why do nonvascular plants grow close to the ground
They are mostly amphibian of the plant kingdom. They are found in the moist and shady places. These plants do not possess true roots, stems and leaves. The vascular tissues are absent. The plant possess root like structure known as the rhizoids. The absorption of water occurs by capillary action, diffusion and cytoplasmic streaming.
The sex organs are formed on the gametophytic plant body. The gametophyte undergoes sexual reproduction by syngamy. The syngamy results in the formation of zygote which later give rise to the diploid sporophyte. The sporophyte which lives on the gametophyte as a parasite.
The sporophytes possess the capsule which produces haploid spores. The spores give rise to the protonema.
Plants originated in the water as free-floating algae. In the aquatic environment, water and nutrients bathed plants constantly, and each cell could simply absorb what it needed from the surrounding environment.
The first plants to move onto land 400 million to 450 million years ago -- the mosses, liverworts and hornworts, collectively known as bryophytes -- contained similar structures to these aquatic ancestors and were best adapted to living in an environment with water constantly available.
As evolution brought about new plant forms, the ability to survive in increasingly dry environments underlay many of the key adaptations. Bryophytes, however, still needed a constant source of moisture to survive.
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