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Tamil Nadu HSE First Year Botany study materials
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Tamil Nadu HSE First Year Botany practice questions

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Question 1Diversity, Classification and Plant Kingdom

In the five-kingdom classification proposed by R.H. Whittaker, which kingdom includes multicellular eukaryotes that are photosynthetic and have cell walls made mainly of cellulose?

  1. Monera
  2. Plantae Correct answer.
  3. Fungi
  4. Protista

Explanation

Whittaker's five kingdoms are Monera, Protista, Fungi, Plantae and Animalia. Plantae is defined by multicellularity, eukaryotic organisation, photosynthesis and a cellulose-rich cell wall, so it matches the description given.

Question 2Diversity, Classification and Plant Kingdom

The binomial system of nomenclature was formalised by Carl Linnaeus in his work Species Plantarum. In a binomial name such as Mangifera indica, what does the second word represent?

  1. The family
  2. The specific epithet Correct answer.
  3. The genus
  4. The author citation

Explanation

A binomial consists of a genus name followed by a specific epithet. In Mangifera indica, Mangifera is the genus and indica is the specific epithet that completes the species name.

Question 3Diversity, Classification and Plant Kingdom

Which group of algae is characterised by the presence of chlorophyll a and b, storage of starch inside the chloroplast, and flagella that are typically two in number and unequal in length?

  1. Cyanophyceae
  2. Chlorophyceae Correct answer.
  3. Rhodophyceae
  4. Phaeophyceae

Explanation

Green algae (Chlorophyceae) contain chlorophyll a and b, store true starch within the chloroplast, and usually bear two unequal flagella. These features separate them from brown, red and blue-green algae.

Question 4Diversity, Classification and Plant Kingdom

A student examines a thallus that is flat, ribbon-like and dichotomously branched, with a central midrib and sex organs grouped in receptacles at the tips. To which genus does this specimen most likely belong?

  1. Spirogyra
  2. Polysiphonia
  3. Volvox
  4. Fucus Correct answer.

Explanation

Fucus is a brown alga with a flattened, dichotomously branched thallus bearing a midrib and swollen receptacles at the branch tips. Those receptacles house the sex organs, which is the diagnostic combination described.

Question 5Diversity, Classification and Plant Kingdom

In bryophytes the dominant photosynthetic phase is the gametophyte. Which statement correctly describes the sporophyte of a moss such as Funaria?

  1. It produces spores by meiosis inside an antheridium
  2. It is independent and bears rhizoids for anchorage
  3. It is the main green plant body seen in the field
  4. It is dependent on the gametophyte and consists of foot, seta and capsule Correct answer.

Explanation

The moss sporophyte is a stalked structure with a foot embedded in the gametophyte, a seta and a capsule. It remains attached to and nutritionally dependent on the gametophyte and produces spores by meiosis in the capsule.

Question 6Diversity, Classification and Plant Kingdom

Which feature distinguishes pteridophytes from bryophytes in relation to the vascular supply and the dominant generation?

  1. Pteridophytes possess xylem and phloem and the sporophyte is dominant Correct answer.
  2. Pteridophytes possess vascular tissue but the gametophyte remains dominant
  3. Pteridophytes lack vascular tissue but have a dominant gametophyte
  4. Pteridophytes lack vascular tissue and have a dominant sporophyte

Explanation

Pteridophytes are the first true vascular plants, with xylem and phloem, and their life cycle is sporophyte-dominant. Bryophytes lack vascular tissue and are gametophyte-dominant, which is the key contrast.

Question 7Diversity, Classification and Plant Kingdom

Selaginella is often called a resurrection plant because of a distinctive physiological ability. Which statement best explains this common name?

  1. It can survive prolonged desiccation and revive on rehydration Correct answer.
  2. It produces seeds that germinate after fire
  3. It flowers repeatedly through the year
  4. It reproduces only by fragmentation

Explanation

Selaginella species can tolerate extreme drying and curl into a ball, then unfold and turn green again when water returns. This desiccation tolerance, not seed or flowering behaviour, gives the resurrection plant name.

