Directions for questions 21 to \(40:\) For each of the following questions, four choices have been provided. Select the correct alternative. Plants that lack xylem and phloem are called (a) Bryophytes (b) Angiosperms (c) Gymnosperms (d) Pteridophytes

Bryophytes represent an ancient and diverse group of non-vascular plants, which includes organisms like mosses, liverworts, and hornworts. Unlike their vascular counterparts, bryophytes do not have an extensive transportation system consisting of xylem and phloem. This absence significantly impacts their size and habitat. They are generally small in stature and found primarily in moist environments where water can be readily absorbed through their surface cells.

Because they lack true roots, stems, and leaves, bryophytes rely on diffusion and osmosis for the movement of water and nutrients. Their simple structure means they are limited to a close relationship with the ground and often inhabit areas like forest floors, rocks, and stream margins. Bryophytes play essential ecological roles, such as soil formation, water retention in ecosystems, and providing habitats for small invertebrates.

Plants have developed a sophisticated transportation system to distribute water, nutrients, and sugars throughout their structures, crucial for their growth and survival. This internal transport happens within two primary tissues: xylem and phloem.

The xylem transports water and soluble mineral nutrients from the roots upwards to the rest of the plant. It is composed of hollow tubes strengthened by lignin, which also provides structural support. On the other hand, phloem transports the sugars and nutrients produced by photosynthesis from the leaves to other parts of the plant where they are needed or stored. Unlike xylem, phloem comprises living cells that can transport substances in both directions. This dual-piped system is what allows vascular plants to grow taller and live in various environments.

Xylem and phloem are the two main types of vascular tissues in vascular plants, fulfilling distinct but complementary roles in plant physiology. The xylem's primary function is transporting water and dissolved minerals absorbed from the soil, which is vital for photosynthesis and maintaining cellular structure. Xylem vessels are made up of dead cells to form non-collapsible tubes, efficiently conducting water upward.

Phloem's role is contrasting as it involves distributing organic nutrients, particularly the sugar glucose, which is a product of photosynthesis, from the leaves to the rest of the plant. Unlike xylem, phloem is made of living sieve-tube elements. These cells form tubes that can move sugars both upward and downward, depending on where they are needed. Together, xylem and phloem form a continuous loop of nutrient and water circulation that supports the plant's life processes.