New view on plants and their ability to sense their environment have brought the scientists from Centre of the region Haná for Biotechnological and Agricultural research in Olomouc. Within last two years they were looking inside the carnivorous sundew plant (Drosera capensis) and compared its electrical activity and physiological response after prey capture and mechanical wounding. They found that the response is very similar and that botanical carnivory has probably evolved from plant defense mechanisms. The paper was published in respected journal New Phytologist.
The object of the study was carnivorous sundew which capture insect by sticky tentacles. The plant was exposed to different stimuli and researchers studied the subsequent reactions which were initiated by generation of electrical signals. In the past, the research on electrical signaling in plants has been neglected, but biophysicists from Olomouc have long-standing experiences with it.
Electrical signal is the most important
“We have shown that electrical signal stands in the first line in plant ability to perceive its environment. In this work we described whole process from generation of electrical signal to final response. The main objective was to compare electrical signaling and physiological response after feeding and mechanical wounding. We wanted to know, if the plants can distinguish two different type of electrical signals,“ say Andrej Pavlovič, corresponding author of the study from Department of Biophysics at Palacký University in Olomouc.
First, the researchers studied plant behavior after prey capture. After the prey is captured, the tentacle heads, which are in contact with captured prey, start to generate electrical signals which spread toward the base of tentacles. Inside the leaf the signals are changed into electrical vibrations. These are sensed by the neighboring tentacles, which start to bend inward and fix the insect prey.
„This rich electrical activity is confined to area with captured insect. In this area, the plant phytohormones from the group of jasmonates start to accumulate and trigger the enzyme activity only in this part of the leaf. We analyzed digestive fluid and we found the proteins which digest proteins, chitin or RNA. All these substances contain a lot of nitrogen and phosphorus. The plant needs to obtain these elements to improve its photosynthesis,“ specified Andrej Pavlovič.
Very similar response was found after mechanical wounding. Injured plant generates completely different type of electrical signal in comparison to signal generated after prey captured and in this case the signal spread to all leaves. As a result, production of jasmonates and digestive enzymes is increased in all leaves on the plant. „We do not know what a purpose of this behavior is. Why the plant produces digestive enzymes when there is nothing to eat? We suggest that it is a result of evolutionary history, when ordinary plants used, as do it today, electrical signals and jasmonates for initiation of defense response. The digestive enzymes are very similar to defense proteins. Carnivory has probably evolved from plant defense mechanisms,” concluded Pavlovič.
The plant can taste its prey
„The experiments showed that plant can not recognize different stimuli and electrical signaling is not very specific. However the plant can taste its prey. As soon as the plant taste chemical components of its prey (e.g. ammonia), the secretion of enzymes increases tenfold. Thus, the plant has mechanisms how to distinguish food from indigestible particles,“ Pavlovič said.
Biophysicist, plant physiologist, analytical chemist, biochemists and cell biologists from four departments of Faculty of Science at Palacký University in Olomouc and Comenius University in Bratislava participated in this research. Thanks to this co-operation the result is very complex. The complex approach was appreciated also by Axel Mithöfer from Max Planck Institute for Chemical Ecology in his commentary in the same issue of New Phytologist: „This study represents a milestone for our understanding of carnivory in sundew plants … .“ The Olomouc scientists will continue further to unravel the secrets of carnivorous plants, which Charles Darwin considered as the most wonderful plants in the world.