Carbohydrate utilization by belowground organs defines the capacity of faba bean to exploit organic phosphorus sources

Abstract

AbstractBackgroundLimited phosphate (Pi) reserves and the economic and adverse environmental impacts of excessive application of mineral fertilizers in soils are alarming. Therefore, the use of organic phosphorus (Porg) is suggested to reduce reliance on chemical fertilizers.AimsThere is currently little information regarding the accessibility of Porg to N2 fixation plants. Therefore, the present study aims to address the question of to what extent Porg substrates can serve as reliable sources of phosphorus (P) for faba bean in its nodulated phase. Specifically, we intended to explore whether N2‐fixing plants employ intrinsic mechanisms to facilitate Porg availability.MethodsA pot experiment was conducted to assess the inherent capacity of two faba bean varieties (Tiffany vs. Mallory) to utilize Porg supplied as phytic acid and Ca‐glycerophosphate. Plants were inoculated with Rhizobium leguminosarum bv. viciae 3841 strain and cultivated on sterilized loamy sand under greenhouse conditions.ResultsPhytic acid was relatively less efficient than Ca‐glycerophosphate in sustaining plant growth. Compared to Mallory, the variety Tiffany displayed a higher capability to use Porg, as evidenced by the relatively higher biomass production, nodulation, phosphorus use efficiency, and P‐ and N‐accumulations in plant tissues. Porg exploitation was intimately linked to the efficient utilization of the host's carbohydrate budget into nutrient‐acquiring structures (roots and nodules). In addition, the preferential allocation of Pi to prolific nodules is essential for plants to thrive best under these circumstances.ConclusionsTogether with N profitability, these findings suggested that N2‐fixing plants (e.g., faba bean) can promote the sustainable exploitation of Porg, thereby diminishing the sizeable environmental footprint.