Plants and animals can also live in marriage

When we think about the life of plants it is difficult to imagine without interaction with the animals, as they establish different symbiotic relationships day after day. These symbiotic relationships include all the herbivores, or in the contradictory way, all the carnivorous plants. But there are many other super important interactions between plants and animals, such as the relationships that allow them to help each other and to live together. So, this time I want to present mutualism between plants and animals.

And, what is mutualism? it is the relationship established between two organisms in which both benefit from living together, i.e., the two get a reward when they live with the other. This relationship increase their biological effectiveness (fitness), so there is a tendency to live always together.

According to this definition, both pollination and seed dispersal by animals are cases of mutualism. Let’s see.

POLLINATION BY ANIMALS

Many plants are visited by animals seeking to feed on nectar, pollen or other sugars they produce in their flowers and, during this process, the animals carry pollen from one flower to others, allowing it reaches the stigma in a very effective way. Thus, the plant gets the benefit of fertilization with a lower cost of pollen production, which would be higher if it was dispersed through the air. And the animals, in exchange, obtain food. Therefore, a true relationship of mutualism is stablished between the two organisms.

 “Video:The Beauty of Pollination” – Super Soul Sunday – Oprah Winfrey Network (www.youtube.com)

The extreme mutualism occurs when the species evolve depending on the other organism, i.e., when there is coevolution. We define the coevolution such as these evolutionary adaptations that allow two or more organisms to establish a deep relationship of symbiosis, due that the evolutionary adaptations of one specie influence the evolutionary adaptations of another organism. For example, this occurs between various orchids and their pollinators, as is the well- known case of Darwin’s orchid. But there are many other plants that also have co-evolved with their pollinators, as a fig tree or cassava.

In no way, this should be confused with the trickery produced by some plants to their pollinators, that is, when they do not obtain any direct benefit. For example, some orchids can attract their pollinators through odours (pheromones) and their curious forms that resemble female pollinator, stimulating them to visit their flowers. The pollinators will be impregnated with pollen, which will be transported to other flowers due to the same trickery.

Bee orchid (Ophrys apifera) (Autnor: Bernard DUPONT, flickr).

SEED DISPERSAL BY ANIMALS

The origin of seed dispersal by animals probably had occurred thanks to a co-evolutionary process between animals and mechanisms of seed dispersal in which both plants and animals obtain a profit. The most probably is that this process began in the Carboniferous (~ 300MA), as it is believed that some plants like cycads developed a false fleshy fruits that could be consumed by primitive reptiles that would act as seed dispersers. This process could have intensified the diversification of flowering plants (angiosperms), small mammals and birds during the Cretaceous (65-12MA).

The mutualism can occur in two ways within the seed dispersal by animals.

The first case is carried out by animals that eat seeds or fruits. These seeds or some parts of the fruits (diaspores) are expelled without being damaged, by defecation or regurgitation, allowing the seed germination. In this case, diaspores are carriers of rewards or lures that result very attractive to animals. That is the reason why fruits are usually fleshy, sweet and often have bright colours or emit scents to attract them.

For example, the red-eyed wattle (Acacia cyclops) produces seeds with elaiosomes (a very nutritive substance usually made of lipids) that are bigger than the own seed. This suppose an elevated energy cost to the plant, because it doesn’t only have to produce seeds, as it has to generate the award too. But in return, the rose-breasted or galah cockatoo (Eolophus roseicapillus) transports their seeds in long distances. Because when the galah cockatoo eats elaiosomes, it also ingest seeds which will be transported by its flight until they are expelled elsewhere.

On the left,  Galah  cockatoo (Eolophus roseicapillus) (Autnor: Richard Fisher, flickr) ; On the right, red-eyed wattle’s seeds (black) with the elaiosome (pink) ( Acacia cyclops) (Autnor: Sydney Oats, flickr).

