Final Report Summary - ROOTS (The roots of plant productivity: how the rhizosphere interact with the aboveground armament for indirect and direct defense against abiotic stressors)
The roots represent at least half, by mass, of the body of a plant; through this hidden part, water and nutrients are assimilated, and together with atmospheric CO2, constitute the basis of the entire reserve food of the planet. Stress events at the root level induce the synthesis of signalling molecules (biologically or chemically active volatile compounds: BVOC or VOC) that allow the communication between plants and other organisms. These compounds are also essential for the indirect defence of plants since they are perceived as "cry for help" from beneficial organisms in the trophic chain, plant-herbivore-carnivore. This project is based on the solid evidences that roots affect the overall plant growth by processes beyond the functions of supplying water and nutrients. Critical experiments indicate that root system signals modulate shoot growth and activity. The project articulated in three main activities, aimed respectively, at the study of the main underground events in response to environmental or nutritional stress, identification of the long-distance signalling and of their effect on plant phenotype and analysis of VOCs as messengers in signalling of belowground stressful events among plants.
The original contribution of the project is the dynamic analysis of the main underground events affecting plant defence priming and activation with a multi-level approach. The perception of signals, the learning procedures, the ability to decide, are all features normally associated with the idea of organisms with a nervous systems. However, the acquisition of information from the environment and their subsequent communication are essential characteristics of life, and, therefore, common also to primitive organisms. Plants too are able to perceive the surrounding environment, to distinguish between biotic and abiotic signals
and to communicate with other plants or animals. Plant ability to perceive the environment and to adapt its responses in order to take advantages can be observed, for example, during soil exploration for nutrient uptake.
Environmental stresses, such as drought and salinity, greatly affect plant growth and the severity of these stresses is likely to increase under the current and predicted climate change. In the past, the research to improve plant productivity has mainly focused on aboveground traits and the study of the root system has been an overlooked area. However, recently there has been renewed interest on the impact of the root system on plant growth; this has therefore
boosted the number of studies focusing on the root system.
There are increasing evidences that understanding and exploiting the regulatory mechanisms behind this exceptional capacity of plant roots to sense and respond to environmental stimuli is the avenue for improving crop production in a sustainable manner. Soil is a physical environment where resources might be scarce. As a result, plants have evolved complex root systems that can sense and respond to a multitude of abiotic and biotic signals, discriminate the identity of their neighbours and incorporate them into growth decisions.
Many interesting findings resulted from the research activities of the project.
Salt stress response in roots of has been characterizes monitoring ion fluxes and ROS production, to have some indications on the speed and the nature of the signals from roots to shoots. Experiments on plant-plant communication suggest that unstressed plants are able to ‘‘eavesdrop’’ on their salt-stressed neighbors and respond by closing their stomata and preparing their metabolism to the upcoming stress. In Eucaliptus gunnii a significant reduction of the stomatal conductance was recorded after the salinity stress in both stressed and non-stressed neighbours with different timing. The nature of the signal emitted by the aerial part of the plant was investigated using PTR-MS-TOF. The headspace analysis revealed an initial decrease of the volatile emission (mainly terpenes and green leaf volatiles). After 1 week, stressed plants increased their emission of VOCs (isoprene, monoterpens, terpenoids and sesquiterpens, and the green-leaf-volatiles).
The same results were obtained in the herbaceous plant Vicia faba L var. minor. Plant exposed to the volatile organic compounds of stressed plants change their physiological parameters (RGR, shoots/root radio, K/Na ratio in the tissues) as if they were coping with a salinity stress themselves. Only Na+ content and photosynthetic rate remained similar to the controls. These changes can be interpreted as an internal adjustment to be better prepared for an upcoming stress. In fact, when the plants which have been kept in contact with stressed plants are exposed to salinity stress, their growth isn’t affected much and the RGR is higher than the stressed controls. These findings reveal that a short-term exposure of VOCs emitted by stressed plants activates a set of physiological adjustments enabling the plants to withstand upcoming saline conditions in a better way.
