Saturday, August 27, 2011

Platycerium alcicorne: was born in Gondwana

About 150 million years ago in the Southern Hemisphere of the Earth had one large continent called Gondwana that was separated of the immense continent unique Pangaea. In the following millions of years during the Late Jurassic this great austral continent Gondwana went fragmenting with the movement of the tectonic plates and two subcontinents formed: moving towards the northwest the subcontinent formed by Africa and South America and moving towards the northeast the subcontinent formed by India, Madagascar, Australia and the Antarctic.

About 100 million years ago South America separated from Africa and went moving towards the west, whereas India and Madagascar separated from the block formed by Australia and the Antarctic and went moving towards the northeast at the vertiginous speed of 15 centimeters per year. About 90 million years ago during the Late Cretaceous Madagascar separated from India and in its displacement towards the north it ran aground when hitting the African plate and slowed down its displacement, whereas India continued ascending towards the northeast until hitting the Asian plate makes about 35 million years, initiating the formation of the mountain range of the Himalayas that has still not finished.

The fern Platycerium alcicorne formed in the great southern continent Gondwana some 150 million years ago during the Late Jurassic, just before they separated Africa and Madagascar, is therefore a very primitive fern that has changed very little over its long existence. At present this species lives in various regions of Africa, mainly in Mozambique and Zimbabwe and in Madagascar, Seychelles and Comoros. African specimens, formerly known by the scientific name Platycerium vassei are somewhat larger than the Malagasy and more resistant to drought. A recent genetic study confirmed the common origin of Malagasy and African subspecies, which, despite having separated more than 100 million years, are few differences in their genome.

Elkhorn fern, like all species of the genus Platycerium, lives as an epiphyte and always retains the antediluvian look 150 million years ago. Hill little to imagine it in ebullient tropical forests on the tops of the primitive coniferous and the arboreal ferns in a very warm and permanently humid atmosphere.

All Platycerium have two kinds of leaves or fronds. At the base of the plant on more o less horizontal position and a fan or kidney form is a basal sterile frond that covers and protects the rhizomes from drying out. The rhizome is short and is firmly anchored on the bark of a tree. From the center of the sterile frond they sprout fertile fronds growing upright at first and gradually becoming pendulous.

The basal sterile frond conserves the reniform typical form of prothallus or gametophyte of all ferns. It looks like a giant gametophyte. This detail reminds us of the great antiquity and primitiveness of the genus Platycerium ferns.

In this image of a sporophyte of Anogramma leptophylla fern springing from the fertilized oosphere of a gametophyte can appreciate the extraordinary resemblance to the sterile frond Platycerium. The gametophyte or prothallus of all ferns have kidney-shaped and are embedded and applied to the substrate, just as the basal frond of Platycerium. From fertilized oosphere of  gametophyte sprouts a tiny frond or sporophyte that in the case of Anogramma is shaped like a small elkhorn. The similarities are remarkable and surprising. Platycerium is possible that they are the ancestors of many modern fern that apparently have nothing to do with them. In the not too distant future the study of the genome of these primitive plants so will bring many surprises when compared with the genomes of other ferns.

Obverse of a fertile frond that is covered with a fine hairiness that confers a off-white green color to it, sometimes grayish. Its form remembers to a horn of elk. The botanist who described the Platycerium sort fixed indeed to this peculiar form and he baptized it for science combining two Greek words: platys that means plane and keras that means horn, that is to say, leaves in the form of equal flat horn to the graft and flattened horns of the elk. The name of the species " alcicorne" it comes from the combination of two Latin words and its translation is obvious: alci-corne = elk horn. 

On the underside of fertile fronds on the tips of the branches are the sori formed by milions of brown sporangia.

Undersides of other fertile frond of Platycerium alcicorne. The sori have the look and soft feel of velvet.

In this image nearest well appreciated the velvety appearance of the sori and the fine gray-white pilosity covering the fronds.

If we get closer we see the structure of a sorus which consists of closely spaced parallel rows of brown sporangia filled with mature spores.

Friday, August 19, 2011

The coffee tree: an example of vegetal inteligence

The coffee plant belongs to the Coffea sort of the Rubiaceae family. Within the sort there is a total of ten species distributed by the south of Asia and subtropical Africa. The most cultivated is the Coffea arabica that is believed to be original of Ethiopia, although some botanists differ and locate its origin in Yemen. The coffee is an evergreen small shrub that gets to reach arboreal dimensions in wild state, surpassing sometimes the 15 meters of height. It prefers to grow in the shade of other trees.

