12-botany-unit-v & VI Plant Physiology & Biology In Human Welfare

Chlorophyll 'a' is regarded as the primary pigment because it is the main pigment responsible for capturing light energy during photosynthesis. It absorbs light in the red and blue regions of the electromagnetic spectrum and reflects green light, giving plants their characteristic green color. Chlorophyll 'b', carotenoids, and xanthophylls are also pigments involved in photosynthesis, but they play secondary roles and assist chlorophyll 'a' in capturing light energy.

Auxin was the first plant hormone to be discovered. In the 1920s, scientists observed that when the tip of a plant shoot was removed, the plant would stop growing. They hypothesized that there must be a substance produced at the tip that promoted growth. This substance was later identified as auxin. Further research revealed that auxin plays a crucial role in various plant processes such as cell elongation, root formation, and tropisms. Its discovery paved the way for further investigations into plant hormones and their functions.

Melvin Calvin is credited with discovering the dark reactions of photosynthesis. In the 1950s, Calvin and his team conducted experiments using radioactive carbon to trace the pathway of carbon dioxide in photosynthesis. Through their research, they were able to elucidate the series of chemical reactions that occur in the dark reactions, also known as the Calvin cycle. This cycle is responsible for converting carbon dioxide into glucose, the primary energy source for plants. Calvin's discovery was a significant contribution to our understanding of photosynthesis and earned him the Nobel Prize in Chemistry in 1961.

The correct answer is Hatch-Slack pathway. The Hatch-Slack pathway, also known as the C4 pathway, is a photosynthetic process that is found in certain plants. It is named after the scientists Marshall Davidson Hatch and Charles Roger Slack who first described it. This pathway is an alternative carbon fixation pathway that allows plants to minimize photorespiration and increase their efficiency in hot and dry conditions. It involves the initial fixation of CO2 into a four-carbon compound, which is then transported to specialized cells where it is decarboxylated to release CO2 for the Calvin cycle.

Magnesium (Mg) is the essential component for the formation of chlorophyll. Chlorophyll is a pigment found in plants and is responsible for capturing light energy during photosynthesis. Magnesium is a central atom in the chlorophyll molecule and plays a crucial role in converting light energy into chemical energy. It is required for the synthesis of chlorophyll molecules, and without magnesium, plants would not be able to produce chlorophyll and carry out photosynthesis effectively.

Drosera is an example of an insectivorous plant because it is commonly known as the sundew plant, which has leaves covered in sticky hairs that trap and digest insects. This plant obtains nutrients from the insects it captures, supplementing its diet as it typically grows in nutrient-poor environments. The other options, Viscum, Monotropa, and Vanda, are not insectivorous plants.

Acalyphine is extracted from Acalypha indica.

Nitrosomonas is the correct answer because it is a type of bacterium that is known to oxidize ammonia to nitrate. This process is called nitrification and is an important step in the nitrogen cycle. Nitrosomonas converts ammonia, which is toxic to many organisms, into nitrite, and then other bacteria convert the nitrite into nitrate. Nitrate is a form of nitrogen that can be used by plants and other organisms as a nutrient.

Ethylene is a gaseous hormone that is involved in various physiological processes in plants. It is known for its role in fruit ripening, leaf senescence, and the regulation of plant growth and development. Ethylene is produced in response to various stimuli such as stress, injury, and environmental cues. Once produced, it can diffuse through the air and affect neighboring plants or tissues. Therefore, ethylene is considered a gaseous hormone.

Carbohydrates are the common respiratory substrate because they are the primary source of energy for cellular respiration. When carbohydrates are broken down through various metabolic pathways, such as glycolysis and the citric acid cycle, they release energy in the form of ATP. This ATP is then used by cells for various physiological processes, including muscle contraction and active transport. Therefore, carbohydrates play a crucial role in providing energy for cellular respiration and are considered the common respiratory substrate.

Ribose is a five carbon compound. It is a monosaccharide and a key component of RNA molecules. It is a pentose sugar, meaning it has five carbon atoms in its structure. Ribose is important for the synthesis of nucleotides and plays a crucial role in genetic processes.

Apical dominance refers to the phenomenon where the main, central stem of a plant inhibits the growth of lateral branches. This is due to the presence of auxin, a plant hormone, which is produced in the apical meristem (the growing tip of the plant). Auxin inhibits the growth of lateral buds, promoting the elongation of the main stem. When the apical meristem is removed or damaged, the inhibitory effect of auxin is reduced, allowing lateral buds to grow and develop into branches. Therefore, auxin is responsible for apical dominance in plants.