And the other type of seed dispersal by animals that establishes a mutualistic relationship occurs when the seeds or fruits are collected by the animal in times of abundance and then are buried as a food storage to be used when needed. As long as not all seed will be eaten, some will be able to germinate.

A squirrel that is recollecting som nuts (Author: William Murphy, flickr)

But this has not finished yet, since there are other curious and less well-known examples that have somehow made that both animals and plants can live together in a perfect “marriage.” Let’s see examples:

Azteca and Cecropia

Plants of the genus Cecropia live in tropical rain forests of Central and South America and they are very big fighters. The strategy that allow them to grow quickly and capture sunlight, avoiding competition with other plants, resides in the strong relationship they have with Azteca ants. Plants provide nests to the ants, since their stems are normally hollow and with separations, allowing ants to inhabit inside. Furthermore, these plants also produce Müllerian bodies, which are small but very nutritive substances rich in glycogen that ants can eat. In return, the ants protect Cecropia from vines and lianas, allowing them to success as a pioneer plants.

Ant Plants: Cecropia – Azteca Symbiosis (www.youtube.com)

Marcgravia and Bats

Few years ago, an interesting plant has been discovered in Cuba. This plant is pollinated by bats, and it has evolved giving rise to modified leaves that act as satellite dish for echolocation performed by these animals. That is, their shape allow bats to locate them quickly, so they can collect nectar more efficiently. And at the same time, bats also pollinate plants more efficiently, as these animals move very quickly each night to visit hundreds of flowers to feed.

Marcgravia (Author: Alex Popovkin, Bahia, Brazil, Flickr)

In general, we see that the life of plants depends largely on the life of animals, since they are connected in one way or another. All the interactions we have presented are part of an even larger set that make life a more complex and peculiar one, in which one’s life cannot be explained without the other’s life. For this reason, we can say that life of some animals and some plants resembles a marriage.

REFERENCES

• Notes from the Environmental Biology degree (Universitat Autònoma de Barcelona) and the Master’s degree in Biodiversity (Universitat de Barcelona).
• Bascompte, J. & Jordano, P. (2013) Mutualistic Networks (Chapter 1. Biodiversity and Plant-Animal Coevolution). Princeton University Press, pp 224.
• Dansereau, P. (1957): Biogeography: an Ecological Perspective. The Ronald Press, New York., pp. 394.
• Fenner M. & Thompson K. (2005). The Ecology of seeds. Cambridge: Cambridge University Press, 2005. pp. 250.
• Font Quer, P. (1953): Diccionario de Botánica. Editorial Labor, Barcelona.
• Izco, J., Barreno, E., Brugués, M., Costa, M., Devesa, J. A., Fernández, F., Gallardo, T., Llimona, X., Parada, C., Talavera, S. & Valdés, B. (2004) Botánica ªEdición. McGraw-Hill, pp. 906.
• Murray D. R. (2012). Seed dispersal. Academy Press. 322 pp.
• Tiffney B. (2004). Vertebrate dispersal of seed plants through time. Annual Review of Ecology, Evolution and Systematics. 35:1-29.
• Willis, K.J. & McElwain, J.C. (2014) The Evolution of Plants (second edition). Oxford University Press, pp. 424.
• National Geographic (2011). Bats Drawn to Plant via “Echo Beacon”. http://news.nationalgeographic.com/news/2011/07/110728-plants-bats-sonar-pollination-animals-environment/

Photosynthesis and vegetal life

In this article we will talk about photosynthesis and about the first kinds of vegetal life. In the current systematic, the term plant fits primarily to terrestrial plants, while the term vegetal is an old term of Aristotelian connotation that refers to organisms with photosynthetic functions. But, as with everything, there are exceptions.

The term plant has existed for many years. But, previously, Aristotle was who classified the living organisms into three mainly groups:

• Vegetals (vegetative soul): can perform nutrition and reproduction.
• Animals (sensitive soul): nutrition, reproduction, perception, movement and desire.
• Humans: can do all these things and also have the ability to reason.