It has been written much on this plant and I am not going to repeat it in this article. I want despite emphasizing two details less well-known than they have allowed it to proliferate extraordinarily of the hand of the man. 

Ripe fruits of cultivated Coffea arabica in the Botanical Garden of the Orotava in the Island of Tenerife. 

I want to talk in the first place on the true purpose of the alkaloid caffein. Logically the coffee does not think about the man when synthesizing this stimulant. About which it really thinks is in defending itself of its main natural predators: the phytophagous insects. It is that caffein is a powerful insecticide that kills the arthropods that dare to eat their leaves, flowers and fruits. Being the most vulnerable parts the shoots and the flower buds on them concentrate more this powerful poison. 

 Coffea arabica branches laden with ripe fruits. I recommend to extend the photos to see better the details.

Also their seeds just germinated synthesize great amounts of this alkaloid with two purposes: first to protect the small plants of the phytophagous insectss and the second and much more surprising one to inhibit the germination of other seeds of coffee that can do the competition to it, so that the first seed that germinates inhibits to that it has close and thus a greater probability makes sure survival. Somehow the other seeds detect the high concentration of caffeine of their sister and they are sacrificed so that it can survive. If they germinated all the competition among them it would be so ferocious that in the end no would be able to reach the adult age and the species as a whole would leave losing.

 Leaves of Coffea stenophylla. The leaves of all the species of coffee plant are green dark, shining, whole and ovate-lanceolate.

Gorgeous flower of Coffea stenophylla of an immaculate target that shines with own light. It is very similar to the flowers of another rubiaceae, the Gardenia thunbergia of South Africa.

Leaves and fruits of Coffea arabica  photographed at the beginning of May in the Botanical Garden of Funchal in the Island of Madeira.
The second detail that I want to stand out makes also reference to the caffein, a stimulant that captivated the first humans who consumed its toasted  fruits more ago than thousand years in the Arabic peninsula. This alkaloid synthesized to defend itself of the hungry of insects has allowed it to proliferate and to colonize all the tropical and subtropical regions of the Earth of the hand of the man, competing with other plants that also synthesize caffeine as tea, cocoa, mate, guarana, kola nut and holly of Yaupon. 

Green and ripe fruits of Coffea arabica.

In the end one is asked: who explodes to whom, who obtains more benefits, the coffee plant or the man. The answer is evident. Without the interested aid of the humans the coffee plant would follow confinated in its reduced origin regions. It would be a shrub more fighting to survive with the intelligent strategy to synthesize poison and to concentrate it in all the parts of its anatomy, from the roots to the leaves, flowers and fruits. Without wanting it, without a premeditaded natural planning, indeed it has been its poison that as much likes the humans which has turned to it into one of the worked plants more extended and numerous, calculating in about 15,000 million unit the total number of coffee plants that occupy more than 100,000 km2s of plantations. The operator apparently is the man, but the one that leaves winning is the coffee plant. The aromatic infusion of that they are consumed hundreds of million cups every day is one more a reward than sufficient for the man. To the coffee plant it does not matter to him to sacrifice 99´99% of its fruits if in return its survival makes sure on a large scale.

Saturday, August 13, 2011

Structural genetics: the Golden Ratio Phi ( φ )

The Golden Ratio Phi, represented with the Greek letter φ in honor the Greek sculptor Fidias, is a mathematical concept that makes reference to a peculiar proportion between straight line segments that can be observed in the nature (flowers, leaves, branches, roots, molluscs, starfishes, structures of chorale, rock crystals, snowflakes, ideal proportion between the parts of the human body, etc…) and in certain geometric figures (triangle, circle, squaring, rectangle, star, ellipse, rhombus, cube, sphere, pentagon, tetrahedron, octahedron, icosahedron, dodecahedron, etc.). It is an irrational algebraic number, a non-periodic infinite decimal, that cannot be reduced nor divided.

It was described and studied for the first time by Euclides towards 300 year B.C. In the Middle Ages an aesthetic and divine character was attributed to it considering perfect the proportions that followed the principles of the golden ratio. Its mathematical formula is φ = 1 + √5/2 = 1´6180339887 ....... until the infinite. The squared Root of 5 is also an irrational algebraic number with an infinite value.