Photosynthesis is the process by which plants convert sunlight, carbon dioxide, and water into glucose and oxygen. This process occurs in the chloroplasts, which are specialized organelles found in plant cells. Chloroplasts contain a pigment called chlorophyll, which captures the energy from sunlight and uses it to carry out photosynthesis. Mitochondria are responsible for cellular respiration, not photosynthesis. Peroxisomes are involved in various metabolic processes, but not photosynthesis. Ribosomes are responsible for protein synthesis and are not directly involved in photosynthesis. Therefore, the correct answer is chloroplasts.

Chlorophyll is the pigment that is highly efficient in absorbing solar energy. It is responsible for the green color of plants and is essential for photosynthesis, the process by which plants convert sunlight into chemical energy. Chlorophyll molecules are able to absorb light energy from the sun and transfer it to other molecules in the plant, where it is used to produce glucose and oxygen. This high efficiency in absorbing solar energy makes chlorophyll the primary pigment involved in photosynthesis.

Glycolysis is the first step in aerobic respiration. It is the process by which glucose is broken down into pyruvate molecules, producing a small amount of ATP and NADH in the process. This occurs in the cytoplasm of the cell and does not require oxygen. The pyruvate molecules then enter the Krebs cycle, where further ATP and electron carriers are produced. Terminal oxidation refers to the final step in aerobic respiration, where the electron carriers produced in glycolysis and the Krebs cycle are used to generate a large amount of ATP in the presence of oxygen. Cyclic photophosphorylation is a process that occurs in photosynthesis, not aerobic respiration.

2, 4 - D is the correct answer because it is a commonly used herbicide that is effective in controlling broadleaf weeds. It works by mimicking the action of the plant hormone auxin, causing uncontrolled growth in the weeds and eventually leading to their death. This chemical is widely used in agriculture and horticulture to control unwanted plants and weeds in fields and gardens.

RuBP, or ribulose-1,5-bisphosphate, is a 5C compound. It is an important molecule in the Calvin cycle, which is the process by which plants convert carbon dioxide into glucose. RuBP is involved in the initial step of carbon fixation, where it reacts with carbon dioxide to form an unstable 6C compound that eventually breaks down into two molecules of 3-phosphoglycerate. Therefore, RuBP is a 5C compound and is crucial for photosynthesis in plants.

Cuscuta is a total parasite because it lacks chlorophyll and is unable to produce its own food through photosynthesis. Instead, it attaches itself to a host plant and derives all its nutrients and water from the host. This dependency on the host plant for survival classifies Cuscuta as a total parasite.

The dark reaction, also known as the Calvin cycle, is the second stage of photosynthesis. It takes place in the stroma of the chloroplasts and does not require light. During this process, carbon dioxide is converted into glucose using the energy from ATP and NADPH produced in the light-dependent reactions. The Calvin cycle is essential for the synthesis of organic compounds, including glucose, which is used as a source of energy by plants and other organisms. The Krebs cycle and pentose phosphate pathway are metabolic processes that occur in cellular respiration, while photorespiration is a wasteful process that occurs in plants when there is a lack of carbon dioxide.

The correct answer is Maryland Mammoth because it was the first plant in which the photoperiodic response in flowering was observed.

Pyricularia oryzae is the correct answer because it is the pathogen that causes the blast disease of rice. Blast disease is a fungal infection that affects rice plants and can cause significant yield losses. Pyricularia oryzae is the scientific name for the fungus that causes this disease.

One molecule of glucose undergoes complete oxidation in cellular respiration, which results in the release of a large amount of energy. The correct answer is 2900 kJ, as this value represents the approximate total amount of energy released from one molecule of glucose during oxidation.

Hexokinase is the enzyme responsible for phosphorylating glucose to form glucose-6-phosphate. This phosphorylation step is an important regulatory step in glucose metabolism and occurs in many different tissues and cell types. Hexokinase catalyzes the transfer of a phosphate group from ATP to the sixth carbon of glucose, resulting in the formation of glucose-6-phosphate. This phosphorylation step traps glucose within the cell and allows for further processing and utilization of glucose in various metabolic pathways.

The wavelength range of 400 nm to 700 nm is most effective for photosynthesis. This is because it includes the visible light spectrum, which is the range of light that plants can absorb and use for photosynthesis. Within this range, different pigments in the plants, such as chlorophyll, can absorb specific wavelengths of light to drive the photosynthetic process.