Question 8Diversity, Classification and Plant Kingdom

In Cycas, the ovules are borne on megasporophylls that are not organised into a true cone. Where are these megasporophylls located?

  1. On lateral roots as coralloid masses
  2. On the underside of every foliage leaf
  3. At the apex of the main stem in a loose rosette Correct answer.
  4. Inside the male cone

Explanation

Cycas is unusual among cycads because the megasporophylls are loosely arranged in a rosette at the stem apex rather than compacted into a cone. The male plants, by contrast, bear a definite cone.

Question 9Diversity, Classification and Plant Kingdom

Which of the following correctly pairs a gymnosperm genus with a distinctive vegetative feature?

  1. Cycas with needle-like leaves in fascicles of two
  2. Ginkgo with fan-shaped deciduous leaves having dichotomous venation Correct answer.
  3. Pinus with jointed stems and scaly reduced leaves
  4. Ephedra with pinnately compound frond-like leaves

Explanation

Ginkgo biloba is the living fossil gymnosperm with distinctive fan-shaped, deciduous leaves whose veins fork dichotomously. The other pairings attach features to the wrong genus.

Question 10Diversity, Classification and Plant Kingdom

A plant shows the following characters: it is an epiphyte with a green photosynthetic stem, leaves reduced to scales, and a single apical root-like structure called a rhizophore. Which genus is being described?

  1. Marchantia
  2. Equisetum
  3. Selaginella Correct answer.
  4. Nephrolepis

Explanation

The rhizophore, a leafless root-bearing organ arising at branch points, is a characteristic of Selaginella. Reduced scaly leaves and epiphytic habits also occur in several Selaginella species.

Question 11Diversity, Classification and Plant Kingdom

In angiosperms, the characteristic triploid tissue of the seed is formed when a pollen tube discharges its contents. Which event directly produces this tissue?

  1. Fusion of one male gamete with the egg cell
  2. Fusion of two male gametes with each other
  3. Fusion of one male gamete with the two polar nuclei Correct answer.
  4. Fusion of the tube nucleus with a synergid

Explanation

Double fertilisation involves syngamy, giving the diploid zygote, and triple fusion, in which one male gamete fuses with the two polar nuclei. Triple fusion produces the triploid primary endosperm nucleus and hence the endosperm.

Question 12Diversity, Classification and Plant Kingdom

Which of the following statements about the classification of algae is correct with respect to the reserve food material stored?

  1. Blue-green algae store true starch in chloroplasts
  2. Green algae store floridean starch
  3. Brown algae store laminarin and mannitol Correct answer.
  4. Red algae store laminarin

Explanation

Phaeophyceae (brown algae) store laminarin and mannitol as reserve food. The other options attach the wrong reserve material or the wrong cellular location to the group.

Question 13Diversity, Classification and Plant Kingdom

The life cycle of a moss such as Funaria is best described as which of the following?

  1. Diplontic, with the sporophyte as the dominant phase
  2. Haplontic, with the gametophyte as the dominant phase Correct answer.
  3. Diplohaplontic, with two multicellular sporophytes
  4. Haplo-diplontic, with both phases equally dominant

Explanation

In bryophytes the plant body is haploid and gamete-producing, so the cycle is haplontic with a dominant gametophyte. The sporophyte is diploid but small and dependent, so the two phases are not equally dominant.

Question 14Diversity, Classification and Plant Kingdom

Which of the following is a correct statement about the heterosporous condition in pteridophytes?

  1. It produces two kinds of spores, microspores and megaspores Correct answer.
  2. It produces two kinds of gametes from one spore
  3. It produces spores of a single size only
  4. It produces seeds enclosed within a strobilus

Explanation

Heterospory means that two morphologically different spore types, microspores and megaspores, are formed. Selaginella and Salvinia are heterosporous pteridophytes, whereas Equisetum and most ferns are homosporous.

Question 15Diversity, Classification and Plant Kingdom

Which feature of Cycas is considered a primitive character retained from its fossil ancestors?

