Question

Age of a plant can be determined by observing its

• A. cork cambium
• B. pith
• C. wood
• D. bark

Answer 1

The Correct Option is C

Wood i.e., secondary xylem forms the bulk of the stem. Width of secondary xylem increases with the age of the plant due to secondary growth. The yearly growth of secondary xylem is distinct in the areas which experience two seasons, one favourable (spring or rainy season) and the other unfavourable (autumn, winter or dry summer). Hence the annual or yearly growth appears in the form of distinct rings which are called annual rings. An annual ring consists of two types of wood, spring wood and autumn wood. The spring or early wood is much wider than the autumn or late wood. It is lighter in colour and of lower density. Spring wood consists of larger and wider xylem elements. The autumn or late wood is dark coloured and of higher density. It contains compactly arranged smaller and narrower elements. The transition from spring to autumn wood in an annual ring is gradual but the transition from autumn wood to the spring wood of the next year is sudden. Therefore, each year's growth is quite distinct. The number of annual rings corresponds to the age of that part of the stem. (They can be counted by increment borer). Dendrochronology is the science of counting and analysing annual growth rings of trees.