Question

Conductivity part of phloem according to Haberlandt(1914) is
A) Sterom
B) Hadrom
C) Leptom
D) Bark

Answer 1

Hint: Transport of nutrients, water and other growth material which is required for plants is transported by xylem and phloem in vascular plants. These xylem and phloem are known as the vascular tissue.

Complete Answer:
- Phloem, also known as bast, is the vascular tissue in plants that flows the foods formed in the leaves to all other parts of the plant.
- Phloem is made up of several types of cells that are sieve tubes, companion cells, phloem fibres, and phloem parenchyma cells.
- Phloem is further to type that is Primary phloem formed by the apical meristems (new cell production) of root and shoot tips; which is protophloem (cells are matured before elongation) or metaphloem(Cells of which mature after elongation).
- Sieve tubes of protophloem are destroyed as the plant ages due to being unable to stretch with the elongating tissues and are torn.
- The other cell in the phloem is converted into fibres.
- Maturing metaphloem is not destroyed and carries their function during the rest of the life in plants such as palms.
- But after the mature primary phloem is replaced by secondary phloem in plants that have a cambium.
- For the conducting part of phloem Haberlandt (1914) uses the term leptom.

So, the correct answer is Leptom.

Note: Leptom is used for the soft wall tissue of phloem.
Various theories for the mechanism of translocation in phloem: Activated diffusion theory, Electro-osmotic theory, Interfacial flow hypothesis and munch hypothesis( widely accepted).