Do polyphosphate fertilizers improve photosynthetic performance and nutrient uptake in salt-stressed wheat?

In the current context of intensive agriculture and the increasing effects of salinity in several regions in the world, different approaches have been proposed and adopted to minimize the harmful effects of this stress on plants development and productivity. Optimising phosphorus (P) nutrition seems to bring positive results. However, the P-fertilizer use efficiency of plants under salt stress differs depending on the severity of salinity in the rhizosphere. The present work posed the question if soluble fertilizers allow wheat plants to counter the adverse effect of salt stress. A pot experiment was performed using a Moroccan variety of durum wheat: Karim. This study focused on different growth and physiological responses of wheat grown under the combined effect of salinity and P-availability. Three soluble fertilizers were used: two Orthophosphates (Ortho-A & Ortho-B) and one polyphosphate (Poly-B) were applied at different P levels (0, 30 and 45 ppm). The plant growth was analysed on some physiological parameters (stomatal conductance (SC), chlorophyll content index (CCI), chlorophyll a fluorescence, shoot and root biomass, and mineral uptake. A decline in CCI, SC and biomass was observed. However, the fully mature leaves of fertilized wheat plants with different P-doses and forms showed a significant increase in the photosynthetic performance (PItot) and nutrient uptake compared to control and salt-stressed and unfertilized plants. These results demonstrated that P-fertilization significantly increased all other growth parameters in plants under salinity. The increased photochemical activity could be due to an enhancement in light energy absorbed by the enhanced Chl antenna.