Botany Plants Plant Processes Competitive Exams
100 questions · General Science
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Question 1 of 100
In C4 plants, PEP carboxylase is located in the
ExplanationMesophyll fixes CO2 into OAA; the Calvin cycle runs in the bundle sheath.
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Question 2 of 100
The female reproductive part of a flower is the
ExplanationPistil = stigma + style + ovary.
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Question 3 of 100
The mass flow (pressure flow) hypothesis of phloem transport was proposed by
ExplanationMunch (1930): sucrose loaded at the source draws water in; turgor pressure pushes sap toward the sink.
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Question 4 of 100
The Casparian strip is present in the
ExplanationIt is impregnated with suberin and forces water to pass through the cell membranes.
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Question 5 of 100
Per CO2 molecule fixed, the Calvin cycle requires
ExplanationPer glucose (6 CO2): 18 ATP and 12 NADPH.
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Question 6 of 100
Plasmolysis occurs when a plant cell is placed in a
ExplanationWater leaves by exosmosis and the protoplast shrinks from the cell wall.
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Question 7 of 100
Agrobacterium tumefaciens is used in plant genetic engineering because it
ExplanationForeign genes are inserted into T-DNA of a disarmed Ti plasmid.
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Question 8 of 100
Mature sieve tube elements lack a
ExplanationTheir functioning depends on the adjacent companion cells.
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Question 9 of 100
Which root system is typical of dicots such as mustard?
ExplanationDicots have a prominent primary root (tap root) with lateral branches; monocots have fibrous roots.
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Question 10 of 100
Photorespiration is negligible in C4 plants because
ExplanationThe C4 pump raises CO2 around RuBisCO, favouring carboxylation over oxygenation.
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Question 11 of 100
Parallel venation of leaves is typical of
ExplanationDicot leaves show reticulate venation.
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Question 12 of 100
Which mineral is essential for the photolysis of water?
ExplanationMn (with Cl-) is required by the oxygen-evolving complex of PS II.
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Question 13 of 100
Stomata open when guard cells
ExplanationK+ uptake lowers water potential, water enters, and the guard cells bulge apart.
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Question 14 of 100
Photoperiodism in plants was discovered by
ExplanationThey studied flowering in tobacco (Maryland Mammoth) in 1920.
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Question 15 of 100
Glycolysis occurs in the
ExplanationIt is common to aerobic and anaerobic respiration and needs no oxygen.
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Question 16 of 100
The oxygen released in photosynthesis comes from
ExplanationShown by Ruben and Kamen using the heavy isotope O-18.
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Question 17 of 100
Photosynthesis takes place in which organelle?
ExplanationChloroplasts contain chlorophyll in thylakoids and the enzymes of the Calvin cycle in the stroma.
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Question 18 of 100
Photorespiration begins when RuBisCO binds
ExplanationIt involves chloroplast, peroxisome and mitochondrion and wastes fixed carbon without producing ATP.
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Question 19 of 100
Which green pigment traps light energy for photosynthesis?
ExplanationChlorophyll absorbs mainly red and blue light.
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Question 20 of 100
Which gas is absorbed by plants during photosynthesis?
ExplanationCO2 is fixed into carbohydrates in the Calvin cycle.
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Question 21 of 100
Transfer of pollen grains from anther to stigma is called
ExplanationPollination precedes fertilisation; it may be self or cross pollination.
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Question 22 of 100
The Calvin cycle (dark reaction) takes place in the
ExplanationThe stroma contains RuBisCO and the other Calvin cycle enzymes.
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Question 23 of 100
Root hairs mainly absorb
ExplanationRoot hairs greatly increase the absorbing surface of the root.
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Question 24 of 100
The terminal electron acceptor in the mitochondrial electron transport chain is
ExplanationOxygen accepts electrons and protons to form water.
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Question 25 of 100
Who is known as the Father of Botany?
