Evaluation of Flowering Potential of Saffron Corms in Different Weight Groups under Hydroponic Conditions

Many of the saffron corms that are planted in the fields do not have the desired weight and have very low potential for flowering in the field conditions. It is hypothesized that due to the elimination of physical resistance of soil and appropriate control of environmental factors in hydroponic cultivation, it is possible to obtain more flowers from small corms in a controlled environment (Behdani & Fallahi, 2015). In some previous studies (Molina et al., 2005; Mollafilabi, 2014; Aghhavani-Shajari et al., 2021) saffron flowering capacity under controlled environment has been evaluated, but using large mother corms. The main goal of this research was to investigate the possibility of producing flowers from very small saffron mother corms in a controlled environment.
 
In this study, the effect of mother corm weight (2-4, 4-6, 6-8 and 8-10 g) on saffron flowering characteristics was investigated under controlled environment, in a completely randomized design with four replications, in horticulture laboratory, University of Birjand, Iran. Flower initiation stage was passed in the soil (in field), but the flower emergence stage took place under controlled conditions (Temperature: 15±1 °C, relative humidity: 75% and light frequency: 8 hours of light and 16 hours of darkness) (Mollafilabi, 2014; Aghhavani-Shajari et al., 2021), with a planting density of 500 corms per m-2. Some properties of used water in hydroponic production system has been provided in Table 1. The studied traits were number of flowers, flower yield, mean flower weight, flower length, stigma and style length, as well as dry weights of stigma, style and petals. Data analysis was done using SAS ver.9.2. Means were compared by FLSD at 5% level of probability.    
 
The results showed that the number of flowers produced in the weight groups of 2-4, 4-6, 6-8 and 8-10 g, were 0, 56.2, 193.7 and 425 No m-2, respectively (Fig 1), which indicates the production of at least one flower per corm is 0, 11.2, 38.7 and 85% of the corms in the mentioned weight groups of corms, respectively. This can probably indicate that regardless of the cultivation environment (field or hydroponic), very small corms are not able to produce flower or their flowering capacity is very limited (Behdani & Fallahi, 2015; Fallahi et al., 2018). Flower yield in the weight groups of 2-4, 4-6, 6-8 and 8-10 g were 0, 24, 96.6 and 198 g m2, respectively (Fig. 3), and dry pistil yield (style & stigma) were 0, 0.25, 0.98 and 2.13 g m-2, respectively (Fig. 7). Under field conditions and planting the corm in the soil at a depth of about 20 cm, usually the mother corms weighing 4-6 g rarely have the ability to flower (Behdani & Fallahi, 2015). The results of this experiment showed that planting these corms in hydroponic environment makes at least 11% of them produce flowers. It seems that if both stages of saffron flowering (flower initiation and flower emergence) are spent in a controlled environment, a higher percentage of small corms are able to produce flowers. The results of this research, compared to the field experiments that have been done on saffron before (such as Fallahi et al., 2018), showed that the cultivation of saffron in a controlled environment can lead to the flowering of a higher percentage of corms, and this advantage increases significantly with the increase in the mother corm weight.