Leaf

                                              Leaf

Definition: Leaves are green flat structures borne on the stem or branches called leaves.Leaves arise form the node.They have bud in their axil. Leaf produce food by photosynthesis.They also carry on transportation

Parts of leaves 

  A typical foliage leave consistes of three parts .Leaf blade or lamina is green expanded portion of leaf.It perform photosynthesis. Petiole The leaf stalk is called petiole. It is absent in some leaf .Therefore lamina is directly attach with stem. Leaf base is part of leaf which attach attach to the stem. They form sheathing in many monocotyledons. Chief Types of Leaves  there are following types of leaves. Foliage leave ordinary green leaves is called foliage leaves.They carry photosynthesis. Cotyledonary Leaves The leaves found in seeds and store food is known as cotyledonary leaves.Scale Leaves  small undeveloped sessile and colorless leaves is called is called scale leaves.Bracts and Bracteoles special leaf in axil of which flower arise.They are usually small and scale like. There primary function is protection.Floral Leaves The specialized leaves which form the part of flower.These are stamen carpel petal and sepal.

       Pair of outgrowth develop on at the base of petiole of the leaf is called stipules. It is present in many angiosperms plants. If stipule is present then it called stipulate.If stipule is absent then it called ex stipulate. some stipule remain in place as long as leaf persists. The stipule like stricture present at base of a compound leaf  called stiples. Its has different types like Scaly stipules, Leafy stipules, Free lateral stipules Adnate stipules ,Axillary stipule, Ochereate stipule, Tendrillar stipule and Spinous  stipule. Phyllotaxis The arrangement of leaf  on the stem is called phyllotaxis. Phyllotaxis reduce overcrowding.Therefore the leaves get maximum sunlight.There are two main types of phyllotaxis. The main type of phyllotaxis is Spiral and cyclic. The phyllotaxis in which single leaf borne at each node is called Spiral phyllotaxis. In this leaves are alternate. Example Sunflower and mustard. The phyllotaxis in which two or more leaf borne at each node is called cyclic phyllotaxis. They have 2 forms opposite cyclic phyllotaxis. Second is world cyclic phyllotaxis. In the case of opposite only two leaves are arise at each node.They are opposite to each other.This condition is opposite.It has two other forms.It has two types 1 is opposite and superposed and 2 is opposite and decussate. Whorled  More than two leaves are present at each node.These are arranged circular shape.

 Venation
       The arrangement of veins and veinlets in the leaf at lamina is called venation.Vein and veinlets dissolved water and minerals into other parts of leaf.It carry prepared material from leaf to stem.The lamina have one or more principle veins. They are also called midrib.There are different types of venation. Parallel venation and  Reticulate venation.
   Leaf are present on the stem for different time. Some leaves are fall early and some re present for long time.

    Caducous: If leaves falls early is is called caducous.Example opuntia. Leaf of some plant falls early.When they produce on the stem as soon as they falls.Their life time  is very short.They does not remain with plant. Deciduous: During this condition leaf are falls off  at the end of each growing season.Example Mulberry. Persistant: The leaves are remain functional on the plants for more than on growing season.
 Presence or Absence of petiole Leave have different types. Petiolate  Leaf stalk or petiole is present.Example Mango, Apple,Peer. Sessile In this case petiole is absent.Its example is poppy.Sub sessile Petiole is very small.Example is Calotropis.