CONIFERALES Coniferales, “the dominant forest-makers of the world’, are represented by about 54 living genera and over 500 species (Li, 1952). According to Foster and Gifford (1958) “the most dominant and conspicuous gymnosperms in the floras of the modern world belong to the order Coniferales”. They occur widely in Northern and Southern Hemispheres. Many of the Coniferales have now become extinct. Exceptional diversity of conifers is represented in Western North America and Eastern and Central China. A rich coniferous flora is also available now in Australia and New Zealand. The Indian coniferous flora of Himalayas is represented by the genera such as Pinus, Abies, Picea, Cedrus, Tsuga, Cupressus, Juniperus, Araucaria and Podocarpus. Distribution: Pinus, one of the most important Coniferales, is represented by about 105 species. These are mainly distributed in the Northern Hemisphere, and found commonly in Northern Europe, Northern and Central America, subtropics of North Africa, India, Myanmar, Pakistan, Afghanistan, Indonesia, etc. Six species of Pinus (P.roxburghii, P. wallichiana, P.insularis, P.gerardiana, P. armandii and P.merkusii) occur in India. They are distributed in Himalayas, north eastern India and some other parts of the country. 1. Pinus roxburghii (popularly known as “Chir”) grows from 460m to 1500m in Western Himalayas, extending to Bhutan and Eastern Nepal. 2. Pinus wallichiana (popularly known as “kail” or “blue pine” or ‘”Bhutan Pine”) grows from 1500m to 3000m in Kashmir valley, Shimla, Mussoorie and Eastern Nepal. 3. Pinus insularis (popularly known as “Khasi pine”) grows from 800m to 2000m in Garo, Khasi and Jaintia hills. 4. Pinus gerardiana (Chilgoza or Nioza) occurs in Northern Afghanistan, Tibet, Kashmir and Pakistan at an elevation of 1830m to 3600m. 5. Pinus armandii (North-eastern Himalayas). 6. Pinus markusii (Tenasarn Pine) is found in Andaman and Nikobar Islands and Myanmar. Some other species, found in India but not indigenously, are Pinus canariensis (Kashmir), P.caribaea (Assam), P.halepensis (Srinagar), P.massoniana, P.patula, P.pinaster and P.taeda (Kulu, Manali), P. radiata (Nilgiris) and P.thunbergii (West Bengal). Pinus trees survive for a very long period. Maheshwan and Konar (1971) have mentioned the presence of a tree of Pinus aristata, which is more than 4600 years old and still occasionally produces cones in Inyo National Forests of California, U.S.A. General Characters of Coniferales: 1. Plant body is sporophytic and the sporophytes are richly branched trees or shrubs. One species (Juniperus horizontals is prostrate. They are generally evergreen and xerophytic but genera such as Larix, Metasequoia and Taxodium are deciduous. 2. They are found from Carboniferous to the present times 3. Their growth habit varies from extremely tall trees as in Sequoia (Taxodiaceae) to miniature forms of Dacrydium (Podocarpaceae) which are only some centimeters high. 4. Branches may be of one kind or they may be dimorphic as in Pinus. 5. Stems contain a small pith and the secondary wood is pycnoxylic. 6. The secondary wood consists of tracheids with large uniseriate or rarely multiseriate pits on their radial walls. 7. Vessels are absent. 8. Resin canals are distributed in pith and cortex and sometimes also in wood. 9. Leaves are of two types, i.e. foliage leaves and scaly leaves. They are generally arranged spirally and only in opposite or whorled manner. Foliage leaves are filiform, needle-like and called needles. Occasionally the leaves are broad. 10. Plants are either monoecious or dioecious. 11. Reproductive organs are unisexual cones. 12. The sporophylls are generally arranged in the form of cones, and, therefore, the common name Conifers is given to them. 13. The micro-strobili or male cones are simple and contain many scale like microsporophyll’s. 14. Pollen grains may be winged (Pinus) or un-winged (Taxodium). They are wind-dispersed. 15. The male gametes are non-motile. 16. The female cone or mega-strobili consist of many sterile bract scales and fertile ovuliferous scales. 17. On the upper surface or in the axil of ovuliferous scales are present one to many ovules. 18. Pollination is anemophyllous. 19. Female gametophyte is completely dependent on the sporophyte. 20. Oospore has the ability to produce more than one potential embryos, and thus conifers show the phenomenon of polyembryony. 21. Seeds are endospermic and winged with hard testa. 