ANATOMY OF STEM.pptx Botany Carrier

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1. ANATOMY OF STEM NAME-Akash Mahakur Bsc in botany

2. STEM :- In plant, stem is the main structral axis that supports leaves, flowers and fruits.It transports water and nutrients between the roots and the rest of the plant. Stem may be herbaceous(soft)or woody. Or Stem is a vital part of a plant, that typically lies above ground, through in some case, it may also grow underground(such as in rhizomes). stem

3. Stem also varies 2 types for their tissue composition that are :- ( i )dicotyledonous stems[ di cot stem] (ii)monocotyledonous stem[ monoc ot stem] (I) DICOT STEM:- Have vascular bundles arranged in a ring ,can under goes secondary growth and havea distinct cortex and pith. (II)MONOCOT STEM :-Have a scattered vascular bundles, lack secondary growth, and do not have a distinct cortex and pith. Anatomy of stem:- There are 3 major zones of the stem that are:- (a)epidermis (B)cortex (C)stele

4. (A) EPIDERMIS :- Epidermis is a single layer of cells that forms the external tissue of a plant stem, called dermal tissue. (B)CORTEX :- Below the epidermis. Also divide in to hypodermis and cortex. The outermost portion of the cortex is usually a few layers of collenchyma cells. The remainder of the cortex and pith consist of parenchyma cells. (C)STELE:- The stele is the central part of a root or stem that contains tissues derived from the procambium .

5. (1) ANATOMY OF DICOTYLEDON STEMS:- ANATOMY OF SUNFLOWER STEM: Anatomy of the sunflower stem shows the internal structure of a typical dicot stem with collateral vascular bundles. In a well strained transverse section, the stem shows the following zones:- ( I)EPIDERMIS :- Outer most layer of stem. Composed of single layer of cells. Some cells bear multicellular hairs and stomata. ( II)CORTEX :- beneath the epidermis and distinguish hypodermis,cortex and endodermis. (III) PERICYCLE :- Inner to endodermis and layer of the stellar zone. It is heterogeneous in nature. Parenchyma and sclerenchyma fibres both MADE up its structure.

6. (IV) VASCULAR BUNDLE :- Vbs arranged in ring. Each vascular bundles contains the protoxylm , meta- xylem,protophloem , metaphloem and cambium. Phloem always located toward the outside of the vb and the xylem always toward the center. ( V)PITH :- Central part of the stem. Pith is made up of thin walled parenchyma cells containing intercellular spaces.

7. (B) ANATOMY OF CUCURBITA STEM: - The internal structure of Cucurbita stem represents a typical structure with bicol lateral vascular bundles. The internal structure shows the following zones:- EPIDERMIS :- Outermost layer consisting of compact cells. This layer possess many multicellular shoot hairs. (II) HYPODERMIS :- Zones made up of collenchymatous cells . Found below the epidermis. (III)CORTEX:- Below the hypodermis. There are 2-3 layers of parenchymatous cells and cell bears chloroplast. Intercellular space found.

8. (IV) ENDODERMIS :- Endodermis is the innermost layer of the cortex in the stem of a dicotyledonous plant and is made up of barrel-shaped cells that are tightly packed with no intercellular spaces. The endodermis is also known as the starch sheath (V) PERICYCLE :- Wavy layer of sclerenchyma that is 4–5 cells thick. (VI) VASCULAR BUNDLES:- -They have two phloem patches on either side of the xylem, with the outer phloem at the periphery of the central cylinder and the inner phloem at the center. The central xylem is also bound by an inner and outer cambium. (V II)GROUND TISSUE :- This zones mainly parenchymatous . (V III)PITH :- Represented by pith cavity which is wavy in margin.

9. ( 2 ) ANATOMY OF A TYPICAL MONOCOTYLEDON STEM (MAIZA):- A monocot stem consists of vascular bundles near the edge of a stem scattered in the parenchymatous ground tissue. However, the monocots lack the pith. A transverse well section of the stem of maize shows the following zones of tissues:- (I) EPIDERMIS :- Epidermis is the outermost layer of the monocot stem that comprises a single layer of parenchyma cells packed with a thick cuticle.  (II)HYPODERMIS :- Hypodermis of the cortex in monocots is made of sclerenchymatous cells.  (I II)GROUND TISSUE:- Monocot stem consists of vascular bundles near the edge of a stem scattered in the parenchymatous ground tissue. Monocots lack the pith.

10. (IV)VASCULAR BUNDLES:- Each of the vascular bundles is found to be surrounded by a thin sheath of sclerenchymatous fibres known as the bundle sheath. Xylem and phloem also constitute the internal structure of the monocot stem.

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