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Self-DRiving hydrOPonic System - Develop automated hydroponic systems that use high frequency pulsing-light and intermittent/alternate nutrient supply to optimize resources and plant adaptation.

Periodic Reporting for period 1 - SunDROPS (Self-DRiving hydrOPonic System - Develop automated hydroponic systems that use high frequency pulsing-light and intermittent/alternate nutrient supply to optimize resources and plant adaptation.)

Reporting period: 2018-01-01 to 2019-12-31

The SunDROPs project focuses on the development of an automated hydroponic cultivation system driven by the plant “itself” able to optimize the request of light, water and nutrients. The aim is to develop an automated system able to detect the needs of the plants by the interpretation of the electrical signals generated by the plants under specific stresses. In particular, the overall project focuses on the development of automated hydroponic cultivation systems able to automatically manage the optimal request of light, water and nutrients.
This project was focused on three linked research lines aimed at developing a particular cultivation system which could be resumed in three main objectives that involved the study and improvement of:
1. LED lights capable of pulsing at high or low frequency and able to modulate the individual spectra in a specific way. For this purpose specific light equipment were used to evaluate the effect of different light spectra regimes on plant development.
2. A particular type of Flood & Flow (F&F) hydroponic system which allowed to supply nutrients with particular intermittent /alternating regimes (flood/drainage cycles) to optimize the resources and acclimation of the plants.
3. An apparatus for the analysis and interpretation of the electrical signals of plants capable of determining the actual needs or state of stress of the plants automatically (mainly water stress). An innovative multi-electrode system has been used for this purpose capable of obtaining information directly from the plant as opposed to the majority of sensors used today which instead concentrate on the external environment.
During the project innovative light equipment have been build and tested for achieve specific purpose of interest for applied and basic research. Specifically light equipment (pulse width modulated-high brightness-light emitting diodes lights (PWM-HB-LEDs) able to pulse at high or low frequency in which each light color intensity is independently and automatically controlled have been tested. The PMW regulated light have been studied as well as the influence of specific color on plant physiology elucidating the effect of frequency and duty on plant photosynthesis. An innovative light control system have been developed able to remotely be controlled for customized light cycles. Additionally, it was investigated a methodology that permit to alternate different nutrient solutions in cycles that can be used to enhance tolerance or specific traits using a flood and flow (F&F) hydroponic system. This method has been used to alternate different saline solutions in cycles to increase salt tolerance or modulate specific compounds content in lettuce. Our results showing a comparison between long-medium salinity period, short high salinity periods and a continuous salt acclimation phase highlighted that alternated cycles can be used to reach high-resistance phenotypic response (i.e. maintain growth at high saline concentration). Additional we have also observed that specific adaptation cycles could be used to maintain the cellular hydration during the early phase of high salt exposure and/or enhance specific ions modulations that can be of nutraceutical interest (e.g. reduce iron or increase calcium). Finally the electrical signals generated by plants subjected to different stresses were studied and the analysis of the physiological status of each plant has been used to correlate different stress intensities with specific electrical patterns. In particular, analysis of electric signal and its variance in plants subjected to different level of drought stress have been used for an automatic detection of plant status and their potential applications for plant cultivation have been evaluated. The apparatus to monitor the electrical activity have been successfully tested in several plants cultivated in hydroponic and in soil. A methodology for the interpretation of the electrical signals has been developed and a model of its functionality proposed.
To date, the implementations of computer science developments in agriculture have been more common and sophisticated. Therefore, advancement in tools and system able to combine low-priced sensor components and operating system will stimulate the use of automatic protocol to be used for research purposes and precision agriculture. In this context the SunDROPS project presents three innovative set-ups (F&F automatic hydroponic system, multi-electrodes set-up for the detection of the electrical signal and the automatic LEDs light controller) to be further developed and integrated. Automatic operating systems able to control cultivation (e.g. the alternate solutions flux or light supply) could become standard systems to manipulate nutrients uptake and reallocation in plants. In particular, these methodologies are able to provide specific nutrient compositions or light to optimize the daily biological metabolism patterns known as circadian rhythms that is observed at cellular and biological level. Hydroponic cultivation as an artificial cultivation technic has been mainly used by continuously supply the ideal nutrient and light when plant metabolism is at its peak, without taking in account potential differences during each plant daily requirements. It is possible that different species of plant could respond better to daily cyclic nutrient supply or light, thus this field deserve further investigations. An automatic light can be synchronized and set to perform any cycle related to the research demand (for example increase similarly to the sunlight supplement). This light has the potential to be used for long term effect of specific light patterns on plant photosynthesis and growth/development. Successfully, it can easily be modulated to automatically supply the light based on specific daily intervals (pre-set cycles). Finally the results obtained by observing the electrical activity of the plants are promising and the methodology presented has a good potential for empirical applications. Electrical properties measurements can be used at early stage to select the most drought tolerant cultivars for increasing productivity in semi-arid conditions. Additionally, the multi-electrodes approach can be easily applied for monitoring a few plants as “biosensor” to check the status of a more numerous group of plants subjected to the same conditions. Future experiments based on this methodology on outdoor mature vegetable or trees are required, in particular accompanied with other measurements, such as stem water potential are necessary to improve their implementation. This approach, if refined, has the advantage of obtaining data directly from the plant instead of an indirect measurement of the soil or the environment and could be possibly applied for the interpretation of the signals of other stress as well.
Measurement on Chinese cabbage with a gas exchange analyzer (Li-6400).
Electrical activity measurements on Tobacco plants
Lettuce under R/B light.
Fava bean plants under RGB light.
Electrical activity measurements on Black Cabbage
Chinese cabbage under HB-LEDs lights.
Measurement on Chinese cabbage with a gas exchange analyzer (Li-6400).
Lettuce under different HB-LEDs lights.