5 Organs - Leaf Adaptations, Roots - Lecture 5 BioSci 1C...

Lecture: 5 BioSci 1C Apr.4.07
Plant Organs, Leaves and Roots
Begin on page 15.

Adaptations for Environmental Extremes
• Xerophytes
– Grow in dry climates
– Leaves designed to conserve water, store
water, insulate against heat
• Sunken stomata
• Thick cuticle
• Sometimes multiple layers to epidermis
stoma
Oleander
multiple
epidermis
Fig

Adaptations for Environmental
Extremes
• Xerophytes
– Abundance of fibers in leaves
• Help support leaves
• Help leaf hold shape when it dries
– Examples
• Oleander ( Nerium oleander )
• Fig ( Ficus )
• Jade plant ( Crassula argentea )

Adaptations for Environmental
Extremes
• Hydrophytes
– Grow in moist environments
– Lack characteristics to conserve water
– Leaves
• Thin
• Thin cuticle
• Often deeply lobed
• Mesophytes
– Grow in moderate climates

Leaf Modifications
• Spines
– Cells with hard cell wall
– Pointed and dangerous to potential predators
Leaf modifications for defense

Leaf Modifications
• Tendrils
– Modified leaflets
– Wrap around things and support shoot
Leaf tendril of
Sweet Pea.

Leaf Modifications
• Bulbs
– Thick leaves sometimes referred to as bulb scales
• Store food and water
– Modified branches with short, thick stem and
short, thick storage leaves
Bulb -
storage
Swollen leaf base
Stem
Leaf Blade

Leaf Modifications
• Plantlets
– Leaves have notches along margins
– Meristem develops in bottom of each notch
that produce a new plantlet
– Plantlet falls off leaf and roots in soil
– Form of vegetative (asexual) reproduction
– Example
• Air-plant ( Kalanchoe pinnata )

Fig. 6-17, p. 101
tendril
plantlets

A fly on a Venus Flytrap plant.
Credit: © Gary Meszaros/Visuals Unlimited
196021

Venus fly trap
Pitcher plants Leaf modifications
for feeding

Leaf Abscission
• Abscission – separation
• Result of differentiation and specialization
at region at base of petiole called
abscission zone
– Weak area due to