الفهرس 
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Abstract
This work was conducted to examine the responses of three plants to cadmium, salinity, heat stress and drought. The chosen plants were radish Raphanus sativus, rocket Eruca sativa and turnip Brassica rapifera. In addition to control treatment, plants were exposed to cadmium concentrations of 0 ppm, 5 ppm, 25 ppm and 50 ppm in the first experiment, and to treatments containing salinity levels of 1000 ppm, 1500 ppm and 3000 ppm in the second experiment.
Cadmium stress on the three leafy vegetables caused clear reduction in plant height, root length, biomass, chlorophyll pigments and overall growth parameters over time, with either of spray or irrigation treatments. Radish, rocket and turnip were found to accumulate Cd in their leaves when exposed to different Cd concentrations. Accumulated Cd was increased in leaves tissue with both growth stages and the increase of Cd concentration level. A general decrease in chlorophyll a and b, with the increase of Cd concentration was also detected.
The growth of radish, rocket and turnip plants exposed to salinity has been affected and main reductions in plant height and root length with salinity level were observed on the last growth stage (120 days). The results indicated that cadmium treatments had a greatest impact than salinity treatment. Moreover, percentage levels of nitrogen, phosphorus and potassium in leaves of treated different plant species have been affected by cadmium and salinity treatments.
Analyze all opened data, statistically, in writing of production averages and spreads
The effect of drought on plants was examined, when the plants were exposed to water stress at the age of 15 days of germination and at the age of 30 days of germination. It was found that plants do not tolerate drought, especially turnip, whether at the age of 15 days or at the age of 25 days.
To examine heat stress impacts on plants, plants were exposed at the age of 15 days of germination to temperatures of 35, 40 and 45 OC, as well as the plants at the age of 30 days of germination were exposed to a temperature of 35, 40 and 45 OC. It was found that the plants do not tolerate higher temperature degrees than 35 degrees. Generally, exposed radish, rocket and turnip showed variation in response to these stresses and confirm that species and genotypes crops are differ in their sensitivities to abiotic stresses.
Conclusion:
Contamination of vegetables with heavy metals due to soil and atmospheric pollution poses a threat to its quality and safety. Dietary intake of heavy metals also poses risk to animals and human health. Heavy metals such as Cd and Pb have been shown to have carcinogenic effects. Human health is affected by Cd pollution in farmland soils because food is the main source of Cd intake. Vegetable plants are highly affected by heavy metals, and absorb heavy metals from emission exhaust. Salinity is another major environmental stress that restricts the growth and yield of crops.
It is recommended to protect cultivated lands from direct contamination, and to avoid cultivation of vegetable plants near high polluted areas due to cars, highways and industrial emissions should be avoided. It is also preferred to use irrigation water that contains low salinity levels. Also, cultivation of salt tolerant crops cultivars is the most effective way to overcome this environmental problem. As climate change is expected to increase the frequency and magnitude of droughts as well as temperature, it is important to implement the appropriate policy measure for adaptation.