1. TBF 3023
Plant Physiology
PBL-
WHEN NATURE STRIKES
Group members:
Wong Siew ChingD20091034815
Chew Mei Ping D20091034816
Ong Shwu Chyn D20091034817
Yee Hon Kit D20091034822
Ngang Huey Chi D20091034861

2. HOW CACTUS AND BROMELIADS CAN
GROW WELL UNDER DRY CONDITION?

3.  Cacti -most water-resourceful plants in the world
 Pineapple- highly tolerant of drought.
 Drought tolerant
 refers to the degree to which a plant is adapted
to arid or drought conditions.
 drought tolerant plants typically make use of
either C4 carbon fixation / crassulacean acis
metabolism (CAM) to fix carbon during
photosynthesis.
 Both cactus and bromeliads are CAM plants.

4. WHAT ARE THE
CHARACTERISTIC
OF CACTUS AND
BROMELIADS?

5. THE CHARACTERISTICS THAT HELP THEM TO SURVIVE
IN DROUGHT.
Cactuses Criteria Bromeliads
Leaves on most cacti are Leaves ~The epidermis of leaf is
absent or extremely tiny especially thick and tough
to resist damage and
desiccation.
~A special layer of water
storage cells on the
underside of the leaf that
act as a reserve in times
of water stress
~have tiny scales on their
leaves called trichomes.
The cactus stem serves Stem Have distinctive, water-
as the plant's main absorbing scales . Their
photosynthetic organ and thinness and large
is used for water storage surface area make the
scales ideal for rapidly
absorbing water.

6. Cactuses Criteria Bromeliads
Cactus roots help to Roots Able to resist wilting
gather and preserve
water in several ways .
open their stomates at Stomata Opens its stomata during
night rather than during the night rather than the
the day in hot or dry daytime
climates (CAM Photosynthesis)
(CAM Photosynthesis)
•Spines Others •Xerophytes
•Skin

7. BROMELIADS LEAVES
 Unique shape and arrangement of the leaves of
bromeliads.
Wide and deeply U-shaped where they join the stem, forming
a series of vessel-like compartments.
 When it rains, water flows down the leaves and pools in the
compartments, where it can be absorbed by the umbrella
scales.
 Remarkable "tank plants" - Nidularium and Billbergia.
 Greatly reduced stem & densely packed leaves have
broad, overlapping bases, resulting in a pitcher or vase-
like center-the tank.
 Rainwater fills the tank ,as the tank is shaded by the
dense crown of leaves around it, the water does not
evaporate quickly and can persist, enabling the plant to
survive periods of drought

8. CACTUSES ROOTS
 Shallow & extensive root systems
 Spread laterally away from the plant.
 Maximize water intake from a large area.
 Change characteristics as the water supply fluctuates.
 Existing dehydrated roots become more water conductive
after rainfall.
 Formation of new rain roots to help soak up water.
 In times of drought, the rain roots shrivel and fall off .The
existing roots dehydrate.
 The shrinkage of the existing roots creates an air gap that
helps to prevent water in the roots from escaping back to the
soil.
 A corky layer on the roots also helps to prevent water loss.

9. SPINES OF CACTUS
 Spines help the cactus in several ways.
 Protection against foragers.
 Water from dew condenses on spines and, in some cactus
species, downward-pointing spines help to direct rainwater to
the roots of the plant.
 Reflect light away from the cactus stem theoretically lowering
the stem temperature.
 Trap in a layer of air next to the cactus stem preventing loss of
water via evaporative cooling.

10. SKIN OF CACTUS
 Translucent & acts as the first line of defense against fungi,
bacteria, and foraging animals.
 The skin has two parts: the epidermis and the hypodermis.
 The skin's hypodermis layer provides mechanical support for the
plant.
 A waxy layer of cells known as the cuticle covers the skin’s
epidermis.
 The wax in the cuticle helps the stem to hold in its water vapor
reducing water loss.
 Waxy cuticle is also lightly colored and reflects some of the incident
light.
 Contains numerous stomata
(However, is less than the number for normal plants - another
water-saving characteristic.)

11. XEROPHYTES
 Possess many of the usual, water-conserving
adaptations of such plants:
 A thick epidermis covered with wax
 Water-storage cells that cause the leaves to appear
succulent (that is thick and fleshy
 Sheathing leaf bases.

12. Light Dependent
Reactions
Non-cyclic
photophosphorylation
Cyclic
photophosphorylation

15. Light Independent
Reaction:
Calvin Cycle

17. HATCH – SLACK PATHWAY
 Only
occurs in
C4 plants
and CAM
plants.

18. COMPARISON BETWEEN C3 ,
C4 , AND CAM PLANTS

19. EXAMPLES
C3 plants C4 plants CAM plants
Tomato Sugarcane Cactus
Legume Maize Bromeliad
Tobacco Sorghum
Wheat Eleusine

20. CO2 FIXATION AND CO2 ACCEPTOR
C3 plants C4 plants CAM plants
Once, only in Twice, first in Once, only in
mesophyll cells. mesophyll cells and then mesophyll cells.
in bundle sheath cells.
Ribulose Phosphoenelpyruvate Phosphoenelpyruv
biphosphate RuBP PEP (3C) -mesophyll ate PEP (3C) -
(5C) –mesophyll cells cells mesophyll cells
Ribulose biphosphate
RuBP (5C) –bundle
sheath cells

21. ENZYME AND FIRST PRODUCT FORMED
C3 plants C4 plants CAM plants
RuBP carboxylase PEP carboxylase PEP
-inefficient at low CO2 -high affinity for CO2 carboxylase
concentration. at low concentration -high affinity for
CO2 at low
RuBP carboxylase concentration
-efficient at high
CO2 concentration.
Glycerate 3- Oxaloacetate, a C4 Oxaloacetate, a
phosphate (GP), a C3 acid. C4 acid.
acid.

22. PHOTORESPIRATION
 CO2+RuBP(5C) 2G3P (3C)
 O2+RuBP(5C) phosphoglycorate (2C)+G3P (3C)
 Phosphoglycorate was the react with O2 to form
CO2 with no production of energy
 Is wasteful

23. PHOTORESPIRATION
-O2 IS USED, CO2 IS RELEASED
C3 plants C4 plants CAM plants
Occurs. Inhibited by high Inhibited by high
Oxygen acts as concentration of CO2. concentration of
competitive inhibitor. Light intensity & CO2.
temperature are
higher, O2 is not a
competitive inhibitor.

24. EFFICIENCY OF PHOTOSYNTHESIS
C3 plants C4 plants CAM plants
Less efficient Photosynthesis Photosynthesis
photosynthesis than C4 more efficient. more efficient.
plant. Yields are usually
Yields usually lower. much higher.

25. LEAF ANATOMY
C3 plants C4 plants CAM plants
Two distinct tissues: Vascular bundle Krantz anatomy
•palisade cell surrounded by two absent
•mesophyll cell rings of cells:  1 type of
Krantz anatomy •mesophyll cell chloroplast in
absent •bundle sheath cell mesophyll cells
1 type of chloroplast Thinner than C3
in mesophyll cells plant
Vascular bundle
packed tightly, many
chloroplasts

26. CROSS-SECTIONS OF LEAVES FROM C3 AND C4
PLANTS.

28. THANK
YOU..