## 3 Results  
### Systematic Review  
The network map shown in Figure 2 categorized the identified literature into 4 clusters of concepts, highlighted in blue, yellow, red and green colors. The blue cluster circulated the networking of plum physiology with respect to ET and the water use efficiency (WUE) in plum orchards. The specific emphasis of this network is how these stated factors influence the quality of the harvested plums. The blue network aims to uncover insights that have the potential to be applied to improve fruit quality. This can be achieved by understanding plums' physiological processes and improved water management. The yellow cluster revolves around the WUE in plum orchards. This network explores various irrigation practices, the physiological aspects of water use in plum orchards and the collective influence of these factors on the overall WUE in plum orchards. The red cluster is based on the relationship between water stress and the factors influencing fruit production in _Prunus salicium_ orchards. The network investigates how various irrigation systems, soil moisture and stem water potential (SWP) impact overall fruit production as well as the crop load in plum orchards. Lastly, the green cluster centers on the application of RDI as a water management technique. The studies focused on the impact of RDI on plum tree growth and growth rates, performance and yield. Additionally, the network investigates the relationships between plant growth in plum orchards, water stress and yields concerning efficient water management practices. Overall, this network explains the retrieved studies' focus on efficiently managing water resources in plum orchards to obtain the maximum crop yields and fruit quality. The results from this review illustrate that 14 plum cultivars were studied in the retrieved articles, as shown in Figure 3. The cv. Black Gold had the most (n = 5) studies [14; 15; 16; 17; 18]. The water requirements for the cv. Angeleno were estimated by three studies [19; 20; 21], while three studies estimated the water requirements for the cv. Red Beaut [17; 22; 23]. According to the retrieved articles, two studies were carried out each for the cv. Fortune [17; 24], cv. Black Star [17; 18], and cv. Black Diamond [17; 18]. The water requirements of mature and seedling crops of the cv. Santa Rosa were estimated by [PERSON] et al. [17]. Thus, two studies were recorded as having been undertaken on this cultivar based on this frequency. The results show that only one study each was carried out for the cv. Timhdit [17], cv. Oblinaja [17], cv. Methyl [25], cv. Black Amber [17], cv. African Rose [26] and cv. African Delight [24]. Three studies by [PERSON] and [PERSON] [14], [PERSON] et al. [15] and [PERSON] et al. [16] were carried out on the same orchard, planted with a young cv. Black Gold grafted onto the Mariana GF81 rootstock. The Black Amber and Black Diamond cultivars in this orchard were planted in guard rows as pollinators. The large size of the fruit of the cv. Black Gold is a critical component for achieving high economic returns. From the results obtained by [PERSON] and [PERSON] [14], crop level (aggregate yield of the fruit tree) and water stress do not have a considerable interactive effect on the performance of the  
Figure 3: The number of studies that carried out experiments on the estimation of CWR for various plum cultivars. Figure 2: Network visualization of the topical concepts in plum water requirement estimation studies derived using the title, abstract and key terms. cv. Black Gold. This speaks to the need to implement various RDI regimes on this fresh market cultivar with dark red skin to investigate its response to varying induced water stress. Understanding the stress recovery rate of plum cultivars under RDI is imperative, as this affects their CWR. [PERSON] et al. (2015) reported that the cv. Black Gold has a high recovery rate under RDI, as there is lower competition between vegetative and fruit growth due to crop load regulation. However, [PERSON] et al.