As temperatures rise, flowers emit less scent

Being confined inside the nanoflasks greatly increased the concentration of the molecules and organized them in a way that caused them to react more readily.

By JUDY SIEGEL-ITZKOVICH
A WOMAN TAKES a selfie in a field of flowers near Kibbutz Nir Yitzhak, just outside the Gaza Strip (photo credit: REUTERS)
A WOMAN TAKES a selfie in a field of flowers near Kibbutz Nir Yitzhak, just outside the Gaza Strip
(photo credit: REUTERS)
The diverse and delicious fragrances of flowers brighten our days and inspire poetry – but the more practical reason that flowers produce scent is to attract pollinating insects to the flowers’ reproductive organs. This ensures the continued existence of plant species. To accomplish this, flowers assemble a mixture of dozens – and sometimes hundreds – of volatile substances from several biochemical groups.
Scientists have known for some time that increasing temperatures associated with global climate change have a negative effect on plant growth. Expanding on this research, a Hebrew University of Jerusalem doctoral student has shown that increases in ambient temperature also lead to a decrease in the production of floral scents.
“Increases in temperature associated with the changing global climate are interfering with plant-pollinator mutualism, an interaction facilitated mainly by floral color and scent,” Alon Can’ani explained in his research.
At HU’s Robert Smith Faculty of Agriculture, Food and Environment, Can’ani has been studying control mechanisms that allow plants to regulate their production of scent. He is now researching strategies to overcome the decrease in production of beneficial volatile substances, a process that requires a huge energy investment from plants.
During his work in the laboratory of the faculty’s Prof. Alexander Vainstein, Can’ani discovered that petunia plants grown at elevated temperature conditions have significant defects in the production and emission of scent compounds.
“In my study, I show that increasing ambient temperature leads to a decrease in phenylpropanoid-based floral scent production in two Petunia×hybrida varieties, P720 and Blue Spark,” Can’ani said. This was linked to arrested expression and activity of proteins that facilitate biosynthesis of the compounds.
Can’ani was awarded the Smith Vision Prize for his body of research, which included projects aimed at finding novel strategies that plants use in order to regulate, or fine-tune, the process of scent emission.
Can’ani also demonstrated an approach to bypass this adverse effect, by expressing the Arabidopsis thaliana PAP1 gene, which boosts the production of scent regardless of the ambient temperature. This research was recently published in Plant, Cell & Environment. When he manipulated the expression of this gene to a halt, petunia flowers ceased to emit scent, but continued to produce it. Interestingly, this gene apparently serves as a switch between two crucial floral traits – color and scent.
TINY ‘FLASKS’ SPEED UP CHEMICAL REACTIONS Miniature self-assembling “flasks” created at the Weizmann Institute of Science in Rehovot may prove a useful tool in research and industry. The nanoflasks, which have a span of several nanometers (millionths of a millimeter), can accelerate chemical reactions for research. In the future, they might facilitate the manufacture of various industrial materials and perhaps even serve as vehicles for drug delivery.
Dr. Rafal Klajn, of the institute’s organic chemistry department, and his team were originally studying the light-induced self-assembly of nanoparticles. They were using a method developed earlier by Klajn in which inorganic nanoparticles are coated in a single layer of organic molecules that change their configuration when exposed to light; these alter the properties of the nanoparticles such that they self-assemble into crystalline clusters. When spherical nanoparticles of gold or other materials self-assembled into a cluster, empty spaces formed between them, like those between oranges packed in a case.
Klajn and his team members realized that the empty spaces sometimes trapped water molecules, which led them to suggest that they could also trap “guest” molecules of other materials and function as tiny flasks for chemical reactions. A cluster of a million nanoparticles would contain a million such nanoflasks.
As reported in Nature Nanotechnology, when the scientists trapped molecules that tend to react with one another inside the nanoflasks, they found that the chemical reaction ran 100 times faster than the same reaction taking place in solution.
Being confined inside the nanoflasks greatly increased the concentration of the molecules and organized them in a way that caused them to react more readily.
Enzymes speed up chemical reactions in a similar manner – by confining the reacting molecules within a pocket.
Although clusters of nanoparticles containing empty spaces have been created before, the advantage of the Weizmann method is that the clusters are dynamic and reversible, so molecules can be inserted and released on demand.
The nanoflasks may prove to have an industrial use – namely, to speed up numerous chemical reactions, such as polymerization reactions needed for the manufacture of plastics. The method might also be applied one day to drug delivery, with the medication inserted in nanoflasks into the target organ and released at the required time when the nanoflasks would disassemble upon exposure to light.