GK: Class 12 General Q&A · Page 172
3,658 free answers on GK (General) for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
Describe the axile placentation with the help of an example.
Solution: Axile Placentation: Ovary is multilocular (2 or more chambers) Placenta develops along the central axis Ovules attached to the central column where septa meet Typical of syncarpous, superior ovaries Example: China rose (Hibiscus), tomato, lemon
- GeneralClass 12All
Explain the vexillary and imbricate aestivation.
Solution: Vexillary (Descending Imbricate) Aestivation: Specific type found in Fabaceae (pea family) 1 large standard (vexillum) petal overlaps 2 lateral wings (alae) Wings overlap 2 smallest keel (carina) petals Example: Pea, bean Imbricate Aestivation: Margins of petals/sepa
- GeneralClass 12All
Explain briefly the modification of stem found in Pistia and Eichhornia.
Solution: Both Pistia and Eichhornia (water hyacinth) exhibit offsets—a type of vegetative propagation. Offsets are lateral branches with: Short internodes Rosette of leaves at each node Adventitious roots hanging in water Used for rapid asexual reproduction in aquatic plants
- GeneralClass 12All
What do you understand by the term venation? Explain its types.
Solution: Venation is the arrangement of veins and veinlets in the lamina (leaf blade). Types: Reticulate Venation Parallel Venation Veins form an irregular network Veins run parallel to e
- GeneralClass 12All
Draw a labelled diagram of a dicot seed.
Solution: A typical dicotyledonous seed (e.g., pea, bean) consists of: Seed coat (testa and tegmen) Hilum (scar of attachment) Micropyle (small pore) Two cotyledons (food storage) Embryonal axis with: Plumule (future shoot) Radicle (future root) <
- GeneralClass 12All
Differentiate between stem tendrils and thorns.
Solution: Stem Tendrils Thorns Modified axillary buds Modified axillary buds or stem Slender, coiled, thread-like structures Woody, st
- GeneralClass 12All
Given below are few floral formulae of some well known plants. Draw floral diagrams from these formulae.
(a) ⊕ ♀ K₂₊₂ C₄ A₂₊₄ G₍₂₎ Solution: This represents the family Brassicaceae (Cruciferae). The floral diagram shows: Actinomorphic flower 4 sepals in 2 whorls (2+2) 4 petals (cruciform) 6 stamens (tetradynamous: 2 short + 4 long) Bicarpellary, syncarpous ovary with parietal placentati
- GeneralClass 12All
Name the two plants, belonging to the Solanaceae family, which are used as medicines.
Solution: Belladonna (Atropa belladonna): Source of atropine, used in ophthalmology and as an antispasmodic Ashwagandha (Withania somnifera): Used in Ayurvedic medicine for stress relief and immunomodulation
- GeneralClass 12All
Rhizome of ginger is like the roots of other plants that grows underground. Despite this ginger is a stem not a root. Justify.
Solution: Ginger rhizome is classified as a stem based on the following anatomical and morphological features: Nodes and internodes are present Scale leaves arise at nodes Axillary and terminal buds present (roots lack buds) Grows horizontally underground Adventitious roots arise from the lower surface
- GeneralClass 12All
What are pitcher plants? Give example.
Pitcher plants are insectivorous plants in which leaves are modified into a pitcher-shaped structure to trap insects. The pitcher contains digestive enzymes that break down the prey to obtain nitrogen and other nutrients, supplementing their nutrition in nitrogen-deficient soils. Examples: Nepenthes (tropical pitcher plant), Sarracenia.
- GeneralClass 12All
Differentiate between hypogynous and epigynous flower.
Solution: Hypogynous Flower Epigynous Flower Ovary position: Superior Ovary position: Inferior Sepals, petals, stamens inserted below the ovary <
- GeneralClass 12All
Define aleurone layer. Give one example.
Solution: The aleurone layer is the outermost proteinaceous layer of the endosperm in monocotyledonous seeds. It is rich in enzymes (e.g., α-amylase) that aid in starch digestion during germination. The layer separates the embryo from the bulk endosperm. Example: Maize (Zea mays), wheat, rice. Ploidy: Triploid (3n), formed during double fertilization.
- GeneralClass 12All
What do the following terms stand for in a floral formula?
♀, %, P, Br Solution: Symbol Meaning ♀ Bisexual flower (both androecium and gynoecium present) % Zygomorphic flower (bilateral symmetry)
- GeneralClass 12All
What are trimerous flowers? Give one example.
Solution: Trimerous flowers have floral parts (sepals, petals, stamens, carpels) arranged in multiples of three or three-merous pattern. This is a characteristic feature of monocotyledons. Example: Family Liliaceae (lily family)—flowers have 3+3 tepals, 3+3 stamens, and a tricarpellary ovary.
- GeneralClass 12All
Define internodes and nodes.
Solution: Node: The region of the stem where one or more leaves are attached. It contains axillary buds and is the site of meristematic activity. Internode: The stem segment between two successive nodes, responsible for stem elongation.
- GeneralClass 12All
Add the missing floral organs of the given floral formula of Fabaceae. Given Formula: ⚥ ♀ K₍₅₎ ____ A₍₉₎₊₁ G₁
Solution: The missing corolla notation is C₁₊₂₊₍₂₎, representing the papilionaceous corolla with: 1 posterior standard (vexillum) 2 lateral wings (alae) 2 anterior petals fused to form a keel (carina) Complete Formula: ⚥ ♀ K₍₅₎ C₁₊₂₊₍₂₎ A₍₉₎₊₁ G₁
- GeneralClass 12All
Which family is commonly called potato family?
Solanaceae is commonly known as the potato family or nightshade family. It includes economically important plants like potato, tomato, brinjal, and chilli.
- GeneralClass 12All
Write down the name of plant in which leaflets are modified into tendrils.
In garden pea (Pisum sativum), the leaflets of compound leaves are modified into leaf tendrils that assist in climbing.
- GeneralClass 12All
What is the unit of gynoecium?
Solution: The fundamental unit of the gynoecium (female reproductive whorl) is the carpel or pistil, consisting of stigma, style, and ovary.
- GeneralClass 12All
What is the nature of ovary in an epigynous flower?
Solution: In epigynous flowers, the ovary is inferior. The thalamus (receptacle) encloses the ovary, and other floral parts (sepals, petals, stamens) appear to arise from above the ovary. Example: Guava, cucumber, sunflower.