ARKHANGELSK, October 5. /TASS/. The Plant Life: Fruits and Seeds Settlement exhibition opened in Arkhangelsk. The project presents mechanisms of plant propagation and evolution, and the opening is timed to coincide with the 190th anniversary of Charles Darwin's return from the expedition on board the Beagle ship (1836), Director of the Academician Laverov Federal Research Center for Integrated Arctic Studies (the Urals Branch of the Russian Academy of Sciences, FITSKIA, Arkhangelsk), Corresponding Member of the Russian Academy of Sciences Ivan Bolotov told TASS.

"We have prepared a permanent exhibition on settlement of fruits and seeds of plants," he said. "This is a very important and interesting question that Charles Darwin and Alfred Russel Wallace were the first to address. These people were at the birth of the evolutionary theory, but at the same time they considered a lot of other issues, including plant settlement. Before them, specialists believed that seeds and fruits could not spread through oceanic barriers. Whenever plans of the same species were found on different islands, the explanation was that initially there was a big surface area, and then the great flood happened, thus formally continuous habitats got divided. Darwin and Wallace, while visiting tropical islands, found big deposits of, for example, coconuts, on beaches. The scientists began to work on how plants can settle."

Charles Robert Darwin (1809-1882) and Alfred Russel Wallace (1823-1913) were the first researchers to focus on settlement mechanisms of fruits and plant seeds in terms of biogeography and evolutionary biology. Darwin's observations on the Cocos and Galapagos Islands and Wallace's observations on the Sunda Islands have promted that plant germs can spread over long distances by sea currents, air currents, as well as birds and mammals.

Therefore, the exhibition has four parts, where plant samples are grouped according to their settlement mechanisms: oceanic drift (marine hydrochory); air transport (anemochory); settlement in birds and animals' digestive tract (endozoochory); combined settlement strategies, including autochory or barochory with subsequent transfer by animals or water streams. (Suffix -chory means 'method of plant or seed dispersal.') The exhibition features 49 plant species from 21 families. The Russian research center's scientists have brought samples from expeditions to eleven countries: Venezuela, Cuba, Madagascar, Indonesia (the Lesser Sunda Islands), Morocco, Seychelles, Spain (the Canary Islands), Russia, Senegal, Thailand, and Sri Lanka.

Interestingly, plants that have chosen the same settlement strategies, such as ocean drift, use different mechanisms, sometimes even opposite mechanisms. The coconut has a very strong outer layer, inside it there is a large amount of nutrients for the embryo development. The powerful protective shell is helpful in overcoming reefs and surf off tropical islands. The barringtonia asiatica acts similarly -  having the shell, it can drift with waves for years to swim from Southeast Asia to even Great Britain.

"But if we take the marine hibiscus, it has very small seeds, with an airy cavity inside. They also drift wonderfully, they settle down with the sea currents, but they do not need a powerful shell, because they are very small, and, having this minimum size, they can escape effects of powerful ocean waves, unlike barringtonia or coconut experience," the scientist said.

As for mangrove trees, they spread by shoots in a similar way. They float on the waves. Due to the specific structure, they remain vertical, like floats. In a suitable place, during low tide, the shoot sticks into the silt, and throws out roots within just hours, literally "anchoring" itself, and leaves almost immediately begin developing from the "float's" top.

Seeds of some plans have the shape of a glider, like those of the Indian oroxylium, or of a helicopter, like those of the Dipterocarpaceae family. "The fruit size depends on the mother tree height. The higher the mother tree, the bigger the fruit is - to ensure maximum distribution by rotation," the expert continued.

The royal delonyx, or fire tree, emits its seeds as soon as first rains come. It uses the mechanism of autochoria - the fruit cracks sharply, the seeds get thrown out and spread with rainwater streams.

Some plants have chosen a distribution mechanism by animals, where different species have different effects. "The abrus precatorius is deadly poisonous. The seed contains a toxin - abrin, but the seed has a very dense peel, birds, thinking it is a bright and sweet berry, would peck them. The seeds are not digested in the stomach, and the bird carries them over long distances. On the other hand, if, say, a mouse nibbles this seed, it will die quickly," the research center's director said.

The exhibition of fruits and plant seeds also features various artifacts from the countries where these species grow. For example, a baton of crocodile wood (Zanthoxylum rhetsa) from the Flores Island. "The locals in villages carry such batons to fend off the [Komodo] monitor lizards. According to the locals, the monitor lizard has a weak spot in its nose, and when hit there, it stops attacking," the scientist said. Birds, in their turn, help spreading the crocodile tree.