Effect of varying auxin concentrations on corm weight allocation, reproductive characteristics, and stigma yield of saffron (Crocus sativus L.) under aeroponic culture

This study was conducted to evaluate the effects of priming saffron corms with different concentrations of auxin (۰, ۱, ۲.۵, ۵, ۱۰, ۲۵, ۵۰, ۱۰۰, ۲۵۰, ۵۰۰, and ۱۰۰۰ ppm) on vegetative, reproductive, and propagative traits under aeroponic conditions, using a completely randomized design with three replications. The results revealed that saffron responses to NAA pretreatment were predominantly dose-dependent and exhibited a biphasic pattern. At the propagation level, the greatest stimulation of lateral bud emergence occurred at lower concentrations, where ۵ and ۱۰ ppm significantly increased the mean number of lateral buds by approximately ۷۵% and ۶۶% compared with the control, respectively. Conversely, intermediate concentrations (particularly ۵۰ and ۱۰۰ ppm) partially suppressed bud formation, while the lowest value (۱.۴ buds) was observed at ۲۵۰ ppm. Reproductive traits followed a quadratic, dose-responsive trend, with the maximum flower number, flower yield, and stigma dry weight obtained at ۲۵۰ ppm. Leaf length (۱۴.۴ cm) and leaf dry weight (۲.۶۸ g per plant) also peaked at this concentration. With respect to corm multiplication, the highest number of reproductive corms per ۱۰۰ mother corms was recorded at ۱۰ ppm (۵۲۵ corms), whereas the lowest (۲۵۸ corms) occurred at ۲۵۰ ppm. However, mean reproductive corm weight was maximized at ۲۵۰ ppm (۱۱.۰۶ g). Corm weight distribution was strongly influenced by auxin concentration: lower doses (۵–۱۰ ppm) produced a higher proportion of small corms (<۵ g; ≈۷۳% at ۵ ppm and ≈۶۳% at ۱۰ ppm), whereas ۲۵۰ ppm increased the proportion of large corms (>۱۰ g) to about ۴۵%. Overall, the findings indicate that lower auxin concentrations (۵–۱۰ ppm) are more suitable for mass propagation, while intermediate levels—particularly ۲۵۰ ppm—are recommended for enhancing flower yield and producing larger corms, which are desirable for economic and production purposes.

کلیدواژه ها:

Corm ، Lateral bud ، Stigma ، Naphthalene acetic acid (NAA)