4. 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

8. 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

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

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

38. Simple Potometer ?
Determine the rate of Transpiration

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

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