ExplanationTheophrastus, a Greek philosopher, wrote Historia Plantarum. Linnaeus is the Father of Taxonomy.
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Question 26 of 100
The ploidy of endosperm in angiosperms is
ExplanationTriple fusion: one male gamete (n) + two polar nuclei (n + n).
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Question 27 of 100
The Hill reaction demonstrates that
ExplanationRobert Hill (1937) showed O2 evolution is independent of CO2 fixation.
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Question 28 of 100
Double fertilisation in angiosperms was discovered by
ExplanationNawaschin (1898) found one sperm fuses with the egg and the other with the polar nuclei.
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Question 29 of 100
Kinetin, the first cytokinin, was discovered by
ExplanationIt was isolated from autoclaved herring sperm DNA.
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Question 30 of 100
Folding of Mimosa pudica leaves on touch is caused by
ExplanationIt is a seismonastic (nastic) movement and is not a growth movement.
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Question 31 of 100
The tiny pores on the leaf surface are called
ExplanationStomata, each bounded by two guard cells, control gas exchange and transpiration.
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Question 32 of 100
Leghemoglobin in root nodules
ExplanationNitrogenase is O2-sensitive; leghemoglobin acts as an oxygen scavenger (gives nodules their pink colour).
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Question 33 of 100
Totipotency, as demonstrated in tissue culture, means
ExplanationThe idea was proposed by Haberlandt; Skoog and Miller refined the auxin-cytokinin balance.
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Question 34 of 100
Which of the following is a C4 plant?
ExplanationMaize and sugarcane have Kranz anatomy and the Hatch-Slack pathway.
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Question 35 of 100
Vascular bundles of a dicot stem are
ExplanationOpen = cambium present; monocot bundles are closed and scattered.
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Question 36 of 100
The pyruvate dehydrogenase complex (link reaction) is located in the
ExplanationPyruvate is converted to acetyl CoA, releasing CO2 and NADH.
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Question 37 of 100
The outer wall (exine) of a pollen grain is made of
ExplanationSporopollenin is extremely resistant, so pollen fossils are well preserved.
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Question 38 of 100
Photolysis of water is associated with
ExplanationThe oxygen-evolving complex of PS II splits water into protons, electrons and O2.
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Question 39 of 100
Water potential (psi w) is equal to
Explanationpsi w = psi s + psi p.
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Question 40 of 100
Cyclic photophosphorylation produces
ExplanationOnly Photosystem I operates, so there is no photolysis of water and no NADPH.
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Question 41 of 100
Which hormone is called the fruit-ripening hormone?
ExplanationEthylene is a gaseous hormone promoting ripening and senescence.
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Question 42 of 100
The orange colour of carrot is due to
ExplanationCarotenes are accessory pigments found in chromoplasts.
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Question 43 of 100
A mature embryo sac of a typical angiosperm is
ExplanationThree antipodals, two synergids, one egg, and one central cell with two polar nuclei.
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Question 44 of 100
Whiptail disease of cauliflower is caused by deficiency of
ExplanationMolybdenum is a part of nitrate reductase and nitrogenase.
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Question 45 of 100
Gibberellins were first isolated from the fungus
ExplanationThe fungus causes bakanae (foolish seedling) disease in rice by producing excess gibberellin.
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Question 46 of 100
Vernalisation refers to
ExplanationIt is required by winter wheat and biennials.
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Question 47 of 100
Which tissue conducts water and minerals upward?
ExplanationXylem (tracheids, vessels) carries water from roots to leaves.
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Question 48 of 100
The most abundant enzyme on Earth is generally considered to be
ExplanationRuBisCO is present in huge quantities in all C3 and C4 leaves.
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Question 49 of 100
The light reactions of photosynthesis occur in the
ExplanationPhotosystems and electron carriers are embedded in thylakoid membranes.
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Question 50 of 100
Lichens are an association of
ExplanationThey are mutualistic and are indicators of air pollution (SO2 sensitivity).
