Effect of Early Planting Dates and Different Treatments of Seed Priming on Germination and Seedling Establishment of Roselle (Hibiscus sabdariffa)

The effect of environmental factors on the developmental stages of a plant causes the planting date to vary from one region to another. Temperature is a very important factor in the maximum percentage germination and germination rate. Priming improves germination rate, brings about the uniformity of germination and reduces seed susceptibility to environmental factors. The purposes of this experiment were to study the effects of priming treatments at different temperatures on the germination characteristics of Hibiscus sabdariffa under laboratory conditions,  to investigate priming treatments on different planting dates and to compare early planting dates on the farms.

The experimental study was carried out as a factorial experiment in a completely randomized design with four replications in the Laboratory of Seed Technology of Kashmar University Jihad. The first factor is five primings (Concentrations of ZnSO4 (10 mM), Humic acid (2.5 cc) and the combination of Humic acid and Zinc sulfate, Biological materials (Pota Barvar 2), no treatment (control) and the second factor is five levels of temperature: 10, 12, 14, 16 and 18 °C. Field studies were carried out in Agricultural and Natural Resources Research Center of Kashmar in three separate experiments in 2018. The research was carried out in a completely randomized block design with three replications on three planting dates (March 25th, April 15th, and May 4th, 2018). In each experiment, priming treatments were applied similarly to field experiments.

The results of the current experimental study showed that temperature, priming and temperature interaction with priming had a significant effect on all the traits studied. The highest percentage and rate of germination were observed at 18 °C and priming with Pota Barvar 2. The results also showed that planting date had a significant effect on all the traits studied in the field experiment. Priming showed a significant difference only in stem fresh weight. The interaction effect of priming and planting date was not significant for the traits studied. The highest germination percentage was obtained on April 15’s planting date. By planting later than March 25 to 15 April, a decrease of 74% was observed in the rate of germination. Among priming treatments, the combination of Zinc Sulfate and Humic acid showed a significant superiority, compared with other treatments.

The findigns suggest that due to the high sensitivity of seed germination of sour tea at low temperatures, the planting date in each area should be carefully chosen so that it does not coincide with temperatures below 18 °C.