Building a predictive framework of genotypically diverse fields, where emitter and receiver plants work together is a main research topic of the Ninkovic research group from the Swedish University of Agricultural Sciences.
A research group at the Swedish University of Agricultural Sciences (SLU), Uppsala, led by Velemir Ninkovic investigates plant-plant communication by volatile organic compounds (VOCs), light reflection and touch sensation.
These forms of communication work together in a complex network and affect plant growth on multiple trophic levels, ranging from the plant itself to insect-plant interactions. Plants accommodate a sessile life firmly at the same spot in the soil. Thus, competition for resources with neighbours is a constant challenge. Questioning how plants, and specifically plants used in agricultural production, are sensing their environment is fascinating and still not completely understood. To survive and ultimately adapt to the specific surrounding environment, plants must therefore be able to detect reliable signals from a wide array of threats and competitors. These signals range from insects feeding on the plants, to environmental conditions, to contact with other nearby plants.
Agricultural sciences: from leaf to root
Plants can detect their neighbours by stimuli sensed either through their leaves or by root exudates. The research team at SLU found that a brief and light touch to the leaf has an impact on above and below ground communication (see Fig.1), affecting the pattern of biomass allocation and reducing their attractiveness for herbivore insects. The chemical composition of the soil is a key factor in the lifespan of any plant as it conveys signals not only about the presence of surrounding neighbours but also their physiological status. Intriguingly, the SLU team have found that brief touch stimuli perceived by the leaves can affect belowground plant interactions. Their recent study demonstrated the extraordinary capacity of maize roots to discriminate between belowground signals and then to respond differentially according to the stress status of their neighbour.
Plants eavesdrop on their neighbours through the detection of volatile organic compounds (VOCs). These compounds can, as mentioned, be emitted from the root system, but can also be found airborne and floral as well. The ability to detect and respond to VOCs of most competitive neighbours is an important strategy for individual plants since it enables them to adjust their physiological status and growth pattern accordingly, especially in the early stages of their life.
For example, early investment into root growth induced by VOCs can be hugely beneficial in order to meet competition with neighbouring plants’ belowground resources.
Interestingly, VOCs trigger not only reactive responses after stress, but also induce a long-term process in plants that grow next to healthy neighbours. The information plants receive from their surroundings and their competitors give them a higher chance in later life stages to grow in a more advantageous position. Induced physiological changes may have broader implications, thus plant-plant communication between specific combinations of cultivars has been shown to induce a natural pest control mechanism (see Fig. 2). These cues from neighbouring plants via VOCs can regulate effective and specific biochemical defence pathways. Furthermore, profiling the differences of VOCs in mixed cultivars showed a decreased population size and performance of aphids.
This information about mixing cultivars in the field can be used for naturally enhancing pest control management without the need for artificial interference. Ultimately this cross-talk of a variety of cultivars shows an increased survival rate and could help with future applications in crop production.
The agricultural sciences research team at SLU has shown that plant-plant communication plays a crucial role in the adaptation to the surrounding environmental of each individual plant. The detection of external signals of hetero- and con-specific neighbours could play an immense part in the development of sustainable agricultural management.
As shown, plants benefit from the recognition of nearby neighbours through different channels (see: Fig. 2). Avoiding direct competition for resources, protecting themselves from future herbivore attacks, minimizing pest damage or attracting mutualists is key for a plant’s survival. Increased plant genotypic diversity in crop fields could hold possibilities for better pest control and efficient use of resources. Plant-plant communication and plant-herbivore interactions on a mechanistic level hold a powerful tool to develop sustainable agricultural practices.
With an improved knowledge of agricultural sciences and an understanding of how plants communicate with each other, we could precisely shape our growing crops to promote better pest management and enhance biodiversity.
Velemir Ninkovic PhD
Senior Lecturer and External Collaboration Specialist
Swedish University of Agricultural Sciences, SLU