Question

a.       Many fossil lycophytes were tree-sized plants. It is hypothesized that seed plants now outnumber lycophytes because of the adaptive advantage of the seed, but there may also be an adaptive advantage to the novel vascular tissue arrangement in seed plants. What might be advantageous about the arrangement of vascular tissues in the dicot stems compared to the ancestral condition? Defend your answer.

​ b. Roots might all share this “ancestral” arrangement of vascular tissue because the ancestral condition is selectively favored in the root. What might be a reason that root organs with this phenotype provide a fitness benefit to the plant relative to the other arrangements you have observed today?   

c. Roots might instead have retained the ancestral conditions for some other reason. Postulate one such reason. Explain your answer.  

Answer 1

a. Ans-

The vascular tissue in the dicot stem is arranged in a ring form instead of being scattered form. This arrangement allows tolerating water pressure in the vascular system. For example, Balloon with thicker walls tolerates greater air volumes than that of thin walls.

b. Ans-

Because the roots of this ancestral arrangement of vascular tissue are acted like an anchor or base and improve the water channel that provides better support for the plant.

c. Ans-

The roots might have retained the ancestral conditions to contribute the successful plant fitness. Dicots have long, thick taproots that go much deeper into the soil and help in lib=ve longer than fibrous roots of monocots.