22. Two to many cotyledons are present in the embryo. External Morphology of Pinus: The full-grown plant of Pinus is a large tree giving rise to a series of widespread branches. In most of pine trees a whorl of branches is produced each year. Sometimes, in young and vigorous trees two such whorls may be produced in one year. The whorls are formed in the axils of scale leaves every year. The main shaft is cylindrical and covered with a rough scaly bark. The branching is confined to the upper part of the stem, giving a pyramid-like appearance to the plant. The branches are dimorphic, the two forms being characterized as long shoots and dwarf shoots (spurs). These shoots are also known as the shoots of unlimited growth and shoots of limited growth respectively. There are two kinds of leaves, the scale leaves and the green acicular foliage leaves which are commonly termed as needles. The dwarf shoots or the shoots of limited growth bear the foliage leaves while the long shoots or the shoots of unlimited growth bear scale leaves on them. The dwarf shoots with their cluster of green leaves are known as ‘spurs’. The number of needles in each spur varies from species to species. Each spur of P. monophylla is unifoliate; the spurs of P. sylvestris and P.pinaster are bifoliate; the spurs of P. roxburghii, P. gerardiqna and P. insularis are trifoliate while the spurs of P. wallichiana are pentafoliate. The pine trees possess tap root. The tap root is elongated and possesses strong lateral roots. The flowers are monoecious, i.e., male and female strobili (cones) are borne on the same plant. The male flowers are catkin-like (cones) but erect in position. They are found in the axils of membranous bracts which are spirally arranged on the axis. The young female cones are solitary, paired or whorled at the apex of the current year’s shoot and consist of a central woody axis on which the two sets of scales are arranged in spiral way. The female cones are usually found on the shoots which do not bear male cones and take the place of shoots of unlimited growth. Internal Morphology (anatomy) of Pinus: Root: The internal structure of root resembles to that of a dicotyledonous root. In transverse section the root shows a piliferous layer bearing unicellular root hairs. The root hairs are found only in the young roots and root tips. In young roots there is fungal growth of ectophytic mycorrhiza. With the appearance of this fungus the root hairs of the root disappear. Just beneath the piliferous layer there lies a broad cortex which consists of 4 to 5 layers of thin-walled parenchymatous cells. The inner-most layer of the cortex is single- layered endodermis consisting of brown suberized cells containing tannin in them. Just below the endodermis there is multi-layered pericycle containing tannin and starch grains. Lateral roots are developed from the second layer of the pericycle. The outermost layer of the pericycle helps in the formation of the digestive sac which enables the lateral roots to penetrate through the cortex to the outside. In the center of the stele there are two to six Y-shaped xylem bundles alternating with them. The xylem has no true vessels and consists of tracheids. The phloem consists of sieve tubes and phloem parenchyma. Companion cells are altogether absent. In between the arms of a Y-shaped xylem bundle there lies a resin canal. In the center is a small pith. The secondary growth takes place as in dicotyledonous roots. A cambial strip develops from parenchymtous cells in between the phloem and metaxylem. This cambium cuts secondary xylem towards the inner side and the secondary phloem towards the outside. Simultaneously a layer of the pericycle functions as a cork cambium and cuts off a layer of cork cells towards the outside. A thick layer of cork develops which separates the cortex from the stele and because of this barrier of cork the cortex does not get food and dies. Stem: The internal structure of the stem of Pinus resembles to that of a dicotyledonous stem, though on the whole it displays the simpler structure. The young stem of Pinus shows the under mentioned structure in transverse section. The young stem is somewhat wavy in outline. It is surrounded by a single-layered cuticularized epidermis. Just beneath the epidermis there is multi-layered hypodermis consisting of lignified sclerenchymatous cells. The hypodermis constitutes the outer region of the cortex. Underneath the hypodermis there lies the inner cortex consisting of thin-walled parenchymatous cells containing chloroplasts and resin canals. Each resin canal is surrounded by a layer of glandular epithelial cells. The innermost layer of the cortex may be considered as endodermis but it is not at all clear. The pericycle is also inconspicuous. It is parenchymatous. The vascular bundles are conjoint, collateral and open forming a ring in the transverse section. The primary bundles are separated from each other by narrow medullary rays. The phloem consists of sieve tubes and phloem parenchyma. The sieve tubes are elongated and possess sieve plates on the radial walls. The companion cells are altogether absent. The xylem consists of tracheids. The protoxylem consists of annular and spiral tracheids. Secondary Growth: The secondary growth in the stem of Pinus takes place exactly in the same way as in dicotyledonous stems.