Abstract: After a preliminary test experiment, wheat grains previously presoaked in phosphate buffer at different pHs as well as an optimum concentration of IAA were sown and grown during 2001 and 2002 growing seasons at the green house of Botany Department, Faculty of Science, Ain Shams University in order to study the possible adaptive mechanisms to ameliorate the pH stress on the growth parameters and anabolic capacities of both the vegetative growth and yield. The results revealed that plants under acidic pH have obvious reduced growth and metabolism. Exogenous application of IAA can stimulate resistance against the unfavourable environmental pH value and improve plant growth under stress by developing various mechanisms, which include increasing both the chlorophyll contents and their stability and consequently the soluble sugars content which play an important role in the readjustment of plant cell`s osmotic potential to prevent water loss under stress condition, minimizing the reduction of the element uptake and also correcting absorption of ions at the root epidermal plasma membrane especially K+ which accumulates more than Ca+2 suggesting that Ca+2 might have a regulatory role than being directly as osmoticum, quantitative increase in the low molecular weight protein (20.4 kDa) and increase in both the soluble protein and proline which acts as a free radical scavenger and limits the cytoplasmic acidification, thus protecting cytoplasmic enzymes. The most interesting mechanism is concerned with the ratio of total polyamine/putresine which is an indication of the deleterious injury induced in the plant cells under stress. This ratio was decreased by elevating the putresine content. In general, it could be concluded that an adaptive mechanism has been developed by Triticum vulgaris cv. Sids 1 in response to exogenous hormonal application under acidic pH stress enabling the plant to grow under such stress and improve the crop yield productivity and quality.