  1. Complete absence of vascular tissue
  2. Production of flowers before seeds
  3. Motile sperm with flagella that swim to the egg Correct answer.
  4. Presence of a true fruit enclosing the seed

Explanation

Cycas retains multiflagellate motile sperm that swim in a fluid within the pollen chamber to reach the egg, a feature recalling ancestral vascular plants. This is a classic primitive character in an otherwise seed-bearing plant.

Question 16Diversity, Classification and Plant Kingdom

Marchantia reproduces asexually by means of specialised structures borne on the dorsal surface of the thallus. What are these structures called?

  1. Gemma cups containing gemmae Correct answer.
  2. Sporangia containing elaters
  3. Archegoniophores bearing archegonia
  4. Antheridiophores bearing antheridia

Explanation

Marchantia forms crescent-shaped gemma cups on the upper thallus surface, and the gemmae inside detach and grow into new thalli. Antheridiophores, archegoniophores and sporangia belong to sexual reproduction.

Question 17Diversity, Classification and Plant Kingdom

A botanist wants to distinguish a fern prothallus from a moss gametophyte. Which observation would support the identification of a fern prothallus?

  1. A thallus with gemma cups on its upper surface
  2. A capsule borne on a long seta arising from the thallus
  3. An upright leafy shoot with a distinct stem and spirally arranged leaves
  4. A small green heart-shaped thallus with rhizoids but no leafy stem or midrib Correct answer.

Explanation

The fern prothallus is a small, green, heart-shaped gametophyte that bears rhizoids and sex organs but has no leafy stem. Leafy shoots and stalked capsules are sporophyte or moss features.

Question 18Diversity, Classification and Plant Kingdom

In the five-kingdom system, which criterion is used to separate Fungi from Plantae?

  1. Number of cells, since fungi are unicellular
  2. Presence of chlorophyll, since fungi are photosynthetic
  3. Presence of a nucleus, since fungi are prokaryotic
  4. Mode of nutrition, since fungi are heterotrophic absorbers Correct answer.

Explanation

Both fungi and plants are eukaryotic and mostly multicellular, so nutrition is the decisive criterion. Fungi are heterotrophic saprophytes or parasites that absorb nutrients, while plants are photosynthetic autotrophs.

Question 19Diversity, Classification and Plant Kingdom

Which of the following correctly describes the nature of the plant body in brown algae such as Laminaria?

  1. A thallus differentiated into holdfast, stipe and blade Correct answer.
  2. A thallus with true roots, stems and leaves
  3. A filament of cells with spiral chloroplasts
  4. A colonial sphere of biflagellate cells

Explanation

Brown algae have a plant body called a thallus, which may be differentiated into a holdfast for attachment, a stipe and a flattened blade. These are not true roots, stems or leaves because vascular tissue is absent.

Question 20Diversity, Classification and Plant Kingdom

The sporophyte of a liverwort differs from that of a moss mainly in which respect?

  1. It bears gemmae for asexual reproduction
  2. It is independent and photosynthetic when mature
  3. It is simpler and lacks a distinct seta and operculum in many forms Correct answer.
  4. It produces seeds instead of spores

Explanation

Liverwort sporophytes are generally simpler than those of mosses, often with a short seta and a capsule that dehisces by valves rather than a defined operculum. Both are dependent on the gametophyte and produce spores.

Question 21Diversity, Classification and Plant Kingdom

Which gymnosperm is known to bear its seeds on a fleshy, brightly coloured aril and is commonly grown as an ornamental in Indian gardens?

  1. Cycas
  2. Pinus
  3. Taxus Correct answer.
  4. Cedrus

Explanation

Taxus species bear a single seed partly enclosed by a fleshy red aril, which makes them popular ornamentals. Pinus and Cedrus have woody cones, and Cycas bears seeds on naked megasporophylls.

Question 22Diversity, Classification and Plant Kingdom

The term 'protista' in Whittaker's system includes which of the following groups of organisms?

