Title : Root electrical capacitance: a novel approach to monitor crop response to climate change
Abstract:
Avigorous, adaptive root system is critical for improved water and nutrient uptake, which in turn increases crop grain yield,especially under stress conditions. High-throughput, in situ root phenotyping techniques are increasingly important in breeding plants for sustainable agriculture. This is the first study that documents the efficiency of monitoring root electrical capacitance (C R*) non-destructively in the field to evaluate crop development under different environmental conditions.A free-air CO 2 enrichment (FACE) experiment was performed with two winter wheat cultivars, two levels (low and high) of nitrogen supply and two (ambient and elevated to 600 ppm) of [CO 2] in three replicate plots over two years. The validity of CR* asa proxy for root uptake activity was confirmed by tracking the ceptometer-based leaf area index from the early vegetative to the flowering stage of wheat.Repeated C R measurements revealed the seasonal dynamics of root development with a peak at flowering, and indicated a delayed growth in the second year caused by the unfavorable meteorological conditions. From the vegetative to flowering stages, C R was strongly correlated with the leaf area index (R2 : 0.897–0.962). The positive effect of elevated nitrogen supply and [CO 2] on crop growth was reflected in higher CR values, associated with increases in leaf area index, shoot dry mass at flowering and grain yield.The maximum C R was closely related to grain yield (R2 0.805 and 0.867) when the data were pooled across the nitrogen and CO2 treatments and the years. Unlike CR and grain yield, shoot dry mass and leaf area index were significantly lower in the second year, presumably due to the enhanced root/shoot ratio induced by a severe spring drought. The increased biomass allocation to the roots was later able to compensate for the yield loss under the more favorable growing conditions that prevailed around flowering. Considering the individual wheat plants, CR measured at the anthesis stage was highly significantly correlated with the total aboveground biomass (R2 : 0.715 and 0.727) and grain yield (R2 : 0.648 and 0.661) for each cultivar. The present results convincingly demonstrated the potential of the non-destructive root capacitance method to assess root responses dynamically, and to predict crop grain yield. One current challenge facing breeding programs is the selection of crop genotypes having higher physiological plasticity and responsiveness to changing climatic events, such as rising [CO2], extreme temperatures and drought. Capacitance measurement, as a simple, in situ, high-throughput root phenotyping tool could partially replace invasive routine field techniques, and may thus be of interest for future application.The project was funded by the National Research, Development and Innovation Fund of Hungary (Project No. 137617, financed under the FK-21 funding scheme), and by the Hungarian Government (GINOP-2.3.2-15-2016-00028).
