Photosynthesis in Higher Plants Test - 56

A) $${ C}_{ 4 }$$ pathway occurs in relatively low $${ CO }_{ 2 }$$ concentration as carbon dioxide is recycled and not wasted.

Correct Option: C

In electron transport process the excited electron from PS II to Pheophytin is accepted by primary acceptor quinone, which sends them to an electron transport system consisting of plastoquinone(PQ), cytochrome complex and plastocyanin(PC).

The excited electron absorbed by PS I reaction centre, then transfer to the ferredoxin (Fe), then the reduced Ferredoxin donates the electron to NADP$$^+$$.

Hence, the correct answer is 'iii,ii,i,iv'

This plant is a $$C_{4}$$ plant. $$C_{4}$$ plants are special as they have a special type of leaf anatomy called Kranz Anatomy. They can tolerate higher temperatures, they show a response to high intensities of light, they lack a wasteful process called photorespiration and they have improved efficiency of nitrogen utilization. Most of the plants that are adapted to dry tropical regions have the $$C_{4}$$ pathway and are known as $$C_{4}$$ plants. In these plants, double fixation of carbon dioxide occurs.

Chlorophyll a absorbs violet, blue and red wavelengths of light and reflects green wavelength of light. It contains photoreceptor for red and blue light. The percentage of blue and red wavelengths of light absorbed by it is 40% : 30%.

C$$_4$$ plants have Kranz leaf anatomy. The vascular bundles in these leaves are surrounded by a layer of bundle sheath cells that contain a large number of chloroplasts.

The chloroplasts in these leaves are dimorphic:

Bundle sheath- Chloroplast larger in size and arranged centripetally. It has unstacked thylakoids called agranal chloroplast. The cells perform C$$_3$$ cycle.

Mesophyll cells- Normal type of chloroplast. It has stacked thylakoids called granal chloroplast. The cells perform C$$_4$$ cycle.

Hence, the correct answer is 'They do not show granal organisation'.

The sites of photorespiration are chloroplast, peroxisome and mitochondria. Lysosomes are a part of emdomembrane system which have several contain several hyrolytic enzymes.

Photo-respiratory reactions occur during the process of photorespiration. It is a process which involves loss of fixed carbon as $$CO_{2}$$ in plants in the presence of light. It is initiated in chloroplasts. This process does not produce ATP or NADPH and is a wasteful process. Photo-respiratory reactions are operated in chloroplasts, mitochondria, and peroxisomes. Loss of $$CO_{2}$$ occurs in mitochondria. Photorespiration occurs usually when there is the high concentration of oxygen. Under such circumstances, RuBisCO, the enzyme that catalyzes the carboxylation of RuBP during the first step of Calvin cycle, functions as an oxygenase. Some $$O_{2}$$ does not bind to RuBisCO and hence $$CO_{2}$$ fixation is decreased. The RuBP binds with $$O_{2}$$ to form one molecule of PGA (3C compound) and phosphoglycolate (2C compound) in the pathway of photorespiration. There is neither the synthesis of sugar nor of ATP. Rather, it results in the release of $$CO_{2}$$ with the utilization of ATP. It leads to a 25 percent loss of the fixed $$CO_{2}$$. $$O_{2}$$ is first utilized in chloroplasts and then in peroxisomes.

Chlorophyll- a:

A) It releases oxygen during the day as it is a $${ C }_{ 3 }$$ plant.