  1. Multicellular fungi such as Agaricus
  2. Bacteria and cyanobacteria
  3. Unicellular eukaryotes such as Euglena and Paramecium Correct answer.
  4. Multicellular plants such as Funaria

Explanation

In Whittaker's five kingdoms, Protista comprises unicellular eukaryotic organisms such as Euglena, Paramecium and diatoms. Prokaryotes belong to Monera, while fungi and plants have their own kingdoms.

Question 23Diversity, Classification and Plant Kingdom

A specimen of Equisetum is examined. Which combination of features would correctly identify it?

  1. Jointed hollow stems with silica in the ridges and whorled branches Correct answer.
  2. Flat thallus with dichotomous branching and receptacles
  3. Pinnately compound fronds with sori on the underside
  4. Unbranched filament with spiral chloroplast

Explanation

Equisetum, the horsetail, has jointed, hollow, ridged stems impregnated with silica and whorls of branches at the nodes. Its spores are borne in strobili at the stem tips.

Question 24Diversity, Classification and Plant Kingdom

Which of the following statements about the classification proposed by Linnaeus is correct?

  1. He proposed the five-kingdom system including Monera
  2. He classified organisms only on the basis of cell wall composition
  3. He used a two-kingdom system dividing organisms into Plantae and Animalia Correct answer.
  4. He introduced the three-domain system based on rRNA

Explanation

Linnaeus recognised only two kingdoms, Plantae and Animalia, which was the prevailing system before microscopy revealed microorganisms. The five-kingdom and three-domain systems came much later.

Question 25Diversity, Classification and Plant Kingdom

In a heterosporous pteridophyte, the microspore and megaspore give rise to gametophytes with different roles. Which statement correctly describes the fate of the megaspore?

  1. It develops into the sporophyte without fertilisation
  2. It germinates to form a male gametophyte bearing antheridia
  3. It fuses directly with a microspore
  4. It germinates to form a female gametophyte bearing archegonia Correct answer.

Explanation

In heterosporous plants the larger megaspore germinates to form the female gametophyte, which bears archegonia. The smaller microspore gives rise to the male gametophyte with antheridia.

Question 26Diversity, Classification and Plant Kingdom

In the life cycle of a flowering plant, the pollen grain that lands on a stigma is best described as which of the following?

  1. A diploid spore mother cell that will undergo meiosis inside the stigma
  2. A megaspore that has divided mitotically to form the egg apparatus
  3. A haploid gamete that fuses directly with the synergid without forming a tube
  4. A microspore that has undergone one mitotic division to form a generative cell and a tube cell Correct answer.

Explanation

The pollen grain is the immature male gametophyte. Before or during germination, the microspore divides mitotically into a large tube cell and a smaller generative cell, which later gives rise to the two male gametes. This makes the pollen grain a two-celled haploid structure, not a gamete itself.

Question 27Diversity, Classification and Plant Kingdom

A student examines a filamentous alga in which the chloroplast is a flat, ribbon-like spiral band lying inside the cell. Which identification is most consistent with this observation?

  1. Volvox, a colonial chlorophyte with spherical colonies
  2. Nostoc, a cyanobacterium forming gelatinous colonies
  3. Spirogyra, a chlorophyte with spiral chloroplasts and conjugation Correct answer.
  4. Sargassum, a brown alga with air bladders

Explanation

The name Spirogyra itself refers to the spirally coiled, ribbon-shaped chloroplast that winds through the cylindrical cell. Sexual reproduction in this genus occurs by conjugation, forming zygospores. The spiral chloroplast is therefore a reliable diagnostic feature at the genus level.

Question 28Diversity, Classification and Plant Kingdom

A plant body is described as follows: it is a terrestrial, dichotomously branched sporophyte with no roots, the sporangia are borne in the axils of small leaves, and the gametophyte is independent and subterranean. Which interpretation is most defensible?

  1. It is a bryophyte in which the gametophyte is dominant and the sporophyte is dependent
  2. It is a gymnosperm in which the gametophyte is retained within the ovule
  3. It is an angiosperm in which the gametophyte is reduced to a few cells
  4. It is a lycophyte in which the sporophyte is dominant and the gametophyte is reduced but free-living Correct answer.

