Q.44 Vivipary can be obserced in-
1. Xerophytes
2. Halophytes
3. Mesophytes
4. Heliophytes
Vivipary can be observed in 2. Halophytes.
Option Analysis
1. Xerophytes: Desert-adapted plants (e.g., cacti) that conserve water through thick cuticles and reduced leaves. They exhibit seed dormancy to survive dry conditions, not vivipary (seed germination on parent).
2. Halophytes: Correct—salt-tolerant plants like mangroves (Rhizophora, Avicennia) in coastal saline habitats. Vivipary is a key adaptation: seeds germinate into propagules while attached to the parent, forming ready-to-root seedlings that float and establish in tidal zones, bypassing saline germination challenges.
3. Mesophytes: Plants adapted to moderate moisture (e.g., grasses, most crops). They rely on standard seed dispersal and dormancy, without vivipary.
4. Heliophytes: Sun-loving plants (e.g., sunflowers) with high light requirements. No association with vivipary; focus on phototropism and heliophily.
Introduction
Vivipary can be observed in halophytes, particularly mangrove species, where seeds germinate precociously into propagules while attached to the parent tree. This “live birth” strategy ensures offspring survival in harsh, salty coastal habitats by allowing direct dispersal as rooted seedlings.
Vivipary Mechanism
In true vivipary, sexual embryos develop continuously on the maternal plant without dormancy, triggered by low ABA (abscisic acid) levels in moist, saline conditions. Propagules drop, float, and root upon settling, enhancing establishment rates.
Plant Adaptation Comparison
| Group | Habitat Adaptation | Vivipary? | Example |
|---|---|---|---|
| Xerophytes | Dry deserts | No | Cactus |
| Halophytes | Saline coasts | Yes | Mangroves |
| Mesophytes | Moderate moisture | No | Wheat |
| Heliophytes | High sunlight | No | Sunflower |
Ecological Significance
Vivipary gives halophytes a competitive edge in dynamic intertidal zones, reducing predation and desiccation risks. Common in Rhizophoraceae family; rare elsewhere.
