Almond tree uses secret weapon to attract potential pollinators

JERUSALEM - A group of scientists has found that a toxin found in almond tree nectar is in fact a secret weapon to give the tree an evolutionary advantage over others in its surroundings, by drawing potential pollinators.

Scientists from the Department of Environmental and Evolutionary Biology and the Department of Science Education at the University of Haifa carried out the research.

Previous studies have already shown that amygdalin can be found in almond nectar at a concentration of 4-10 milligrams per liter.

It also known that the almond tree is the only plant to have this toxin in its flowers’ nectar; in fact, the tree’s subgenus classification is Amygdalus, after the toxin it produces.

For small mammals, this is a deadly substance and as it is highly concentrated in the seeds of unripe wild bitter almonds, these almonds are also dangerous for human consumption.

A group of researchers, headed by Prof. Ido Izhaki along with Prof. Gidi Ne’eman, Prof. Moshe Inbar and Dr. Natarajan Singaravelan, investigated why it is that this plant produces such a potent toxin - a by-product of which is cyanide - in its nectar.

They explained that the presence of amygdalin in the nectar is seemingly incompatible with the nectar’s purpose of attracting insects to the flower to extract food and pollinate it and thereby contribute to the plant’s reproduction.

The researchers exposed honey bees to plates of nectar that had varying concentrations of the toxin and a plate of nectar without the toxin.

The team first monitored four different amygdalin concentrations, resembling the natural levels of the toxin in almond tree nectar: 2.5-10 milligrams per liter.

A second experiment monitored levels much higher than those found in the natural form: 5-50 milligrams per liter.

In both cases and for each of the compositions, the bees preferred nectar containing amygdalin over the amygdalin-free option.

“It is difficult - and sometimes impossible - to determine the workings of evolution, but it is likely that amygdalin is produced in the almond nectar so as to give the almond tree an advantage in reproduction,” said Prof. Izhaki.

“Based on our observations, we can make a guess at which mechanisms come into play for amygdalin to provide this advantage,” he added..

For example, even though amygdalin is poisonous for mammals, it is not poisonous for insects, such as the honey bee, and it even produces a stimulant that attracts such insects.

Therefore, it is possible that the plant produces it so as to attract potential pollinators. (ANI)