STD 11 - 6. Anatomy flowering plants — BIOLOGY STD 11 Science — Question

a
Spring wood plus autumn wood of a year constitute annual ring. The spring wood (also called early wood) is light in colour and constitute major part of annual ring. The autumn wood (also called late wood) is darker in colour.

Wood consists of secondary xylem. The central hard, tough and darker region of wood constitutes heart wood while peripheral portion constitutes sap wood. But these are not specified in annual rings.