The correct answer is Aegle marmelos.

In C3 plants, the light reactions and dark reactions of photosynthesis occur in the mesophyll cells. Mesophyll cells are located in the middle layer of the leaf, where they contain chloroplasts that are responsible for capturing light energy during the light reactions and carrying out the Calvin cycle during the dark reactions. The bundle sheath cells, epidermal cells, and vascular cells do not directly participate in these reactions.

The photosynthetic pigments are located in the thylakoid. Thylakoids are membrane-bound compartments found in the chloroplasts of plant cells. They are stacked together to form structures called grana, where the pigments are embedded. The pigments, such as chlorophyll, capture light energy during photosynthesis and convert it into chemical energy. Therefore, the thylakoid is the correct location for photosynthetic pigments.

During photosynthesis, plants use sunlight, water, and carbon dioxide to produce glucose and oxygen. Oxygen is released as a byproduct of photosynthesis, making it the correct answer.

Aconitase is the correct answer because it catalyzes the conversion of cisaconitic acid into isocitric acid by adding a molecule of water.

Sugarcane is a C4 plant because it uses the C4 photosynthetic pathway. This pathway allows the plant to efficiently fix carbon dioxide and minimize water loss. C4 plants are adapted to hot and dry environments, making sugarcane a suitable example.

Auxin prevents abscission, which is the process of shedding or dropping of leaves, fruits, or flowers from a plant. Auxin promotes cell elongation and inhibits the formation of the abscission zone, a layer of cells that allows for the detachment of plant parts. By inhibiting the formation of the abscission zone, auxin helps to keep plant parts attached to the plant.

Cercospora personata is the pathogen that causes Tikka disease of groundnut. Tikka disease is a fungal disease that affects groundnut plants, causing dark brown lesions on the leaves, stems, and pods. This disease can significantly reduce crop yield and quality. Cercospora personata is the specific fungus responsible for this disease, and it spreads through spores that are carried by wind or rain splashes. Control measures for Tikka disease include crop rotation, use of resistant varieties, and fungicide application.

The correct answer is C2 cycle. Photorespiration is also known as the C2 cycle because it involves the addition of one carbon dioxide molecule to a molecule of ribulose 1,5-bisphosphate (RuBP), resulting in the production of a two-carbon compound called phosphoglycolate. This process occurs in plants when the concentration of carbon dioxide is low and oxygen levels are high, leading to the wasteful consumption of energy and reduction in photosynthetic efficiency.

Abscisic acid is responsible for the closure of stomata. Stomata are small openings on the surface of leaves that allow for gas exchange. When plants experience water stress or drought conditions, abscisic acid is produced and triggers the closure of stomata. This helps to reduce water loss through transpiration and conserve water within the plant. Therefore, abscisic acid plays a crucial role in regulating the water balance of plants and ensuring their survival in challenging environmental conditions.

The correct answer is log phase. In sigmoid curve, the log phase represents the period of rapid growth where the population or system experiences exponential growth. During this phase, the growth rate is at its maximum, and the population size increases rapidly. This phase is characterized by a steep upward slope on the sigmoid curve.

RuBP (ribulose-1,5-bisphosphate) is the acceptor molecule of CO2 in the C3 pathway, also known as the Calvin cycle. It is a 5-carbon compound that combines with CO2 in the first step of the cycle to form an unstable 6-carbon compound. This compound then breaks down into two molecules of 3-phosphoglycerate (PGA), which is further converted into other molecules to produce glucose. Therefore, RuBP is the correct answer as it is the initial acceptor molecule for CO2 in the C3 pathway.

An epiphyte is a type of plant that grows on the surface of another plant, usually a tree, but does not derive nutrients from it. Instead, it obtains nutrients from the air, rain, and debris that accumulate around it. Vanda plants are commonly found growing on trees in tropical regions, making them epiphytes.

Pyruvic acid is converted into acetyl-CoA through a process called oxidative decarboxylation. This reaction is catalyzed by an enzyme called pyruvic dehydrogenase. Pyruvic dehydrogenase removes a carboxyl group from pyruvic acid and produces NADH and CO2 as byproducts. Acetyl-CoA is an important molecule in cellular respiration as it enters the citric acid cycle to generate energy. Therefore, pyruvic dehydrogenase plays a crucial role in the metabolism of glucose.

