Effect of organic and biological fertilizers on some growth characteristics of evening primrose (Oenothera biennis L.) under salinity conditions

  Salinity is an important environmental tension limiting growth and productivity of plants worldwide. About 7% of the world’s total land area is affected by different degrees of salinity. Saline soil can be defined as soil having an electrical conductivity of the saturated paste extract (ECe) of 4 dSm−1 (4 dSm−1 ∼40mM NaCl) or more. The harmful effects of high salinity on plants can be observed in different levels such as the death of plants or necrosis of plant organs and/or decreases in productivity. Some tolerant plants develop mechanisms either to exclude salt from their cells or to tolerate its presence within cells. Major processes such as photosynthesis, protein synthesis, and energy and lipid metabolism are affected in plants during the beginning and development of salinity stress.
Oenothera biennis L., an important medicinal plant, known as evening primrose. Organic fertilizers develop favorable physical, chemical and biological environment in the soil. They stimulate plant root growth, increase nutrient uptake and soil water-holding capacity, decreases evaporation from the soil and surface water runoff, facilitate drainage, regulate soil temperature and provide a rich substrate for soil microbes. This study was conducted to determine the effects of soil salinity and organic amendments on some growth characteristics, concentration of phosphorus, sodium and potassium and catalase enzyme activity in evening primrose plant (Oenothera biennis L.). Material and In a factorial experiment and completely randomized design (CRD), six levels of organic amendments (control (without soil amendments), 1.5 and 3 g.L-1 mycorrhizal fungi, 16 and 32 mg l-1 humic acid and 25% v/v madder residue plant) and three levels of soil salinity (4, 7 and 12 dS.m-1) with three replications per treatments were applied in Mahmoodabad research field of Esfahan municipality. In this experiment, media without organic amendment was considered as control. Results showed that increasing soil salinity levels progressively decreased the growth characteristics and nutrients concentration. Salinity causes growth reduction due to the low osmotic potential of the medium and by a specific ion effect as a secondary cause in several vegetable crops. The results of present study showed that the organic media can improve plant height. This can be due to increased media moisture storage and enhanced nutrient absorption. In EC = 4 dS.m-1 the highest plant height, root length and P concentration obtained in plants treated with 3 g/kg mycorrhizal fungi. Where in 7 and 12 dS.m-1 salt, organic matter showed the best effect on relative water conductivity, reducing time to flowering, increasing the P and K concentration, fresh and dry weigh of root and shoot, also ratio of dry weight to fresh weight. Mycorrhizal treatment in 7 dS.m-1 showed the highest root length. In 12 the most dry weighet of root, ratio of dry weight to fresh weight, the number of active leaves and K concentration in 16 mg/l humic acid and the most number of active leaves, chlorophyll and the lowest concentration of Na obtained in madder residue plant. Also madder residue plant reduced Na concentration in 7 and 12 dS.m-1 levels. In 12 dS.m-1 plants didn’t show reproductive phase, but adding soil amendments caused flowering induction. Excess soluble salts in the root zone restrict plant roots from withdrawing water from surrounding soil, effectively and causes drought for the plant. The loss of photosynthesis in salt stress condition resulted in the loss of dry weight production at the leaf level of evening primrose. Generally, all treatments in all salt levels caused increasing growth and yield of plant. According to the results, it is cleared that in normal condition, evening primrose plant could tolerate salt stress until 7 dS.m-1 but by suitable media culture its threshold tolerate will be increased until 12 dS.m-1. Also it was revealed that all treatments could increase plant tolerate to salt stress and growth characteristics.