Page 105 - PG 101-Course notes مذكرة النظري 24-25 with spec

Medicinal plants (PG 101) Level 1 Clinical Pharmacy-PharmD

Annual rings:

▪ In spring, when a new branches and leaves are being formed, water conducting
elements are developed wider than in the following season (early or spring
wood).

▪ The wood formed later in the season, in summer or in early autumn is called
(late, summer or autumn wood).

▪ No line exits between the two parts of a ring but there is a sharp line between the
late wood of one year and the early wood of the next year

▪ Concentric zones or rings which may be served as a mean for counting the age
of plant

▪ An annual ring therefore consists of two parts, an inner layer is the spring wood
and an outer (darker layer) is the summer Wood.

▪ The annual rings can be visible even to naked eye and serve as a mean of counting
the age of the plant.

Spring wood Summer wood

■ Is wider ■ Much denser

■ Bigger proportion of vessels and ■ Narrow elements, mainly fibers and
less fibers less vessels.

■ Vessels wider, less thick wall, less ■ More thickened and lignified walls

lignified. and small lumen.

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