Phosphate-Dependent Regulation of Growth and Stresses Management in Plants

Abstract

The importance of phosphorus in the regulation of plant growth function is well studied. However, the role of the inorganic phosphate (Pi) molecule in the mitigation of abiotic stresses such as drought, salinity, heavy metal, heat, and acid stresses are poorly understood. We revisited peer-reviewed articles on plant growth characteristics that are phosphorus (P)-dependently regulated under the sufficient-P and low/no-P starvation alone or either combined with one of the mentioned stress. We found that the photosynthesis rate and stomatal conductance decreased under Pi-starved conditions. The total chlorophyll contents were increased in the P-deficient plants, owing to the lack of Pi molecules to sustain the photosynthesis functioning, particularly, the Rubisco and fructose-1,6-bisphosphatase function. The dry biomass of shoots, roots, and P concentrations were significantly reduced under Pi starvation with marketable effects in the cereal than in the legumes. To mitigate P stress, plants activate alternative regulatory pathways, the Pi-dependent glycolysis, and mitochondrial respiration in the cytoplasm. Plants grown under well-Pi supplementation of drought stress exhibited higher dry biomass of shoots than the no-P treated ones. The Pi supply to plants grown under heavy metals stress reduced the metal concentrations in the leaves for the cadmium (Cd) and lead (Pb), but could not prevent them from absorbing heavy metals from soils. To detoxify from heavy metal stress, plants enhance the catalase and ascorbate peroxidase activity that prevents lipid peroxidation in the leaves. The HvPIP and PHO1 genes were over-expressed under both Pi starvation alone and Pi plus drought, or Pi plus salinity stress combination, implying their key roles to mediate the stress mitigations. Agronomy Pi-based interventions to increase Pi at the on-farm levels were discussed. Revisiting the roles of P in growth and its better management in agricultural lands or where P is supplemented as fertilizer could help the plants to survive under abiotic stresses.

Keywords: adaptation; phosphate; phosphorus; plant growth; stress tolerance.

Figure 1

Boxplots and scatter data of the photosynthesis rate (A) total chlorophyll content (B) stomatal conductance (C) leaf area (D) under sufficient-P (+P), and deficient (–P) conditions of soybean, cowpea, wheat, and maize plants. ¹ Average change (%) of +P applied over P-deficient plants. Means + bootstrap at 95% CIs of two tested P treatments that do not overlap indicate a significant relative increase difference.

Figure 2

Cellular Pi-dependent regulation of the plant photosynthesis activity displaying the major process. PGA, 3-phosphoglycerate; diPGA, 1,3-diphosphoglycerate; FBP, Fructose-1,6-bisphosphate; F2,6, Fructose-2,6-bisphosphate; F6P, Fructose 6-phosphate; Ru5P, Ribulose-5-phosphate; RuBP, Ribulose-1,5-bisphosphate; SBP, Sedoheptulose-1,7-bisphosphate; S7P, Sedoheptulose-7-phosphate; G6P, Glucose 6-phosphate; G1P, Glucose 1-phosphate; Triose-P, Triose phosphate; ADPG, ADP-glucose UDPG, UDP-glucose; PMP, Pentose monophosphate; 6PG, 6- phosphogluconate; ATP, Adenosine triphosphate; ADP, Adenosine di-phosphate; NADP, Nicotinamide adenine dinucleotide phosphate; UTP, Uridine-5′-triphosphate; PP, pyrophosphate. The image illustration was redesigned by NB and MJ.

Figure 3

Boxplots and scatter data of shoot dry weight (A) shoot-P (B) root-P (C) concentrations, and P uptake (D) under +P and −P conditions of soybean, cowpea, wheat, and maize plants. ¹Average change (%) of the sufficient-P applied over P-deficient plants. Means + bootstrap at 95 % CIs of two tested P treatments that do not overlap indicate a significant relative increase difference.

Figure 4

Boxplots and scatter data of shoot (A) root (B) dry weights, shoot-P (C) and root-P (D) internal concentrations under +P and −P under drought or water deficit conditions of soybean, cowpea, wheat, and maize plants. ¹Average change (%) of the +P applied over P-deficient plants. Means + bootstrap at 95% CIs of two tested P treatments that do not overlap indicate a significant relative increase difference.

Figure 5

Pi-dependent regulation of the plant growth process at the cellular levels. UDP-glucose, Uridine diphosphate glucose; PEPC, Phosphoenolpyruvate carboxylase; Hexose-P, Hexose phosphate; OAA, Oxaloacetate; ASP, aspartate; PEP, Phosphoenolpyruvate; SUS, Sucrose synthase; PKc, Cytosolic pyruvate kinase; MDHc, Cytosolic malate dehydrogenase; MDHm, Mitochondrial malate dehydrogenase; MEm, Mitochondrial malic enzyme; PDCm, mitochondrial pyruvate dehydrogenase complex; CS, Citrate synthase. The image illustration was redesigned by NB and MJ.

Figure 6

Boxplots and scatter data of shoot Pb (A) Cd (B) and Zn (C) contents under +P and –P conditions of wheat, sedum, rice, barley, maize, and rapeseed plants. ¹Average change (%) of the +P applied over P-deficient plants. Means + bootstrap at 95% CIs of two tested P treatments that do not overlap zero indicate a significant relative increase difference.