Comparison # 1
Vessels | Sieve tubes |
These have open ends. | These have sieve plates at the ends. |
Vessels are wider. | These are narrow. |
They have various types of thickenings. | They have no such types of thickenings. |
Vessels have thick, rigid, and lignified walls. | These have thin, extensible, and cellulosic cell walls. |
On maturity, they are dead. | They are alive when they mature. |
They are permeable for all compounds. | They are semi-permeable. |
Absorb water or air on cutting. | Exude cell sap on cutting. |
Have low sap concentration. | Have high sap concentration. |
Translocate both solutes and solvents. | Translocate solute only. |
Do not have turgor pressure. | Turgid cells have high turgor pressure. |
May partially collapse on functioning. | Distended by pressure on functioning. |
Translocation speed is up to 75 cm/mm. | Translocation speed is up to 5 cm/mm. |
Comparison # 2
Protophloem | Meta phloem |
The first phloem formed is the protophloem. | After growth, the phloem differentiates and forms metaphloem. |
It is found in an active and functional state in the young and actively growing parts of plants. | It is present in mature parts of plants. |
Sieve elements are thin and inconspicuous. | Sieve elements are wide, long, and conspicuous. |
Protoplasts are vacuolated and without nuclei. | Protoplasts contain one or more nuclei. And disappear in mature sieve elements. |
Companion cells may be present or absent. | Companion cells are always present. |
Elements of protophloem are short-lived. | Metaphloem elements remain functional for a longer period. |
Comparison # 3
Primary Phloem | Secondary Phloem |
Derived from the procambium of apical meristem. | Derived from the vascular cambium of the lateral meristem. |
Protophloem and metaphloem elements are clearly demarcated. | There is no differentiation in the proto and metaphloem of secondary phloem. |
Sieve tubes are long and narrow. | Sieve tubes are short and wide. |
Phloem parenchyma is less developed and scanty. | Parenchyma is well developed and abundant. |
Sclereids are generally absent. | Sclereids are present in secondary phloem. |
Callus formation is absent or very little. | Callus formation is abundant. |
Primary medullary rays are formed from the activity of apical meristems. | Secondary medullary rays are formed from the activity of initials of the cambium. |
Medullary rays are homocellular. | Medullary rays are homocellular or may be heterocellular. |