Optimization of seed germination and detection of germination inhibitors in gardenia fruits

ObjectiveGardenia seeds were processed by different treatments to investigate the causes of inhibiting seed germination and its inhibitor positions in order to seek out the best method for improving germination rate, which provided ref-erences for artificial cultivation. MethodGardenia fruits collected from two main producing areas of Zhangshu in Jiangxi and Bozhou in Anhui were used to investigate the effects of concentrated sulfuric acid soaking for 2-24 hours on water absorp-tion of gardenia seeds. The effects of methyl alcohol extracting solution(0.005-0.050 g/mL) of gardenia seeds, and pulp and peel on germination rate of cabbage seeds and seedling growth were studied. The germination rate of gardenia seeds was measured in different treatments of concentrated sulfuric acid, gibberellin(0-1.5 g/mL), auxin(0.1-5.0 g/mL), temperature(15.0-30.0℃) and germination substratum (vermiculite, gauze, filter paper, and wet sand). ResultAfter the treatment of concentrated sulfuric acid, water absorption of gardenia seeds from different producing areas was generally improved. Mean water absorption of the saturated seeds was 34.31%higher than seeds without acid etching. Inhibiting effects of pulp methyl alcohol extracting solution on cabbage seeds were greater. With the increase of peel or seeds methyl alcohol extracting solution concentration, the germination vigor and rate of cabbage seeds showed slowly declining trend, and the same results was also observed in treat-ments of 0.005-0.015 g/mL pulp methyl alcohol extracting solution. When the pulp methyl alcohol extracting solution was over 0.015 g/mL, the germination vigor and rate of cabbage seeds sharply decreased. Higher methyl alcohol extracting solution con-centration of gardenia fruits made root and seedling shorter and growth weaker of cabbage. The pulp had the strongest inhibiting effects, followed by peel and seed. Moreover, the inhibiting effects of extracting solution on root was greater than seedling. Gardenia seeds treated by concentrated sulfuric acid could not germinate and were easy to mould. Higher auxin concentration could obviously reduce gardenia germination rate and seeds became black. In the range of 0.3-1.2 g/mL gibberellins, more gib-berellins meant higher gardenia germination rate, and the highest rate occurred in treatment of 1.2 g/mL gibberellins. In the range of 20-30℃, gardenia germination rate was relatively high, while it was exceedingly low under 20℃. At the optimum temperature of 30℃, the order of germination rate and vigor was filter paper, wet sand, gauze and vermiculite.ConclusionThe substances inhibiting germination of seeds did exist in pulp and peel of gardenia fruits and they were primary inhibiting germination elements. Kind and number of chemical substances inhibiting seed germination in gardenia peel, seed and pulp may be different. Concentrated sulfuric acid and auxin inhibited gardenia germination, while gibberellins promoted gardenia germination. The optimum conditions for gardenia seed germination was as follows:seed soaked in 1.2 mg/mL gibberellins solu-tion for 48 h under dark condition, and then culturing on filter paper at 30°C in the dark.