Explanation

Dichotomous branching, axillary sporangia on microphyllous leaves and an independent though small gametophyte point to a lycophyte such as Lycopodium. In pteridophytes the sporophyte is the dominant, independent generation, while the gametophyte is free-living but much reduced. The presence of vascular tissue separates it from bryophytes.

Question 29Plant Morphology and Anatomy

In a typical dicot root, the water-conducting xylem is described as exarch because the protoxylem lies towards the periphery and metaxylem towards the centre. Which arrangement of xylem is seen in a dicot stem?

  1. Radial, with xylem alternating with phloem along the same radius
  2. Mesarch, with protoxylem surrounded by metaxylem on both sides
  3. Endarch, with protoxylem towards the pith and metaxylem towards the periphery Correct answer.
  4. Exarch, with protoxylem towards the periphery and metaxylem towards the centre

Explanation

In a dicot stem the vascular bundles are conjoint and collateral, and the first-formed xylem (protoxylem) lies towards the centre (pith) while the later-formed metaxylem lies towards the periphery. This centripetal maturation is termed endarch. Exarch maturation is characteristic of roots, not of dicot stems.

Question 30Plant Morphology and Anatomy

A student examines a transverse section of a grass stem and finds that the vascular bundles are scattered in the ground tissue with a sclerenchymatous sheath around each bundle. This specimen is identified as a monocot stem mainly because of which feature?

  1. Radially arranged vascular bundles
  2. Absence of any ground tissue
  3. Presence of a distinct pith at the centre
  4. Scattered vascular bundles with bundle sheaths Correct answer.

Explanation

Monocot stems characteristically show scattered vascular bundles in the ground tissue, each bundle enclosed by a sclerenchymatous bundle sheath, and they lack a clearly defined pith. Dicot stems, in contrast, arrange bundles in a ring around a central pith.

Question 31Plant Morphology and Anatomy

The region of a root in which cells are thin-walled, isodiametric and actively dividing to add new cells to the root is the

  1. region of maturation
  2. root cap
  3. meristematic region Correct answer.
  4. region of elongation

Explanation

Just above the root cap lies the meristematic region, whose thin-walled, densely protoplasmic cells divide actively to produce new cells. These cells then pass into the region of elongation, where they lengthen, and finally into the region of maturation, where differentiation occurs.

Question 32Plant Morphology and Anatomy

In a leaf, the tissue that lies between the upper and lower epidermis and consists of palisade and spongy cells is called

  1. mesophyll Correct answer.
  2. pericycle
  3. endodermis
  4. periderm

Explanation

The mesophyll is the photosynthetic ground tissue of the leaf, differentiated into upper palisade cells and lower spongy cells. Periderm, endodermis and pericycle are tissues of the stem and root, not of the leaf blade.

Question 33Plant Morphology and Anatomy

The arrangement of flowers on the main axis of a plant is termed

  1. inflorescence Correct answer.
  2. venation
  3. placentation
  4. aestivation

Explanation

Inflorescence refers to the arrangement of flowers on the floral axis. Aestivation describes the arrangement of sepals or petals in a flower bud, placentation the arrangement of ovules on the placenta, and venation the arrangement of veins in a leaf.

Question 34Plant Morphology and Anatomy

A plant shows a tap root system, reticulate venation and flowers with five petals. These three characters together suggest that the plant is most likely a

  1. pteridophyte
  2. dicot Correct answer.
  3. monocot
  4. gymnosperm

Explanation

Tap root systems, reticulate venation and flowers in fours or fives are classic dicot characters. Monocots usually show fibrous roots, parallel venation and trimerous flowers. Gymnosperms and pteridophytes do not produce true flowers with petals.

Question 35Plant Morphology and Anatomy

In a transverse section of a dicot root, the single layer of cells that regulates the passage of water and solutes into the vascular cylinder is the

  1. endodermis Correct answer.
  2. epidermis
  3. pericycle
  4. cortex

Explanation

The endodermis is the innermost layer of the cortex, forming a sheath around the stele, and its Casparian thickenings control the entry of substances into the vascular cylinder. The epidermis, cortex and pericycle do not perform this selective barrier function.