The respiratory quotient (RQ) is the ratio of carbon dioxide produced to oxygen consumed during cellular respiration. In the case of glucose, the RQ is equal to 1 because glucose is completely oxidized during respiration, producing equal amounts of carbon dioxide and oxygen. Therefore, the correct answer is "unity".

Xylulose phosphate is a 5C compound because it contains a 5-carbon sugar called xylulose. The phosphate group attached to xylulose makes it a phosphorylated compound. This compound is important in various metabolic pathways, such as the pentose phosphate pathway and glycolysis. It plays a role in the production of ribose-5-phosphate, which is used in nucleotide synthesis, and also serves as a precursor for the synthesis of fructose-6-phosphate and glyceraldehyde-3-phosphate.

Auxin prevents abscission, which is the process of shedding or dropping of leaves, fruits, or flowers from a plant. Auxin promotes cell elongation and strengthens the cell walls, preventing the detachment of plant parts. This allows the plant to retain its leaves, fruits, and flowers for a longer period of time.

Foolish seedling disease of rice is caused by gibberellins. Gibberellins are a type of plant hormone that promotes stem elongation and overall plant growth. In the case of rice, an excess of gibberellins leads to elongation of the stem, resulting in a weak and floppy plant that is susceptible to disease. This condition is known as foolish seedling disease.

The complete oxidation of one molecule of glucose yields 38 ATP. This is because during cellular respiration, glucose is broken down through a series of reactions, such as glycolysis, the Krebs cycle, and oxidative phosphorylation. These reactions generate energy in the form of ATP. In total, the complete oxidation of glucose produces a net gain of 38 ATP molecules.

When FADH2 is oxidized, it donates its electrons to the electron transport chain in cellular respiration. This results in the pumping of protons across the inner mitochondrial membrane, creating an electrochemical gradient. The energy from this gradient is then used by ATP synthase to produce ATP. Each FADH2 molecule produces enough energy to generate 1.5 ATP molecules. Therefore, when one molecule of FADH2 is oxidized, it yields approximately two ATP molecules.

Bakanae disease in paddy is caused by gibberellic acid. Gibberellic acid is a plant hormone that promotes plant growth and elongation. In the case of Bakanae disease, the presence of gibberellic acid leads to excessive elongation of the infected plant, causing symptoms such as tall and weak stems, reduced grain yield, and ultimately death of the plant. This disease is commonly found in paddy fields and can have significant economic impacts on rice production.

Dark respiration is the process by which cells break down organic compounds to release energy in the absence of light. This process occurs in the mitochondria, which are known as the powerhouses of the cell. Mitochondria are responsible for generating ATP, the energy currency of the cell, through the process of cellular respiration. Therefore, the correct answer is mitochondria.

IAA, or Indole-3-acetic acid, is the natural auxin found in higher plants. Auxins are a class of plant hormones that regulate various aspects of plant growth and development, including cell elongation, root formation, and fruit development. IAA is synthesized in the apical meristems of the plant and is involved in tropic responses, such as phototropism and gravitropism. It also plays a role in the initiation of adventitious roots and the development of fruits. GA (Gibberellic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) are other plant hormones, while Zeatin is a cytokinin, another class of plant hormones.

Wheat is not a C4 plant because it follows the C3 photosynthetic pathway. C4 plants have a specialized mechanism that allows them to efficiently fix carbon dioxide, while C3 plants do not possess this mechanism. Wheat belongs to the C3 group of plants, which means it uses the C3 photosynthetic pathway. This pathway is less efficient in capturing carbon dioxide compared to the C4 pathway used by plants like Amaranthus, Maize, and Tribulus.

Oxidative phosphorylation refers to the process in which ATP is formed during the electron transport chain. This process occurs in the inner mitochondrial membrane and involves the transfer of electrons from NADH and FADH2 to oxygen, creating a proton gradient. The flow of protons back into the mitochondrial matrix through ATP synthase generates ATP. Therefore, oxidative phosphorylation is the correct term for the formation of ATP during the electron transport chain.

In the light reaction of photosynthesis, NADPH2 is produced as a reducing power. This molecule carries high-energy electrons that are used in the Calvin cycle to convert carbon dioxide into glucose. NADPH2 is formed by the transfer of electrons from water to NADP+ through a series of electron transport reactions. It acts as a source of reducing power for the synthesis of carbohydrates and other organic molecules in the dark reaction of photosynthesis.