Survivors of the Fire.

Posted by on September 25, 2017

The pictures below show the destruction of all vegetation and buildings, yet amongst the debris new life has emerged after three months. The stems are blackened and charred, but the new leaves stand proud and defiant.

 

Cycads have survived for over 50 million years with little change in their basic character.  Neither fire or drought presents any real danger to their survival, only man.

Once found worldwide, they now grow only in tropical and subtropical regions: Florida and the New World tropics, southern Africa, south and east Asia, Australia and the South Pacific. Some of the 250 living species are relatively common, others endangered.

These pioneers may have invented some of the fundamental relationships between plants and other organisms: symbiosis, pollination, seed dispersal. And they may have been among the first to evolve toxins to defend their leaves and seeds from animals.

Cycads formed a partnership with nitrogen-fixing bacteria long before beans and other modern plants followed suit. The bacteria colonize special coralloid roots that grow to the soil surface. The nitrogen they provide helps their hosts persist in nutrient-poor environments.

Temperature fluctuation was probably the most testing factor in the earlier phase of survival and species today suffer less permanent damage than most other plants under wide fluctuations of temperature. After the evolution and spread of the grasses and the advent of generally drier conditions within the environment, Cycads were put to the critical test of fire. To meet this new hazard, the stems of Encephalartos species already possessed the protection of persistent leaf-bases and scales to a thickness of 2 – 7.3cm.  This protective covering has withstood the test of fire periodically for many centuries.

As with many perennial herbs and bulbs in grassland, fire may now act as a stimulus to fresh growth. This is illustrated by an account by Mr. V. L. Pringle of Bedford in the Cape Province:—“ I have been very interested this season in the behaviour of the Cycads (Encephalartos cycadifolius) which grow in these mountains. In August lastyear I burnt down some stretches in the mountain which had become overgrown with coarse grass and all the Cycads, of which there are hundreds, had their leaves burnt off. They soon came out in full leaf and are now looking better than ever before—and there is scarcely one in hundreds which has not fruited. I notice that where others grow, which were not burnt, there is no sign of any fruit as yet. The good rains at the end of July might have helped them but it has been dry through September-October-November. The only explanation which I can see is that the burning has stimulated the plants ” .

Here it may be added that Stangeria, which is no doubt similarly responsive to the stimulus of fire, but whose stems do not have the protection of leaf-bases, is restricted to one species with a subterranean stem. The kernel or endosperm surrounding the embryo has proved poisonous in all species of Encephalartos which have been reliably tested. Encephalartos is not an exception in the Family in this respect, which suggests that the toxicity of the seed has also had a significant bearing on the persistence of the family throughout the ages.

Cycads are protected in all the Provinces and strict protective laws and heavy penalties are laid down in each province. Permits are required for the possession, sale  or transport of cycads.

 

2 Comments

  1. Thank You Esther!

  2. A lovely article thanks Esther

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