Pinus Plant
The genus Pinus has about 90 species. It has worldwide distribution. They are mostly present in mostly temperate regions. Four species of pinus are found in Pakistan. Pinus wallichiana, Pinus halepensis, Pinus roxburghii and Pinus gerardiana are present there.
General structure (Vegetative plant body)
The plant body is sporophyte. It is evergreen tall tree. Plant body is divided in to root stem and leave. Stem The main stem is unbranched. It has branches confined to the apical region. These branches form a characteristic canopy. Scaly bark cover it. Its branches are dimorphic. It has to type of branches. Branches of limited growth which are grow on specific limit and the nits growth is stop. Branches of unlimited growth its growth is continue with the growth of plant. These are about 1-2 cm in length. These are are one or two scale leave. Foliage leave bear it. A dwarf shoot with foliage leaf is called spur. Leaf Pinus has two type of leaf. Scale leaf and Foliage leaf.Scale leaf are small, membranous and brownish color. These are protective in function, The are present on the main dwarf. In the case of foliage leaf which are green and needle like and found in only dwarf shoot forming spur. They are also give protection.
Root Pinus is well developed tap root. It remain short and grows on hard ground rocks. These roots spread over a large area. Young root are infested with a fungus michorrhizae.
Root Pinus is well developed tap root. It remain short and grows on hard ground rocks. These roots spread over a large area. Young root are infested with a fungus michorrhizae.
Reproduction
Pinus is monoecious. Plant develop both male and female cones on the same plants. The cones are monosporous. Megasporangia and megaspores are produced in female cone. There are no vegetative reproduction in Pinus.
Male Cone The male cone is much smaller. They are produced in clusters near the tip of the long shoots. It produced in spring. Male cone has central axis. It bears a number of spirally arranged microsporophylls or stamens. Each microsporophyll has sac like microsporangia on ventral side. Each microsporengium produce large number of microspore. It wall has outer exine and inner intine. It has balloon like wings.
Female cone Female cone are produced in the axils of the scale. The production of female cones is initiated in the winter. These become ready for pollination during spring. Each young female cone has a central axis. It bears spirally arranged scales. The arranged scales are of two types. Some are thin membranous and directly attached to the central axis. They are bract scale. Woody ovuliferous scale are present on the ventral surface of each bract scale. The broader end of the ovuilferous has projection called umbo. They are situated side by side on upper side. Ovule Each ovule has mass of the nuvellar tissue. They are surrounded by a single integument. The micropylar end of the ovule is directed towards the central axis. A single megaspore mother cell is differentiated in the nucellus near the micropylar end. This megaspore mother cell is undergoes meiosis to form four megaspore mother cell. Only lower most remain functional.Functional megaspore increase in size.Functional megasopre take part in pollination.
Male Cone The male cone is much smaller. They are produced in clusters near the tip of the long shoots. It produced in spring. Male cone has central axis. It bears a number of spirally arranged microsporophylls or stamens. Each microsporophyll has sac like microsporangia on ventral side. Each microsporengium produce large number of microspore. It wall has outer exine and inner intine. It has balloon like wings.
Female cone Female cone are produced in the axils of the scale. The production of female cones is initiated in the winter. These become ready for pollination during spring. Each young female cone has a central axis. It bears spirally arranged scales. The arranged scales are of two types. Some are thin membranous and directly attached to the central axis. They are bract scale. Woody ovuliferous scale are present on the ventral surface of each bract scale. The broader end of the ovuilferous has projection called umbo. They are situated side by side on upper side. Ovule Each ovule has mass of the nuvellar tissue. They are surrounded by a single integument. The micropylar end of the ovule is directed towards the central axis. A single megaspore mother cell is differentiated in the nucellus near the micropylar end. This megaspore mother cell is undergoes meiosis to form four megaspore mother cell. Only lower most remain functional.Functional megaspore increase in size.Functional megasopre take part in pollination.
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