**2.8 Root and shoot growth**

Phosphorus is inextricably involved in plant growth from cellular to whole plant level, playing a significant role in cell division and cell enlargement that are crucial for root and shoot development. It stimulates root development required for the plant to get nutrients and support from the soil. Phosphorus is essential for better growth parameters of plants such as height, biomass of shoot, area and number of leaves, and timely appearance and development of tillers in cereals [36]. The deficiency of P can lead to limited cell divisions and enlargement in leaves, resulting in reduced shoot biomass. Plant growth is considered to be more sensitive to P-availability compared to photosynthesis [37]. Under long-term Pi-deficient conditions, the relative growth rate decreases as a result of reduced ATP concentration in roots [38]. Limited leaf expansion under low P-supply might be due to low turgor pressure for leaf expansion resulting from decreased water transport in the leaf from the growth medium.

*Sustainable Management of Phosphorus in Agriculture for Environmental Conservation DOI: http://dx.doi.org/10.5772/intechopen.113086*

#### **2.9 Flower, fruit, and seed formation**

Phosphorus is responsible for the reproductive development of plants such as formation of flower, fruits, and seeds as well as crop maturity at the right time. P-deficient plants take longer period to mature and bear few fruits and seeds with poor quality. Phosphorus nutrition can regulate anthocyanin production in leaves flower stalks by modulating the activities of phenylalanine ammonia-lyase (PAL) and chalconeisomerase (CHI) and epidermal pH values [39]. Optimum amount of P in soil ensures a higher number, dry matter, and yield of fruits and seeds with a greater harvest index. For development and maturation, both fruits and seeds require large quantities of P, and an inadequate supply of P can reduce the size, number, viability, and quality of seeds. In cereal crops such as rice, wheat, and maize, the majority of total P (about 75%) is stored as phytin or associated compounds, whereas 4–9% is stored as inorganic phosphate and 15–25% as cellular-P [40].

#### **2.10 Disease and stress resistance**

Phosphorus is crucial for the general health and vigor of plants, and it enhances resistance and tolerance to stress and diseases, which otherwise can reduce crop quality and production. P-balancing with other nutrient inputs is of prime importance to decline the risk of disease infection. In a complete and balanced fertility program, P is a major element that can improve crop health to withstand stress and to become less susceptible to disease occurrence. However, the role of P in disease resistance is variable and inconsistent [41].
