Tag: botany

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.

Tectona grandis - Hard wood is present.

The large sized, slightly raised sports or aerating pores present in the cork tissue or are called Lenticels. These are the patches on the surface of the bark. These are found in old dicotyledonous stems. These are formed in the place of stomata. They have outer raised margins and internally, loosely arranged colourless parenchyma cells are present, called as complementary cells, These are meant for gaseous exchange.

Secondary xylem without vessels is called non-porous wood. It is found in the wood of gymnosperms. 

In dicotyledonous stems, during intra stellar secondary growth, a ring of cambium called vascular cambium is formed.  In the plants growing temperate regions, the activity of vascular cambium is influenced by the existence of maximum seasonal variations. In the spring or early summer, due to the existence of favourable conditions, a large amount of secondary xylem is formed. it is called Springwood or early wood. It is lighter in colour with low density. In the autumn season, due to the presence of unfavourable conditions, less amount of wood is formed. it is called autumn wood or latewood. It is darker in colour with higher density.

So the correct option is ‘Spring wood and autumn wood’.