Why have biologists hypothesized that the first land plants had a low, sprawling

Question

Why have biologists hypothesized that the first land plants had a low, sprawling growth habit?

a. They were tied to the water for reproduction and thus needed to remain in close contact with the moist soil.
b. There was less competition for space; only once land plants spread out did they start to grow upright.
c. At the time of the first land plants, the carbon dioxide, which is necessary for photosynthesis, was primarily located close to the ground.
d. Land animals of that period were small so they needed short plants to eat.
e. The ancestors of land plants, green algae, lack the structural support to stand erect in air.

Explanation / Answer

a)To obtain water, they had to keep their tissues in direct contact with moist soil.

soon afther a) ->e)The other logic is that their algae-like tissues lacked the rigidity required to withstand gravity and remain erect outside of water. If this hypothesis is correct, then competition for space and light would have become intense soon after the first plants began to grow on land.

Fossils indicate that afther protecting wax layer and after the evolution of stomata, plants began to diversify. The next major innovation, which occurred during the Silurian-Devonian explosion, was the evolution of vascular tissue. Due to the deposition of lignin in the secondary cell walls of water-conducting cells, vascular plants were sturdy enough to grow upright. Wood and the tree growth habit appeared independently in several lineages.

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