φ = AC / BC = 1´61803.
In this flower of Potentilla reptans is very easy to find the golden ratio uniting with straight lines the recesses of each of its five petals drawing a regular pentagon. Soon it is enough to draw up another straight line uniting the recesses of two noncontiguous petals and we both obtain values to calculate the golden ratio. Sometimes the obtained number is not exact although very approximated. In order to sharpen plus the result the values of each one of the five angles of the pentagon can be obtained and to remove the average, and so a golden ratio is obtained practically exact.

φ = AB / BC = 1´61803.
In this flower of Eruca sativa is also very easy to find two values to calculate the golden ratio. When having four identical petals are sufficient with drawing a straight line uniting each two petals and so is obtained a perfect squaring. Soon the four sides of the squared one with two lines are united that are crossed in center of the flower and the four squaring identical smallest ones are obtained. Drawing up a line in diagonal that goes from the corner of squaring to the opposed corner of contiguous squaring it obtains first value AB. The other value BC is obtained drawing a diagonal line connecting  two opposed corners of a same one squaring. 

φ = AB / BC = 1´61803.
This small flower of Ophrys speculum has the mystical beauty attributed by the mathematicians to the forms that fulfill the proportions of the golden ratio. It was very simple to find two values to calculate it with an amazing exactitude.

The properties and possible applications of this euclidian number profusely have been studied by the mathematicians from the century eighteen to the present time, giving rise to diverse theorems, mathematical equations and formulas, like the famous Theorem of Kolmogórov-Arnold-Moser or theorem KAM.

It was found one close relation between the golden ratio and the Sequence of Fibonacci. Both mathematical concepts are widely represented in the nature.

φ = AB / CD = 1´61803.
This small flower almost albino of Solenopsis balearica, endemic to Majorca, it also has a structure in the form and distribution of its five petals that seem designed by a mathematician. A simple outline uniting the vertices of both lateral major petals gives the  first value AB and another outline uniting the vertices of both smaller petals gives to the other value CD. The simplicity and the beauty of the design are amazing. The obtained golden ratio is surprising exact.

φ = AB / AC = 1´61803. 
φ = AB / BC = 1´61803. 
This flower of marine lily, Pancratium maritimum, of an immaculate target and a perfect symmetry account with a design that facilitates much to find two values to calculate the golden ratio. First value AB is obtained uniting with a straight line the vertices of two opposite petals. In order to find the second value two lines draw up that go from the vertex of each one of the two previous petals to the vertex of a noncontiguous petal. These two lines are crossed in point C and form a cross with two long arms and two short arms. Each one of the long arms are the second value.
φ = AB / CD = 1´61803.
φ = CD / EF = 1´61803. 
 In the leaves it is something more complicated to find two values that allow to obtain an exact golden ratio. Nevertheless in this leaf of canary blackberry, Rubus palmensis, the proportions of their five leaflets have decreasing values that when dividing between them give a surprisingly accurate result.

φ = AC / AB = 1´61803.
 And finally another example of a canary plant, the Hedera canariensis, photographed in the gorgeous Bosque de Los Tiles of the Island of La Palma. Their cordate leaves of a perfect symmetry allow to find with facility two diagonal lines that when being divided between them give the golden ratio, the magic number of the divine beauty and the perfection.

Throughout the centuries this mathematical proportion with so abundant examples in the alive beings and rocks has been used by the painters, sculptors and architects to realise their more beautiful works in an eagerness to shape the ideal of perfection, symmetry and balance that so wisely the nature designs. 


Saturday, August 6, 2011

Structural genetics: the perpetuation of evolutionary models successfully

When nature is able to generate a successful structure in a living being, perpetuates the genes that encode the new things emerged by evolution from primordial ancestor. Never mind the millions of years separating them. The basic structure, the intimate setting of its anatomy is always essentially the same and of course genes too.

One of the basic structures are the most striking inflorescences of conifers and palm trees that bear a remarkable resemblance to the fertile fronds of the Osmundaceae family ferns. Pollen from these inflorescences are dispersed by anemocoria through wind, just like the spores of the fern sporangia.

 Fertile fronds of the fern Osmunda regalis end of which develops a branching structure of sporangia naked without indusium. When the spores mature, the wind scattered as far away from its mother to conquer new territory.

Detail of the reproductive structure of Osmunda regalis.

Pinus halepensis male inflorescence loaded with pollen is dispersed by the wind. Each set of flowers is very similar structural groups of sporangia of the fern Osmunda regalis.

