1. Floral Color Changes in
Boswellia sacra Flueck
Flora-Morphology, Distribution, Functional Ecology of Plants
Volume 206, Issue 9, September 2011
Botany 2110
Samantha Kane

2. Facts about Boswellia sacra
 Also known as Frankincense; found in the Bible
 Part of the Burseraceae family
 Used for perfume and medicine
 Popular in trade

3. Facts about Boswellia sacra
 Found in South Arabia and North East Asia
 Found in extreme locations
 Population is decreasing because of overgrazing
and human destruction
 National Park in WadiDowkha

4. Boswellia sacra
 Flowering stage begins in the winter until April
 Fruiting bodies are ripe by March
 Characteristics:
 green calyx
 radial symmetry
 five white petals
 ten stamens that have yellow anthers
 one pistil
 nectariferous ring is present in the ovary and can
change colors from yellow to red to black

6. Purpose & Hypothesis
 Purpose: to figure out why the nectariferous ring
changed colors
 Hypothesis: the color change helped lure pollinators
towards the flower with the reward of nectar

7. The Study
 Took place along the coasts of Dhofar and in the
WadiDowkha National Park
 Flowers were collected in February and March from
2006-2010
 Nectar and pollination were observed in the
morning (7:30-8am) and sunset (6-6:30) for a week
 Microscopical observations were observed in labs in
Florence

8. Under the Microscopes
 Different stains were used to see detail under the
light microscopes including:
 ToluidineBlue for testing lignin
 Mercuric Bromophenol Blue for proteins
 Acriflavinestain for total polysaccharides
 Alcian Blue for acidic polysaccharides
 Fluorol Yellow-088 for lipids

9. Methods
 The pistils and nectariferous discs were covered in
glutaraldehyde (a disinfectant and preservative)
 stained with PAS (Periodic Acid Schiff) to see
undissolvablepolysaccharides
 stained with Blue Nile Sulfate to see the neutral and
acidic lipids
 The nectariferous rings were cut off and covered in
an alkaline and an acidic solution to test for
anthocyanins. (may appear in different colors
depending on pH)

10. Results of Flower Organs
(Nectariferous Ring)
 Located between the stamens and the ovary (3mm in diameter)
 Changes color from yellow to red depending on the maturity of the
flower
 Before anthesis, (flower opens its petals) the nectariferous ring is fully
developed
 Trichomes are covered in a cuticle layer where nectar drops can be
found
 The drops show a positive response to the PAS reagent, Alcian Blue,
and Mercuric Mromopenol Blue. (shows polysaccharides exist!)
 Stomata always open with guard cells appearing outward

11. Results of Flower Organs
(Pistil)
 The stigma (top of pistil) has a
positive response towards the
Alcain Blue, and Blue Nile
Sulfate stains (test acidic
polysaccharides and neutral
lipids)
 After fertilization, the ovary
swells transforms into a fruit
with a seed in each open
compartment

12. Results of Flower Organs
(Anthers)
 Anthers on the flower are all the same size with
longitudinal dehiscence (spontaneously opening)
 yellow in color with trichomes sparsely located
 anthers swell due to the large amount of pollen
 dehiscence takes place

13. Color Changes
 The nectariferous ring is already a yellow color when the
petals begin to open; many liquid drops found
 Changes to orange and few drops are present. Nectar
begins to be reabsorbed. Largest amount of pollen
germination occurs. Anthers empty and the stigma
changes its green color to a brown
 Changes to red and is completely dry and lacking nectar.
Anthers begin to fall and stigma dry up and darken
 Only fifteen hours are needed for the color changes

15. Color Changes
 Lastly, the nectariferous ring will turn brown with black
patches. The surface is wilted and rough. The ovary is growing
into the fruit
 Takes two days to change from yellow to brown
 Red stage changes to a green-blue color once dipped into an
alkaline medium and will change back to red once rinsed in
acid showing that there are many anthocyanins present.

16. Field Observations
(Pollinators)
 Many pollinators
 Main pollinators in the day-
bees, wasps, and ants
 Other visitors-butterflies and
little flies
 pollinators preferred flowers
with the yellow nectariferous
ring , the red were not
visited at all

17. Conclusions
 Color changes help lead the pollinators towards the rewarding
flowers
 Mutualistic relationship (plants get pollinated and pollinator
gets pollen and nectar as nutrients)
 Insects are attracted to the yellow and orange phase; no nectar
reward in the red phase
 The color change occurs because of high amounts of
anthocyanins
 that flowers with nectar rewards and an attractive color for
pollinators have a greater chance of reproducing and
outcompeting other plants