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Question 51 of 100
Guttation occurs through
ExplanationGuttation is the exudation of water droplets at leaf margins and provides evidence of root pressure.
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Question 52 of 100
Parthenocarpy is
ExplanationSeedless banana is an example; it can be induced by auxins.
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Question 53 of 100
Transpiration pull is mainly generated by
ExplanationEvaporation creates tension (negative pressure) transmitted through the continuous water column.
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Question 54 of 100
In bryophytes the dominant, independent plant body is the
ExplanationIn pteridophytes and seed plants, the sporophyte is dominant.
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Question 55 of 100
Pneumatophores (breathing roots) are found in
ExplanationMangroves of the Indus delta grow in waterlogged saline soil with poor oxygen.
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Question 56 of 100
Which gas is released as a by-product of photosynthesis?
ExplanationOxygen is released from the splitting (photolysis) of water.
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Question 57 of 100
The Krebs (citric acid) cycle occurs in the
ExplanationAcetyl CoA is oxidised to CO2 producing NADH, FADH2 and ATP/GTP.
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Question 58 of 100
Anaerobic respiration (fermentation) in yeast produces
ExplanationPyruvate is decarboxylated to acetaldehyde, then reduced to ethanol.
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Question 59 of 100
Loss of water vapour from aerial parts of a plant is called
ExplanationMost transpiration occurs through stomata; it drives water uptake and cools the leaf.
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Question 60 of 100
Apical dominance (suppression of lateral buds) is caused by
ExplanationAuxin from the apical bud inhibits lateral buds; cytokinin counteracts it.
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Question 61 of 100
The Avena coleoptile curvature test is a bioassay for
ExplanationDeveloped by F.W. Went (1928).
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Question 62 of 100
Secondary growth in dicot stems is brought about by
ExplanationVascular cambium adds secondary xylem and phloem; cork cambium forms periderm.
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Question 63 of 100
A synthetic auxin widely used as a selective weedicide is
Explanation2,4-D kills broadleaf (dicot) weeds in cereal crops.
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Question 64 of 100
The first stable product of CO2 fixation in C4 plants is
ExplanationPEP carboxylase fixes CO2 into the 4-carbon OAA.
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Question 65 of 100
Symbiotic nitrogen fixation in legume root nodules is carried out by
ExplanationAzotobacter is free-living, whereas Rhizobium is symbiotic.
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Question 66 of 100
A potometer is used to measure
ExplanationWater uptake by a cut shoot is measured as movement of an air bubble; most absorbed water is lost by transpiration.
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Question 67 of 100
The main component of the plant cell wall is
ExplanationCellulose microfibrils form the framework of the primary cell wall. Chitin is found in fungal walls.
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Question 68 of 100
Phloem mainly transports
ExplanationPhloem translocates organic solutes, chiefly sucrose, from source to sink.
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Question 69 of 100
The male reproductive part of a flower is the
ExplanationA stamen consists of an anther and a filament.
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Question 70 of 100
ATP synthase (F0F1) in mitochondria is located in the
ExplanationProtons flow back through F0 into the matrix, driving ATP synthesis in F1.
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Question 71 of 100
The first stable product of CO2 fixation in C3 plants is
Explanation3-PGA is a 3-carbon compound; hence the name C3 pathway.
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Question 72 of 100
Conversion of ammonia to nitrite in soil is done by
ExplanationNitrosomonas: NH3 -> NO2-; Nitrobacter: NO2- -> NO3-.
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Question 73 of 100
The chemiosmotic hypothesis of ATP synthesis was proposed by
ExplanationATP synthase uses the proton gradient across thylakoid or mitochondrial membranes.
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Question 74 of 100
The primary CO2 acceptor in the Calvin cycle is
ExplanationRuBisCO catalyses the carboxylation of RuBP.
