NEET2019BotanyAnatomy of Flowering PlantsActual
Phloem in gymnosperms lacks:
Options
- AAlbuminous cells and sieve cells
- BSieve tubes only
- CCompanion cells only
- DBoth sieve tubes and companion cells
Correct answer
D. Both sieve tubes and companion cells
Step-by-step solution
Sieve elements are the chief conducting elements of the phloem which are of two types: sieve cells and sieve-tube members. Pores in sieve cells are narrow, there is seemingly uniformity in the structure of sieve areas and are found to be distributed evenly on all walls. The presence of sieve plates in sieve-tube members is one of the principal differences between sieve cells (absent) and sieve-tube members. In most gymnosperms and seedless vascular plants, sieve cells are the only kind of food-conducting cells wher