Question

Autumn wood can be differentiated from spring wood by
(a)Broad vessels and tracheids
(b)Narrow vessels and tracheids
(c)Red colour of xylem
(d)Cambium

Answer 1

Hint: The activity of the cambial ring is not uniform throughout the entire year but markedly affected by the variations in the external environment i.e. climate as well as the internal environment of the plant. There is less need for water in the autumn season as there is less transpiration and water loss in winter.

Complete answer:
In temperate regions, like Asia, central North America, etc. the climatic conditions are not uniform throughout the year and different seasons show different climates. The secondary xylem of the wood produced is different in different seasons due to the differential activity of cambial.

SPRING WOOD	AUTUMN WOOD
In the spring season, Cambial is very active and produced a large number of xylary elements i.e. vessels, tracheid, xylem fibres, and xylem parenchyma.	In the winter season, Cambial is less active and as a result, fewer xylary element are formed
The vessels are produced with the wider lumens as more water is needed to meet the requirements by an increased transpiring surface.	The vessels have narrow lumen as less water is needed in the season.
The wood formed during this season is called the springwood or earlywood.	The wood formed in this season is called autumn wood or latewood.
The springwood is lighter in colour and is less dense.	Autumn wood is darker in colour and has a higher density.
The transition from springwood to autumn wood is gradual (slow)	The transition from autumn wood to springwood is sudden (fast).

 
The two kinds of wood (spring and autumn wood) that appear as alternate concentric rings of light and dark colour constitute an annual ring. Hence, one annual ring includes one circle of spring and one circle of autumn wood.
So, the answer is, “Narrow vessels and tracheids”

Note: -The annual ring represents one year, it is also called a growth ring because as the growth keeps on taking place this annual ring keeps on increasing in numbers.
-One annual ring is the combination of one ring each of spring and autumn wood seen by the difference in colours.
-Thus by counting the number of annual rings we can determine the age and number of seasons a tree has lived through.