Male inflorescence of Pinus canariensis. These flowers without petals and no nectar have no attraction for pollinating insects. Pollen is dispersed by anemocoria through wind.

 Pinus canariensis branch with male inflorescences.

Male inflorescence of the palm Syagrus romanzoffiana called Coco feathery Brazil, formed by groups branched pollen-laden flowers as in all these plants are dispersed by wind. Its basic structure is identical to the fertile fronds of Osmunda regalis.

If we extended this image with a double click we will be able to see the masculine inflorescences of this palm of the fortune, Trachycarpus fortunei, original of China. As all the masculine inflorescences of the Arecaceae keep a great structural similarity with the groups from esporangia of the fertile fronds of the Osmundaceae.

If we delve into the intimacy of these structures and focus on each of the subgroups of sporangia and male flowers, we will find even more similarities. A striking example is the strobili of the ferns of the families of the Ophioglossaceae and Equisetaceae and inflorescences of the Cupressaceae, Cycadaceae and Pinaceae.

 Fertile fronds of the fern Equisetum telmateia with strobili in its extremes.

Each strobilus consists of a conical structure of sporangiophores with sacks of sporangia on the inside.

 Equisetum telmateia strobilus with hexagonal sporangiophores in the form of honeycomb that are spreading to allow the dispersal of spores.

Equisetum telmateia spores bags breaking off and start their dispersal by wind.

Giant Cycas revoluta male inflorescence with a conical structure identical to the strobili of the Equisetaceae.

Close-up image of the previous inflorescence with separate scales for the wind to disperse pollen from the flowers without petals hidden in the back of the inflorescence.

Masculine inflorescences of Zamia furfuracea, an extraordinarily primitive Mexican plant. Its inflorescences are identical to the strobili of the Equisetum.

  In this image we can see the interior of a masculine inflorescence of  Zamia furfuracea with the small already empty coats of pollen after its dispersion by the wind. Its structure surprises by its great similarity with the coats of esporangia of a Equisetum. A few million years of evolution allowed to give the jump of spores to pollen, or rather, of masculine microspores to pollen, since the feminine megaspores were transformed into seeds.

Looking at each of the small subgroups of male flowers of the inflorescence of Pinus canariensis, we note its resemblance to the strobili of the Equisetaceae and inflorescences of the Cycadaceae and Zamiaceae.

These beautiful male inflorescences of Abies pinsapo also have the same structure as the strobili of the Equisetaceae, Zamiaceae and Cycadaceae.

A simplified structure very similar to the above is that of the tiny strobilus of fern Ophioglossum lusitanicum formed by two rows of sporangia.

Another example are these tiny simplified inflorescences of Tetraclinis articulata conifer, endemic to Murcia. Each ones have a basic structure identical to the previous examples.

Also, the male catkins of hazel follow the same pattern that a structural and functional fertile frond Osmunda regalis.

Macroscopic image of a hazel catkins with trefoil detail cottony scales which separate at maturity and thus allow the pollen grains contained in the 8 stamens are hidden on the inside could be dispersed by wind.

If we look at the female inflorescences of these plants will see their basic structure also bears a remarkable resemblance to the strobili of the ferns Ophioglossum and Equisetum. Nature is very conservative and has a strong tendency for the economy. When, after many experiments to get a successful structure, stop wasting time and energy in finding new adaptations and merely repeating the same structure in all living descendants of the primeval. Only in some cases partially changed some details for better reproductive efficiency and/or adaptive.

Tiny female inflorescence of Pinus halepensis, almost equal to the strobilus of the ferns of the family Equisetaceae.

Female inflorescence of Pinus pinea.

Strobilus of Equisetum ramosissimum.

Detail of sporangiophores in the form of honeycomb cells.

 Female inflorescence of Encephalartos lehmannii of South Africa the family Zamiaceae, an antediluvian plant midway between a fern and a conifer. In fact it has found a possible ancestor fossil unfortunately extinct. Fern was a very evolved which was capable of producing female megaspores were not dispersed by wind but remained in the sporangium, it germinated and gave rise to a female gametophyte with a oosphere, which was fertilized by a antherozoids from a male gametophyte. After fertilization, an embryo is formed, a paralyzing sporophyte growth and entered diapause or resting. Had just been born the first seed. When dropped in a suitable medium, restarted the growth of the embryo and gave rise to a new plant, the first capable of reproducing by seed.