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Question 75 of 100
Cork cambium (phellogen) produces
ExplanationPhellogen, phellem and phelloderm together form the periderm.
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Question 76 of 100
The hormone that induces stomatal closure under water stress is
ExplanationABA is called the stress hormone and also promotes seed dormancy.
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Question 77 of 100
Dendrochronology is the study of
ExplanationOne annual ring is formed per year in temperate regions.
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Question 78 of 100
Emerson's enhancement effect shows that
ExplanationIt led to the discovery of two cooperating photosystems.
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Question 79 of 100
Approximate net ATP yield per glucose in aerobic respiration (modern estimate) is
ExplanationOlder textbooks quote 36-38 ATP.
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Question 80 of 100
Which tissue is made of actively dividing cells?
ExplanationMeristems are located at root and shoot tips and in cambium.
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Question 81 of 100
Lenticels function in
ExplanationThey are loose-celled pores in the periderm.
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Question 82 of 100
Net gain of ATP in glycolysis per glucose molecule is
Explanation4 ATP are produced and 2 are used, giving a net of 2.
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Question 83 of 100
Which organelle is called the powerhouse of the cell?
ExplanationMitochondria produce most of the cell's ATP through aerobic respiration.
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Question 84 of 100
A plant that completes its life cycle in two years is called
ExplanationBiennials grow vegetatively in year one and flower in year two (e.g. carrot, beet).
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Question 85 of 100
The process by which a seed grows into a seedling is
ExplanationGermination needs water, oxygen and a suitable temperature.
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Question 86 of 100
How many cotyledons does a monocot seed have?
ExplanationMonocot = one cotyledon (wheat, maize); dicot = two (gram, pea).
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Question 87 of 100
Magnesium is an essential component of
ExplanationMg2+ is the central atom of the chlorophyll porphyrin ring; its deficiency causes chlorosis.
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Question 88 of 100
After fertilisation, the fruit develops from the
ExplanationThe ovary wall becomes the pericarp (fruit wall).
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Question 89 of 100
The membrane surrounding the large central vacuole of a plant cell is the
ExplanationThe tonoplast regulates transport between vacuole and cytoplasm.
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Question 90 of 100
Phytochrome is a pigment that absorbs
ExplanationPr (660 nm) and Pfr (730 nm) interconvert and regulate flowering and germination.
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Question 91 of 100
Which of the following is a micronutrient for plants?
ExplanationMicronutrients (Fe, Mn, Zn, Cu, B, Mo, Cl, Ni) are needed in trace amounts.
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Question 92 of 100
The cohesion-tension theory of ascent of sap was proposed by
ExplanationDixon and Joly (1894): transpiration pull and cohesion of water molecules lift the sap.
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Question 93 of 100
In CAM plants such as Opuntia, stomata open
ExplanationCO2 is stored as malic acid at night and used in the day, reducing water loss.
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Question 94 of 100
The water potential of pure water at standard conditions is
ExplanationSolutes make water potential negative.
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Question 95 of 100
The scientific study of plants is called
ExplanationBotany (Greek botane = plant) is the branch of biology dealing with plants.
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Question 96 of 100
The respiratory quotient (RQ) when carbohydrate is the substrate is
ExplanationRQ = CO2 evolved / O2 consumed; fats ~0.7, proteins ~0.9.
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Question 97 of 100
Which of the following is an insectivorous plant?
ExplanationInsectivorous plants grow in nitrogen-poor soil and trap insects to obtain nitrogen.
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Question 98 of 100
The primary carbohydrate product of photosynthesis is
Explanation6CO2 + 12H2O -> C6H12O6 + 6O2 + 6H2O in the presence of light.
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Question 99 of 100
Cytokinins mainly promote
ExplanationCytokinins act with auxin in tissue culture to induce shoot formation.
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Question 100 of 100
After fertilisation, the seed develops from the
ExplanationThe fertilised ovule becomes the seed; the zygote becomes the embryo.
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