saeedeh savadkoohi

Salinity is one of the greatest environmental challenges facing plant growth and development in the 21st century. Salicylic acid (SA) is a phenolic compound and signal molecule involved in the regulation of plants responses to biotic and abiotic stresses. This greenhouse experiment was conducted to determine effects of SA application on Kentucky bluegrass (Poa pratensis L.) responses to salinity stress. The three salinity levels (0, 40 and 80 mM NaCl) were applied in nutrient solutions, and foliar SA treatments (0, 1 and 2 mM) were applied at 2-weeks intervals. The study was carried out as a factorial experiment based on completely randomized experimental design with four replications. Salinity reduced root and shoot dry weight, visual turf quality, leaf chlorophyll and potassium content, whereas electrolyte leakage, proline and sodium content were increased with salt concentration in nutrient solution. Salicylic acid application ameliorates adverse effects of salinity in all factors and this effect was more pronounced in 80 mM NaCl. In terms of root dry weight, leaf sodium and proline content as well as electrolyte leakage, SA application at 2 mM had better results than 1 mM. These results suggest that further studies are required to find proper SA application rate in different salinity levels.

This experiment was conducted in order to investigate morphological and physiological responses of Kentucky bluegrass (Poa pratensis L.) to salinity and silicon application in horticultural science department at the University of Zanjan in 2015. The salinity levels (0, 40 and 80 mM NaCl) and sodium silicate (0, 0.75 and 1.5 mM) were applied in complete nutrient solutions. Salinity reduced root and shoot growth, visual turf quality, leaves chlorophyll and potassium content, whereas electrolyte leakage, proline and sodium content increased with increasing salt concentration in nutrient solution. Silicon application ameliorate adverse effects of salinity in all factors except in potassium content and this effect was more pronounced in 80 mM NaCl. Although there was no significant difference between 0.75 and 1.5 mM sodium silicate in visual turf quality, root growth and chlorophyll content, altogether, application of 1.5 mM silicon had better results to increase salinity tolerance in Kentucky bluegrass, suggesting that higher concentrations of silicon must be evaluated.

Bermudagrass [Cynodon dactylon (L.) Pers.] is a perennial grass and has been long used as a medicinal herb in Iranian traditional medicine to treat varied ailments. Different parts of bermudagrass such as leaves, stolons, rhizomes and culms are rich sources of metabolites such as proteins, carbohydrates, mineral constituents, β- sitosterol, flavonoids, alkaloids, glycosides and triterpenoides. Growth regulators change plant physiological processes such as phytochemical accumulation. Paclobutrazol (PBZ) and Trinexapac-ethyl (TE) are two popular growth retardant that inhibit gibberellic acid (GA) biosynthesis. This greenhouse experiment was conducted to determine effects of TE and PBZ application on bermudagrass growth and phytochemical content. Paclobutrazol was applied twice at four weeks intervals at 0, 1, 2, 3 and 4 g a.i. (active ingredient) 100 m2 and TE treatments (0, 0.25, 0.5, 0.75 and 1 g a.i. /100 m2) were applied biweekly over 8 weeks period. Shoot and root growth, were decreased with increasing PBZ and TE application rates except for TE0.5 treatments that showed higher root growth than control plants. Chlorophyll, Total non-structural carbohydrates, soluble flavonoids and protein content were increased with increasing PBZ and TE application rates unless TE1 treatment that exhibited lower total non-structural carbohydrates (TNC) content than untreated plants. The results suggest that TE and PBZ treatments were beneficial for bermudagrass phytochemical content enhancement. However, puclobutrazol application, because of higher phytotoxity than trinexapac ethyl (lower plant quality and sever shoot depression), seems to be less effective in raising medicinal properties.