Gymnosperms
Gymnosperms are those plants whose seeds are unprotected, i.e., the ovules and the seeds that develop from those ovules are not enclosed in fruit wall. In other words, ovary is absent. The gymnosperms are the most ancient seed plants that originated during the late Paleozoic era. Gymnosperms are mostly evergreen but few deciduous plants are also known. The leaves may be either large fern-like or small and simple. The various characteristic of gymnosperms are as following:
- They are the flowering plants but do not bear true flowers as like that of angiosperms.
- They are naked seeded plants i.e. seeds are not enclosed within the fruit.
- They are cosmopolitan in distribution and mainly found on xerophytic habitats.
- The plant body is sporophyte which is differentiated into root, stems and leaves.
- The gymnosperms are evergreen plants.
- The male flowers are called male cone.
Difference between gymnosperms and angiosperms
| Gymnosperms | Angiosperms |
|---|---|
| 1) They are not herbaceous. | 1) Majority of angiosperm are herbaceous. |
| 2) They are terrestrial. | 2) They are either aquatic or terrestrial. |
| 3) They show xerophytic habitat. | 3) They may or may not show xerophytic habit. |
| 4) Two types of leaves i.e. scale and foliage. | 4) Leaves are only one type. |
| 5) The ovules are naked. | 5) The ovules are protected by the carpels. |
| 6) Seeds are endospermic. | 6) Seeds may or may not be endospermic. |
Pinus
Kingdom — Plantae
Division — Tracheophyta
Sub-Division — Spermatophyta
Class — Gymnospermae
Order — Coniferales
Family — Pinaceae
Genus — Pinus
Pinus is commonly called pine. Pinus is a tall evergreen tree which sometimes attains a height of 30 m. The plant is sporophyte i.e. differentiated into root, stems and leaves.
Root
It is tap root i.e. the main root goes deeper into the earth and bears lateral roots. In many species, the fungal hyphae are found to grow symbiotically with the root of Pinus, such roots are called mycorrhizal roots. The mycorrhizal roots accumulate or increases phosphate content of the soil.
Stem
Stem is the main tree trunk of the Pinus. It is woody in nature. The main stem bears branches. The branches are of two types i.e. long shoots — the main branch or normal branch that usually grows indefinitely and dwarf shoots — it is the additional branch to the long shoots which grows definitely and bears leave.
Leaves
The leaves are also of two types i.e. scale leaves — the scale leaves are small flat and brown coloured leaves developed at the base of the foliage leaves. The scale leaves mainly concerned with protection and foliage leaves — they are green leaves develops from the tip of the dwarf shoots. The foliage leaves are highly reduced in their surface area, thus highly elongated. Such leaves are called needles.
Distribution of Pinus in Nepal
Some common species of Pinus distributed in Nepal are as follows:
- Pinus roxburghii: It is also known as chir pine. It is also called khote sallo or rani sallo. It is abundant.
- Pinus wallichiana: It is also known as gobre sallo. It forms pure or mixed forests on hill slopes at elevation varying between 6000 to 11000 feet above the sea level.
- Pinus gerardiana: It grows in north-west Himalayas at 5000 to 12000 feet above the sea level.
- Pinus insularis: It is also known as khasi pine. It grows in hills of eastern Himalayas.
- Pinus merkus: It grows in eastern Himalayas. Its dwarf shoot possesses two needles.
- Pinus armandi: It has five needles per dwarf shoot. It is a Chinese species.
Xerophytic characteristics of Pinus
- Pinus usually found growing in such habitat where there is least availability of moisture.
- The leaves are reduced and modified into needles. This decreases the surface area for transpiration.
- The root is highly developed. It helps in absorption of water.