Aristotle (Public domain)

This simplistic way of perceiving the living world has lasted for a long time, but has varied due to different studies by several authors like Linnaeus or Whittaker, among others.

A very current classification was proposed in 2012, The Revised Classification of Eukaryotes. J. Eukariot. Microbiol. 59 (5): 429-493; this one reveals a true tree of life.

Sina ;. Adl, et al. (2012) The revised classification of Eukaryotes.  J Eukaryot Microbiol.; 59 (5): 429-493

WHAT IS PHOTOSYNTHESIS? IS IT A UNIQUE PROCESS?

Photosynthesis is a metabolic process that allows to use light energy to transform simple inorganic compounds into organic complexes. To do this, they need a number of photosynthetic pigments that capture these light rays and that through a series of chemical reactions allow to perform internal processes that give rise to organic compounds.

This nutritious option has been developed by many organisms in multiple groups and branches of the tree of life of eukaryotes. And among them appears  the Archaeplastida, the lineage of organisms that has led to land plants.

Terrestrial plants (Embryophyta) are easily definable, but what about the algae? Usually, they are defined as eukaryotic organisms living primarily in the aquatic environment and with a relatively simple organization, but this is not always true. For this reason, all Archaeplastida groups falling outside the concept of land plants (a small group within Archaeplastida) are called “algae“.

There are also photosynthetic prokaryotes into Eubacteria domain, and it is in these where photosynthesis is highly variable. While in eukaryotes is unique, oxygenic photosynthesis.

The Eubacteria domain is very broad, and among its branches there are up to 5 large groups of photosynthetic organisms: Chloroflexi, Firmicutes, Chlorobi, Proteobacteria and Cyanobacteria. The latter are the only eubacterial performing an oxygenic photosynthesis; with release of oxygen from water molecules and using hydrogen from water as electron donor. The rest performs an anoxygenic photosynthesis: the electron donor is sulfur or hydrogen sulfide and, during this process, oxigen is never released, since water rarely intervenes; which is why they are known as purple sulfur bacteria.

Photosynthesis is probably older than life itself. Oxygenic photosynthesis, which is tightly related to this group of bacteria, the cyanobacteria, probably occurs later. But it was crucial for the development of life on our planet, since transformed the atmosphere in a more oxygenated one and, due to this, life on Earth had become more diverse and has evolved.

Amazon, the lungs of the Earh (Author: Christian Cruzado; Flickr)

WHAT PIGMENTS ARE USED?

Cyanobacteria share pigments with terrestrial plants and other photosynthetic eukaryotes. These pigments are primarily chlorophylls a and b (the universal ones); c and d are only present in some groups. There are two more pigments that are univeral: carotenes, these ones act as antennas that transfer the captured energy to chlorophylls and also protect the reaction center against autoxidation, and phycobiliproteins (phycocyanin, phycoerythrin, etc.), which appear in both cyanobacteria and other eukaryotic groups photosynthetic and are responsible for capturing light energy.

But, why exist this variability of accessory pigments? because each pigment have a different absorption spectrum, and the fact to present different molecules allows to collect much better the wavelenght of sunlight; i.e., energy capture is much more efficient.

On the other hand, the anoxygenic photosynthetic bacteria don’t present chlorophylls and, instead, have specific molecules of the prokaryotes, the bacteriochlorophylls.

Absorption spectrum of different pigments (Reference: York University)

Where are pigments located?

In the organisms with oxygenic photosynthesis, that is, in cyanobacteria and photosynthetic eukaryotes, pigments are located into complex structures. In cyanobacteria, there are various concentric flattened sacs called thylakoids in the peripheral cytoplasm, which are only surrounded by a membrane. And it is in the lumen of the thylakoid where pigments are located. In eukaryotes, however, we found chloroplasts, which are intracellular organelles full of thylakoids with at least two membranes and they are particular of photosynthetic eukaryotes. In these chloroplasts is where photosynthesis takes place. Both groups, therefore, perform oxygenic photosynthesis within the thylakoids; the difference is that in eukaryotes, the thylakoids are located into the chloroplasts.

