Drought stress is considered as the main factor of yield limitations in arid and semi-arid areas, where drought and salinity stress are combined the negative effects of these stresses are more conventional on crop yield. Kochia species have recently attracted the attention of researchers as forage and fodder crop in marginal lands worldwide due to their drought and salt tolerant characters. This field experiment was performed at the Salinity Research Station (36°15´N, 59°28´E) of Ferdowsi University of Mashhad, Iran, in a split plot based on a randomized complete block design with three replications in 2008. Three levels of drought stress (control, no irrigation in vegetative stage (recovery treatment) and no irrigation at reproductive stage for one month (stress treatment)), and two Kochia ecotypes (Birjand and Borujerd) were allocated as main and sub plots, respectively. Plants were irrigated with ground water having electrical conductivity (EC) of 5.2ds.m-1. Photosynthetic pigment, proline, soluble carbohydrate, Na and K concentrations were assayed at the beginning of anthesis. Results showed that stress treatment caused a significant increase in proline, soluble sugar and photosynthetic pigment compared with control and recovered conditions. It seems that these parameters may play a role in minimizing the damage caused by dehydration. Na and K concentration didn't differ between treatments. According to the results, there were no differences between recovered plants and control treatment, therefore, Kochia can recover quickly after removing stress. Birjand ecotype from the arid regions, revealed a better response to drought stress than Borujerd ecotype. This could be due to initial adaptation of Birjand ecotype especially in stress condition. Proline showed that the most differential between measured parameter, therefore proline can be one of the best stress indexes in this condition.

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