Root navigation by self inhibition

Abstract

Circumventing physical obstacles is critical for a plant's survival and performance. Although the ability of roots to circumvent obstacles has been known for over 100 years, the phenomena and its mechanisms have received relatively little attention. In this study it is demonstrated that roots of Pisum sativum are able to detect and avoid growth towards inanimate obstacles and the hypothesis that this behaviour is based on the sensitivity of roots to their own allelopathic exudates that accumulate in the vicinity of physical obstacles is tested. The development of lateral roots of Pisum sativum towards an obstacle (a piece of nylon string, similar in dimensions to a plant root) was followed. Lateral roots were similar in number, but significantly shorter in the direction of the nylon string. In addition, up to half of the lateral roots that developed towards the nylon string withered, whereas no withering was observed in the absence of the nylon string. These avoidance growth patterns were suppressed in the presence of potassium permanganate or activated carbon, indicating a role of allelopathic exudates in promoting obstacle avoidance. The demonstrated obstacle avoidance by self inhibition could increase plant performance by limiting resource allocation to less promising parts of the root system.

The role of ABC transporters in kin recognition inArabidopsis thaliana

“…It appears that primary root length maybe a self/ non-self response as it was independent of the identity of non-self secretions. Falik et al 31 and Gruntman and Novoplansky, 32 suggest the possibility of gradients or oscillating levels of chemicals produced by roots that may allow for a self/non-self recognition rather than a unique chemical cue for individual plants.…”

Plant Root Interactions

“…However, when partitions (either as plastic or mesh barriers) were present to separate the root systems of the two plants, plant performance increased in the presence of the activated carbon. Physical obstacles may restrict root growth and the addition of activated carbon or potassium permanganate (a strong oxidizer of organic compounds) can alleviate this restriction (Falik et al 2005) suggesting a role for root-released compounds in regulating root growth. However, while activated carbon addition has been widely used in root interactions investigations (see Mahall and Callaway 1992;Semchenko et al 2007;Kulmatiski and Beard 2006), the results need to be treated with caution and appropriate controls included, as activated carbon can result in a number of other modifications to the substrate and/or plant.…”

Chemical communication between roots and shoots: towards an integration of aboveground and belowground induced responses in plants

“…Roots show a high morphological and physiological plasticity in response to the physical and chemical properties of soil. They are able to avoid obstacles, toxins and roots of other plants by guiding the direction of root-tip growth and by controlled withering of tips that grow towards an obstacle (Falik et al 2005). Moreover, plants can quickly respond to nutrient-rich patches by specifically proliferating into the patch and by increasing local nutrient uptake rates in newly formed root tips (Hutchings and De Kroon 1994;De Kroon et al 2005).…”