**2. Root signaling**

plants to counteract nutrient scarcities with different forging strategies [2]. Root-specific traits such as root system architecture, sensing of edaphic stress and root-to-shoot communication can be exploited to improve resource capture (water and nutrients) and plant development

The uptake of nutrients depends upon both the supply of available nutrients in the rooting media and the root system [4]. The ability of plants to respond appropriately to nutrient availability is of fundamental importance for their adaptation to the environment. Nutrients such as nitrate, phosphate, sulfate and iron act as signals that can be perceived. These signals trigger molecular mechanisms that modify cell division and cell differentiation processes within the root and have a profound impact on root system architecture. Important developmental processes, such as root-hair formation, primary root growth and lateral root formation, are particularly sensitive to changes in the internal and external concentration of nutrients [5]. There is no doubt that differences occur in response to mineral nutrition both among species

Phosphorus plays a vital role in crop production and is involved in energy transfer in plants. Carbon dioxide fixation by plants is not possible without phosphorus. Many plant physiological functions such as utilization of sugars, starch, photosynthesis, energy storage and transfer are dependent on phosphorus. It is also a constituent of cell nucleus and is essential for cell division and development of meristematic tissues [6]. Phosphorus has been reported to increase the strength of cereal straw, resist abiotic stresses, stimulate root development, promote flowering, fruit production, and formation of seed and hasten maturity of the crops [7]. Phosphorus utilization efficiency can be improved by mixing it with farm yard manure to increase the yield of wheat. Farm yard manure mixed with single superphosphate in 1:2 ratio increases phosphorus efficiency significantly [8]. It would be advantageous if we select, screen or improve plants for higher capacity to adapt to mineral stresses. This approach is beneficial in developing countries like Pakistan where capital input resources are limited. Farmers in these countries require nutrient efficient crop cultivars which perform better or do something

better than other cultivars when given a considerable amount of mineral nutrient.

Cereals are facing acute problem of drought and temperature stress [9]. Low water availability is the major environmental factor which limits crop productivity. Root is the place where plants first encounter drought stress, it is likely that roots may be able to sense and respond to stress condition. Drought stress is the most common adverse environmental condition that can seriously reduce crop productivity [10, 11]. The mechanism of drought tolerance and breeding for droughtresistant crop plants has been major goal of plant biologists and crop breeders. Significant progress has been made in understanding root growth under drought stress. However, there has been no genetically defined drought-adaptive response in root development. But inhibition of lateral root development is a typical adaptive response of roots to drought stress. Despite the lack of understanding of drought tolerance mechanisms, physiological and molecular biological studies

Lack of sufficient water is the most important factor affecting world agriculture. Thus, increasing the efficiency of water and nutrient use is essential in order to improve yield whilst minimizing damage to the environment [13–18]. Plant depends upon the capacity of roots to obtain water and nutrients from the soil. The root respiration, carbohydrates allocation (root: shoot

under water-limited conditions [3].

2 Global Wheat Production

and cultivars, that is, genotypes belonging to the same species.

have documented several plant responses to drought stress [12].
