**2.4 Glycolysis**

Phosphorus is involved in every reaction of the glycolysis process in plants. In the initial reactions of glycolysis, energy from ATP is necessary. However, in the subsequent reactions, ATP is generated with a net release of energy. Actually, ATP is the energy end product of glycolysis, which is the predominant pathway of carbohydrate metabolism in plant tissue. Pentose phosphate pathway is one of the major aerobic processes of carbohydrate degradation and synthesis where a series of oxidationreduction reactions begin with five carbon sugars having a phosphate molecule attached to them. The activities of several glycolytic enzymes phosphofructokinase (PFK), nicotinamide adenine dinucleotide (NAD)-glyceraldehyde 3phosphate dehydrogenase (G3PDH), 3-Phosphoglyceric acid (3-PGA) kinase, and pyruvate kinase (PK) depend on the concentration of adenylate and Pi. The levels of respiratory intermediates, viz. hexose phosphates and 3-phosphoglyceric acid (PGA), reduce during P-deficiency. The activities of PFP and nonphosphorylating NAD-G3P-DH, phosphoenolpyruvate (PEP) carboxylase, and PEP phosphatase have been found to increase under P-deprived conditions.

#### **2.5 Nutrient transport**

Plant roots extract nutrients from soil solution and translocate them within the body, and most of this movement depends on a transport system through the cell membrane that requires energy to override the opposing force of osmotic equilibrium, which is provided by ATP through its high-energy phosphate bonds. ATP or some other phosphorylated compounds conduct the transport of nutrients through membranes of plant organs such as roots and leaves by an energy-driven process.

Several plasma membrane-bound transport proteins play vital roles in nutrient transport, and for example, proton pump named H+ -ATPase imports nutrients into the plant together with the export of H<sup>+</sup> by utilizing ATP [27]. Therefore, to enable nutrient transport smoothly with the use of ATP, these membrane proteins are abundant in the epidermal and endodermal root cells, xylem and phloem cells [28–30].
