Plant Morphology — Set 2

Correct Answer: C. Morphology

• **Morphology** = The branch of biology that describes and analyses the external form, shape, size, colour, and structure of plant organs such as roots, stems, leaves, flowers, fruits, and seeds. • **Classification foundation** — morphological characters are the oldest and still one of the most reliable tools for naming, identifying, and grouping plant species in taxonomy. • Plant morphology laid the basis for Linnaeus's binomial nomenclature system still used worldwide today. • 💡 Option A (Anatomy) is wrong because anatomy examines the internal arrangement of cells, tissues, and organs through cross-sections; Option B (Ecology) is wrong because ecology studies relationships between organisms and their environment; Option D (Physiology) is wrong because physiology investigates the functional processes such as photosynthesis, respiration, and transpiration.

Correct Answer: C. Taproot

• **Taproot** = A single, prominent primary root that grows vertically deep into soil, with smaller secondary and tertiary lateral roots branching off from it. • **Dicot feature** — taproots are characteristic of dicotyledonous plants like carrot, radish, mango, neem, and sunflower, often used for deep water and nutrient extraction. • The deep penetration of taproots also makes these plants drought-resistant compared to shallow-rooted monocots. • 💡 Option A (Adventitious root) is wrong because adventitious roots arise from non-root parts such as stems or leaves, not from a single embryonic root; Option B (Fibrous root) is wrong because fibrous roots form a dense mat of similarly sized roots with no dominant main root, typical of monocots; Option D (Prop root) is wrong because prop roots drop from branches to the ground and provide extra support, as seen in banyan trees.

Correct Answer: C. Inflorescence

• **Inflorescence** = The specific pattern in which flowers are borne on the floral axis (peduncle), covering the mode of branching, the order of flower opening, and the overall shape of the cluster. • **Two main types** — racemose (indeterminate) inflorescences have a main axis that keeps growing with flowers opening from base to tip, while cymose (determinate) inflorescences terminate in a flower and open from apex to base. • Understanding inflorescence type helps botanists classify families: e.g., the head (capitulum) of sunflower and the spike of wheat are distinctive inflorescence forms. • 💡 Option A (Phyllotaxy) is wrong because phyllotaxy describes how leaves are arranged on a stem, not how flowers are arranged; Option B (Aestivation) is wrong because aestivation refers to how sepals and petals are arranged relative to each other inside an unopened bud; Option D (Placentation) is wrong because placentation describes the position and arrangement of ovules within the ovary.

Correct Answer: D. Mesocarp

• **Mesocarp** = The thick, juicy middle layer of the mango pericarp, rich in sugars, vitamins, and flavour compounds — this is the part we eat as 'mango pulp'. • **Three pericarp layers** — the pericarp (fruit wall) is divided into epicarp (thin, waxy outer skin), mesocarp (fleshy edible middle), and endocarp (hard, woody stone surrounding the seed). • Mango is classified as a drupe (stone fruit) because of its hard, single-seeded endocarp, similar to peach and coconut. • 💡 Option A (Thalamus) is wrong because the thalamus is the receptacle or base of the flower, not a layer of the fruit; Option B (Endocarp) is wrong because endocarp is the hard inner stone that protects the seed and is not edible; Option C (Epicarp) is wrong because the epicarp is the thin, smooth outer skin of the mango that is peeled off before eating.

Correct Answer: B. Xylem

• **Xylem** = Specialised vascular tissue composed of dead, hollow, lignified cells (tracheids and vessels) that form a continuous pipeline for conducting water and dissolved mineral salts from roots up to the aerial parts. • **Dual function** — beyond conduction, the thick lignin-impregnated walls of xylem elements give the plant its mechanical strength, enabling trees to grow tall against gravity. • The upward movement of water through xylem is driven by transpiration pull — the evaporation of water from leaves creates a negative pressure that sucks water up the column. • 💡 Option A (Pith) is wrong because pith is the spongy, parenchymatous central tissue of stems that stores food but does not conduct water; Option C (Stomata) is wrong because stomata are tiny pores in the leaf epidermis used for gas exchange and water vapour release, not for long-distance transport; Option D (Phloem) is wrong because phloem transports dissolved sugars (food) manufactured in leaves downward to roots and other growing regions.

