In this article we will discuss about the morphology of pinus with the help of diagrams.
The plant is a native of temperate regions and high altitudes of tropics. The genus is an evergreen tree of over 100 species. It is spread over Northern Europe, North and Central America, subtropics of North Africa, Canary Islands, Afghanistan, Pakistan, India, Mynmar, Philippines and Indonesia.
Six species of Pinus are indigenous of which four are restricted to Himalayas. These are: P. roxburghii, P. wallichiana, P. insularis and P. girardiana. Of the other two species, P. armandii grows in hills of Arunachal Pradesh and P. merkusii, the most tropical in nature, grows in the hills of Andaman and Nicobar Islands.
P. roxburghii (syn. P. longifolia) known as ‘Chir’ is the most valuable for its timber while P. wallichiana (syn. P. excelsa), known commercially as ‘Kail’ is native of Western Himalayas. P. insularis (syn. P. khasiana) known as ‘Khasi pine’ is restricted to Eastern Himalayas. P. girardiana, the source of edible seeds ‘Chilgoza’, occurs in North West Himalayas, Afghanistan, Pakistan and India.
Pyramidal appearance of Pinus (Fig. 16.1) as an evergreen tree makes it attractive to garden lovers. Its decorative value is also depicted in old Chinese paintings. Fragrance of the pine wood on burning, has been used in rituals in religious ceremonies of old civilizations.
Pinus has two types of root systems. Tap root, the main root of indefinite growth and its branches of limited growth and short life, known as short or dwarf root.
The main stem is erect and woody, with scaly bark which peels off. Branches are of two types: long shoots (LS) and dwarf shoots. The former are of unlimited growth and arise as a lateral bud in the axil of scale leaf. These long shoots grow horizontally on the main stem and subscribe to nodal growth. There are uninodal pines, producing single shoots at the node in a year, as against multinodal pines that produce many long shoots.
The dwarf shoot (Fig. 16.2B,C) or branches of limited growth-brachyblasts or foliar spurs-are borne on long shoots in the axil of scaly leaves. Each dwarf shoot when mature has a short axis with an aborted apex and 10-15 scales as prophylls (pr), followed by more cataphylls (ca).
Foliage leaves on dwarf shoots are needle-like (n), their number is constant for species and is a taxonomic character. P. monophylla has one needle, P. sylvestris has two, P. roxburghii has three (Fig. 17.2A,B,C) and P. wallichiana has five needles (Fig. 16.2D).
