Tag: secondary growth in stem

Heartwood is the dead, inner part of the wood that no longer conducts water. Its primary function is to provide structural support and mechanical strength to the tree.

Wood is the common name for secondary xylem, which is produced by the vascular cambium during secondary growth in dicot stems and roots.

In most of the gymnosperms such as conifers and cycads. Vessels are not present and the wood is made entirely of tracheids. These woods are known as nonporous. In angiosperms, the wood consists of both tracheids and vessels. The wide vessels are appearing with pores between. Such wood is called porous. 

In these porous woods, if vessels have essentially equal diameters the wood is known as diffuse-porous. It is the characteristic of plants growing in tropical regions.

So, the correct option is D.

The older woody trees show two characteristic types of wood namely heartwood and sapwood. The heartwood is made up of dead xylem vessels that have been filled with tyloses and are rich in deposits of resins and tannins. These are non-functional and appear darker. 

The sapwood contains the newly formed vessels that are functional and appear lighter. The hardwood provides resistance from the pest attack and increases the durability of the wood.

Hence, the correct answer will be having dead and non-conducting elements.

The correct option is B.

In the dicotyledonous trees growing temperate regions, during secondary growth, vascular cambium is less active in autumn season because of the existence of unfavourable conditions.

So, the correct option is ‘Less active’.

In the dicotyledonous trees growing temperate regions, during favorable conditions, large amount of secondary xylem is formed. It is called Spring wood or early wood. It consists of large, thin walled broad tracheary elements. In the unfavorable conditions, less amount of secondary xylem is formed. It is called autumn wood or late wood. It consists of small, thick walled narrow tracheary elements.

So, the correct option is ‘Narrow tracheary elements’.

The inner or central dark coloured non-functional wood or secondary xylem formed during secondary growth in dicot stem is called Heartwood or duramen.

So, the correct option is ‘Inner part of secondary xylem’.

Heartwood or duramen is a source for the manufacture of different varieties of furniture items. So heart wood is the wood of commerce.

So, the correct option is ‘Heartwood(duramen)'.

A.Collenchyma – cells are living present in the younger parts of the plant body.

B.Chlorenchyma – cells are living, possess more number of chloroplast.

C.Periderm – a multilayered tissues composed with both living and non living or dead cells

D.Endodermis – cells are living, vertically elongated, appear barrel shape.

So, the correct option is 'Periderm'.

Secondary xylem, light in density and porous are called lightest wood. It is obtained from the tree Ochroma lagopus, a member of Malvaceae.