Evaluation of different dormancy breaking methods and effects of salt (NaCl) and drought (PEG600) stresses on germination characteristic of Mesquite (Prosopis stephaniana Willd)

Seed dormancy is one of the major problems in evaluating the effect of different environmental factors on germination characteristics of weed seeds. In order to realize the type of Mesquite seed dormancy an experiment were conducted based on a completely randomized design (CRD) with twelve treatment and four replications. Treatments were six different times seed soaking (10، 20، 30 40، 50 and 60 minutes) in sulfuric acid 95-98%، mechanical scarification with sandpaper for 5 minutes، seed soaking in distilled water at 24 and 48 hour and soaking seeds boiling water (95-98 0C) for 5 and 10 minutes with control. Results showed that all chemical and mechanical scarification treatments germination was conducted and highest germination rate، root and stem length، root and stem fresh weight were in time 60 minutes of seed storage in sulfuric acid. In order to study effects of salt and drought stress (as NaCl and PEG6000) on germination characteristic of Mesquite two separate experiment were conducted in growth chamber. The Experimental design was a completely randomized plot design (CRD) with four replications. Treatments were salt and drought stress as osmotic and matric potential، respectively، at four levels (0 (distilled water)، -0. 3، -5، -10 and -15 bars). Result showed when stress increased، germination percent، germination rate decreased significantly (p≤ 0. 001)، there were higher in drought stress than salt stress. When water potential decreased، time to 50% of maximum germination increased. The functional three-parameter logistic model provided a successful estimation of the relationship between salt and drought stress levels and germination response of Mesquite. Results of this model showed that salinity and drought at -16. 23 and -6. 26 bar، respectively caused 50% reduction in maximum germination percentage of Mesquite.