Which element is located at the centre of the porphyrin ring in chlorophyll ? 
A non ionic Mg atom is held in the centre of porphyrin (of chlorophyll) held by N atom of pyrrole ring.
Which fractions of the visible spectrum of solar radiations are primarily absorbed by carotenoids of the higher plants? 
Carotenoids are a group of yellow, red and orange pigments which function as acessary pigments and protect chlorophyll molecules from destruction by intensive light rays. Carotenoids have three absorption peaks in the blue-violet range of the spectrum.
Which one of the following is wrong in relation to photorespiration ? 
Tropical plants have evolved C4 cycle to overcome photorespiration.
In C3 plants, the first stable product of photosynthesis during the dark reaction is 
3-phosphoglyceric acid, 3 carbon compound is the first product formed in the C3 cycle. It is then converted to glyceraldehyde 3-phosphate. Oxaloacetic acid, 4 carbon compound is the first product formed in C4 cycle. It is then converted to malic acid.
Plants adapted to low light intensity have 
The Proteinaceous Photosynthetic unit (PSU) size increases as light levels decline. At lower light levels, chloroplasts have larger PSU to increase the probability that a photon will strike the chlorophyll antenna. So, plants adapted to low light intensity have larger photosynthetic unit size than the sun plants. Plants adapted to low light intensity does not have a higher rate of CO2 fixation, more extended root system and leaves are not modified to spines.
As compared to a C3 – plant, how many additional molecules of ATP are needed for net production of one molecule of hexose sugar by C4 – plants: 
Equation for C4 pathway 6 PEP + 6 RuBP + 6CO2 + 30 ATP + 12 NADPH 6PEP + 6 RuBP + C6H12O6 + 30 ADP + 30 H3PO4 + 12 NADP+
The net reaction of C3 dark fixation is 6RuBP + 6CO2 + 18ATP + 12 NADPH 6 RuBP + C6H12O6 + 18 ADP + 18 P + 12 NADP+
Chlorophyll in chloroplasts is located in: 
Internally a chloroplast contains a matrix or stroma which is similar to cytoplasm in its constitution. It contains DNA, RNA, ribsomes, enzymes for CO2 assimilation, proteins, starch grains and fat droplets or plastoglobuli.
In the matrix or stroma embedded a number of flattened membranous sacs called thylakoids or lamellae. At places the thylakoids are aggregated to form stacks called grana.
Photosynthesis in C4 plants is relatively less limited by atmospheric CO2 levels because:
The fixation of CO2 in C4 -plants takes place in two places and by two different organic compounds. Phosphoenol Pyruvate (PEP) is found in mesophyll cells which primarily fixes atmospheric CO2 into oxalo acetic acid (4C).
RuBisCO is present in bundle sheath cells where final fixation of CO2 in hexose sugars takes place. CO2 is primarily fixed by PEP carboxylase because this enzyme has greater affinity to CO2 than RuBisCO.
In photosystem-1the first electron acceptor is 
In photosystem I or photoact I electrons released by P-700 are accepted by a substance of iron-sulphur-protein complex denoted as A(FeS). A(FeS) is thus reduced and it passes these high electrons to oxidised ferredoxin and it gets reduced. From reduced Fd these electrons are passed to FAD which now reduced to FADH2 and then electrons and hydrogen are accepted by NADP which makes NADPH2. Here photosystem I end.
During photorespiration, the oxygen consuming reaction(s) occur in 
The first reaction of photorespiration occur in stroma of chloroplast. In this reaction the RuBP(Ribulose 1-5 biphosphate) consume one oxygen molecule in presence of enzyme Rubisco.
In peroxisome the glycolate transferred from chloroplast takes up O2 and formed the glyoxylate whereas the H2O2 release as byproduct.
The first acceptor of electrons from an excited chlorophyll molecule of photosystem II is 
The first acceptor of electrons from an excited chlorophyll of PSII is quinone.
In the leaves of C4 plants, malic acid formation during CO2 fixation occurs in the cells of 
In C4 plants, C4 cycle occurs in mesophyll cells and C3 - cycle occurs in a bundle sheath.
The wavelength of light absorbed by Pr form of phytochrome is 
The Pr form absorbs light between 660 to 680 nm and absorbs at a peak of 666 nm. It is the form synthesized in darkgrown seedlings. When Pr absorbs red light, it is converted to the Pfr form.
The C4 plants are photosynthetically more efficient than C3 plants because:
Based on metabolic activities in plants, they are broadly classified into CAM, C3, C4, etc. These are pathways for carbon fixation during photosynthesis.
In C3 plants, chloroplasts are not present in the bundle sheath cells. Whereas, it is present in C4 plants.