Question 36Plant Morphology and Anatomy

A botanist finds a root in which the xylem is in the form of a solid central cylinder with no pith, and the number of protoxylem groups is six. This root is best described as

  1. polyarch and endarch
  2. triarch and endarch
  3. hexarch and exarch Correct answer.
  4. diarch and mesarch

Explanation

Six protoxylem groups make the root hexarch, and in roots the protoxylem lies towards the periphery, making the xylem exarch. Endarch xylem is a stem feature, and polyarch roots have many more than six xylem poles.

Question 37Plant Morphology and Anatomy

In a monocot leaf such as grass, the bulliform cells that help in rolling of the lamina are found in the

  1. bundle sheath
  2. lower epidermis
  3. mesophyll
  4. upper epidermis Correct answer.

Explanation

Bulliform (motor) cells are large, thin-walled, vacuolate epidermal cells present on the upper surface of grass leaves. Loss of turgor in these cells causes the lamina to roll and reduces water loss. They are not mesophyll or bundle-sheath cells.

Question 38Plant Morphology and Anatomy

In a dicot stem, the cambium that appears later within the vascular bundles and the interfascicular cambium together form the

  1. cork cambium
  2. pericycle
  3. fascicular and interfascicular cambium ring Correct answer.
  4. apical meristem

Explanation

During secondary growth in a dicot stem, the fascicular cambium within the bundles joins with the interfascicular cambium formed in the medullary rays to produce a continuous ring of cambium. This ring then produces secondary xylem inside and secondary phloem outside. Cork cambium arises later in the cortex for periderm formation.

Question 39Plant Morphology and Anatomy

The placentation in which ovules are borne on a central axis in a multilocular ovary, as in tomato and lemon, is

  1. marginal
  2. parietal
  3. free central
  4. axile Correct answer.

Explanation

In axile placentation the ovary is multilocular with septa meeting at the central axis, and ovules are attached to this axis, as in tomato and lemon. Marginal placentation has ovules on a single ventral suture, parietal has ovules on the ovary wall, and free central has ovules on a central column without septa.

Question 40Plant Morphology and Anatomy

In a flower, the arrangement in which sepals or petals are free and not touching each other is called

  1. imbricate Correct answer.
  2. twisted
  3. valvate
  4. vexillary

Explanation

Imbricate aestivation is one in which the perianth parts are free and overlap irregularly, with one part fully outside and one fully inside. Valvate has parts meeting edge to edge without overlap, twisted has regular overlapping, and vexillary is the papilionaceous pattern of pea flowers.

Question 41Plant Morphology and Anatomy

A fruit that develops from a single flower with a syncarpous ovary and is fleshy throughout, such as the tomato, is classified as a

  1. aggregate fruit
  2. dry indehiscent fruit
  3. multiple fruit
  4. simple berry Correct answer.

Explanation

A berry is a simple fleshy fruit derived from a single syncarpous ovary, with the pericarp fleshy and seeds embedded in the pulp, as in tomato. Aggregate fruits develop from many free carpels of one flower, multiple fruits from an entire inflorescence, and dry indehiscent fruits have a dry pericarp.

Question 42Plant Morphology and Anatomy

The edible part of the mango fruit is derived from the

  1. receptacle
  2. mesocarp Correct answer.
  3. epicarp
  4. endocarp

Explanation

The mango is a drupe in which the pericarp is differentiated into epicarp, mesocarp and endocarp. The fleshy edible portion is the mesocarp, while the stony endocarp encloses the seed. The epicarp forms the thin skin and the receptacle does not contribute to the edible pulp.

Question 43Plant Morphology and Anatomy

In a root, the tissue that gives rise to lateral roots and lies immediately inside the endodermis is the

  1. cortex
  2. pericycle Correct answer.
  3. phloem
  4. pith

Explanation

Lateral roots arise from the pericycle, a layer of thin-walled cells lying just inside the endodermis. The cortex lies outside the endodermis, the pith lies at the centre of the stele, and phloem conducts food.

