Q.1. Give distribution and morphology of Pinus.
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Q. Write the systematic position of Pinus and distribution and those species which occure in India. (1999)
Ans. Systematic Position
Group - Spermatophyta
Sub-group - Gymnospermae
Division - Coniferophyta
Class - Coniferopsida
Order - Coniferales
Family - Pinaceae
Genus - Pinus
Distribution: -
The genus Pinus with about 105 species, is more common forming dense forests in north temperate regions extending upto sub-alpine regions. In India the genus is represented by six species of which four growing in northeast and North-West Himalayas. The species are as follows:
1. P. gerardiana (chilgoza pine): - The tree may attains a height of 11-12 metres. Leaves are needle like and trifoliar. Seeds are edible. The plants grew it an attitude 2100-3300 metres in Kashmir and Himanchal Pradesh.
2. P. merkusii (Teenusserim pine): - Trees are nearly 3 metres in height with bifoliar leaves. The plant grows at 150-600 m height in East India and Bengal.
3. P. wallichiana (blue-pine): - Trees are 50m high with fluish, shining pentafoliar leaves. It grows in Kashmir, H P and Punjab at an attitude 1800-2100m. The plant commonly called “Kait”.
4. P. roxburghii (chir pine): - Plant 50m high,pyramid like with triangular and trifoliar leaves. It grows wild in Kashmir, Punjab, H.P sup at 460-1500 Metres attitude.
5. P. insularis (Khasi pine): - 30m in height with whorls branches and trifoliar leaves. Seeds are with wings. It grows in north eastern hill ranges of Assam at attitude 700-1850 metres.
6. P. armandi (Armand’s pine): - 18m high with penta foliar leaves. It grows in NEFA at 1500 m some exotic species of Pinus grown in India in U.P., H.P. Kashmir and W. Bengal. They are P.sylvestris, P. montana, P. laricio, P.nigra, P. pinaster, P. radiata etc.
Morphology: -
The adult plant of pinus, which represents the sporophytic phase of life cycle, is a tall tree attaining fairly good height. This is evergreen tree, consisting of a tall straight trunk having numerous wide spread branching. The plant body is well differentiated into leaf, root and stem.
Stem: -
The main stem is cylindrical erect, woody and covered with rugged thick and scaly bark. The stem is branched, and the branching is very regular and symmetrical, the branches arise laterally from the axial scale leaves after each year growth. The branches are longer on the lower part of stem and becoming gradually shorter towards the apex. The arrangement of branches gives the tree a graceful tapering or cone like appearance.
The branches are dimorphic, i.e., of two types which are as follow :
(i) branches of unlimited growth or long shoots and (ii) branches of limited growth or dwarf shoots. The long shoots are provided with apical bud and grow indefinitely in apparent whorls each year from the buds present in the axils of scale leaves. These spread out horizontally. Dwarf shoots lack apical buds and grow for a short period. These arise in the axils of scale leaves on the long shoots and possess needle-like leaves at their apex.
Konar (1960) states that each dwarf shoot or spur shoot of P. roxburghii, in addition to prophylls, bears about 8 to 10 spirally arranged cataphylls (scale leaves), that when young, are green but later turn brown.
Leaves: -
Plants are dimorphic, i.e., possessing two types of leaves.
1. Scale Leaves: -
Scale leaves are borne both on long and dwarf shoots. These are thin, brown, flattened and minute structures that fall off with the maturity of the branches. When developed at the base of needles, these wrap round their basal portions.
2. Foloage Leaves: -
Foliage leaves are borne only on drawf shoots. These, when mature, are needles-like, long acicular and green.
The dwarf shoot, bearing foliage leaves (needles), is called as spur. On the basis of number of needles a spur (dwarf shoot) possesses, it may be called monofoliar - with one, e.g. P. monophylla; bifoliar - with two, e.g. P. merkusii and P. sylvestris; trifoliar - with three, e.g. P. gerardiana and P. longifolia (= P. roxburghii) and pentafoliar - with 5 needless e.g. P. excelsa.
Root: -
It is tap root arising from the base of the stem. It branches to form lateral long roots. Dwarf roots arise in cluster on long roots. Root hairs are scanty. The roots of pinus have mycorrhiza i.e., the roots are covered with an ectotrophic symbiotic fungus.