Research has shown that people's lightest touch can already have a major impact on plants. By touching a plant, the plant can initiate a huge 'genetic defensive' which costs a lot of energy and can be detrimental to the growth of the plant. If you touch a plant repeatedly, the growth can be reduced by up to 30%.
On the other hand, it is a good thing that plants touch each other. Plants can feel that there is a plant near them. Through a natural struggle, for who will get the best position for the most light, the plants grow faster. In our greenhouse, the plants grow right next to each other, which ensures rapid growth! This is also the case when you place a plant against a transparent colourless object.