Investigation of the Effect of Drought Stress on the Morpho-Physiological Characteristics of the Lallemantia Plant (Lallemantia iberica L.) in Different Levels of Humic Acid

To investigate the effect of different levels of humic acid on some characteristics of the lallemantia plant under different water deficit treatments, a split-plot field experiment was conducted in the form of a completely randomized block design in three replications in 2014. The treatments included four irrigation levels of 50, 70, 90, and 110 mm of evaporation from the surface of the evaporation pan, equivalent to no stress, mild stress, moderate stress, and severe stress respectively as the main factors, and four levels of humic acid were zero, five, 10 and 15 liters per hectare as subfactors. The results illustrated that plant height, leaf number, secondary stems number, chlorophyll b, total chlorophyll, P concentration of aerial parts, RWC decreased under drought stress, and Na and K content of aerial parts and leaf proline increased. The use of humic acid increased the morpho-physiological indicators of the number of leaves per stem and the number of secondary stems. In addition, the use of humic acid improved the relative water content of the leaves, water use efficiency and proline content. The interaction effect of drought and humic acid treatments on N shoots and chlorophyll was significant. Furthermore, the highest amount of N was at the level of 15 litres per hectare of humic acid and 50 mm of evaporation. In general, the use of humic acid, partiucularly in 15 litres per hectare concentration, improved the morphological and physiological indicators and greatly decreased the effects of drought stress.