Last but not least, it has been found that plants of Pisum sativum are able to discriminate their neighbours and adjust their growth and biomass allocation accordingly, and according to the nutrient availability. In particular plants that are genetically closer tend to cooperate by sharing the space and avoiding competition, especially when the resources are limited, to achieve a better performance in term of fitness at the end of their life-cycles.
The results of the project are a step towards a better understanding of plant growth and behaviour. In fact, by understanding (and manipulating) the intrinsic physiological and metabolic effects of stress perception and plant – plant relationships on plant's growth and yield, it is possible to improve crop production in a sustainable way. The results of this project are a step towards these achievements.
The original contribution of the project is the dynamic analysis of the main underground events affecting plant defence priming and activation with a multi-level approach. The perception of signals, the learning procedures, the ability to decide, are all features normally associated with the idea of organisms with a nervous systems. However, the acquisition of information from the environment and their subsequent communication are essential characteristics of life, and, therefore, common also to primitive organisms. Plants too are able to perceive the surrounding environment, to distinguish between biotic and abiotic signals
and to communicate with other plants or animals. Plant ability to perceive the environment and to adapt its responses in order to take advantages can be observed, for example, during soil exploration for nutrient uptake.
Environmental stresses, such as drought and salinity, greatly affect plant growth and the severity of these stresses is likely to increase under the current and predicted climate change. In the past, the research to improve plant productivity has mainly focused on aboveground traits and the study of the root system has been an overlooked area. However, recently there has been renewed interest on the impact of the root system on plant growth; this has therefore
boosted the number of studies focusing on the root system.
There are increasing evidences that understanding and exploiting the regulatory mechanisms behind this exceptional capacity of plant roots to sense and respond to environmental stimuli is the avenue for improving crop production in a sustainable manner. Soil is a physical environment where resources might be scarce. As a result, plants have evolved complex root systems that can sense and respond to a multitude of abiotic and biotic signals, discriminate the identity of their neighbours and incorporate them into growth decisions.
Many interesting findings resulted from the research activities of the project.
Salt stress response in roots of has been characterizes monitoring ion fluxes and ROS production, to have some indications on the speed and the nature of the signals from roots to shoots. Experiments on plant-plant communication suggest that unstressed plants are able to ‘‘eavesdrop’’ on their salt-stressed neighbors and respond by closing their stomata and preparing their metabolism to the upcoming stress. In Eucaliptus gunnii a significant reduction of the stomatal conductance was recorded after the salinity stress in both stressed and non-stressed neighbours with different timing. The nature of the signal emitted by the aerial part of the plant was investigated using PTR-MS-TOF. The headspace analysis revealed an initial decrease of the volatile emission (mainly terpenes and green leaf volatiles). After 1 week, stressed plants increased their emission of VOCs (isoprene, monoterpens, terpenoids and sesquiterpens, and the green-leaf-volatiles).
The same results were obtained in the herbaceous plant Vicia faba L var. minor. Plant exposed to the volatile organic compounds of stressed plants change their physiological parameters (RGR, shoots/root radio, K/Na ratio in the tissues) as if they were coping with a salinity stress themselves. Only Na+ content and photosynthetic rate remained similar to the controls. These changes can be interpreted as an internal adjustment to be better prepared for an upcoming stress. In fact, when the plants which have been kept in contact with stressed plants are exposed to salinity stress, their growth isn’t affected much and the RGR is higher than the stressed controls. These findings reveal that a short-term exposure of VOCs emitted by stressed plants activates a set of physiological adjustments enabling the plants to withstand upcoming saline conditions in a better way.
Last but not least, it has been found that plants of Pisum sativum are able to discriminate their neighbours and adjust their growth and biomass allocation accordingly, and according to the nutrient availability. In particular plants that are genetically closer tend to cooperate by sharing the space and avoiding competition, especially when the resources are limited, to achieve a better performance in term of fitness at the end of their life-cycles.
The results of the project are a step towards a better understanding of plant growth and behaviour. In fact, by understanding (and manipulating) the intrinsic physiological and metabolic effects of stress perception and plant – plant relationships on plant's growth and yield, it is possible to improve crop production in a sustainable way. The results of this project are a step towards these achievements.