Q.4 The conventional ovule is lacking in the members of family:
- Cucurbitaceae
- Loranthaceae
- Rutaceae
- Apiaceae
Loranthaceae lacks conventional ovules, unlike other options. The correct answer is Loranthaceae, as its members are hemiparasites producing epiphytic seeds with rudimentary embryos instead of typical ovules.
Option Analysis
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Cucurbitaceae: Features conventional ovules; tricarpellary, syncarpous, inferior ovary with parietal placentation and many anatropous, bitegmic ovules (e.g., in cucumber, pumpkins).
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Loranthaceae: Correct. Lacks conventional ovules; produces small, dry seeds with haustorial embryos via epigyny or reduced gynoecium, relying on host attachment rather than soil germination.
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Rutaceae: Contains conventional ovules; typically 2-5 carpels, axile placentation, with unitegmic or bitegmic ovules (e.g., Citrus with many ovules per locule).
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Apiaceae: Has conventional ovules; inferior, bicarpellary ovary with 1 pendulous ovule per locule on axile placentation (e.g., carrot, fennel schizocarp fruits).
Introduction to Conventional Ovule Lacking Loranthaceae
Conventional ovule lacking Loranthaceae highlights a unique trait: mistletoes (Loranthaceae) skip standard ovules, producing haustorial seeds for host parasitism. This contrasts with families like Cucurbitaceae having parietal ovules.
Conventional Ovule Structure
Conventional ovules feature nucellus, integuments (bitegmic), funiculus, micropyle, chalaza; develop into seeds post-fertilization. Angiosperms standardize this for embryo sac formation.
Loranthaceae Ovule Exception
Loranthaceae (mistletoes) lacks conventional ovule; reduced ovary yields dry berries with embryos and endosperm, no true integuments. Seeds adhere to hosts via viscid exterior, germinating as hemiparasites drawing water/nutrients.
Family Ovary Type Ovule Features Placentation Cucurbitaceae Inferior, 3-carpellary Many, bitegmic, anatropous Parietal Loranthaceae 2-4 locular, reduced Absent conventional; haustorial seeds Axile (vestigial) Rutaceae Superior/inferior Many, unitegmic/bitegmic Axile Apiaceae Inferior, 2-carpellary 1 pendulous per locule Axile Comparison with Other Families
Cucurbitaceae has numerous horizontal ovules for pepo fruits. Rutaceae (citrus) packs winged/arillate ovules. Apiaceae forms dry schizocarps from single ovules. Only Loranthaceae adapts via ovule absence for aerial parasitism.
Biological Significance
Conventional ovule lacking Loranthaceae enables host-specific dispersal, impacting ecology (e.g., Viscum album). This hemiparasitic strategy boosts survival without soil dependency.
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