Plant Pathology — Part 2 MCQs with Explanations

In C 4 plants, initial carbon dioxide fixation occurs in the chloroplasts of Spongy parenchyma. C 4 carbon fixation is one of three known photosynthetic processes of carbon fixation in plants. C 4 leaves generally differentiate into two partially isolated compartments called mesophyll cells and bundle-sheath cells. CO 2 is initially fixed in the mesophyll cells by the enzyme PEP carboxylase which reacts with the three carbon. Mesophyll cells are parenchymatous cells. The CO 2 is fixed by RuBisCo to produce phosphoglycerate (PGA) while the pyruvate is transported back to the mesophyll cell, together with about half of the phosphoglycerate (PGA).

The passage of minerals from topsoil to subsoil through seepage of water is known as Leaching. Leaching is the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss. Leaching is a natural environmental concern when it contributes to groundwater contamination.

Plants exchange water with the environment through structures of two cell Stomata. Stomata are cell structures in the epidermis of tree leaves and needles that are involved in the exchange of carbon dioxide and water between plants and the atmosphere. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that are responsible for regulating the size of the stomatal opening.

Can is a nitrate fertilizer and ammonium fertilizer. Calcium ammonium nitrate or CAN, also known as nitro-limestone or nitrochalk, is a widely used inorganic fertilizer, accounting for 4% of all nitrogen fertilizers. CAN is a nitrogen fertilizer that contains equal parts of fast acting nitrate-nitrogen and longer lasting ammonium-nitrogen. This ensures a more continuous nitrogen supply to the crop and thus better efficiency of use, and also makes it suitable for unseasonal application during summer or winter.

Organelles involved in photorespiration are Mitochondria peroxisomes and chloroplasts. Plant mitochondria also serve a unique role in photorespiration, the conversion of glycine to serine, CO 2 and NH 3 . This respiratory organelle has a major role in photosynthetic carbon and nitrogen metabolism in the leaves of C 3 plants. The most prominent role of peroxisomes in photosynthetic plant tissues is their participation in photorespiration, a process also known as the oxidative C 2 cycle or the oxidative photosynthetic carbon cycle.

In sugarcane, 14 CO 2 is fixed in malic acid. The enzyme is PEP carboxylase. Phosphoenolpyruvate carboxylase is an enzyme in the family of carboxy-lyases found in plants and some bacteria that catalyzes the addition of bicarbonate (HCO 3 - ) to phosphoenolpyruvate (PEP) to form the four-carbon compound oxaloacetate and inorganic phosphate. This reaction is used for carbon fixation in CAM and C 4 organisms, as well as to regulate flux through the citric acid cycle in bacteria and plants.

Certification, Inspection and Quarantine strategies involve the exclusion of pathogens. This principle is defined as any measure that prevents the introduction of a disease-causing agent into a region, farm, or planting. Quarantine is a restriction on the movement of people or goods so that spread of disease can be prevented. so a period when a person, plant or animal that has or may have an infectious disease must be kept away in isolation from others. To facilitate safe global trade in agriculture by assisting the producers and exporters by providing a technically competent and reliable phytosanitary certificate system to meet the requirements of trading partners.

Oxathiin is not an inorganic fungicide from the given options. It is a six-membered, unsaturated heterocycle containing four carbon atoms, one sulphur, one oxygen atom and two double bonds. The current study shows that certain oxathiin carboxamides are selectively active against particular mutated SDCs of U. maydis and A. nidulans.

The cell wall of Chytridimycetes class of fungi is composed of Glucan + Ch.itin. Chytridiomycetes also known as Cytrids is the major class of the phylum Chytridiomycota, which contains several parasitic species. Chytrids lack a true mycelium. The thallus is irregularly shaped and the cell wall, as in other true fungi, contains chitin and glucans. Unlike other true fungi, however, chytrids produce motile zoospores that possess a single, posterior, whiplash flagellum.

