2017 ASHS Annual Conference

The effects of heat, storage, Giberellic Acid (GA₃), Potassium Nitrate (KNO­­­₃), and combined GA₃+KNO on the germination of fresh (harvested 0 days prior) and stored (harvested 2 years prior) Carica papaya L. cv. Kapoho seeds was studied. A factorial design was used with the factors of heat and pre-plant soaking. The heat factor consisted of a heated (30°C) and unheated growth environment. The soaking treatments were soaked in solutions of GA₃, KNO­­­₃, GA₃+KNO₃, and a control (H₂0). Each treatment had four replicates, with 50 seeds per replicate. The study was conducted in a lab at the Komohana Research and Extension Center, Hilo, HI from 21 July 2016 to 22 August 2016. Measurements were taken every other day on a Monday through Friday schedule. Radicle protrusion and cotyledon emergence were recorded. Radicle and cotyledon emergence percentages, and days to emergence were assessed. Fresh seeds germinated at lower percentages compared to stored seeds, most likely due to higher concentrations of growth-inhibiting compounds in the sarcotesta and seed coat of fresh seeds, mainly phenolic compounds. Fresh seeds treated with GA₃ and germinated on heat mats showed the fastest radicle protrusion at an average of 8 days from imbibition. Heat overall did not significantly increase rate of radicle protrusion (p=0.1221), but did significantly increase rate of cotyledon emergence (p<0.0001). Heat did increase the germination percentage in the control group. Stored seeds had greater germination percentages and faster germination rates compared to fresh seeds under control treatments. GA₃ treatments resulted in faster radicle protrusion when compared to all other treatments (p<0.0001). The addition of KNO₃ improved shoot emergence compared to GA₃ and the control. Fresh seeds showed improved results when comparing the three treatments to the control except for the effect of GA₃ on shoot emergence. It is essential to have radicle protrusion and shoot emergence for viable plants. A combination of GA₃+KNO₃ resulted in the second highest radicle protrusion and highest shoot emergence. Heated mats can potentially be used to increase the percentage of viable seedlings during germination. This data can be used to inform producers of effective treatments to increase germination percentages and decrease days to germination, potentially reducing the seed costs associated with papaya production.