Also, In C4 plants, photosynthesis occurs even when pores called stomata are closed.
C4 plants show high efficiency in photosynthesis than the C3 plants because they contain more chloroplasts.
Electrons from excited chlorophyll molecule of photosystem II are accepted first by: 
Electrons from excited chlorophyll molecule of photosystem II are accepted first by Quinone. Photosystem II is a photosynthetic pigment system along with some electron carriers that is located in the appressed part of the grana thylakoids. Photosystem II has chlorophyll a, b and carotenoids. Other components of PS II are phaeophytin, plastoquinone (PQ), cytochrome complex and blue coloured copper containing plastocyanin.
In leaves of C4 plants malic acid synthesis during CO2 fixation occurs in 
In leaves of C4 plants, malic acid synthesis during CO2 fixation occurs in mesophyll cells. The mesophyll cells perform C4 cycle and the cells of bundle sheath perform C3 cycle. CO2 taken from the atmosphere is accepted by phosphoenol pyruvic acid (PEP) present in the chloroplasts of mesophyll cell of these leaves, leading to the formation of a 4-C compound, oxaloacetic acid (OAA). This acid is converted to another 4-C acid, the malic acid which enters into the chloroplast of bundle sheath cells and these undergoes oxidative decarboxylation yielding pyruvic acid (3C - compound) and CO2.
Importance of day length in flowering of plants was first shown in 
Photoperiodism was first studied by Garner and Allard (1920). They observed that “Maryland Mammoth” variety of tobacco could be made to flower in summer by reducing the light hours with artificial darkening. It could be made to remain vegetative in winter by providing extra light.
Oxygenic photosynthesis occurs in: 
Oxygenic photosynthesis occurs in Oscillatoria. Oscillatoria is a genus of filamentous cyanobacteria which is named for the oscillation in its movement.
Cyclic photophosphorylation results in the formation of 
Cyclic photophosphorylation results in the formation of ATP. This process is called photophosphorylation, which occurs in two different ways. Adenosine triphosphate (ATP) is considered by biologists to be the energy currency of life. It is the high-energy molecule that stores the energy we need to do just about everything we do. It is present in the cytoplasm and nucleoplasm of every cell, and essentially all the physiological mechanisms that require energy for operation obtain it directly from the stored ATP.
PGA as the first CO2 fixation product was discovered in photosynthesis of : 
Phosphoglyceric and (PGA) is the first stable product of photosynthesis. It was first discovered by Calvin, Benson and their colleagues in Chlorella, algae.
Photoperiodism was first characterised in: 
Photoperiodism is the response to duration and timings of light and dark period. It was first characterised in tobacco plant.
C4 plants are more efficient in photosynthesis than C3 plants due to: 
In C3 plants, CO2 is pumped directly into the Calvin cycle, leaving rubisco exposed to O2. Rubisco in a C3 will take up O2 rather than CO2 to undergo photorespiration. Photorespiration occurs under low concentrations of CO2 and high concentrations of O2. This process reduces efficiency of photosynthesis, potentially reducing photosynthetic output by 25% in C3 plants. C4 plants capture carbon dioxide in their mesophyll cells forming oxaloacetate. This oxaloacetate is then converted to malate and is transported into the bundle sheath cells, where oxygen concentration is low to avoid photorespiration. So, C4 plants are more efficient in photosynthesis than C3 plants.
Of the total incident solar radiation the proportion of PAR is : 
Out of total incident solar radiation, about 50% of it forms Photosynthetically Active Radiation (PAR).
CAM helps the plants in : 
CAM plants are most common in arid environments. Being able to keep stomata closed during the hottest and driest part of the day reduces the loss of water through evapotranspiration.
A process that makes important difference between C3 and C4 plants is : 
Photorespiration is absent is C4 plants. Photorespiration does not produce energy or reducing power. Rather, it consumes energy. Further, it undoes the work of photosynthesis. There is 25% loss of fixed CO2. Therefore, photorespiration is a highly wasteful process. This happens only in case of C3 plants.
The correct sequence of cell organelles during photorespiration is : 
Pigment-containing membranous extensions in some cyanobacteria are : [NEET 2013]
In some photo auto trophic bacteria bacteriochlorophyll and bacteriophaeophytin or bacterioviridin pigments containing membraneous extensions called chromatophores are present. These are sites of bacterial photosynthesis .
Bundle sheath cells [NEET Kar. 2013]
In C4 plants, bundle sheath cells are rich in RuBisCO, but lack PEPcase. The CO2 released in the bundle sheath cells enters the C3 or the Calvin pathway, common to all plants. Thus, the basic pathway that results in the formation of sugars, the calvin pathway is common to the C3 and C4 plants.