### Theory:

Difference between sieve cells and tubes:
 Sieve cells Sieve tubes Sieve cells there is no companion cells. In Sieve tubes always there will be companion cells. Sieve plates are not formed in sieve areas. In Sieve tubes, Sieve plates act as boundaries to sieve areas. Sieve cells are elongated and are unique long. Walls are with tapered ends. Cells containing vertical cells placed one above the other form long tubes. These Long tubes are connected at the walls by means of sieve pores. Sieve cells consists of Sieve pores smaller in size and are larger in number. Sieve tubes consists of sieve pores larger in size and are smaller in number Pteridophytes and gymnosperms consists of Sieve cells. Angiosperms consists of Sieve tubes.
Differences between Tracheid's and Vessels:
 Tracheid Vessels Tracheid are formed from single cells Vessels are made up of number of cells Ends of the Tracheid are oblique and taper Ends of the vessels are round and transverse Length of the tracheid is of fraction of a centimetre in length. Vessels are several centimetres in length Tracheid walls are thick. Vessels' walls are less thick. Lumen is narrow Lumen is wider
Differences between Xylem and Phloem:
 Xylem Phloem Xylem conducts minerals and water. Phloem conducts food and organic solutes. Xylem conducts in one way i.e., unidirectional conduction from roots to apical parts (tips of the plant ) of the plant. Phloem conducts in two ways. i.e., bidirectional conduction of food from leaves to storage organs.And also from storage organs to growing parts of the plant. Channels that helps Xylem for conduction are Tracheid and vessels. Channels that helps phloem for conduction are sieve tubes. Xylem consists of the components such as tracheid, vessels, xylem parenchyma and xylem fibres. Phloem consists of the components such as sieve elements, companion cells, phloem parenchyma and phloem fibres. Lumen is narrow. Lumen is wider.