1.1 Background to the Study
The tomato (Solanum lycopersicum) belongs to the solanaceae (night shade) family. It is native to tropical America where its indigenous name was tomati. From Mexico the tomato was taken to Europe and then to Asia. An important vegetable crop, it is grown in most home gardens and by market gardeners and truck farmer. It is also produced by forcing in green houses (Malik and Bashir, 1994). It can be eaten either fresh or processed into many different products. It plays a vital role in maintaining health and vigor. Tomatoes are very helpful in healing wounds because of the antibiotic properties found in the ripe fruit. It is a good source of vitamins A, B and C. It is widely used in salad as well as for culinary purposes. Tomato gain popularity very rapidly and attain the status of widely consumed. Although tomato is a tender perennial crop, which is susceptible to frost as well as high temperature but it is being grown in a variety of climatic conditions, ( Malik and Bashir, 1994).
In Pakistan tomato is grown over an area of 24,144 hectares annually, which produces 2,75,241 tons of tomato. KPK is the major producing region where it is grown on an area of 4230 hectares with a total production of about 51,062 tons annually.
In Peshawar valley, quite a sizeable area of 944 acres is put under tomato cultivation with a production of 2.978 thousand tones.
In nature, water is usually the most limiting factor for plant growth. If plants do not receive adequate rainfall or irrigation, the resulting drought stress can reduce growth more than all other environmental stresses combined. A plant responds to a lack of water by halting growth and reducing photosynthesis and other plant processes in order to reduce water use. As water loss progresses, leaves of some species may appear to change color usually to blue-green. Foliage begins to wilt and, if the plant is not irrigated, leaves will fall off and the plant will eventually die.