The symptoms of powdery mildew of peas (caused by Erysiphe polygoni) first appear on Leaves. Powdery mildews are easily recognized by the white, powdery growth of the fungus on infected portions of the plant host. The powdery appearance results from the superficial growth of the fungus as thread-like strands (hyphae) over the plant surface and the production of chains of spores. Symptoms consist of a light, greyish, powdery growth on the leaves, pods, and occasionally on the stems.

Nitrogen fertilization is applied for growth, but its excess delays maturity. Nitrogen Fertilization Increases Root Growth and Coordinates the Root-Shoot Relationship in Cotton. The root system plays an important role in the growth and development of cotton, and root growth is closely related to shoot growth, both of which are affected by N availability in the soil. Excessive nitrogen causes fruiting plants to produce relatively more foliage, reducing their fruit production and delaying fruit maturity.

Among the given options, Carbon dioxide is oxidized and water reduced is true for photosynthesis. During photosynthesis, plants take in carbon dioxide (CO 2 ) and water (H 2 O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose.

Meristem is the plant cells that will show totipotency. Totipotency is the ability of a single cell to divide and produce all of the differentiated cells in an organism. Spores and zygotes are examples of totipotent cells. Meristematic cells are undifferentiated or incompletely differentiated. They are totipotent and capable of continued cell division. Division of meristematic cells provides new cells for the expansion and differentiation of tissues and the initiation of new organs, providing the basic structure of the plant body.

1. Net ATP produced in glycolysis is 8. During glycolysis, glucose ultimately breaks down into pyruvate and energy; a total of 2 ATP is derived in the process (Glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H 2 O). 2. Positive Benedict's test shows the presence of glucose. The presence of brick red indicates the positive indication of Benedict's reagent. This indicates the presence of about two percent sugar in the solution. 3. Genes unable to express in presence of their recessive alleles. Recessive alleles only show their effect if the individual has two copies of the allele. 4. A character controlled by many genes is known as polygenic gene. A polygenic trait is a characteristic, such as height or skin colour, that is influenced by two or more genes.

Pressure of tracheary elements is not associated with ascent of sap in tall. The ascent of sap in the xylem tissue of plants is the upward movement of water and minerals from the root to the aerial parts of the plant. The theory assumes that in the uppermost parts of the tallest trees, the vessels of the xylem are coated with thin films of sap. Pressure of tracheary elements is due to pressure in roots also termed root pressure. And root pressure is not associated with the ascent of sap.

Cauliflower Mosaic Virus (CaMV) is a type of virus that can infect cauliflower plants and cause diseases. Viruses are very small infectious agents. They are different from bacteria or fungi. A key difference is what they use to store their genetic information. Genetic information is like a set of instructions telling the virus how to reproduce. Some viruses use DNA for these instructions, while others use RNA . CaMV is unique because it uses DNA to store its genetic instructions. It doesn't use RNA. Therefore, the correct answer is A: DNA .

In glycolysis ultimately (or end product of glycolysis) Glucose is converted into pyruvic acid. During glycolysis, glucose ultimately breaks down into pyruvate and energy; a total of 2 ATP is derived in the process. Glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H 2 O. The hydroxyl groups allow for phosphorylation. The specific form of glucose used in glycolysis is glucose 6-phosphate.

The number of amino acids in TMV is 158. The coat protein (TMVP) of the virus contains 158 amino acid residues and was the first viral protein to be sequenced and to have its three-dimensional structure elucidated by X-ray crystallography. Capsomeres in TMV have several amino acids. TMV viruses are those viruses that cause mosaic disease in tobacco.

In double fertilization, the male gamete and secondary nucleus form the Endosperm. Double fertilization is a complex fertilization mechanism of flowering plants (angiosperms). This process involves the joining of a female gametophyte (megagametophyte, also called the embryo sac) with two male gametes (sperm). It begins when a pollen grain adheres to the stigma of the carpel, the female reproductive structure of a flower. The pollen grain then takes in moisture and begins to germinate, forming a pollen tube that extends down toward the ovary through the style. The cells of an unfertilized ovule are 8 in number and arranged in the form of 3+2+3 (from top to bottom) i.e. 3 antipodal cells, 2 polar central cells, 2 synergids & 1 egg cell.

