Effect of phosphorus on iron, zinc and potassium uptake and the characteristics of root and shoot of wheat in different moisture regimes

Drought is one of the most widespread abiotic stresses which has a negative effect on the growth and yield of plants in most parts of the world. Drought stress reduces plant yield by reducing the uptake of water and nutrients. The dry and semi-arid weather conditions of Iran have caused many problems in the production of plants, including wheat (Triticum aesivum L.). Phosphorus, as one of the essential nutritional elements for wheat, can be effective in alleviating the effects of drought stress. In recent years, to deal with drought stress, the use of plants and cultivars efficient in uptake nutrients, including phosphorus, as an appropriate strategy to increase crop yield has been the focus of researchers. Therefore, it is necessary to pay attention to the mechanism of efficient cultivars against drought stress for accurate fertilizer recommendations.

To evaluate Sirvan wheat cultivar (resistant to drought stress), in the uptake of nutrients and its growth and development at different levels of moisture and phosphorus, a research in the greenhouse was performed as factorial based on a completely randomized design with two factors and three replications during the vegetative growth period. The factors included phosphorus from mono-calcium phosphate monohydrate source (0, 15 and 25 mg P kg soil-1) and three moisture regimes including 50 and 70% of field capacity (T1, T2: stress conditions) and 95% of field capacity (T0: control).

According to the results, it was observed that the interaction effect of drought stress and phosphorus levels on total dry weight, uptake of iron, zinc and potassium nutrients, total soluble sugar, root growth (cumulative length, diameter and root area) and chlorophyll index was significant at the 0.01 % and 0.05 % level of probability, respectively in Sirvan cultivar. The results showed that the increase of phosphorus (25 mg kg-1) in the presence and absence of drought stress was effective on the growth and development of the studied wheat cultivar; So the addition of phosphorus in the amount of 25 mg kg-1 in the drought stress condition of 50% of the field capacity increased the total dry weight of Sirvan variety from 5.80 to 8.52 g pot-1 compared to the level without phosphorus application. The increase of phosphorus in the condition of drought stress (50%), increased the uptake of iron nutrients by about 2 times, zinc and potassium by 60 and 50%, respectively, compared to the control level that this increase in uptake can be due to the increase in root growth and its characteristics (cumulative length, area and diameter); Also, according to the results of this experiment, it was observed that the resistance of Sirvan cultivar to drought stress was due to the increase in the amount of total soluble sugar, root growth and uptake of iron, zinc and potassium which led to an increase in total dry weight and its good growth and development under drought stress conditions.

The application of the appropriate amount of phosphorus at the level of 25 mg kg-1 under drought stress conditions increased the total dry weight, root area, root diameter and length, uptake of nutrients, chlorophyll index, height, number of tillers and the amount of total soluble sugar in the plant, this level of phosphorus with a positive effect on the growth and development of Sirvan variety in the vegetative growth stage made it adapt to drought stress conditions; Considering the importance of cultivar selection in adjusting drought stress, Sirvan cultivar was able to show a good response to phosphorus fertilizer to reduce drought stress.