**8. Phosphorus and photosynthetic efficiency**

The efficient functioning of the dark phase of photosynthesis is directly impacted by the availability of P, a vital component in the production of energy transfer molecules ATP and NADPH [9, 62]. Without sufficient P, plants cannot produce these molecules, leading to reduced photosynthesis and decreased crop yields. Several studies have shown the importance of P in photosynthesis and crop productivity. For example, P-deficiency can significantly reduce the photosynthetic rate and yield [63]. Similarly, P-deficient soils can negatively impact the growth and yield of teff, a staple crop in Ethiopia [64]. Moreover, P-deficiency can also lead to a decrease in the activity of key enzymes involved in the Calvin cycle, such as RuBisCO, further contributing to the reduction in photosynthetic efficiency [65]. Being a key component of ADP and ATP synthase P is required for optimal photosynthetic activity. Hence, P-deficiency limits or halts the biochemical process of phosphorylation and limits the catalytic activity of energy-producing enzymes [66, 67].

Unfortunately, P is often limited in soils, making it a scarce resource for plants. Excessive use of P-fertilizers can also lead to environmental problems. The overapplication of P-fertilizers, surpassing crop demand, poses a heightened risk of P-loss from soil to water resources and can result in the degradation of water quality through eutrophication [68]. Therefore, it is important for farmers to understand how to manage phosphorus effectively in their soils to ensure sustainable crop production. One approach to managing P effectively is using precision agriculture techniques. For example, a study conducted in Ghana showed that precision application of P-fertilizer based on soil testing and yield potential resulted in higher crop yields and reduced phosphorus runoff compared to traditional broadcasting of fertilizer [69]. In response to P-deficiency, plants can develop adaptive mechanisms, such as increasing the expression of high-affinity phosphate transporters and enhancing the secretion of acid phosphatases, which help to increase phosphorus uptake and utilization [70]. Plants also modify their metabolic pathways and root morphology, and this involves changes in their gene expression. A range of proteins involved in the various metabolic pathways are differentially expressed in response to phosphate stress, suggesting that they may play important roles in regulating complex adaptation activities for Pi deprivation to facilitate P-homeostasis [71]. The proteins that respond to P shortage may be involved in various processes including phytohormone biosynthesis, signal transduction, cellular organization and defense, and energy and carbon metabolism [72]. These proteins are likely to play a crucial role in sensing the changes in external Pi concentration and regulating complex adaptation activities that enable plants to maintain P homeostasis.
