Feeling Blue

By Evelyn Roe, Botanist with North-West Naturalists' Society of Zambia

Does Lobelia feel blue? Is Wahlen bergia ringing a sad note from its bell-like flower? Maybe they’re a little lonesome because blue is rare in the plant kingdom, occurring in less than 10% of the world’s 350,000 flowering plant species.

Aptosimum decumbens

In the Livingstone area, we seem to have our fair share of floral blueness, from the delicate petals of Lobelia kirkii which grace the paths at the Victoria Falls, to the dense hairs in which the stamens of Cyanotis longifolia are enmeshed; and from the creeping Aptosimum to the climbing Evolvulus, both of which bear blue-hued tubular flowers.

Cyanotis longifolia

However, some plant families cannot produce blue flowers, not even under duress! Horticulturalists have been trying for decades to produce a blue rose, but the latest genetic technology has managed only a pale imitation - a lilac rose.

Wahlenbergia_denticulata

So, what is the secret of the blue-flowering plant?

Certain families are capable of performing a kind of floral magic. First, they make red anthocyanins, which are found commonly in the plant kingdom, and store them in the watery vacuoles of their cells. Later, they transform them into blue pigments when they have the right conditions of light, acidity, a supply of particular metal ions, and a stack of other essential plant chemicals. The complexity of the transformation has been noted by scientists, but exactly how it happens remains a mystery.

Evolvulus alsinoides

We might ask, is flower colour significant for the plant? Many birds and insects are attracted to blue flowers and harvest their nectar, helping with pollination on such feeding forays. However, they also visit flowers with red and yellow hues, so it’s difficult for researchers to work out what it means to be blue. Perhaps it’s not the outward appearance of blueness that makes a difference; it could be that other qualities of the pigments– such as their metallic nature - influence the plant’s development and wellbeing.

Commelina forskaolii

In Tradescantia, which is a close relative of Commelina and Cyanotis, the blue stamen hairs mutate to pink in the presence of nuclear or chemical pollution. Experiments over the past 40 years have shown that spiderwort, as Tradescantia is commonly known, can be used as a reliable detector of such environmental contaminants.

Lobelia kirkii

In some cultures, the blue flower is a symbol of inspiration, hope and love. It can also represent the striving for the divine, and the merging of the self with nature. How does this tie in with our association of the colour blue with feelings of sadness, I wonder? Perhaps the coolness and spaciousness of the Earth’s azure skies and deep-blue seas create feelings of alone-ness; or maybe our human striving for union with the divine and the infinite is simply unreachable and unobtainable...just like the blue rose.

More from this issue:
ZT17 (June 2014) - Main Menu
ZT17 (June 2014) - Full Content Listing

More from the Zambezi Traveller:
Livingstone News

More articles in this series:

Silent Trumpets (ZT, Issue 16, Mar 2014)
Christmas crackers (ZT, Issue 15, Dec 2013)
Don't eat the daffodils (ZT, Issue 14, Sept 2013)
Rainforest Riches (ZT, Issue 13, June 2013)
Berry banquet (ZT, Issue 12, March 2013)
Marvellous Mangoes (ZT, Issue 11, December 2012)
Underground Forests (ZT, Issue 10, September 2012)
The healing powers of Aloes (ZT, Issue 09, June 2012)
Dogbane Drugs (ZT, Issue 08, March 2012)
Devil’s Claw (ZT, Issue 07, December 2011)
Elephant Toothpicks (ZT, Issue 06, Sept 2011)