In a new study, it has been shown that the presence of neighboring plants can affect the rate of growth and metabolism of different molecules in plants.
Plants, like any other organism on earth, can sense and respond to environmental stimuli. Every organism has the molecular and biochemical machinery to interact with environmental factors which could affect their survival. Light and temperature are two of the most important environmental factors for plants. But plants also sense the presence of other plants in their vicinity and can give appropriate response.
Effect of neighbors’ roots on tobacco plant
In a new study by an international team of researchers, it has been shown that the presence of neighbors belowground can initiate defense responses in plants roots. In order to investigate their hypothesis, researchers grew tobacco plants in hydroponic conditions, either with or without other neighboring plants. Then, they investigated the expression of primary and defense-related secondary metabolism and hormone expression. They also studied the rate of growth in these plants.
The lead researcher, Dr Hajiboland from Tabriz University says:” Hydroponic condition does not have the complexities of soil condition and it is a better option for physiologic investigations. We used hydroponic condition so that we can detect the chemical molecules secreted from roots of the plants.”
She also added:” The effect of neighbors on plants physiology is not a new concept. It has been many years that this idea has been examined by different scientists. Many of the previous researches have investigated the interaction between shoots of neighbor plants, but we focused on the roots. We already know that plants can sense the roots of other neighboring plants and even identify the level of genetic kinship of their neighbors. But unlike previous studies, we didn’t just investigate growth alterations. We also studied defense responses and expression of various molecules and hormones.”
Neighbors initiate defensive actions
The results of the study showed that non-self root interactions reduced photosynthetic activity and both root and shoot growth. Tobacco plants which had non-self interactions also showed enhanced expression of phytohormones, particularly jasmonic acid, salicylic acid and cytokinin in roots and abscisic acid in leaves. These tobacco plants also accumulated more phenolics (as a chemical defense) in their roots and more lignin (as structural defense) at the whole plant. Researchers concluded that the presence of non-self roots induced defense mechanisms at the expense of growth. Since the presence of neighbors might increase the chance of attacks from pathogens or pests, this defense mechanism act as an adaptation of plants to possible upcoming attacks.
Researchers emphasized that a better understanding of plant interactions would be valuable for intercropping and sustainable agriculture in the future.