Question

Sugar transport elements of gymnosperms and pteridophytes are
A. Sieve cells
B. Sieve elements
C. Sieve tubes
D. Sieve tube elements

Answer 1

Hint: These cells are the ancestral sugar-conducting cells present in all non-flowering plants. They are one type of sieve.

Complete answer:
Phloem is the vascular tissue responsible for the storage and transportation of organic nutrients. The phloem is also a route to signaling molecules and has a structural role in the body of the plant. It is usually composed of three types of cells: parenchyma, sieve elements, and sclerenchyma.
Sieve elements are commonly associated with parenchyma and sometimes with any sclerenchyma in a typical tissue known as phloem. Sieve elements are elongated cells with only a primary wall without a lignified cell membrane. This primary wall has specialized pores, which are aggregated into sieve regions. There are two types of sieve elements:-sieve tube and sieve cells. Sieve cells contain only the sieve areas on both the end and side walls. The members of the sieve tube have both sieve plates and sieve areas. The sieve plates consist of one or more sieve areas at the end of the wall junction of two sieve tube elements; however, the pores of the sieve plate are considerably greater than those of the sieve areas found on the side wall. Both the sieve cells and the sieve tube members have parenchymal cells bound to them.
Sieve cells (and related albumin cells) are ancestral sugar-conducting cells present in all non-flowering vascular plants. Sieve tube members are derived from sieve cells and can only be found in flowering plants, angiosperms.

Thus, the correct answer is option A i.e., Sieve cells.

Note: There are two more unique types of sieve elements:-the sieve cells that exist in conifers, and the sieve tube elements that are synapomorphy for angiosperms. The sieve cells are usually narrow, long, and tapered at the ends.