Plant cells where we can see chloroplasts (Author: Kristian Peters – Fabelfroh)

On the other hand, in organisms with anoxygenic photosynthesis there are different options. The purple bacteria contain pigments in chromatophores, a kind of vesicles in the center or periphery of the cell. In contrast, the green bacteria (Chlorobi and Chloroflexi) present several flattened vesicles at the periphery of the cell, on the plasma membrane, where bacteriochlorophyll are located. In Heliobacterium, the pigment is attached to the inner surface of the plasma membrane. They are generally not complex structures, and often this structures have simple membranes.

ORIGIN OF THE PHOTOSYNTHETIC ORGANISMS

The fossil evidence of the earliest photosynthetic organisms are the stromatolites (3.2 Ga ago). They are structures formed by overlapping thin layers of organisms together with their own calcium carbonate deposits. These occurs in shallow waters, in warm and well-lit seas. Although many seem straight columns, deviations are observed because they try to be oriented towards the sunlight to perform photosynthesis. In the past they had a crucial importance in building reefs-like formations and they also participated into the atmospheric composition changes. Currently, there are some which are still alive.

Stromatolites (Author:Alessandro, Flickr)

REFERENCES

• Notes from the Environmental Biology degree (Universitat Autònoma de Barcelona) and the Master’s degree in Biodiversity (Universitat de Barcelona).
• Font Quer, P. (1953): Diccionario de Botánica. Editorial Labor, Barcelona.
• Izco, J., Barreno, E., Brugués, M., Costa, M., Devesa, J. A., Fernández, F., Gallardo, T., Llimona, X., Parada, C., Talavera, S. & Valdés, B. (2004) Botánica 2.ªEdición. McGraw-Hill, pp. 906.
• Willis, K.J. & McElwain, J.C. (2014) The Evolution of Plants (second edition). Oxford University Press, 424 pp.

Flowers wearing turban, the Tulip fever

The spring beginning has allowed some of you to enjoy the beautiful colours of those flowers that have already bloomed. This time I’m going to talk about one of the most colourful, simple, but wonderful flowers you probably already will have had the opportunity to observe in many gardens or in nature. It is the tulip. Besides introduce you this plant, in this article I will make a more detailed description of its morphological parts. I think it’s a good example to start learning vocabulary, because its structure is quite clear and simple. Therefore, if you are interested in learning some technical vocabulary, now it’s a perfect chance. But, do not think I’m just going to talk about the technical aspects, because reading this article you will also be able to learn the history behind the tulips. And as you will see, these flowers caused a good fever!

Artistic image of several tulips (Photo taken by Adriel Acosta).

 INTRODUCTION

The tulips (Tulipa sp.) are flowers that when are closed seem a turban. This plants have been very popular and well-known for very long time, because of its high ornamental interest.

Its genus is distributed in the central and western Asia, in the Mediterranean and in Europe. It is known that its origin belongs to the centre of Asia and, from there, their distribution has been expanded naturally and by human actions. And, although about 150 species are known in the nature, human intervention has greatly increased the species list. Caused both by hybridization (forcing the offspring of two interesting species) and by selective breeding (choosing the offspring which has more value).

Tulip crop in Amsterdam (Photo taken by Rob Young). 

 THE TULIP FEVER

As already mentioned above, tulips are one of the most ornamental plants used, both in decoration as in landscaping. And while the tulip crop is rather old, the boom occurred in Europe during the seventeenth century. Giving rise to what is known as Tulip mania or the Tulip fever. In those moments, especially in Netherlands and France, a high interest in the cultivation of these plants awoke. The fever was so great that people were selling goods of all kinds to buy tulip bulbs, even reaching up to sell the most valued as the house or farm animals.

