6.
The
Pinus
is characterised by:
a) short tree with heavy-branches
16 two types of Shoots and tho types of cones
0 Large Scented flowers.
Id Large piccts beavings Seeds.
Answers
Answer:
character of pinus:-
They are evergreen, perennial lofty trees with spirally growing branches which give pyramidal or conical appearance.
The body is divided into stem, roots and needle-like leaves.
The stem is erect and cylindrical and is cov¬ered with bark.
There are two types of branches: the long shoot of unlimited growth and dwarf shoot of limited growth.
The long shoot bears apical bud and grows indefinitely with many scaly leaves.
Dwarf shoot does not contain any apical bud and they arise on the long shoot in the axil of scaly leaves.
Each dwarf shoot bear two scaly leaves which is also known as prophylls.
Leaves are dimorphic: the long green needle shaped foliage leaves and small, brown, membranous scale leaves.
Scale leaves are thin and brownish in color which is developed only on long as well as dwarf shoots while the foliage leaves are large, needle-like and found only at the apex of the dwarf shoots.
The pine bears tap root system with insufficient hairs but it disappears soon. Many lateral roots also develop which play an important role to absorb the mineral containing water.
The branch roots are infested with mycorrhizal fungus and hence it is called the mycorrhizal root.
They have endarch vascular bundles. Individual vascular bundles are separated by means of medullary rays.
The anatomy of leaves shows xerophytic structure: thick cuticularised epidermis with sunken stomata and sclerenchymatous hypodermis.
Resin ducts are present in the mesophyll tissue and the cells of the mesophyll have ridges on the walls which project inside the cell cavities.
Microsporophylls are arranged spirally on the central axis and forms male cone.
Megasporophyll of the female cone is composed of large ovuliferous scale and lower smaller bract scale, which are the free from each other.
Each ovuliferous scale bears two anatropous ovules or megasporangia.
The pollen grains are winged.
During the development of male gametophyte, two prothalial cells are formed which later on degenerates. Besides these, 2-3 archaegonia are formed with a neck of eight cells.