investigation of thermal requirement, growth and yield characteristics of two species of persian shallot (allium altissimum and a. hertifulium ) in different density, bulb weight and flowering stem removing

persian shallot is one of the important medicinal and industrial plants in iran which is under very dense utilization. study of morphological characteristics in this plant in agronomical systems is very important for expanding agronomic production of this plant. in order to evaluate some physiological, yield characteristics and thermal requirement of two species of shallot, a field experiment was conducted in 2012-2013at research field of fersowsi university of mashhad. in this study allium altissimum from khorasan and a. hertifulim) from lorestan, two groups of bulb weight (10-20 and 20-30 g), with three plant densities (10, 20 and 30 plantsm2). a factorial experiment based on completely randomized design with three replications was conducted. the results showed that in all phonological and yield charactristics, a.hertifulium was significantly weaker than a.altissimum. leaf area and shoot dry weight in different plant densities and bulb weight in a.hertifulium was significantly lower than a.altissimum. the results also indicated that thermal requirement of a. hertifulium was more less than the other species. growth duration in a.hertifulium was 239 days with 1664 growing degree days (gdd) whereas a.altissimum needed 252 days with 2000 gdd. plant density of 30 plant/m2 caused a significant reduction in yield and bulb weight of a.altissimum but the number of bulb per m2 was increased significantly. same results were shown in a.hertifulium up to 20 plant/m2. removing flowering stem treatment had significant effect on yield charactristics in both species. removing flowering stem caused accumulation of more dry and fresh weight, diameter and volume in harvested bulbs compared to control.