum temperature required for photosynthesis is greater than 40 °C
Cells involved are mesophyll cells	Cells involved are both mesophyll cells and bundle sheath cells	Both C3 and C4 occurs in mesophyll cells
Stomata open during day	Stomata open during day	Stomata open during night
Mesophytic, hydrophytic, xerophytic	Mesophytic,	Xerophytic

Some plants follow the C4 or Hatch and Slack pathway before Calvin or C3 cycle. Plants, especially in the tropical region, follow this pathway. It is a two step process where Oxaloacetic acid (OAA) which is a 4-carbon compound is produced. When the 4-carbon compound is produced, it is sent to the bundle sheath cell, here the 4-carbon molecule further get splits into a carbon dioxide and the 3-cabon compound. Eventually, the C3 pathway starts to produce energy, where the 3-carbon compound act as the precursor. It occurs in mesophyll and bundle sheath cell present in a chloroplast. C4 plants are also known as warm-season or tropical plants. These can be perennial or annual.The perfect temperature to grow for these plants is 30-40 °C .

Cu Path way 4 PEP PEP o naloacetate 4 carbonylase I LAMP+PPi Malate ATP+ Pi Mesophyel cele Pyruvate Bundle Sheath Cell rubisco Calvin cycle Sugars

Some plants that are adapted to dry environments use the crassulacean acid metabolism (CAM) pathway to minimize photorespiration. At night, CAM plants open their stomata, allowing CO_2​ to diffuse into the leaves. This CO₂ is fixed into oxaloacetate by PEP carboxylase then converted to malate or another type of organic acid.

The organic acid is stored inside vacuoles until the next day. In the daylight, the CAM plants do not open their stomata, but they can still photosynthesize. That's because the organic acids are transported out of the vacuole and broken down to release CO₂​ that enters the Calvin cycle. This controlled release maintains a high concentration of CO₂ around rubisco.

Plant species that use CAM photosynthesis not only avoid photorespiration, but are also very water-efficient. Their stomata only open at night, when humidity tends to be higher and temperatures are cooler, both factors that reduce water loss from leaves. CAM plants are typically dominant in very hot, dry areas, like deserts.

CAM Pathway co2 PEP PEP carbonytala Onaloacetate Malate & rubisce Calvin cycle sugars Mesophyel cell

Thats why, C4 and CAM plants tend to be found more at low latitudes than at higher latitudes.