Oserve the diagram and answer the following.
(a) Which group of plants exibit these two types of cells?
(b) What is the first product of $\mathrm{C}_4$ cycle?
(c) Which enzyme is there in bundle sheath cells and mesophyll cells?
(a) Monocot plants belonging to Graminae/Poaceae family, e.g., sugarcane, maize etc., possess these two types of cells. i.e., bundle sheath and mesophyll cell (in kranz anatomy).
(b) A 4-carbon compound oxaloacetic acid is the first product of $\mathrm{C}_4$ cycle.
(c) Mesophyll cells have PEP carboxylase to fix atmospheric $\mathrm{CO}_2$ to form a 4-carbon compound oxalo acetic acid, whereas bundle sheath cells have RuBP carboxylase which fix $\mathrm{CO}_2$ by this enzyme to form 3-carbon compound 3 PGA (3 phosphoglyceric acid).
A cyclic process is occurring in $C_3$ plant, which is light dependent and needs $\mathrm{O}_2$. This process doesn't produce energy rather it consumes energy.
(a) Can you name the given process?
(b) Is it essential for survival?
(c) What are the end products of this process?
(d) Where does it occur?
(a) Photorespiration is the process, which do not produce energy rather consum it.
(b) It is not needed for the survival of $\mathrm{C}_3$ plant.
(c) The end product of this process is $\mathrm{H}_2 \mathrm{O}_2$.
(d) This process involves three cell organelles of the plant cell.
(i) Chloroplast (ii) Peroxisome (iii) Mitochondria
Suppose Euphorbia and maize are grown in the tropical area.
(a) Which one of them do you think will be able to survive under such conditions?
(b) Which one of them is more efficient in terms of photosynthetic activity?
(c) What difference do you think are there in their leaf anatomy?
(a) Euphorbia is a CAM plant. It fixes $\mathrm{CO}_2$ during night and uses it in day time. It will be able to survive in hot tropical climate.
(b) Maize being a $\mathrm{C}_4$ plant is more efficient in terms of photosynthetic activity as it is able to use $\mathrm{CO}_2$ at lower level as well as high $\mathrm{O}_2$ and temperature.
(c) Maize plants show kranz anatomy in their leaves. They have granal chloroplast in mesophyll cells and agranal in bundle sheath cells. Euphorbia does not have $\mathrm{C}_4$ cycle so kranz anatomy is not found in them.
Photosynthesis is a process which mainly occurs in leaves of all green plants. The plants have designed their leaf in such a way that it is able to trap solar radiation and effectively convert solar/light energy to chemical energy. But biology is science of exceptions. Some plants carry out photosynthesis in modified plant parts other then leaves.
Few examples are as follows
1. Root as Photosynthetic Organ
When roots develop chlorophyll and start photosynthesis, they are called assimilitory roots. Trapa and Tinospora are the examples of assimilatory roots.
2. Stem as Photosynthetic Organ
In Opuntia, the stem gets modified to take up the function of leaves. It becomes flattened, thick and succulent and perform photosynthesis. Such structures are called phylloclade.
3. Petiole as Photosynthetic Organ In Australian Acasia the petiole takes the shape and function of photosynthesis because leaf lamina soon falls off.
The entire process of photosynthesis consists of a number of reactions. Where in the cell do each of these take place?
(a) Synthesis of ATP and NADPH ............ .
(b) Photolysis of water ............ .
(c) Fixation of $\mathrm{CO}_2$ ............
.(d) Synthesis of sugar molecule ............ .
(e) Synthesis of starch ............ .
(a) Synthesis of ATP and NADPH takes place in outer side of thylakoid membrane.
(b) Photolysis of water occurs in inner side of thylakoid membrane.
(c) Fixation of $\mathrm{CO}_2$ occurs in stroma of chloroplast.
(d) Synthesis of sugar molecule occurs in chloroplast.
(e) Synthesis of starch occurs in cytoplasm.