Potassium and phosphorus content ratio in hydroponic culture affects tomato plant growth and nutrient uptake

Mineral nutrient deficiencies induce a cascade of physiological, morphological, and biochemical changes in plants which reduce vegetative growth. In this work, the impact of P and K concentration levels on tomato plant development grown in hydroponic culture was investigated. Root morphology, chlorophyll a fluorescence, phosphorus (P) and potassium (K) content, and shoot and root biomass were analyzed. Root morphology showed significant differences among the plants grown in hydroponic culture with different concentrations of P and K. Plant root/shoot dry biomass ratio decreased by 22 and 35% for P₁₅K₀ and P₃₀K_0, respectively, compared to the control (P₃₀K₂₃₂). The deficiency of P and K (individually or both) reduced significantly the root mass density parameter. For example, root mass density decreased by 38% at P₁₅K₀ treatment compared to control. Correlation analysis showed that the P and K content ratio in shoot and root was significantly and positively correlated with root volume. Deficiencies in K and P decreased the relative size of the PSI final electron acceptor pool and the electron flow on the acceptor side of PSI. Tomato growth response depend on the availability of P and K, however, interactions between these two nutrients could influence their uptake and utilization.