The effect of plant-growth promoting rhizobacteria (PGPR) on chlorophyll and carotenoid contents of the coriander (Coriandrum sativum L.) under salinity stress

In order to study the effects of biofertilizers on the growth properties and the physiological parameters of the Coriander (Coriandrum sativum L.) under salinity stress, a completely-randomized, factorial-design experiment was carried out with three replications under the greenhouse conditions at Sari Agricultural Sciences and Natural Resources University. The factors under treatment included the salinity stress (by sodium chloride) at four levels (control, 30, 60 and 90 mM) and the pretreatment of the commercial biofertilizers, such as Nitroxin (including Azospirillium and Azotobacter) and Supernitroplus (including Aspirillium, Bacillus subtilis, Pseudomonas fluorescens). The results indicated that the interaction effect of the biofertilizers and the salinity was significant on chlorophyll a, chlorophyll b, and a+b contents at P< 0.01. According to the results, the bacterial inoculation had a positive and significant effect on the amount of chlorophyll at all salinity levels under study except for the 60 mM level. The maximum amount of chlorophyll b and a+b contents (6.06 and 20.08 μg/ml, respectively) were obtained from the Supernitroplus treatment at 90 mM salinity level, which increased up to 57.4% and 30% in comparison to the plants under the non-inoculated treatment, respectively. In addition, the interaction effect of salinity and inoculation was significant for all of the traits studied except for the plant height and the dry weight. The highest leaf surface area belonged to the plants under Nitroxin treatment at the control salinity level (with 37.71 cm) which demonstrated a 44.9% increase compared to the plants under the non-inoculated treatment at the same level. Generally speaking, all of the above-mentioned morphological traits significantly decreased by an increase in salinity levels.