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| 1. | Which group of plant is known as first vascular and true land plants? Write their characteristics in detail. | 
| Answer» 1. Pteridophytes are known as first vascular and true land plants. 2. Habitat: Pteridophytes grow in moist and shady places, e.g. Ferns, Horsetail. Some are aquatic (Azolla, Marsilea), xerophytic (Equisetum) and epiphytic (Lycopodium). 3. Plant body: It is differentiated into root, stem and leaves. 4. Primary root: The primary root is short lived and is soon replaced by adventitious roots. 5. Stem: The stem may be aerial or underground. 6. Leaves: This group contains plants with pinnate (feather – like) leaves. Leaves may be scaly (e.g. Equisetum), simple and sessile (e.g. Lycopodium), small (microphylls e.g. Selaginella) or large (macrophylls) and pinnately compound (e.g. Nephrolepis l Ferns). 7. Vascular tissues: In these members xylem consists of only tracheids and phloem consists of only sieve cells. 8. Secondary growth: Secondary growth is not seen in pteridophytes due to absence of cambium. 9. Alternation of generations: Pteriodphytes show heteromorphic alternation of generations in which the sporophyte is diploid, dominant, autotrophic and independent. Gametophyte is haploid multicellular, generally autotrophic and short lived. | |