Correct Answer: A. Stomata

• **Stomata** = Microscopic pores in the leaf epidermis, each flanked by a pair of kidney-shaped guard cells that regulate opening and closing to control CO₂ entry for photosynthesis and O₂ and water vapour exit. • **Lower surface preference** — most stomata are on the lower (abaxial) surface of leaves to reduce direct sun exposure and limit water loss through transpiration. • Guard cells swell with water (turgid) to open the pore during the day and become flaccid at night or during drought to close it, conserving water. • 💡 Option B (Hydathodes) is wrong because hydathodes are specialised water-secreting pores found at leaf margins that release liquid water droplets in a process called guttation, not gas exchange; Option C (Nodes) is wrong because nodes are points on the stem where leaves are attached, not pores; Option D (Lenticels) is wrong because lenticels are loosely packed cells in the bark of woody stems that allow gas exchange in non-leafy tissues.

Correct Answer: D. Banyan tree

• **Banyan tree** = The banyan (Ficus benghalensis) produces hanging aerial roots called prop roots or pillar roots that descend from horizontal branches and penetrate the soil, eventually supporting the expanding canopy. • **Adventitious origin** — these roots grow from the stem and branches (non-root tissues), making them adventitious; over time they thicken into trunk-like pillars giving the banyan its iconic multi-stemmed appearance. • The Great Banyan tree in the Indian Botanic Garden, Howrah, spreads over 14,500 sq m through hundreds of prop roots — the largest known example of this adaptation. • 💡 Option A (Pea) is wrong because pea is a dicot with a normal taproot system arising from the radicle; Option B (Gram) is wrong because gram (chickpea) also has a taproot that can fix atmospheric nitrogen via root nodules; Option C (Mustard) is wrong because mustard is a dicot with a taproot system and does not produce adventitious aerial roots.

Correct Answer: A. Phyllotaxy

• **Phyllotaxy** = The specific pattern in which leaves are arranged on a stem, evolved to minimise overlapping and maximise every leaf's access to sunlight for photosynthesis. • **Three common patterns** — alternate (one leaf per node in a spiral, e.g., sunflower), opposite (two leaves per node facing each other, e.g., tulsi), and whorled (three or more leaves per node in a ring, e.g., oleander). • The mathematical sequence governing leaf spirals in alternate phyllotaxy follows the Fibonacci series, which naturally produces the most efficient light-capture geometry. • 💡 Option B (Vernalization) is wrong because vernalization is the process by which prolonged cold treatment triggers flowering in certain plants — it has nothing to do with leaf arrangement; Option C (Venation) is wrong because venation describes the pattern of veins within a leaf blade, not how leaves are positioned on the stem; Option D (Aestivation) is wrong because aestivation refers to the overlapping arrangement of sepals or petals inside an unopened flower bud.

Correct Answer: A. Radicle

• **Radicle** = The embryonic root present in the seed, and the first structure to emerge during germination; it grows downward (positively geotropic) to anchor the seedling and begin absorbing water and minerals. • **Priority in germination** — the radicle emerges before the plumule because securing water and anchorage is essential before the shoot can push upward toward light. • The radicle ultimately gives rise to the entire primary root system; in dicots it becomes the taproot, while in monocots it is soon replaced by adventitious roots. • 💡 Option B (Plumule) is wrong because the plumule is the embryonic shoot that develops into the aerial stem and first true leaves — it emerges after the radicle; Option C (Cotyledon) is wrong because cotyledons are seed leaves that absorb or store food reserves but do not develop into the root; Option D (Endosperm) is wrong because endosperm is nutritive tissue inside the seed grain (especially in monocots) that feeds the growing embryo but is not a part of the embryo itself.

Correct Answer: A. Filament

• **Filament** = A thin, elongated stalk that elevates the anther into a position where air currents or visiting pollinators can most effectively carry pollen away. • **Part of stamen** — the filament and anther together make up the complete stamen; the filament also conducts water and nutrients to the metabolically active anther. • Filament length varies enormously across species — long filaments in wind-pollinated plants expose anthers freely, while short filaments position anthers to contact insect bodies. • 💡 Option B (Pedicel) is wrong because the pedicel is the individual stalk supporting each flower in an inflorescence, not a structure within the flower itself; Option C (Style) is wrong because the style is part of the female carpel, connecting the sticky stigma to the ovary for pollen tube guidance; Option D (Petiole) is wrong because the petiole is the leaf stalk connecting the leaf blade to the stem.