**2. The role of phosphorus in plant physiology and growth**

Among the most critical essential macronutrients, P is required by plants for their proper growth and development. It plays a crucial role in plants' physiological and biochemical processes, including photosynthesis, energy transfer, cell division, nucleic acid synthesis, and membrane transport. Therefore, understanding the role of P in plant physiology and growth is crucial for plant scientists, agronomists, and farmers to optimize crop production and improve the sustainability of agricultural systems.

### **2.1 Phosphorus acquisition and uptake**

Phosphorus is an essential nutrient for plant growth and development, playing a crucial role in various metabolic processes such as ATP synthesis and nucleic acid formation [2]. Plants require large amounts of P, which is often the limiting factor in its growth [10]. Plants take it up as phosphate ions (H2PO4 and HPO4 2−) found in the soil [11]. The availability of phosphate ions in the soil is affected by soil pH, temperature, moisture, and microbial activity [3]. However, P is often present in limited amounts in soil, mainly in insoluble phosphates [12]. Therefore, plants have developed various mechanisms to acquire and uptake P from the soil [13]. One of the strategies plants use to obtain P is through production of phosphatase enzymes (**Figure 1**). These enzymes can hydrolyze organic phosphates in the soil, releasing inorganic phosphate ions that the plant can take up. Several studies have shown that plants can increase the production of phosphatase enzymes in response to low soil-P levels [4, 14]. Plants can also secrete organic acids, such as citrate and malate, to solubilize insoluble P compounds in *Regulation of Plant-Microbe Interactions in the Rhizosphere for Plant Growth and Metabolism… DOI: http://dx.doi.org/10.5772/intechopen.112572*

#### **Figure 1.**

*Representation of the major processes involved in phosphorus-aquision by plants involving organic acid secretion.*

the soil. These organic acids can chelate with metal ions, reducing their ability to bind with phosphates and making them more available for plant uptake [15].

Furthermore, many plants form symbiotic associations with mycorrhizal fungi, which can enhance P-uptake and -translocation in the plant. Mycorrhizal fungi can extend their hyphae into the soil, increasing the surface area for P-uptake. They can also release phosphatase enzymes and organic acids, increasing P-availability [16].

#### **2.2 Phosphorus and plant metabolism**

Phosphorus is vital in plant metabolism as an essential macronutrient for growth and development. According to Rao and Pessarakli [17], P is absorbed by plant roots as phosphate ions and then transported to various plant tissues and organs (**Figure 2**). Once inside the plant, P is involved in numerous metabolic pathways, including photosynthesis and respiration. In photosynthesis, P is a fundamental component of ATP, the primary energy source for plant cells. ATP is synthesized in the thylakoid membranes of chloroplasts through the phosphorylation of ADP (adenosine diphosphate) using energy from light [10]. P also regulates photosynthetic carbon metabolism by activating specific enzymes and proteins involved in the process. P is also crucial to nucleic acids, such as DNA and RNA. Nucleic acids are involved in gene expression and protein synthesis, essential for plant growth and development. In addition, P is involved in forming phospholipids, crucial components of cell membranes [18]. Phospholipids serve as precursors for synthesizing signaling molecules, such as inositol phosphates, which are involved in various cellular signaling pathways [19]. P also plays a crucial role in regulating various metabolic processes in plants. P regulates the synthesis and activity of various carbohydrate, lipid, and protein metabolism enzymes [20].

Understanding the role of P in plant metabolism is crucial for optimizing its availability in the soil and improving agricultural productivity and sustainability. Research into P and its plant functions can help develop strategies to enhance soil P levels, leading to healthier and more productive crops.

**Figure 2.**

*Representation of the major modes of phosphorus uptake in plants.*

**Figure 3.**

*Representation of the major roles of phosphororus in plant growth, development and yield.*

*Regulation of Plant-Microbe Interactions in the Rhizosphere for Plant Growth and Metabolism… DOI: http://dx.doi.org/10.5772/intechopen.112572*