Female inflorescence of Macrozamia communis, Burrawang call, also a very primitive plant native to New South Wales in Australia.

 The structure of this feminine inflorescence of Macrozamia communis is looked extraordinarily like a conifer cone, a tropical pineapple, an strobilus of Equisetum, etc. I recommend to extend the photo with a double click.

Bromeliaceae also have a strobilus-like inflorescences of Equisetaceae. Here is the inflorescence of pineapple, Ananas comosus, a very primitive plant also holds a remarkable resemblance in its inflorescence with Cycadaceae and Zamiaceae.

Pineapple of Pinus pinea, whose grudges are abren when maturing and allow the dispersion of the pinions. If they have luck and they fall in a very illuminated place far from the shade of its mother, they germinate and little by little it is formed a small copse of brother pines. If we paid attention to the structure of this pineapple and we compared it with strobilus of Equisetum, the grudges would be the hexagonal sporangiophores slightly modified and the great pinions would be the equivalent to the coats of spores. Since or we have seen previously in the explanation of the birth of the first seed proper in the extinguished fern, each of these great pinions would be in fact the oosphere of a feminine gametophyte been born from a megaspore that has been fertilized by a anterozoide or grain of pollen taken by the wind coming from a masculine gametophyte. These fertilized oospheres or pinions with the sporophyte or embryo partially developed in their interior grow of two in two occupying all the space that occupied million ago years the coats of spores of the sporangia of their original ancestor, that had the audacity to give a great jump in the evolution and transformed megaspores into seeds. The Spermatophytas or superior plants that reproduce by seeds were born this way.

A tree whose fruit shaped strobilus clearly speak us of its age or primitivism is the Magnolia grandiflora. The basic structure remains the same with very small variations.

 The scales of the fruit remind us the sporangiophores of a strobilus of Equisetum, the scales of the male flowers of the hazel tree and the Murcian conifer  Tetraclinis articulata, the scales of the pineapple, the female fruit of Macrozamia communis and the male strobilus of Cycas revoluta.

The beautiful red fruits of Magnolia grandiflora would be female oospheres transformed into seeds. The Magnoliaceae are trees with flowers, beautiful flowers by the way, however their fruits have remained unchanged over millions of years. They have not had any need to change the structural model. It has been great,  allowing them to survive innumerable climatic changes.

Many other plants, generally very primitive have inflorescences in strobilus more or less modified. This is the case of the Araceae, whose reproductive system has ceased to depend on wind for pollen dispersal and has evolved to adapt to the rotten flies that are their pollinators. One of the most famous is the Araceae Amorphophallus titanum, the world's largest flower.

 Arum italicum inflorescence with fragrant spadix-like strobilus that emits an unpleasant smell of rotting meat and attracts meat flies.

Intimate anatomy of the inflorescence of Arum italicum. When a meat fly, attracted by her favorite perfume, lands on the inner surface of the spathe, the hair falls over and slides down toward the bottom of the inflorescence, where the female flowers. Once inside it realizes the deception and want to leave, but the down hairs prevent it. Other flies, some with their bodies covered with pollen from another Arum, fall into the same trap and desperate to go out again and again over the female flowers and pollinate them. When Arum find that its female flowers have been fertilized, mature male flowers which are covered with pollen. Dehydrated while leaving the hair down to a barrier and flies can go, but they goes over the male flowers and take with them the Arum pollen. Once outside, desperate with hunger are lured by the inflorescences of other Arum and starts other time the process of pollination.

As much the masculine flowers as the feminine ones have a great similarity with the sporangiophores of strobilus of Equisetum telmateia.

Other Araceae, the Monstera deliciosa, also has its inflorescence as strobilus.

Its fruits have the form and the typical structure of a strobilus.

So great it is the similarity of the inflorescence of Monstera deliciosa with a strobilus that even repeats faithfully the hexagonal structure of the sporangiophores of Equisetum telmateia. In the case of the Monstera deliciosa the masculine flowers are hidden between the hexagonal feminine flowers. It is seen leave pollen between the hexagons. This one is perhaps the most demonstrative example of the repetition of a successful evolutionary model.

Combined image with the comparison of the hexagons of Equisetum telmateia and Monstera deliciosa.

And for to finish these beautiful purple inflorescences of Arum pictum, Tyrrhenian endemism growing in Corsica, Sardinia, Mallorca and Menorca. Its spadix nearly black also has the structure in strobilus.