The cause of this was originated in the Netherlands, where the single-coloured tulip bulbs were being sold at that time. But afterwards, the Eastern bulbs that give rise to flowers with variegated colours appeared. And they were very attractive. Although the cause was uncertain in that moment, it was known that if a single-coloured bulb touched other marbled-coloured bulb, the first one would turned into a marbled-coloured bulb. This caused the tulip’s price began to increase and soon after occurred the first speculative bubble in history.

Nowadays, we know that the cause is due to a virus which is transmitted from some bulbs to others; this virus is known as Tulip breaking virus.

Anonymous gouache on paper drawing, 17th century, of the “Semper Augustus”. A representation of one of the most popular tulips which was sold at record price in Netherlands (Public Domain).

MORPHOLOGICAL CHARACTERS

 The plant

 Tulips are geophytes, that is, they have resistance bodies underground to survive during unfavourable seasons, the winter. These organs are bulbs, which have been used on crops to preserve these plants.

Its leaves are linear or linear-lanceolate, i.e., they are long, narrow and acute. Parallel venation can be observed on its leaves, so a nerve is by side other and with the same direction. Their arrangement is usually in rosette: this means that the leaves are born agglomerated in the bottom of the plant above the bulb, and at the same level. Even so, you can sometimes see some leaves along the stem, cauline ones. These are sessile, without petiole, and wrap a little the stem.

To cultivate tulips, we can use their bulbs or fruits. These seconds are capsules, a dried fruits, opened due the action of some valves. At first, the seeds are hooked inside these capsules and then are released and distributed on the environment.

Tulip (Photo taken by Adriel Acosta).

The flowers

Tulips appear in early spring, due they are plants adapted to very dry Mediterranean climate or cold areas.

As you have seen, the flowers are solitary or appear to 3 gathered in one stem. They are usually large and showy, hermaphrodite, therefore, they have both male and female reproductive organs, and are actinomorphous, that is, they can be divided symmetrically for more than two planes of symmetry.

These flowers have 3 inner tepals and 3 external that are free among them, without being bound or fused. We talk about tepals when the sepals (calyx pieces) and petals (corolla parts) are similar between them. In this case, the tepals are petaloid, because they adopt typical colours and shapes of the petals.

In the inner part of the flower, we can see 6 stamens divided equally into 2 whorls; being these two closely spaced between them, so they seem to arise from the same point. And right in the centre, surrounded by these stamens, there is the gynoecium, female part of the flower. This gynoecium consists of the ovary and 3 stigmas attached to this directly. The stigmas are this part of female reproductive organs where it should arrive pollen to fertilize the ovaries.

Parts of tulip flower: 1. Sepal, 2. Petal, 3. Stamen, 4. Female reproductive organ (ovary and 3 stigmas) (Photo taken by Adriel Acosta).

 As you have seen in this article, some flowers have caused curious stories and a great impact on our society. Also, you have had the opportunity to observe in detail the tulip’s structure. One more time, I wish you liked it.

REFERENCES

• A. Aguilella & F. Puche. 2004. Diccionari de botànica. Colleció Educació. Material. Universitat de València: pp. 500.
• Bolòs, J. Vigo, R. M. Masalles & J. M. Ninot. 2005. Flora manual dels Països catalans. 3ed. Pòrtic Natura, Barcelona: pp. 1310.
• Notes of Phanerogamae and Applied Plant Physiology, Degree of Environmental Biology, Ambiental, UAB
• F. Schiappacasse. Cultivo del tulipan. http://www2.inia.cl/medios/biblioteca/seriesinia/NR21768.pdf
• Fundación para la Innovación Agraria; Ministerio de Agricultura. 2008. Resultados y Lecciones en Tulipán. Proyecto de Innovación en XII Región de Magallanes. Flores y FOllajes/ Flores de corte (11).