Essential macronutrients are absorbed from the soil. Macronutrients absorbed from the soil are nitrogen, potassium, magnesium, phosphorus, calcium and sulphur. Carbon, hydrogen, and oxygen are also considered macronutrients as they are required in large quantities to build the larger organic molecules of the cell; however, they represent the non-mineral class of macronutrients.

Mineralization releases nutrients in soils that are tied up in Organic matter. Mineralization is the phrase used to describe the process whereby organic forms of nitrogen (N) in the soil are converted to available forms of N. This process is driven by microorganisms present in the soil decomposing organic matter for their energy supply. Soil organic matter (SOM) mineralization is an important process in which carbon (C) and nutrients are transformed into CO 2 and plant-available forms of nitrogen (N), phosphorus (P) and sulphur (S).

The relay pump theory was given by Godlewski. Godlewski (1884) proposed his clambering or relay-pump theory to explain the vertical movement of water through the plant. He thought that a rhythmic change in the water potential of the living cells like the xylem parenchyma and medullary rays caused a pumping action to raise water vertically against gravity.

Photosynthetic synthesis of carbohydrates uses CO 2 and Water in the presence of sunlight with the help of chlorophyll. Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy, through cellular respiration. Some of this chemical energy is stored in carbohydrate molecules, such as sugars and starches, which are synthesized from carbon dioxide and water.

Sterility mosaic disease of pigeonpea spread by Mites. The agent of sterility mosaic, a disease that is a major constraint on pigeonpea (Cajanus cajan) production in the Indian subcontinent, is transmitted by the eriophyid mite, Aceria cajani. Sterility mosaic disease (SMD), caused by Pigeonpea sterility mosaic virus (PPSMV), is the economically most important viral disease in India, causing an estimated annual loss of more than US$300 million.

Vander Plank is regarded as the father of Epidemiology. James Edward Vanderplank, best known to plant pathologists globally simply as 'Vanderplank', is widely regarded as one of the world's most influential plant scientists. This recognition stems from his reputation as the founding father of modern quantitative plant disease epidemiology. Epidemiology is the study and analysis of the distribution patterns and determinants of health and disease conditions in a defined population.

The bacterial colony is known as Ooze. Bacterial disease sign is bacterial ooze. This is an exudate/discharge coming out from the bacteria-infected surface. In plants, this occurs in leaf cracks and stomata. Bacterial ooze often serves as a mode of spread, especially during heavy rainfall and strong winds.

P. A. Micheli proposed that fungi arise from their spores. Pier Antonio Micheli was a noted Italian botanist, professor of botany in Pisa, curator of the Orto Botanico di Firenze, and author of Nova plantarum genera iuxta Tournefortii methodum disposita. He discovered the spores of mushrooms, was a leading authority on cryptogams, and coined several important genera of microfungi including Aspergillus and Botrytis.

The correct order of events is Infection - incubation period - invasion - colonization. Pathogenic mechanisms of the viral disease include (1) implantation of virus at the portal of entry is an infection of the pathogen, (2) local replication is the incubation period of the pathogen, (3) spread to target organs (disease sites) is an invasion of the pathogen, and (4) spread to sites of shedding of virus into the environment is colonization.

Apodachlya oomycetes fungi contain both chitin and cellulose. Apodachlya is characterized by the structure of their hyphae, which are constricted into septae-like structures which enclose cellulin plugs, preventing the loss of cytoplasm in the case of cell rupture. Apodachlya sp has Chitin and cellulose in the cell walls of the oomycete.

