Frankincense…

Twelve years ago the BBC published two stories about the probable disappearance of frankincense – here and here. Frankincense continues to be produced so perhaps concerns about the sustainability of its production were listened to, and suitable action taken. It is a valuable commodity for those involved in its production.

Frankincense is the hardened resin from the trunk of the tree Boswellia sacra. The bark is cut and the resin forms on the outside or drips onto the ground. There are two sets of vessels in plants that carry fluids – xylem and phloem. Xylem transports water and minerals from the roots to the top of the tree. Each year the xylem channels die off and new ones are produced. The rings you see when a tree trunk is cut are the old xylem channels, one ring for each year of life. Phloem carries the sticky, sugary sap. This is made up of the sugar made during photosynthesis, which is then fed back into the tree and leaves as food to provide energy for growth.

Unfortunately, the harvesting process of frankincense is very damaging to the tree. So, every time people go there and make wounds and then collect the sap, that doesn’t give enough time to rest for the tree and heal itself. So, one of our findings is this tree is really under a threat.

Kindeya Gebrehiwot, an Ethiopian resin tapper.

This aromatic resin is used in incense and perfume. It can vary in quality depending upon its colour and odour. It is a highly prized and valuable substance. Essential oil made from frankincense can reach $6000 per litre. It has been estimated that the Roman Catholic Church uses 50 tonnes of frankincense each year as part of the incense burned during services.

The main tree from which it is produced, Boswellia sacra, grows in Ethiopia, northern Somalia, south-western Oman, southern Yemen and the Arabian Peninsula. It favours rocky limestone terrain and can grow in very harsh conditions. The trees hold on to rocks with a strange swelling at the base of the trunk. This base helps it to steady the tree and is most noticeable in trees growing on steep or exposed rocks.

Boswellia sacra is deciduous and produces its flowers clustered along short stems called racemes. It has anthers that produce pollen and it relies upon insects to transfer this to the stigma on the flowers of other trees. There is some evidence that trees that are over exploited, and tapped for resin too often, produce seeds that are less able to germinate.

Questions…

1. What does deciduous mean?
2. What is the chemical name for limestone?
3. Why is the soil that Boswelia sacra grows in unlikely to be acidic?
4. What structure in a flower produces the male gamete?
5. How does the photograph suggest that Boswellia sacra is insect pollinated?
6. What advantage does the tree gain by reproducing sexually rather than asexually?