Structural adaptation of xylem tissues   Cell type Features Adaptation Xylem vessel -- elongated cell one on top of another forming vertical column. hollow tubes result and facilitate mass/free flow of water   -- end wall and cell content lost -- cell dead -- cell wall lignified and strengthened -- to prevent collapse/pressure change due to -ve tension developed during transpiration. -- to give mechanical support -- pits -- allow inter-communication between cells. -- vessels for free passage of water. -- prevent air lock in transpiration stream -- hex/octagonal shape -- close packing for strength Tracheid -- elongated hollow cell, imperforated with pit-closing membrane present in the region of pits. water flow from cell to cell through pits. to give mechanical support Fibre long cell with cell wall thickened and lignified Parenchyma cell cell wall may or may not be lignified as storage cells. e.g. starch, oil  

Structural adaptation of phloem tissues   Cell type Features Adaptation Sieve tube/ element -- tube shape/elongated. -- reduce resistance to transport nutrients -- end wall perforated forming sieve plates with pores -- to facilitate translocation of food substance /cell to cell activity of transport.   -- cell contents: nucleus degenerated, tonoplast disappear, endoplasmic reticulum and ribosome degenerated -- to facilitate translocation -- cytoplasmic strands -- active movement of nutrients/particles. -- plasmodesmata link with companion cells -- allow energy supply, protein synthesis, potential for activity. Companion cell -- large nucleus -- for metabolic active. -- numerous mitochondria -- may help in translocation Fibre -- long cell with cell wall thickened and lignified -- for mechanical support Parenchyma cell wall may or may not be lignified as storage cells. e.g. starch, oil  

T.S. of Dicot. Root Epidermis Phloem Root hair Cambium Xylem Exodermis Endodermis Cortex Pericycle

T.S. of Dicot. Stem Epidermis Phloem Cambium Xylem Cortex Sclerenchyma Pith

Simple Potometer ? Determine the rate of Transpiration

Weight Potometer L2 – L1 = ? W2 – W1 = ? Transpiration rate = ?

Water A: Source (Leaf) C: Sink (Storage organs/growing points)