Single super phosphate is manufactured from Rock phosphate. Superphosphate was made from rock phosphate ore by treatment with sulfuric acid. Triple superphosphate is a component of fertilizer that primarily consists of monocalcium phosphate, Ca(H 2 PO 4 ) 2 . Traditional routes for extraction of phosphate rock using sulfuric acid give single superphosphate, an approximate 1 : 1 mixture of Ca(H 2 PO 4 ) 2 and CaSO 4 phosphogypsum.

Late blight of potato turned into an epidemic in the year 1845. Phytophthora infestans is an oomycete or water mold, a fungus-like microorganism that causes the serious potato and tomato disease known as late blight or potato blight. The Irish Potato Famine, also known as the Great Hunger, began in 1845 when a mold known as Phytophthora infestans (or P. infestans) caused a destructive plant disease that spread rapidly throughout Ireland.

The path of the dark reaction of photosynthesis was traced through the use of 14 CO 2 . Calvin and his co-workers by using the isotope of C which is 14C to trace the path of the carbon fixation in light reaction. Due to his discovery, the cycle is known as the Calvin cycle (Dark reaction) which is the common path for all plants in photosynthesis.

CO 2 is one product in respiration and a reagent in photosynthesis. Cellular respiration converts ingested nutrients in the form of glucose (C 6 H 12 O 6 ) and oxygen to energy in the form of adenosine triphosphate (ATP). CO 2 is produced as a byproduct of this reaction. During photosynthesis, plants take in carbon dioxide (CO 2 ) and water (H 2 O) from the air and soil. Within the plant cell, the water is oxidized, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons.

A photosynthesizing plant is releasing 18 O more than normal. The plant must have been supplied with H 2 O with 18 O. Ruben, Hassid and Kamen (1941) using a heavy isotope of oxygen, ` 18 O` in water, found that oxygen evolved in photosynthesis comes from water evolution of oxygen does not require carbon dioxide.

Infection of smut of maize (Ustilago maydis) occurs during the Vegetative stage. Corn smut is a plant disease caused by the pathogenic fungus Ustilago maydis that causes smut on maize and teosinte. The fungus forms galls on all above-ground parts of corn species. The fungus infects all parts of the host plant by invading the ovaries of its host. The infection causes the corn kernels to swell up into tumor-like galls, whose tissues, texture, and developmental patterns are vegetative and mushroom-like.

The source of oxygen that evolved during photosynthesis is H 2 O. Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy, through cellular respiration. Two water molecules are oxidized by the energy of four successive charge-separation reactions of photosystem II to yield a molecule of diatomic oxygen and four hydrogen ions. The oxidation of water is catalyzed in photosystem II by a redox-active structure.

Pollenkitt is formed from Tapetum. Tapetum is the innermost cell layer in the anther, which surrounds the developing pollen mother cells (PMCs) and/or microspores supplying nutrition and enzymes required for microsporogenesis and pollen maturation. Pollenkitt is a covering of yellow sticky substance which is present around the pollen grain. It is formed from tapetum.

An ammonical form of nitrogenous fertilizer will be preferred for paddy and potatoes. Ammonium sulphate [(NH 4 ) 2 SO 4 ]: This is a nitrogenous fertilizer that is used for raising the production level of crops like paddy, potato, etc. In this fertilizer, there is nearly 25% ammonia which is transformed into nitrate by the denitrifying bacteria present in the alkaline soil.

Brown leaf spot disease of rice is caused by Drechslera oryzae. Drechslera oryzae causes brown leaf spot disease in rice (Oryza sativa L.). This fungal pathogen produces a series of ophiobolins that cause some of the characteristic symptoms of the disease when applied to rice leaves at 10 -4 and 10 -5 M.

The leaf curl of the tomato is spread by Whiteflies. Tomato yellow leaf curl virus (TYLCV) is the name given to a complex of geminiviruses infecting tomato cultures worldwide. TYLCV is transmitted by a single insect species, the whitefly Bemisia tabaci. Over a long distance, the virus is primarily spread through the movement of infected plants, especially tomato transplants.