Plant Process and Function

en Physiological and morphological responses of peppermint (Mentha × piperita L.) to the application of seaweed under salinity stress Hamideh Jafarzadeh Koshkenow, Mohammad Ali Hakimzadeh Ardakani*, Hamid Sodaeizadeh and Motahareh Esfandiari تنش شوري Salt Stress پژوهشي Research <div style="text-align: left;">Biofertilizers, e.g., seaweed extract, have been effective in environmental and agricultural ecosystems. The effects of seaweed extract were studied on the physiological characteristics of peppermints irrigated with water at different salinity levels in a factorial experiment based on a randomized complete block design with four replications in the greenhouse of Yazd University in 2020. The experimental factors included salinity stress at four levels of 0, 2, 4, or 8 dS/m provided from a sodium chloride source and the foliar application of seaweed at four levels of 0, 1/1000, 2/1000, or 4/1000 provided from an Ascoclepe source. In examining morphological traits, results demonstrated that the fresh and dry weight of leaves, aerial parts, total fresh and dry biomass, and harvest index were significant at the P≤0.01 level. The use of seaweed at 4 ppt under stress-free conditions resulted in the highest weight of leaves, aerial, and total biomass. Based on the results, the salinity stress and the foliar application of the seaweed extract were significantly influential on chlorophyll a and b, total chlorophyll, and proline amino acid at the P≤0.01 level and on dissolved sugars at the P≤0.05 level. The comparison of means revealed that the highest relative water content was 65.8% related to the no-salinity conditions. The highest proline content was obtained from the salinity levels of 4 and 8 dS/m, exhibiting a 37.5% increase versus the control. Total chlorophyll exhibited a positive and significant correlation with other traits, including chlorophyll a, chlorophyll b, and carotenoids, with correlation coefficients of 0.61, 0.96, and 0.98, respectively. A negative and significant correlation was observed between proline and total chlorophyll, chlorophyll b, and relative humidity with correlation coefficients of 0.56, 0.52, and 0.62, respectively. The results generally showed that the application of seaweed extract at the rates of 2/1000 and 4/1000 to the plants exposed to high levels of salinity (4 and 8 dS/m) alleviated the adverse impacts of salinity by improving physiological traits, e.g., proline content.</div> Biofertilizers, e.g., seaweed extract, have been effective in environmental and agricultural ecosystems. The effects of seaweed extract were studied on the physiological characteristics of peppermints irrigated with water at different salinity levels in a factorial experiment based on a randomized complete block design with four replications in the greenhouse of Yazd University in 2020. The experimental factors included salinity stress at four levels of 0, 2, 4, or 8 dS/m provided from a sodium chloride source and the foliar application of seaweed at four levels of 0, 1/1000, 2/1000, or 4/1000 provided from an Ascoclepe source. In examining morphological traits, results demonstrated that the fresh and dry weight of leaves, aerial parts, total fresh and dry biomass, and harvest index were significant at the P≤0.01 level. The use of seaweed at 4 ppt under stress-free conditions resulted in the highest weight of leaves, aerial, and total biomass. Based on the results, the salinity stress and the foliar application of the seaweed extract were significantly influential on chlorophyll a and b, total chlorophyll, and proline amino acid at the P≤0.01 level and on dissolved sugars at the P≤0.05 level. The comparison of means revealed that the highest relative water content was 65.8% related to the no-salinity conditions. The highest proline content was obtained from the salinity levels of 4 and 8 dS/m, exhibiting a 37.5% increase versus the control. Total chlorophyll exhibited a positive and significant correlation with other traits, including chlorophyll a, chlorophyll b, and carotenoids, with correlation coefficients of 0.61, 0.96, and 0.98, respectively. A negative and significant correlation was observed between proline and total chlorophyll, chlorophyll b, and relative humidity with correlation coefficients of 0.56, 0.52, and 0.62, respectively. The results generally showed that the application of seaweed extract at the rates of 2/1000 and 4/1000 to the plants exposed to high levels of salinity (4 and 8 dS/m) alleviated the adverse impacts of salinity by improving physiological traits, e.g., proline content. Medicinal plant, Photosynthesizing Pigments, Proline Amino acid, Seaweed extract Medicinal plant, Photosynthesizing Pigments, Proline Amino acid, Seaweed extract 91 102 http://jispp.iut.ac.ir/browse.php?a_code=A-10-720-3&slc_lang=en&sid=1 Hamidehe Jafarzadeh Koshkenow Hamidehe Jafarzadeh Koshkenow jafarzadehhamideh@gmail.com No School of Natural Resources and Desert Studies, Yazd University, Yazd, Iran School of Natural Resources and Desert Studies, Yazd University, Yazd, Iran Mohammad Ali Hakimzadeh Ardakani Mohammad Ali Hakimzadeh Ardakani Hakim@yazd.ac.ir Yes School of Natural Resources and Desert Studies, Yazd University, Yazd, Iran School of Natural Resources and Desert Studies, Yazd University, Yazd, Iran Hamid Sodaeizadeh Hamid Sodaeizadeh hsodaie@yazd.ac.ir No School of Natural Resources and Desert Studies, Yazd University, Yazd, Iran School of Natural Resources and Desert Studies, Yazd University, Yazd, Iran Motahareh Esfandiari Motahareh Esfandiari motiesfandiari@gmail.com No School of Natural Resources and Desert Studies, Yazd University, Yazd, Iran School of Natural Resources and Desert Studies, Yazd University, Yazd, Iran