Question 44Plant Morphology and Anatomy

A transverse section of a monocot root shows a large pith, numerous xylem poles and well-developed conjunctive tissue. Compared with a dicot root, the monocot root is best distinguished by

  1. polyarch xylem with a well-developed pith Correct answer.
  2. absence of endodermis
  3. exarch xylem only in dicots
  4. presence of secondary growth

Explanation

Monocot roots typically show polyarch xylem (many xylem poles) and a large, well-developed pith, whereas dicot roots are usually diarch to hexarch with little or no pith. Both root types possess an endodermis and exarch xylem, and monocot roots generally lack secondary growth.

Question 45Plant Morphology and Anatomy

In a leaf, the vein that runs along the middle of the lamina and is continuous with the petiole is called the

  1. pulvinus
  2. stipule
  3. rachis
  4. midrib Correct answer.

Explanation

The midrib is the prominent central vein of a leaf lamina, continuous with the petiole and giving off lateral veins. The rachis is the axis of a compound leaf, a stipule is a basal appendage, and a pulvinus is a swollen leaf base.

Question 46Plant Morphology and Anatomy

A compound leaf in which the leaflets are borne on a common rachis that branches, with leaflets attached at the tips of the branches, is described as

  1. palmately compound
  2. bipinnately compound Correct answer.
  3. simple leaf
  4. pinnately compound

Explanation

When the rachis of a compound leaf branches again and leaflets are borne on the secondary axes, the leaf is bipinnately compound, as in Acacia. Pinnate and palmate leaves have a single order of leaflet attachment, and a simple leaf has an undivided lamina.

Question 47Plant Morphology and Anatomy

The root modification in which roots arise from the lower nodes of the stem, grow downwards and provide mechanical support, as in sugarcane and maize, is called

  1. pneumatophores
  2. prop roots
  3. stilt roots Correct answer.
  4. tuberous roots

Explanation

Stilt roots arise from the lower nodes of the stem and grow obliquely downwards to support the plant, as in sugarcane and maize. Prop roots arise from branches and hang down, as in banyan, pneumatophores are respiratory roots, and tuberous roots are swollen storage roots.

Question 48Plant Morphology and Anatomy

In a transverse section of a dicot stem, the starch sheath that stores food and lies as the innermost layer of the cortex is the

  1. hypodermis
  2. endodermis Correct answer.
  3. medullary ray
  4. pericycle

Explanation

In many dicot stems the innermost cortical layer is the endodermis, which becomes starch-filled and is called the starch sheath. The hypodermis is the outer protective layer, the pericycle lies inside the endodermis, and medullary rays connect the pith with the cortex.

Question 49Plant Morphology and Anatomy

A plant breeder notes that a particular root shows a central solid core of xylem with protoxylem groups lying close to the pericycle, and that no pith is present. If the number of protoxylem groups is four, the root is

  1. diarch and exarch
  2. tetrarch and endarch
  3. tetrarch and exarch Correct answer.
  4. polyarch and mesarch

Explanation

Four protoxylem groups make the root tetrarch, and the location of protoxylem near the periphery (pericycle side) makes the xylem exarch. Endarch and mesarch conditions are not characteristic of roots, and diarch roots have only two xylem poles.

Question 50Plant Morphology and Anatomy

In a dicot stem, the cambium present within a vascular bundle is called fascicular cambium, while the cambium formed in the medullary ray region is called interfascicular cambium. The significance of their union is that

  1. it gives rise to the endodermis
  2. it produces only primary phloem
  3. it produces a complete cambial ring for secondary growth Correct answer.
  4. it forms the root cap during primary growth

Explanation

The fascicular and interfascicular cambia join laterally to form a complete ring of vascular cambium. This ring then produces secondary xylem centripetally and secondary phloem centrifugally, enabling secondary growth in the dicot stem. It is not involved in forming root cap, endodermis or primary phloem.